JP4370904B2 - Semiconductor laser element - Google Patents

Description

The present invention relates to a semiconductor laser device having a good far field pattern (FFP), and relates to a group III-V nitride semiconductor (In _x Al _y Ga _{1- xy} ) composed of GaN, AlN, InN, or a mixed crystal thereof. N, 0 ≦ x, 0 ≦ y, x + y ≦ 1).

2. Description of the Related Art In recent years, semiconductor laser elements have become smaller, lighter, more reliable and have higher output, and are used in personal computers, electronic devices such as DVDs, medical devices, processing devices, and light sources for optical fiber communication. Among them, nitride semiconductors (In _x Al _y Ga _1-xy N, 0 ≦ x, 0 ≦ y, x + y ≦ 1) are attracting attention as semiconductor laser elements capable of emitting red light from a relatively short wavelength ultraviolet region. Yes.

  Such a semiconductor laser device includes a buffer layer, an n-type contact layer, a crack prevention layer, an n-type cladding layer, an n-type light guide layer, an active layer, a p-type cap layer, a p-type light guide layer, p on a sapphire substrate. A mold cladding layer and a p-type contact layer are formed in this order. Further, a stripe-shaped light emitting layer is formed by etching or the like, and then a p-side electrode and an n-side electrode are formed. Further, after forming the light emitting surface with a predetermined resonator length, a light reflecting mirror surface is formed so that the oscillation light can be efficiently extracted from the light emitting side mirror surface.

  However, such a structure has a problem that irregularities (ripples) occur in the far field pattern (FFP), resulting in a non-Gaussian distribution. In the semiconductor laser device in which the FFP has a non-Gaussian distribution, there has been a problem that the FFP shape calculation has a large error and cannot be efficiently coupled to the optical system, which increases the drive current.

Further, the conventional semiconductor laser device has a problem that the emission end face is easily deteriorated.
Accordingly, a first object of the present invention is to provide a semiconductor laser device capable of obtaining a good FFP having no ripple and close to a Gaussian distribution during high output operation.

  It is a second object of the present invention to provide a semiconductor laser device that can prevent deterioration of the end face and obtain a good FFP even when a high output operation is performed.

In order to solve the above problems, a semi-conductor laser element according to the present invention includes a first conductive semiconductor layer, an active layer, and a semiconductor layer of a second conductivity type different from the first conductivity type comprising a laminated structure are laminated in this order, the laminate structure possess a cavity surface of the laser resonator in the waveguide region and both ends for guiding light in one direction, out of the cavity surface of the opposite ends In the semiconductor laser device having one light emitting surface, the stacked structure is formed on the light emitting surface side so as to include an active layer cross section separately from the resonator surface, and is perpendicular to the light guiding direction. The resonator surface, which is a non-resonator surface, has a non-resonator surface, protrudes from the non-resonator surface, and a light shielding layer is formed on the non-resonator surface .

  By adopting such a configuration, light (stray light) that oozes out of the waveguide region is prevented from being emitted from the non-resonator surface to the outside and prevented from overlapping with the main beam emitted from the resonator surface. (That is, since only the main beam can be emitted, generation of ripples can be prevented), and an excellent FFP can be obtained.

In addition, the semiconductor laser device according to the present invention can efficiently prevent the stray light from being emitted to the outside because the resonator surface protrudes beyond the non-resonator surface.
In this way, the light emitted from the resonator surface is not blocked by the non-resonator surface.

  Furthermore, in the semiconductor laser device according to the present invention, a more excellent FFP can be obtained by using a resonator surface in which a non-resonator surface is formed in the vicinity as a laser light emitting surface.

In the semiconductor laser device according to the present invention, the side surface of the stacked structure includes a first side surface including the active layer cross section, and is positioned closer to the waveguide region than the first side surface and includes the active layer cross section. And a light shielding layer may be formed on the second side surface.

In the semiconductor laser device according to the present invention, the non-resonator surface and the second side surface may be continuous.

In the semiconductor laser device according to the present invention, a stripe-shaped convex portion is formed in the multilayer structure, and the waveguide region is formed by the stripe-shaped convex portion,
  The second side surface may be located on a different surface from the side surface of the convex portion and may be formed outside the convex portion.

In the semiconductor laser device according to the present invention, the non-resonator surface may be a surface provided by removing both corners of the laminated structure in the vicinity of the light emitting surface to below the active layer.

In the semiconductor laser device according to the present invention, the non-resonator surface may be a surface in which a rectangular groove is formed so as to sandwich the stripe-shaped convex portion and is orthogonal to the resonance direction of the groove.

In the semiconductor laser device according to the present invention, the light shielding layer may be formed in contact with the laminated structure.

In the semiconductor laser device according to the present invention, the light shielding layer may be formed on an insulating layer provided in the stacked structure.

In the semiconductor laser device according to the present invention, the light shielding layer may be made of any one of a conductor, a semiconductor, and an insulator.

In the semiconductor laser device according to the present invention, the light shielding layer may be formed of a dielectric multilayer film.

In the semiconductor laser device according to the present invention, a nitride semiconductor may be used for the first conductive type semiconductor layer, the active layer, and the second conductive type semiconductor layer.

In the semiconductor laser device according to the present invention, the first conductivity type semiconductor layer includes an n-type nitride semiconductor, and the second conductivity type semiconductor layer includes a p-type nitride semiconductor. Also good.

In the semiconductor laser device according to the present invention, the light shielding layer is a conductor material, and includes Ni, Cr, Ti, Cu, Fe, Zr, Hf, Nb, W, Rh, Ru, Mg, Al, Sc, Any of Y, Mo, Ta, Co, Pd, Ag, Au, Pt, and Ga alone, an alloy, a multilayer film, or an oxide or nitride thereof may be used.

Further, in the semiconductor laser device according to the present invention, the light shielding layer is a conductive material, and Ni, Cr, Ti, Cu, Fe, Zr, Hf, Nb, W, Rh, Ru, Mg, Ga alone, Any one selected from an alloy, a multilayer film, or an oxide or nitride thereof may be used.

In the semiconductor laser device according to the present invention, the light shielding layer is a semiconductor material and may be any one of Si, In, GaN, GaAs, and InP.

In the semiconductor laser device according to the present invention, the light shielding layer is an insulator material, and is made of TiO. ₂ , CrO ₂ Any of these may be sufficient, and the said light shielding layer may have an Rh oxide at least.

Hereinafter, the present invention will be described with reference to the drawings. However, the semiconductor laser element of the present invention is not limited to the element structure and the electrode configuration shown in the embodiments described later.
Embodiment 1 FIG.
1 is a perspective view showing the outer shape of the laser device according to the first embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and FIG. 3 is III in FIG. It is sectional drawing about the -III line.
The semiconductor laser device of the first embodiment obtains an excellent FFP by blocking light emitted from other than the cavity surface by the light shielding layer 9. As a specific form, the stacked structure 100 in which the semiconductor layer 1 of the first conductivity type, the active layer 3 and the semiconductor layer 2 of the second conductivity type different from the first conductivity type are stacked is striped. The convex portion (ridge) 8 is provided (FIG. 2), and a striped waveguide region is formed in the vicinity of the active layer immediately below the striped ridge 8. Then, by forming both end faces perpendicular to the longitudinal direction of the ridge 8 as resonator planes, an optical resonator having the longitudinal direction of the stripe as the resonance direction (light waveguide direction) is formed. One of the two resonator surfaces is a light emission side resonator surface (light emission surface) mainly having a function of emitting light to the outside, and the other is a light reflection having a function of mainly reflecting light into the waveguide region. This is the side resonator surface (monitor surface). Further, a first insulating film 10 is formed on the side surface of the stripe-shaped convex portion 8 and the surface (upper surface) of the laminated structure continuous from the side surface, and the first insulating film 10 is formed. Striped ohmic electrodes 5 that are in ohmic contact with the second conductivity type semiconductor layer 2 are provided on the upper surface of the convex portion 8 of the second conductivity type semiconductor layer that is not present. On the first conductive type semiconductor layer 1 exposed along the laminated structure 100, ohmic electrodes 7 that are in ohmic contact with the first conductive type semiconductor layer 1 are formed in stripes. Both ohmic electrodes are provided so as to be substantially parallel. In the laser element of the first embodiment, a second insulating film 11 having an opening is formed on these electrodes so as to cover the entire element, and the ohmic electrode and the second insulating film 11 are formed through the second insulating film 11. Pad electrodes (n-side pad electrode 6 and p-side pad electrode 4) are formed in contact with each other.

  Here, in the semiconductor laser device of the first embodiment, as shown in FIGS. 1 and 3, the semiconductor layers on both sides of the ridge are removed below the active layer 3 in the vicinity of the light emitting side resonator surface. The laminated structure 100 has a shape with the corners removed. Thereby, on the light emitting side, a resonator surface 101a having a width smaller than the width of the laminated structure 100 is formed, and light is emitted from the resonator surface 101a. Further, by removing the corners of the laminated structure 100 on both sides of the resonator face 101a on the emission end face side, the non-resonator face is located on a plane different from the resonator face 101a and orthogonal to the resonance direction. 101b is formed. The surface 101b formed by removing the corners of the laminated structure 100 reflects a part of the guided light, but is smaller than the light reflected by the resonator surface 101a. Since it does not substantially contribute to the resonance of light, it is called a non-resonator surface in this specification. As described above, in the first embodiment, one of the end faces in the direction perpendicular to the light guiding direction of the stripe-shaped waveguide region of the multilayer structure is not a single surface but a light emitting surface. The resonator surface 101a and the non-resonator surface 101b including the cross section of the active layer located behind the resonator surface (provided with a step) are formed. Further, with respect to the plane (side surface) parallel to the light guiding direction of the laminated structure 100, the light emitting side of the laser element is more in the waveguide region than the first side surface 102 that is the main side surface of the laminated structure. A second side surface 102a formed at a position near the center is formed. In the laser element of the first embodiment, the light shielding layer 9 is provided on the non-resonator surface 101b and the second side surface 102a formed as described above, as shown in FIGS. FIG. 4 is a diagram in which the insulating film and the electrode are omitted in order to clearly show the shape of the light shielding layer in the semiconductor laser device of the first embodiment shown in FIGS. is there. The non-resonator surface 101b and the second side surface 102a are also referred to as light shielding layer forming surfaces. In FIGS. 1 and 4, the reference numerals of the above-described surfaces are shown in parentheses because those surfaces do not appear on the surface.

  In the laser device of the first embodiment configured as described above, the light generated in the active layer (light emitting region) is mainly guided in the waveguide region and emitted from the resonator surface 101a to be emitted from the main beam (laser). Light). In the conventional laser element, a part of the light oozes out from the waveguide region, propagates in the element as stray light, and is emitted to the outside from the part other than the emission part of the resonator surface, which is emitted from the resonator surface. Ripple was generated by mixing with the beam, and FFP was deteriorated. However, since the light shielding layer 9 is formed in the laser element of the present invention, this stray light can be blocked from being emitted outside from the cavity surface 101a. The light shielding layer 9 provided as a layer that blocks stray light may have a function of blocking light by reflecting or absorbing light. When the light shielding layer 9 is formed using a material that reflects light, stray light can be reflected inside the device to improve the light output efficiency. Further, when the light shielding layer 9 is formed using a material that absorbs stray light, the stray light can be prevented from being emitted to the outside.

  In general, the light emitted to the outside from the surface other than the resonator surface is the largest at the end face near the resonator face, and is emitted in the same direction as the emission direction of the laser beam as the main beam at the resonator end face on the light emission side. Therefore, it is easy to mix. Therefore, the stray light can be effectively prevented from being emitted to the outside by providing the light shielding layer 9 that blocks the light in the vicinity of the resonator surface as in the first embodiment. In particular, in the first embodiment, the non-resonator surface 101b is formed on a surface different from the resonator surface 101a, and the light shielding layer 9 is provided on this surface to effectively prevent stray light from being emitted to the outside. Ripple is prevented from occurring in the light. The light shielding layer 9 is not provided with a non-resonator surface separately from the resonator surface as in the first embodiment, but is shielded so as to limit the emission portion on the resonator surface composed of one surface as in the prior art. Although a layer may be formed, in such a configuration, if the thickness of the light non-absorbing layer is increased, the main beam is blocked. Therefore, it is necessary to select a material that does not transmit light even if it is thin. However, as in the first embodiment, the resonator surface 101a is formed so as to protrude from the non-resonator surface 101b, and the light shielding layer 103 is provided on the non-resonator surface 101b. It can be formed thick without blocking. Moreover, since the light shielding layer 103 is provided in front of the light emitting surface (resonator surface) 101a, stray light can be blocked more efficiently.

  Further, the stray light that oozes out from the waveguide region is emitted not only from the surface (end surface) in the direction perpendicular to the light guiding direction as described above but also from the surface (side surface) parallel to the waveguide direction. As shown in FIGS. 3 and 4, stray light can be prevented from being emitted by providing the light shielding layer 9 also on the second side surface 102 a. In the case where an insulating film, an electrode, or the like is provided on the side surface of the element, depending on the material of the insulating layer or the electrode, it can function as a light shielding layer. However, as shown in FIG. 1, the semiconductor layer may be exposed without providing an insulating film or an electrode in order to easily divide the wafer in the vicinity of the ridge at the position where the wafer is divided for each element. In such a case, stray light can be prevented from being emitted to the outside by providing the second side surface 102a at the position close to the waveguide region and providing the light shielding layer 9 as in the present invention. A laser beam having a good FFP without ripples can be obtained.

  As described above, stray light is generated because the width of the laminated structure is larger than the width of the waveguide region that guides the light. That is, this is because a layer capable of propagating light, such as an active layer, is also present outside the waveguide region (outside the waveguide region). It is possible to eliminate stray light by eliminating the portion located outside that does not constitute the waveguide region. For example, the region where stray light is guided can be eliminated by etching the laminated structure so as to have a width equal to the width of the waveguide region. However, if the width of the entire laminated structure 100 (the width of the active layer) is narrowed, fluctuations in the width greatly affect the characteristics of the element, so it is necessary to control the width with high accuracy. However, as will be described later, in order to make the waveguide region suitable for laser oscillation, the width of the stripe is about 5 μm at a maximum, and the width of all the active layers is accurately managed with such a narrow width. It is not easy to form, and even if it is formed with high accuracy, it is too thin to have durability, and it is difficult to form an electrode and is not practical. In the present invention, in consideration of these, a laminated structure having a width wider than that of the waveguide region is formed, and in the laminated structure, a stable stripe-shaped waveguide region (a portion sandwiched between the first side surfaces) is formed. And a waveguide region (a portion sandwiched between the second side surfaces) whose width is limited to such an extent that the device characteristics are not adversely affected. And the light shielding layer is provided in the light shielding layer formation surface formed in order to comprise the waveguide area | region where the width | variety was restrict | limited.

  In the first embodiment, the thickness of the light shielding layer 9 is preferably 1500 mm to 30000 mm, more preferably 1500 mm to 5000 mm. A film thickness of less than 1500 mm is not preferable because light is easily transmitted. Moreover, when providing thickly, it is preferable to provide the light shielding layer 9 so that the removed part may be filled to the surface. By providing a thicker layer, the active layer can be less likely to be damaged even if the width of the active layer is narrow.

Moreover, as a material used for the light shielding layer 9, any of a conductor, a semiconductor, and an insulator can be used. However, in the case of using a conductor, it may be provided so as to be in direct contact with the laminated structure. However, in order to prevent a short circuit and to prevent a current flow in the element structure from being interrupted, an insulating film is used. It is necessary to provide it so as not to be in direct contact with the electrode. If an insulating film is formed in advance, the same material as the electrode can be used, and the effect of blocking light is enhanced. In the case of using a semiconductor, it is preferable to use a semiconductor having a narrower band gap than the active layer. If the band gap is wider than that of the active layer, it is difficult to obtain a light absorption effect, which is not preferable. In the case of using a semiconductor, after forming all necessary layers, a light shielding layer forming surface can be formed by etching, and the layers can be stacked to fill the surface. Alternatively, after laminating at least up to the layer above the active layer, the reaction is temporarily stopped, a portion other than the active layer constituting the waveguide region is removed, a step is provided, and then the reaction is restarted and laminated. Also good.
In the case of using an insulator, it may be easy to handle because it may be in contact with the electrode, but the light blocking effect is slightly inferior to that of the conductor. As described above, in the present invention, since the light shielding layer can be formed using various materials, the most preferable materials can be selected according to the structure of the element, the manufacturing process, the manufacturing method, and the like. .

A dielectric multilayer film can also be used as the light shielding layer 9. Thereby, in addition to the effect of blocking light, a function of protecting the exposed end face, particularly the active layer, can be accompanied.
Specific materials used for the light shielding layer 9 include Ni, Cr, Ti, Cu, Fe, Zr, Hf, Nb, W, Rh, Ru, Mg, Al, Sc, Y, Mo, Ta as conductor materials. , Co, Pd, Ag, Au, Pt, and Ga alone, alloys, multilayer films, and compounds selected from compounds such as oxides and nitrides thereof can be used. These may be used alone or in combination. Preferred materials are materials using Ni, Cr, Ti, Cu, Fe, Zr, Hf, Nb, W, Rh, Ru, Mg, Ga, and more preferably Ni, Cr, Ti, Ga, Rh, RhO. It is a material using. As the semiconductor material, Si, InGaN, GaAs, InP, or the like can be used. As the insulator material, TiO ₂ , CrO ₂ or the like can be used. In order to form the target position, various methods such as vapor deposition and sputtering can be used.

  Among these materials, Rh oxides such as RhO are particularly preferable materials. By using this RhO as a light shielding layer, light can be efficiently blocked. And since it is a thermally stable layer, it can be set as the stable light shielding layer with little deterioration in a process or at the time of use. In particular, by forming it at a position slightly away from the waveguide region, an excellent FFP can be obtained without lowering the slope efficiency. The Rh oxide can be particularly preferably used when the main beam wavelength is visible light having a relatively short wavelength from ultraviolet. Specifically, by using it in a semiconductor laser device made of a nitride semiconductor and having a main beam wavelength in the range of about 360 to 420 nm, the light blocking effect is increased, so that stray light is blocked and ripple is reduced. It is effective for.

In the present invention, the light shielding layer can reduce ripples more effectively by using a multilayer film. In the case of a multilayer film, a multilayer film made of different materials can be used, or the same material can be used. Even with the same material, the film characteristics can be changed by changing the formation method or the like, so that a multilayer film in which optically or electrically different layers are laminated can be obtained.
The light shielding layer 9 is preferably formed so as to be in direct contact with the laminated structure as shown in the first embodiment. Thereby, it is possible to prevent intrusion into, for example, an insulating film or the like other than the laminated structure of light, and efficiently block stray light from being emitted to the outside. In particular, when the non-resonator surface 101b is provided in the vicinity of the element dividing surface, the laminated structure is provided with no protective film or the like on the surface in the vicinity of the dividing surface (end surface) in consideration of easiness of dividing. In many cases, the light shielding layer is directly formed on the exposed non-resonator active layer surface of the laminated structure in the vicinity of the end face.

However, in the present invention, when the insulating layer is formed on the surface of the laminated structure, the light shielding layer 9 may be formed on the insulating layer. Thereby, it is possible to use a material having poor adhesion to the laminated structure as the light shielding layer. In addition, by providing the light shielding layer on the insulating layer as described above, it is possible to avoid contact with the electrode, and it is possible to suppress diffusion of the material of the light shielding layer into the laminated structure even during the heat treatment. There is also an effect such as being able to. Examples of the material for the insulating layer include oxides such as SiO ₂ and ZrO ₂ .

When such an insulating layer is used, it is preferable to use Ti as the light shielding layer and use SiO ₂ as the insulating layer. With such a configuration, a light-shielding layer having an excellent light blocking effect can be obtained, and light absorption can be suppressed, so that loss of light guided in the stacked structure is suppressed as much as possible. Therefore, it is possible to output laser light efficiently and to obtain an excellent semiconductor laser element with little increase in Vf. The Rh and Rh oxides described above can also be provided on an insulating layer such as SiO ₂ or ZrO ₂ .
5 to 8 show modified examples of the end surface structure on the light exit surface side of the first embodiment.
Hereinafter, the non-resonant surface and the light shielding layer of the modification will be described with reference to FIGS.

(Non-resonator surface)
In the present invention, the surface in the direction perpendicular to the light guiding direction is the end surface, and the surface in the direction parallel to the light guiding direction is the side surface. In the first embodiment, the non-resonator surface 101b provided on a plane different from the resonator surface is a surface perpendicular to the light guiding direction, and the cross section of the active layer is also exposed on the surface. However, it does not have a function as a resonator end face. However, as described above, it is a surface that can emit light that has oozed out of the waveguide region. In particular, in the vicinity of the resonator surface, light that is not laser light is often emitted. In the present invention, stray light is prevented from being emitted to the outside by providing a light shielding layer on a non-resonator surface located on a plane different from the resonator surface.

  As described above, the non-resonator surface 101b is formed on a different plane from the resonator surface 101a. As a typical example, as shown in FIGS. 4 to 6, it is a surface provided by removing a corner portion of a laminated structure. However, the present invention is not limited to this. For example, as shown in FIG. 8, two rectangular grooves 71 sandwiching the ridge 8 are formed on the resonator surface on the emission side, and the resonance direction of the grooves 71 is determined. The bottom surface orthogonal to the non-resonator surface 101d may be used. That is, in the present invention, the non-resonator surface 101d may be formed so as not to reach the side surface of the multilayer structure. 4 to 6, the non-resonator surface is formed at the end of the element. However, as shown in FIG. 7, a rectangular groove 72 sandwiching the ridge 8 is formed on the side surface of the output side laminated structure. The side surface orthogonal to the resonance direction of the groove 72 may be the non-resonator surface 101c. That is, in the present invention, the non-resonator surface may be provided in the middle of the striped waveguide of the laminated structure. Even with such a configuration, the resonator surface and the non-resonator surface are provided in a direction perpendicular to the waveguide direction. By providing the light shielding layer 9 here, stray light can be blocked. In addition, it is preferable to provide one nonresonator surface 101b on both sides of the resonator surface, but there is no problem even if there are two or more. When two or more are provided, they may be separated or may be continuous. Further, since it only needs to face the direction perpendicular to the light guiding direction, it does not have to be completely perpendicular and may be inclined.

(Second aspect)
In the present invention, among the surfaces (side surfaces) in the direction parallel to the light guiding direction, the second side surface is a surface closer to the waveguide region, and the first side surface 102 is from the second side surface. Is a surface located outside. In the configuration of FIGS. 7 and 8, the second side surface is indicated by the reference numerals 102c and 102d. Both the first and second side surfaces include a cross section of the active layer. Further, the side surface of the n-electrode forming surface and the side surface of the substrate are surfaces that do not include the active layer and do not need to provide the light shielding layer 9 (not exposed). No problem. The first side surface and the second side surface including the cross section of the active layer can emit light that oozes out of the waveguide region in the same manner as the non-resonator surface. In particular, stray light is likely to be emitted near the resonator surface. In the present invention, stray light is effectively prevented from being emitted to the outside by forming the light shielding layer 9 on the second side surface in the vicinity of the resonator surface and close to the waveguide region.

  The second side surface is preferably located closer to the waveguide region than the first side surface and is provided in the vicinity of the resonance end face, and particularly preferably in contact with the resonance end face. Such a 2nd side surface can be easily formed by removing the corner | angular part of a laminated structure like FIG. 1, for example, and the light shielding layer 9 can be formed easily. This is because, when a wafer is processed, the waveguide region is provided between adjacent elements in a stage before division, but in the case of the shape shown in FIG. Since the light shielding layer can be formed simultaneously, it is advantageous in terms of the process. However, the second side surface has no problem in preventing the emission of stray light even if it is not in contact with the resonance end surface. For example, as shown in FIG. A groove may be formed so as to be partially stepped from the first side surface. Further, in FIG. 8, the first side surface and the second side surface are formed so as to overlap (partially face each other), but even in such a configuration, the side surfaces are formed on different surfaces. In addition, by providing the light shielding layer on the second side surface closer to the waveguide region, stray light can be prevented from being emitted to the outside. The second side surface may be one or two, and may be separated or continuous. In addition, since it does not have to be completely parallel to the light guiding direction, there is no problem even if it is inclined as long as it faces a plane parallel to the guiding direction. Also, as a plane parallel to the waveguide direction, a third side and a fourth side may be provided at a position closer to the side than the first side farthest from the waveguide region, and the side having a plurality of steps may be provided. Alternatively, a light shielding layer may be formed on the surface. . Further, when forming a stripe-shaped convex portion (ridge), as shown in FIG. 3 (a cross-sectional view in the vicinity of the emitting portion in FIG. 1), it is located on the same plane as the side wall (side surface) of the convex portion 8. By forming the second side surface, there is a merit in the process such that the mask at the time of etching can be shared.

  However, in the present invention, the second side surface may be located on a different surface from the side surface of the convex portion 8, and may be formed outside the convex portion 8, for example, as shown in FIG. As shown in FIG. 9, when the distance between the second side surfaces 102e on both sides is made larger than the width of the stripe-shaped convex portion (ridge) 8, the beam characteristic of the laser beam is changed to the second characteristic in addition to the ripple reducing effect by the light shielding layer. The distance can be changed in accordance with the interval between the side surfaces 102e (the width of the active layer sandwiched between the second side surfaces). In other words, the width of the active layer sandwiched between the second side surfaces can be appropriately selected according to the target beam characteristics. For example, when the width of the active layer sandwiched between the second side faces 102e is reduced, the lateral light confinement effect becomes stronger and the beam radiation angle can be increased. A preferable range of the width of the end face of the active layer sandwiched between the second side surfaces is about 1.5 to 10 μm, more preferably 4 to 8 μm, and particularly preferably 5.5 to 7 μm. When the width of the active layer sandwiched between the second side surfaces (the width of the active layer on the resonator surface) exceeds 10 μm, the distance between the second side surface and the waveguide region is increased, thereby blocking stray light. Less. On the other hand, if the thickness is smaller than 1.5 μm, the light confinement effect is increased, the radiation angle is increased, the light is concentrated, the load is increased, and COD is easily generated.

  By providing the light shielding layer of the present invention on both the non-resonator surfaces 101b, 101c, and 101d and the second side surfaces 102a, 102c, and 102d as described above, the stray light can be efficiently blocked and emitted to the outside. Can be prevented. In the present invention, as shown in FIG. 4, it is preferable to continuously provide the non-resonator surface and the second side surface. However, it is also possible to emit stray light by providing only one of them as shown in FIGS. The effect of preventing is obtained. Further, the inclined surface may be such that the non-resonator surface 101b and the second side surface 102a are the same surface. Furthermore, there is no problem even if the light shielding layer 9 is provided on the surface, the end face, and the side face of the exposed n-type layer, and on the surface, the side face, and the end face of the substrate 12. Even if they are on the same plane as the resonator surface, they are separated from the emitting portion, so there is almost no problem with blocking the emitted light. Furthermore, it may be provided on a part of the surface (upper surface) of the p-type layer continuous from the second side surface 102a and the non-resonator surface 101b. However, it is preferably provided on the surface of the p-type layer other than the stripe-shaped convex portion (ridge) 8. As described above, since light leaks also from the upper surface of the p-type layer in the vicinity of the optical resonator surface 101a, ripple can be suppressed by blocking the light leaking from here. Moreover, the upper surface of the p-type layer is a surface in a different plane direction from the second side surface and the non-resonator end surface, and the light shielding layer is not easily peeled off by continuously forming the surface in such a positional relationship. can do. In particular, even in a portion where a thin film layer is difficult to be formed, such as a corner portion or an edge portion, strong adhesion can be obtained by continuously forming the portion. Since the light shielding layer can be stably formed, deterioration of the layer itself can be prevented, and the life characteristics are also improved.

  The non-resonator surface and the second side surface are preferably flat and smooth planes, but may be rough surfaces or curved surfaces. The light shielding layers formed on these surfaces are the same, but there is no problem even if they are formed in accordance with the state of the non-resonator surface or the second side surface. Moreover, you may form in the surface state which changes with places. Further, for example, in the structure shown in FIG. 1, the boundary portion between the second side surface and the non-resonator surface is structurally easy to deposit the light shielding layer material, and the corner portion is formed thick, There is no problem because the effect of not transmitting light is not inferior.

  Further, since the light shielding layer 9 may be provided so as to cover the layer on which light propagates on the second side surface and the non-resonator surface, it may be provided so as to cover at least the cross section of the active layer. It may not be formed on the entire second side surface. In the case where a guide layer or the like is formed and there is a layer in which light easily propagates other than the active layer, it is preferably provided so as to cover them. In consideration of the process, the n-type layer and the substrate may be covered.

  In the semiconductor laser device of the present invention, the light shielding layer forming surface is formed on the end surface and the side surface. As a method for forming these surfaces, an appropriate process and method are selected depending on the position to be formed and the material of the light shielding layer. be able to. For example, it may be formed at the same time in the etching process for exposing the n-electrode formation surface, or may be formed using masks having the same width or different widths in the etching process for forming stripe-shaped convex portions. In addition, if the stripe-shaped convex portions are formed before the formation, the resonator surface with a narrower active layer width can be obtained, so that the light shielding layer can be formed at a position closer to the waveguide region. This makes it possible to prevent the stray light from being mixed into the main beam and to reduce the width of the active layer, thereby providing a waveguide structure with excellent light confinement.

(Waveguide region)
In the semiconductor laser device of the present invention, the striped waveguide region is mainly formed in the vicinity of the active layer sandwiched between the first conductive type semiconductor layer and the second conductive type semiconductor layer. The stripe direction and the resonator direction substantially coincide with each other. Here, the waveguide region is mainly composed of the active layer and the vicinity thereof. A light guide layer sandwiching the active layer is formed, and the region up to the guide layer sandwiching the active layer is defined as an optical waveguide layer. It may be a waveguide region.

(Resonator surface)
The pair of resonator surfaces formed at both ends of the waveguide region are flat surfaces formed by cleavage or etching. In the case of forming by cleaving, it is necessary that the substrate or the laminated structure layer has cleaving property. However, if the cleaving property is used, an excellent mirror surface can be easily obtained. Further, when the resonator surface is formed by etching, the number of times of etching can be reduced by simultaneously performing the exposure when the n electrode forming surface is exposed. The resonator surface can also be formed at the same time by an etching process for forming stripe-shaped convex portions. In this way, the number of steps can be reduced by forming simultaneously with each step. However, in order to obtain a more excellent resonator surface, it is preferable to provide another step. In addition, on the resonator surface formed by cleaving or etching in this way, a reflective film made of a single film or a multilayer film is formed in order to efficiently reflect the light emission of the active layer or adjust the reflectance. You can also One of the resonator surfaces consists of a relatively high reflectivity surface and serves mainly as a light reflecting side resonator surface that reflects light into the waveguide region, and the other consists of a relatively low reflectivity surface that primarily transmits light to the outside. It functions as a light emitting side resonator surface that emits light.

(Striped convex part)
In the semiconductor laser device of the present invention, the stripe-shaped waveguide region can be easily formed by providing a convex portion in the laminated structure. Specifically, in the second conductivity type semiconductor layer of the stacked structure, striped convex portions are formed by removing both sides of the peak by etching or the like so that the central portion remains in the peak shape. A striped waveguide region can be formed in the vicinity of the active layer immediately below the striped convex portion. The convex portion is not limited to the forward mesa shape in which the width on the bottom surface side of the convex portion is wide and the stripe width decreases as it approaches the top surface, and conversely, the reverse mesa shape in which the width of the stripe decreases as it approaches the bottom portion of the convex portion may be used. Moreover, the convex part which has a perpendicular | vertical side surface so that a width | variety may become fixed irrespective of the position of a lamination direction may be sufficient, and the shape which combined these may be sufficient. Also, the striped waveguides need not have the same width over the entire length. Further, it may be an embedded laser element in which a semiconductor layer is regrown on the surface of the convex portion after such a convex portion is formed.

In the present invention, the active layer end face and the side face can be stepped by partially changing the etching depth for forming the stripe-shaped convex portion thus provided. For example, in FIG. 1, on the light emitting surface side of the stripe-shaped convex portion, both sides of the convex portion are etched deeper than the active layer, so that a step is formed on the end surface on the light emitting surface side. A non-resonator surface is formed. Further, on the emission end face side, a second side face continuous with the side face of the stripe-shaped convex portion is formed, and the other side face is the first side face. By forming the end faces and the side surfaces so as to correspond to the convex portions of the stripes in this way, it is possible to efficiently form the surface on which the light shielding layer is provided without going through a complicated process.
Either the stripe-shaped convex portion or the light shielding layer forming surface may be formed first. As described above, the stripe-shaped convex portion is formed first, and then a step is provided, so that it can be easily formed corresponding to the stripe. Since the waveguide region is formed corresponding to the stripe-shaped convex portion, the distance from the waveguide region on the light shielding layer forming surface can be accurately controlled by forming the stripe in advance.

Alternatively, a part of the active layer may be removed first, and then a stripe-shaped convex portion may be provided so as to correspond to the removed position. When the stripe-shaped convex part is formed first, it is difficult to form the active layer sandwiched between the second side surfaces narrower than the width of the convex part. This is because it is technically difficult to form a narrower mask on the stripe-shaped convex portion after forming the convex portion. However, it is relatively easy to form a mask that is thinner than the mask that is formed to form the ridge, as long as it is on a relatively wide flat surface before forming the stripe-shaped convex portions. Therefore, a thin mask (where the mask portion is the portion where the narrow active layer sandwiched between the second side surfaces is to be formed) is formed on the portion where the narrow active layer sandwiched between the second side surfaces is to be formed, The portions on both sides thereof are etched to the bottom of the active layer to first form a light shielding layer forming surface. At this time, the mask is formed on the entire portion other than both sides of the thin mask. After that, a material to be a light shielding layer is embedded in the portion removed by etching until it is located on the surface of the semiconductor layer. Next, a mask for forming a ridge is formed, and both sides of the mask are etched to form a ridge. In this way, as shown in FIG. 10, an active layer having a width narrower than the convex portion 8 can be formed in the vicinity of the emission surface.
This makes it possible to confine lateral light more strongly. In that case, when a resonator surface is formed by cleavage, an appropriate semiconductor layer is grown outside the second side surface so as to bury at least the side surface of the stripe-shaped active layer formed to be thin. It is possible to prevent the vicinity of the emission end face from being damaged.

  In the present invention, as described above, stray light can be more effectively prevented from being emitted to the outside by providing a light-shielding layer forming surface by providing a narrow portion of the active layer on the emission end face side of the laminated structure. The waveguide characteristic of the waveguide can be changed by changing the width of the active layer in this way as well as the structure. In particular, when the second side surface is formed so that the width of the active layer becomes narrow to the vicinity of the waveguide region, the refractive index difference (exact refractive index difference, not an effective refractive index difference) is completely removed from the outside in the waveguide region of that portion. (Difference in refractive index) is provided, so that the controllability of the transverse mode is particularly good. On the other hand, the portion having the first side surface is a waveguide region in which a refractive index difference is effectively provided by forming a stripe-shaped convex portion. In one waveguide region, a region where a refractive index difference is completely provided and a region where a refractive index difference is effectively provided are formed. By utilizing this, the spread angle of the emitted light can be adjusted in the laser element of the present embodiment.

(Laminated structure)
In the semiconductor laser device of the present invention, as a semiconductor used as the first conductivity type semiconductor layer, active layer, and second conductivity type semiconductor layer of the stacked structure, a nitride semiconductor such as GaN, AlN, or InN, A group III-V nitride semiconductor (In _x Al _y Ga _1-xy N, 0 ≦ x, 0 ≦ y, x + y ≦ 1) which is a mixed crystal of these can be used. In the following, preferred examples of the semiconductor laser device of the present invention will be described specifically using nitride semiconductors. Here, the laser element using a nitride semiconductor means that any one of the layers of the stacked structure in which the first conductive type semiconductor layer, the active layer, and the second conductive type semiconductor layer are sequentially stacked is nitride. A semiconductor laser element using a semiconductor, preferably a nitride laser element using a nitride semiconductor in all layers. Specifically, each of the first conductivity type semiconductor layer and the second conductivity type semiconductor layer is provided with a clad layer having a nitride semiconductor, and a waveguide is formed in the active layer and its vicinity. Is. As a more preferable configuration of a semiconductor laser element (nitride semiconductor laser element) configured using a nitride semiconductor, an n-type nitride semiconductor layer is provided on the first conductivity type semiconductor layer, and a second conductivity type is provided. A p-type nitride semiconductor layer is used for the semiconductor layer, and a layer including a nitride semiconductor layer containing In is used for the active layer.

(Nitride semiconductor)
The nitride semiconductor used in the laser device of the present invention includes GaN, AlN, InN, or a III-V group nitride semiconductor that is a mixed crystal thereof (InbAldGa1-b-dN, 0 ≦ b, 0 ≦ d, b + d). ≦ 1). In addition, a mixed crystal in which B is used as the group III element or a part of N of the group V element is substituted with As or P can be used. Further, such a nitride semiconductor can be made to have a desired conductivity type by adding impurities of each conductivity type. As the n-type impurity used in the nitride semiconductor, specifically, a group IV or group VI element such as Si, Ge, Sn, S, O, Ti, Zr can be used, and preferably Si, Ge, Sn is used, and most preferably Si. Specific examples of the p-type impurity include Be, Zn, Mn, Cr, Mg, and Ca, and Mg is preferably used. Hereinafter, a laser element using a nitride semiconductor will be specifically described with respect to the laser element of the present invention. Here, a laser element using a nitride semiconductor means that a nitride semiconductor is used for any one of the layers of the laminated structure in which the first conductive type layer, the active layer, and the second conductive type layer are stacked. Yes, preferably for all layers. For example, a cladding layer made of a nitride semiconductor is provided in each of the first conductivity type layer and the second conductivity type layer, and a waveguide is formed by providing an active layer between the two cladding layers. More specifically, the first conductive type layer includes an n-type nitride semiconductor layer, the second conductive type layer includes a p-type nitride semiconductor layer, and the active layer includes a nitride semiconductor layer containing In. Shall be.

In the nitride semiconductor laser device according to the present invention, when an n-type cladding layer and a p-type cladding layer are provided to form a waveguide region, a guide is provided between each cladding layer and the active layer. A layer, an electron confinement layer, or the like may be provided.
Hereinafter, preferred configurations of the respective layers in the nitride semiconductor laser device according to the present invention will be described.

(N-type cladding layer)
In the laser device using the nitride semiconductor of the present invention, the nitride semiconductor used for the n-type cladding layer may be a refractive index difference sufficient to confine light, as in the p-type cladding layer. A nitride semiconductor layer containing Al is preferably used. Further, this layer may be a single layer or a multilayer film. Specifically, as shown in the embodiment, it may have a superlattice structure in which AlGaN and GaN are alternately stacked. In addition, the n-type cladding layer functions as a carrier confinement layer and a light confinement layer, and in the case of a multilayer film structure, as described above, a nitride semiconductor containing Al, preferably AlGaN is grown. Good to do. Further, this layer may be doped with an n-type impurity or may be undoped. As shown in the examples, in the multilayer film layer, at least one of the layers is doped. May be. In a laser element having a long oscillation wavelength of 430 to 550 nm, the cladding layer is preferably GaN doped with an n-type impurity. Further, the film thickness is not particularly limited as in the case of the p-type cladding layer, but it is sufficient to form it in a range of 100 to 2 μm, preferably in the range of 500 to 1 μm. Functions as a confinement layer.

(Active layer)
In the present invention, when a semiconductor laser device according to the present invention is configured using a nitride semiconductor, the active layer includes a nitride semiconductor layer containing In, so that a wavelength from blue to red in the ultraviolet region and the visible region. In the nitride semiconductor layer containing In, if the active layer is exposed to the atmosphere, it may cause extremely serious element degradation in laser element driving. Since the waveguide region separated from the portion is a waveguide region constituted by a ridge provided at a depth that does not reach the active layer, it is possible to minimize such element deterioration. Because, since In has a low melting point, a nitride semiconductor containing In is a material that easily decomposes and evaporates, is easily damaged during etching, and has a crystallinity in processing after the active layer is exposed. This is because it is difficult to maintain the resistance, and as a result, the lifetime of the element is reduced.

Here, the active layer may have a quantum well structure, in which case either a single quantum well or a multiple quantum well may be used. A quantum well structure is preferably used, so that a laser element and an edge emitting element having excellent light emission efficiency and high output can be obtained. As described above, a nitride semiconductor containing In is preferably used as the active layer of the nitride semiconductor. Specifically, Al _x In _y Ga _1-xy N (0 ≦ x ≦ 1, 0 It is preferable to use a nitride semiconductor represented by <y ≦ 1, x + y ≦ 1). In this case, the active layer having the quantum well structure means that the nitride semiconductor shown here is preferably used as the well layer. In the wavelength region from near ultraviolet to visible light green (380 nm to 550 nm), In _y Ga _1-y N (0 <y <1) is preferably used, and longer wavelength region (red). However, similarly, In _y Ga _1-y N (0 <y <1) can be used, and at this time, a desired wavelength can be obtained mainly by changing the In mixed crystal ratio y. In a short wavelength region of 380 nm or less, since the wavelength corresponding to the forbidden band width of GaN is 365 nm, the band gap energy needs to be approximately the same as or larger than that of GaN. For example, Al _x In _y Ga _1-xy N (0 <x ≦ 1, 0 <y ≦ 1, x + y ≦ 1) is used.

  When the active layer has a quantum well structure, the specific well layer thickness is in the range of 10 to 300 mm, preferably in the range of 20 to 200 mm to reduce Vf and the threshold current density. Can be made. Further, from the viewpoint of crystal growth, when the thickness is 20 mm or more, a layer having a relatively uniform film quality without large unevenness in film thickness can be obtained. It becomes possible. The number of well layers in the active layer is not particularly limited and is 1 or more. At this time, when the number of well layers is 4 or more, if the thickness of each layer constituting the active layer increases, the active layer Since the entire film thickness is increased and Vf is increased, it is preferable to keep the film thickness of the active layer low by setting the film thickness of the well layer to 100 mm or less. In a high-power LD, it is preferable that the number of well layers is 1 or more and 3 or less because an element with high luminous efficiency tends to be obtained.

The well layer may be doped with p-type or n-type impurities (acceptor or donor), or may be undoped or non-doped. However, when a nitride semiconductor containing In is used as the well layer, the crystallinity tends to deteriorate as the n-type impurity concentration increases. Therefore, the well layer should have a good crystallinity by keeping the n-type impurity concentration low. Is preferred. Specifically, the well layer is preferably grown undoped in order to maximize the crystallinity, and specifically, the n-type impurity concentration should be 5 × 10 ¹⁶ / cm ³ or less. preferable. Note that a state where the n-type impurity concentration is 5 × 10 ¹⁶ / cm ³ or less is a state where the impurity concentration is extremely low. In addition, when doping the n-type impurity in the well layer, if the n-type impurity concentration is doped in the range of 1 × 10 ¹⁸ or less and 5 × 10 ¹⁶ / cm ³ or more, the deterioration of crystallinity is suppressed, In addition, the carrier concentration can be increased.

The composition of the barrier layer is not particularly limited, and a nitride semiconductor similar to the well layer can be used. Specifically, a nitride semiconductor containing In such as InGaN having a lower In mixed crystal ratio than the well layer, or A nitride semiconductor containing Al, such as GaN or AlGaN, can be used. At this time, the barrier layer needs to have a larger band gap energy than the well layer. As a specific composition, In _β Ga _1-β N (0 ≦ β <1, α> β), GaN, Al _γ Ga _1-γ N (0 <γ ≦ 1) or the like can be used. the _{in β Ga 1-β N (} 0 ≦ β <1, α> β), the barrier layer can be formed with good crystallinity by using GaN. This is because, when a well layer made of a nitride semiconductor containing In is directly grown on a nitride semiconductor containing Al such as AlGaN, the crystallinity tends to be lowered and the function of the well layer tends to be deteriorated. Because. When Al _γ Ga _1-γ N (0 <γ ≦ 1) is used as the barrier layer, a barrier layer containing Al is provided on the well layer, and the In _β Ga _{1− β N (0 ≦ β <1} , α> β), can be avoided this by a barrier layer of a multilayer film using the barrier layer of GaN. As described above, in the multiple quantum well structure, the barrier layer sandwiched between the well layers is not limited to one layer (well layer / barrier layer / well layer), and may be composed of two or more layers. As the barrier layer, a plurality of barrier layers having different compositions and impurity amounts may be provided, such as “well layer / barrier layer (1) / barrier layer (2) /... / Well layer”. Here, α is the In composition ratio of the well layer, and it is preferable that the In composition ratio β of the barrier layer is smaller than that of the well layer, with α> β.

The barrier layer may be doped with an n-type impurity or may be non-doped, but is preferably doped with an n-type impurity. At this time, the n-type impurity concentration in the barrier layer is preferably at least 5 × 10 ¹⁶ / cm ³ or more, and the upper limit is 1 × 10 ²⁰ / cm ³ . Specifically, for example, in the case of an LD that does not require high output, it is preferable to have an n-type impurity in a range of 5 × 10 ¹⁶ / cm ^{3 to} 2 × 10 ¹⁸ / cm ³ , In a high output LD, it is doped in the range of 5 × 10 ¹⁷ / cm ^{3 to} 1 × 10 ²⁰ / cm ³ , preferably in the range of 1 × 10 ¹⁸ / cm ^{3 to} 5 × 10 ¹⁹ / cm ³ . In the case of doping at such a high concentration, it is preferable that the well layer is substantially free of n-type impurities or is grown undoped. By doping in the preferred range, as described above, it is possible to inject high concentration carriers with good crystallinity.

When doping an n-type impurity, all the barrier layers in the active layer may be doped, or some barrier layers may be doped. When some of the barrier layers are doped with n-type impurities, it is preferable to dope the barrier layers disposed on the n-type layer side in the active layer, and specifically, n is counted from the n-type layer side. Doping the second barrier layer B _n (n = 1, 2, 3...) Allows electrons to be efficiently injected into the active layer, resulting in an element with excellent luminous efficiency and internal quantum efficiency. This applies not only to the barrier layer but also to the well layer. When both are doped, the n-th barrier layer B _n (n = 1, 2, 3... Counting from the n-type layer). ), Doping the m-th well layer W _m (m = 1, 2, 3...), That is, doping from the side closer to the n-type layer, the above-mentioned effect tends to be obtained.

The thickness of the barrier layer is not particularly limited, and can be 500 mm or less, and more specifically, the range of 10 to 300 mm can be applied as in the case of the well layer.
In the laser element using the nitride semiconductor of the present invention, the stacked structure includes an n-type nitride semiconductor in the first conductivity type layer and a p-type nitride semiconductor in the second conductivity type layer. Preferably, specifically, an n-type cladding layer and a p-type cladding layer are provided on each conductive type layer to constitute a waveguide. At this time, a guide layer, an electron confinement layer, or the like as described later may be provided between each cladding layer and the active layer.

(P-type cap layer)
As the p-type cap layer provided between the p-type cladding layer and the active layer, AlGaN or the like can be preferably used, whereby a layer having an effect of confining carriers in the active layer can be obtained. Therefore, it is possible to oscillate more easily. AlGaN may be doped with p-type impurities or non-doped. The film thickness is preferably 500 mm or less.

(Guide layer)
In the present invention, an excellent waveguide can be formed by forming an optical waveguide by providing n-type and p-type guide layers sandwiching the active layer on the inner side (active layer side) than the cladding layer. At this time, the film thickness of the waveguide (the active layer and both guide layers sandwiching it) is preferably 6000 mm or less, and if the film thickness is less than this, a rapid increase in the oscillation threshold current can be suppressed. More preferably, by setting it to 4500 mm or less, it is possible to perform continuous oscillation with a fundamental mode and a long lifetime with a low oscillation threshold current. Further, both guide layers are formed with substantially the same film thickness, preferably 100 mm to 1 μm, more preferably 500 mm to 2000 mm. As a nitride semiconductor used for the guide layer, an appropriate refractive index is selected for forming a waveguide as compared with a clad layer provided on the outer side thereof, and either a single film or a multilayer film may be used. Specifically, undoped GaN is preferable when the oscillation wavelength is 370 nm to 470 nm, and it is preferable to use an InGaN / GaN multilayer structure in a relatively long wavelength region (450 nm or more).

(P-type cladding layer)
In the laser device using the nitride semiconductor of the present invention, a p-type cladding layer including a p-type nitride semiconductor (first p-type nitride semiconductor) is used as the second conductive type layer or the first conductive type layer. It is preferable to provide it. At this time, an n-type cladding layer including an n-type nitride semiconductor is provided in a conductive type layer different from the conductive type layer provided with the p-type cladding layer, and a waveguide is formed in the stacked structure. The nitride semiconductor used for the p-type cladding layer only needs to have a sufficient refractive index difference for confining light, and a nitride semiconductor layer containing Al is preferably used. Further, this layer may be a single layer or a multilayer film. Specifically, as shown in the embodiment, it may have a superlattice structure in which AlGaN and GaN are alternately stacked. Then, crystallinity can be made favorable, which is preferable. Further, this layer may be doped with a p-type impurity, or may be undoped. As shown in the examples, in the multilayer film layer, at least one of the layers is doped. May be. In a laser element having a long wavelength of 430 to 550 nm, the cladding layer is preferably GaN doped with a p-type impurity. Further, the film thickness is not particularly limited, but it is formed in a range of 100 to 2 μm, preferably in a range of 500 to 1 μm, and functions as a sufficient light confinement layer.

  In the present invention, an electron confinement layer and a light guide layer, which will be described later, may be provided between the active layer and the p-type cladding layer. At this time, when the light guide layer is provided, it is preferable to provide a light guide layer also between the n-type cladding layer and the active layer so that the active layer is sandwiched between the light guide layers. In this case, the SCH structure is obtained, and the Al composition ratio of the cladding layer is made larger than the Al composition ratio of the guide layer to provide a refractive index difference, so that the light is confined in the cladding layer. When the cladding layer and the guide layer are each formed of a multilayer film, the magnitude of the Al composition ratio is determined by the Al average composition.

(P-type electron confinement layer)
The p-type electron confinement layer provided between the active layer and the p-type cladding layer, preferably between the active layer and the p-type light guide layer is a layer that also functions as confinement of carriers in the active layer. It contributes to easy oscillation by lowering the threshold current. Specifically, AlGaN is used. In particular, a more effective electron confinement effect can be obtained by providing a p-type cladding layer and a p-type electron confinement layer in the second conductivity type layer. When AlGaN is used for the p-type electron confinement layer, the function can be exhibited more reliably by doping with a p-type impurity. However, even when non-doped, the carrier confinement can be achieved. It has a function. The lower limit of the film thickness is at least 10 mm and preferably 20 mm. Further, the above effect can be sufficiently expected when the film thickness is 500 Å or less and the composition of Al _x Ga ₁ -xN is x is 0 or more, preferably 0.2 or more. An n-side carrier confinement layer that confines holes in the active layer may also be provided on the n-type layer side. The confinement of holes can be performed without providing an offset (difference in band cap from the active layer) as much as confining electrons. Specifically, the same composition as the p-side electron confinement layer can be applied. Further, in order to improve the crystallinity, it may be formed of a nitride semiconductor that does not contain Al. Specifically, almost the same composition as the barrier layer of the active layer can be used. In this case, the n-side barrier layer for confining carriers is preferably disposed on the n-type layer side most in the active layer, or may be disposed in the n-type layer in contact with the active layer. Thus, the p-side and n-side carrier confinement layers are preferably provided in contact with the active layer, so that carriers can be efficiently injected into the active layer or the well layer. In this case, the layer in contact with the p-side and n-side layers may be a carrier confinement layer.

(electrode)
In the semiconductor laser device of the present invention, the p-side electrode formed on the stripe-shaped convex portion and the n-side electrode provided on the n-side layer (n-type contact layer) are not particularly limited, A material capable of obtaining a good ohmic contact with the nitride semiconductor can be preferably used. By forming the stripe-shaped projections corresponding to the waveguide regions, carriers can be injected efficiently. Further, a nitride semiconductor can be provided so as to be in contact with an insulating film described later. In addition, an ohmic electrode provided so as to be in contact with the semiconductor and a pad electrode made of a material suitable for bonding may be provided. In this embodiment, after forming the first insulating film, an opening is provided to form an ohmic electrode, a second insulating film having an opening is further formed thereon, and a pad electrode is formed thereon It is a structured. Specific examples of materials for the p-side electrode include Ni, Co, Fe, Ti, Cu, Rh, Au, Ru, W, Zr, Mo, Ta, Pt, Ag, and oxides and nitrides thereof. These single layers, alloys, or multilayer films can be used. Examples of the n-side electrode include Ni, Co, Fe, Ti, Cu, Rh, Au, Ru, W, Zr, Mo, Ta, Pt, and Ag. These single layers, alloys, or multilayer films can be used. Can be used.

(Insulating film)
In the semiconductor laser device of the present invention, it is preferable to form a protective film on the side surface of the stripe-shaped convex portion and the exposed surface (plane) continuous to the side surface. If it is formed only on the part that protects the convex part, it does not matter if it is insulative, but by using an insulating protective film, it functions as an insulating film to prevent short-circuiting between electrodes and protects the exposed layer It can be set as the film | membrane which has the function as a film | membrane together. Specifically, a single film or a multilayer film such as SiO ₂ , TiO ₂ , or ZrO ₂ can be preferably used. Further, as described above, a multilayer film may be formed through electrodes.

  Here, in the laser element using the nitride semiconductor, the position where the stripe-shaped ridge is provided is in the nitride semiconductor layer containing Al, and the insulating film is provided on the exposed nitride semiconductor surface and the convex side surface. Good insulation is achieved, and a laser element free from leakage current can be obtained even if an electrode is provided on the insulating film. This is because the nitride semiconductor containing Al has almost no material that can make a good ohmic contact, so even if an insulating film, an electrode, or the like is provided on the surface of the semiconductor, there is almost no generation of leakage current. Is to be made. Conversely, if an electrode is provided on the surface of a nitride semiconductor that does not contain Al, an ohmic contact is likely to be formed between the electrode material and the nitride semiconductor, and the electrode is provided on the surface of the nitride semiconductor that does not contain Al via an insulating film. If the insulating film is formed, the insulating film and electrode film quality may cause leakage when the insulating film has minute holes. Therefore, in order to solve them, it is necessary to consider such as forming an insulating film with a film thickness sufficient to ensure insulation, or not covering the exposed semiconductor surface with the electrode shape and position. In the design of the structure, a great restriction is added. Also, the position where the ridge (projection) is provided becomes a problem because the nitride semiconductor surface (plane) on both sides of the ridge exposed when the ridge (projection) is formed is compared to the side surface of the ridge (projection). It occupies an extremely large area, and by ensuring good insulation on this surface, it becomes a laser element with a high degree of design freedom in which various electrode shapes can be applied and the electrode formation position can be selected relatively freely, This is extremely advantageous in the formation of ridges (convex portions). Here, as the nitride semiconductor containing Al, specifically, AlGaN or the above-described superlattice multilayer structure of AlGaN / GaN is preferably used.

Embodiment 2. FIG.
In the semiconductor laser device according to the second embodiment of the present invention, the light leaking from the waveguide region (stray light) is emitted to the outside by providing a light shielding film in the vicinity of the resonator surface, as in the first embodiment. In order to prevent the light-shielding film from being peeled off easily, a light-transmitting film 9a made of the same element as that constituting the light-shielding film is formed between the light-shielding film and the laminated structure. The configuration is the same as in the first embodiment except that it is provided in between.
The laser element according to the second embodiment uses the fact that even if it is a compound composed of the same element and the composition ratio is different, the physical properties and the chemical properties are different. Is formed on the surface of the laminated structure with good adhesiveness. For example, when a specific metal oxide film is used as the light shielding film, an oxide having a different oxygen ratio from the light shielding film is used as the light transmitting film between the light shielding film and the laminated structure. The light-transmitting film uses a highly light-transmitting oxide containing oxygen, and the light-blocking film uses a high light-blocking oxide containing metal. As described above, when the metal content is changed from the low metal content to the high metal content, the light transmittance may change greatly, and the second embodiment has such properties. Things can be used. Further, such a film can be easily obtained by changing the conditions during film formation. The growth conditions to be changed are conditions that can be changed in the apparatus used for film formation, such as the flow rate and composition ratio of the gas used, the gas supply direction, or the degree of vacuum, atmosphere, and temperature in the apparatus.

If only ones having different transmittances are provided, the effect of blocking light can be obtained by forming a metal layer on an insulating light-transmitting film such as SiO ₂ . However, if different materials are used as raw materials, the manufacturing method may differ, and problems may occur with respect to adhesiveness.On the other hand, using the same raw materials, the optical characteristics can be changed simply by changing the film formation conditions using the same equipment. If it can be changed, the film can be continuously formed, so that foreign matters can be prevented from being mixed. In the second embodiment, an intermediate film having a light transmittance between the light-transmitting film and the light-shielding film may be formed. Thus, the transmittance is changed sequentially. As a result, the light can be blocked almost completely by the light shielding film. As described above, when films having the same constituent elements are stacked in combination, a protective film (light-shielding film) having extremely good adhesiveness can be obtained as compared with the case where films made of different elements are stacked.

  In addition, the light-transmitting film and the light-shielding film are formed as a compositionally graded layer by gradually changing the conditions instead of the method of forming the film formation conditions in stages and forming a multilayer film. can do. Even in such a case, it is only necessary to change the composition so that the light can be finally shielded. Therefore, in the present invention, a film having such a composition gradient is used, and the lower side of the film (the side in contact with the laminated structure) is transparent. The film may be a film that has a low light-transmitting property as it goes upward, that is, a film that has a higher light-shielding property.

  Examples of a method for forming a light-transmitting film and a light-shielding film on the surface of the laminated structure include a vapor deposition method such as a physical vapor deposition method (PVD method) and a chemical vapor deposition method (CVD method). When these production methods are used, films having different composition ratios can be easily obtained by changing the conditions. In the present invention, the PVD method is preferably used, and a sputtering method, a vacuum evaporation method, or the like can also be used. When such a method is used, since the light-transmitting film and the light-shielding film made of the same element are formed using the same raw material as in the present invention, they can be continuously formed. Therefore, it is possible to form a high-purity film by preventing impurities and the like from being mixed, and it does not take time to exchange raw materials. By forming under different conditions, a light-shielding film having both adhesion and optical characteristics can be formed.

  As a preferable material used for the light-shielding film and the light-transmitting film, a material whose light transmittance can be changed by changing the composition ratio is preferable. For example, preferable materials include metal oxides, nitrides, fluorides, and the like. Can be mentioned. Specific materials include Rh, Si, Ti, Al, Cr, Nb, Mg, V, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Mo, Ru, Pd, Ag, Sn, In , Hf, Ta, W, Ir, Pt, and Au. These may be used alone or in combination.

  Alternatively, films having different crystallinity corresponding to the composition ratio may be used. If the crystallinity is different, the optical characteristics are also changed. By utilizing this, a light-shielding film can be formed with good adhesion. For example, a film with high crystallinity can be used as the light-transmitting film, and a film with low crystallinity can be used as the light-shielding film. This is because a film with high crystallinity is densely formed, and it is easy to form a film with high crystallinity and high transmittance, and the film with low crystallinity is a crystal lattice irregular to light. Therefore, the fact that the translucency tends to be low is utilized. When a film is formed by sputtering or the like, it tends to be a film that tends to be peeled off when an irregular crystal having a light-shielding property is formed by relaxing the conditions (for example, atmospheric pressure). It can be used as a light-shielding film by forming it on a dense light-transmitting film made of the same element and having good crystallinity.

  In the present invention, among the above materials, as a material for forming the light-shielding film and the light-transmitting film, an Rh oxide typified by RhO is particularly preferable. By using this Rh oxide as a light-shielding film and a light-transmitting film, a film capable of efficiently blocking light can be formed with good adhesion. In addition, since the Rh oxide is thermally stable, a stable light-shielding film with little deterioration can be obtained in the process or during use. In particular, by forming it in the vicinity of the resonator surface and slightly away from the resonator surface, an excellent FFP can be obtained without reducing the slope efficiency. This Rh oxide can be particularly preferably used in a laser element in which the wavelength of the main beam is in the visible light range from ultraviolet to a relatively short wavelength. Specifically, by using it in a semiconductor laser element made of a nitride semiconductor and having a main beam wavelength in the range of about 360 to 420 nm, the light blocking effect can be increased, so that stray light can be blocked and ripple can be reduced. It is effective for.

The total thickness of the light-shielding film is preferably 500 to 10,000 mm, more preferably 1000 to 5000 mm. A film thickness of less than 1000 mm is not preferable because light is easily transmitted and the light shielding effect is reduced.
Moreover, as a total film thickness of a translucent film, 100 to 1000 mm is preferable, More preferably, it is 200 to 600 mm. If the film thickness is less than 200 mm, the light-transmitting film itself tends to peel off, which is not preferable. Moreover, it is not preferable to provide a thick layer in consideration of mass productivity.
The total thickness of the protective film including the light-shielding film and the light-transmitting film is preferably 500 mm to 20000 mm including the case where an intermediate layer is provided therebetween.

  Further, the place where the light shielding film is provided is preferably in the vicinity of the resonator surface, and may be on the same surface as the resonator end surface or on a different surface, but preferably on a different surface. Specifically, in the same manner as in the first embodiment, in the vicinity of the light emitting side resonator surface, the end surfaces on both sides of the resonator surface are removed to below the active layer, and the corners of the laminated structure are removed. It is. If it carries out as mentioned above, it has the same operation effect as a laser element of Embodiment 1.

Embodiment 3
The semiconductor laser device according to the third embodiment of the present invention has at least two protective films (first protective film 109 and first protective film) having different light transmittances on the end faces in the direction perpendicular to the light resonance direction. The second protective film 110) having a transmittance lower than 109 is provided, and the emission of light emitted from the end face is controlled by providing two protective films having different light transmittances on the end face. is there. A specific form is shown in FIGS. 14A to 14C. In addition, in the figure of Embodiment 3, the same code | symbol is attached | subjected and shown to the thing similar to Embodiment 1. FIG. 14C is a cross-sectional view taken along the line XIVC-XIVC in FIG. 14A. In the third embodiment, as shown in FIG. 14C, a first conductive type semiconductor layer (n-type nitride semiconductor layer) 1, an active layer 3, a second conductive type semiconductor layer ( The laminated structure in which the p-type nitride semiconductor layer) 2 is laminated is provided with stripe-shaped convex portions (ridges) 8 and by providing resonator end faces on both end faces perpendicular to the longitudinal direction of the stripes. A waveguide region having a stripe direction as a waveguide direction (resonance direction) is formed. One of the resonator end faces is a light emitting side resonator end face (light emitting face) mainly having a function of emitting light to the outside, and the other is a light reflecting side resonance having a function of mainly reflecting light into the waveguide region. It is a container end face (monitor face). A first insulating film 10 is formed on the side surface of the stripe-shaped convex portion (ridge) 8 and the upper surface of the laminated structure continuous with the side surface. A stripe-shaped p-side ohmic electrode 5 that is in ohmic contact with the p-type nitride semiconductor layer is provided on the upper surface of the convex portion 8 of the p-type nitride semiconductor layer 2 via the first insulating film 10. In addition, n-side ohmic electrodes 7 that are in ohmic contact with the n-type nitride semiconductor layer are formed in stripes on the n-type nitride semiconductor layer exposed along the stacked structure. Both electrodes are provided so as to be substantially parallel. A second insulating film 11 having an opening is further formed on these electrodes, and the p-side pad electrode 4 and the n-side pad electrode 6 are respectively in contact with the ohmic electrode through the second insulating film 11. It is formed.

  In the semiconductor laser device of the third embodiment, the emission of light is controlled by providing protective films having different light transmittances on the end faces of the waveguide region in the direction perpendicular to the light guiding direction. By providing the first protective film 109 having a higher light transmittance at the emission portion of the emission-side resonator surface, the resonator surface is prevented from being deteriorated and the laser beam is easily emitted. Further, by providing the second protective film 110 having a light transmittance lower than that of the first protective film 109 on both sides of the emission part on the emission-side resonator surface, stray light is not emitted from the vicinity of the emission surface. I have to. As a result, in the semiconductor laser device of the third embodiment, stray light can be prevented from being emitted to the outside and ripples can be suppressed.

  In the semiconductor laser device according to the third embodiment configured as described above, the light generated from the light emitting region including the active layer is mainly guided in the waveguide region to end the end of the waveguide region on the resonator surface ( It is emitted from the emission surface and becomes laser light (main beam). However, if the output-side resonator surface is exposed, the output surface is likely to deteriorate at high output, and COD is likely to occur. Also, part of the light oozes out of the waveguide region, propagates in the element as stray light, and is emitted to the outside from other than the exit surface. This overlaps with the main beam, resulting in ripple. Here, the stray light is emitted to the outside of the element, which is light propagated to the end face of the element at an angle that does not cause total reflection. The totally reflected stray light is reflected again toward the inside of the element and is repeatedly reflected in the element until reaching the end face at the total reflection angle. It is amplified by resonance while repeating reflection. When this amplified stray light is emitted to the outside, a ripple is generated in the main beam. As in the third embodiment, two kinds of protective films having different light transmittances are formed on the end face, thereby controlling light emission (suppressing light emitted from portions other than the emission surface). Can

  In the semiconductor laser device of the third embodiment, all or part of the protective films may overlap at the position where the protective films having two different transmittances are in contact. As shown in FIG. 14A, the second protective film 110 is provided on both sides of the resonator surface except the emission surface, and the first protective film 109 is provided so as to cover the second protective film 110 as shown in FIG. 14B. Thus, only the first protective film 109 is formed on the emission surface, and the first protection film 109 is laminated on the second protection film 110 on both sides of the emission surface (near the emission surface). ing. Further, in the present invention, the end face structure on the emission side is configured in the same manner as in the first embodiment, and as shown in FIG. The second protective film 110 may be provided over a wide range of the whole, except for the resonator end face.

  In this manner, if the portion where the first protective film 109 and the second protective film 110 overlap is a portion other than the light exiting surface, whichever of the first protective film 109 and the second protective film 110 is the first? It does not matter if it is formed. A preferable order can be selected and formed depending on the material of the protective film. In addition, by overlapping the semiconductor layer, the semiconductor layer can be formed so as not to be exposed at the boundary.

  In the present invention, as shown in FIG. 15, the first protective film 109 and the second protective film 110 can be prevented from overlapping each other. By providing in this way, the difference in light transmittance can be used effectively, and since there is no overlapping portion, the film thickness does not increase, so that the main beam is hardly physically blocked.

Further, an end face on which neither the first protective film 109 nor the second protective film 110 is provided may be formed. Depending on the process, when the end face appears after the formation of the protective film, neither protective film is formed on the end face of the substrate 12 as shown in FIG. 16, for example. Because it is away from the part where it is done, there is no problem in particular.
When the ripple of the laser light emitted from the resonator surface is small, the first protective film 109 having a high light transmittance is provided on the resonator surface on the emission side, and the first protective film 109 is used as the first protective film 110. The same film as the film 109 may be used.

  As described above, in the third embodiment, by providing two protective films having different light transmittances on the end face of the resonator surface, the light emission portion is limited to a predetermined range, and emission is controlled. Thus, a good FFP can be obtained stably. In the third embodiment, good FFP can be stably obtained without processing the element itself as shown in the first embodiment and without affecting the beam characteristics.

Embodiment 4 FIG.
In the semiconductor laser device of the fourth embodiment, as shown in FIGS. 17A, 17B, 18A, and 18B, both sides of the resonator end face are removed below the active layer in the vicinity of the light emitting side resonator face. The first protective film 109 and the second protective film 110 of the third embodiment are applied to the semiconductor laser element having the same end surface structure as that described in the second embodiment, in which the corners of the laminated structure are removed. It is applied. That is, in the semiconductor laser device of the fourth embodiment, the end face in the direction perpendicular to the light guiding direction of the stripe-shaped waveguide region of the multilayer structure is not a single face but a resonator end face that is a light emitting face. And a non-resonator end face located on a different plane from the resonator end face. In addition, when viewed from the plane (side surface) parallel to the light guiding direction of the light in the stripe-shaped waveguide region of the multilayer structure, the first side surface having the active layer cross section away from the waveguide region, A second side surface having an active layer cross section formed at a position close to the waveguide region is formed. A first protective film 109 is provided on the resonator surface, which is the emission surface (FIG. 17B), and a second protective film 110 is provided on the non-resonator surface and the second side surface (FIG. 17A). ). Specifically, at least a second protective film 110 is provided on the non-resonator surface including the active layer cross section that is not on the same plane as the resonator end surface, and the second side surface closer to the waveguide region. A first protective film 109 is provided so as to cover both the end face and the second protective film 110.

  As described above, in the fourth embodiment, the second protective film having a low light transmittance is provided on the second side surface close to the waveguide region and the non-resonant end surface to make it difficult to emit light, and the resonator on the output side By forming a first protective film having a high light transmittance on the surface, laser light is emitted efficiently and stray light is prevented from being emitted.

  Further, in the semiconductor laser device of the fourth embodiment, as in the first embodiment, the beam characteristic can be improved by limiting the width of the active layer on the emission side. In the fourth embodiment, since the device itself needs to be processed before the first and second protective films are provided on the surface of the device, the workability of the third embodiment is superior to the active layer. There is an advantage that the beam characteristics can be improved, such as that a beam having a wide divergence angle can be obtained by controlling the width of the first embodiment. In addition, since the second protective film 110 can be provided in front of the resonator surface, ripples can be reduced more efficiently.

  In the semiconductor laser device of the fourth embodiment, the ridge side wall (side surface) and the second side surface may be formed in the same plane as in the first embodiment. However, when the ridge is formed thin, it becomes difficult to confine light within the width of the ridge, and good characteristics cannot be obtained. Therefore, as shown in FIG. 17 and FIG. It is preferable to form the second side surface so that the width of the active layer becomes wider. Moreover, since the strength can be increased by making the width of the active layer on the end face on the emission side larger than the width of the ridge, it is difficult to break, and the resonator surface can be formed stably. In particular, when the width of the ridge is narrowed, if the width of the active layer cross section exposed on the emission surface is narrowed corresponding to the width of the ridge, it is cleaved at the target position when the resonator surface is formed by cleavage. However, it is possible to stably cleave by exposing the active layer cross section having a width wider than the width of the ridge to the exit surface.

When the second protective film of the present invention is applied to an end face structure in which both the resonator end face and the second side face are provided as in the fourth embodiment, it is effective to provide both. , It may be provided only on one of them, or may be provided continuously. Moreover, you may form in the surface (slope) formed over a resonator end surface and a 1st side surface.
The non-resonator surface and the second side surface can be variously modified as described in the first embodiment.

Further, the second protective film may be provided so as to cover at least the layer through which light propagates, and thus may be provided so as to cover at least the active layer, and may not be formed over the entire surface including the active layer. . It is preferable to provide a guide layer or the like in a layer where light can easily propagate.
Hereinafter, preferable materials for the first protective film 109 and the second protective film 110 in Embodiments 3 and 4 will be described.

As a material used for the first protective film and the second protective film, any of a conductor, a semiconductor, and an insulator can be used. However, in the case of using a conductor, it is necessary to provide a conductor so as not to be in direct contact with the electrode so as to prevent a short circuit and prevent a current flow in the element structure. When a semiconductor is used, the first protective film preferably has a larger band gap than the active layer, and the second protective film has a smaller band gap than the active layer. preferable. The most preferable materials for these materials can be selected according to the structure of the device, the manufacturing process, the manufacturing method, and the like.
A dielectric multilayer film can also be used as the first protective film. Thereby, it becomes easy to transmit light, and the function of protecting the exposed end surface, especially the active layer can be accompanied.

  Specific materials used for the first protective film and the second protective film include the following materials. Of these, the one having the higher light transmittance is used as the first protective film, A film having a light transmittance lower than that of the first protective film is defined as a second protective film. Therefore, since the first and second protective films are relatively compared in light transmittance, the second protective film is combined with another material depending on the material selected, depending on the material selected. It may be a protective film.

  That is, it goes without saying that the laser beam is mainly emitted from the end surface of the waveguide region. In this specification, the end surface of the waveguide region is used as the exit surface or the exit portion. For example, in the first embodiment, the resonator end face itself having a limited width is the emission face. However, when the exit-side end surface is configured as a single surface as in the third embodiment, the portion that becomes the end surface of the waveguide region of the single surface is the exit portion or the exit surface.

In contrast to the laser light emitted from this emitting part, the light emitted from other than the emitting part is light that adversely affects the shape of the laser beam, but its intensity is extremely high compared to the light emitted from the emitting part. small. Therefore, even if the transmittance of the second protective film is made slightly weaker than that of the first protective film, the light emitted from other than the emission part is considerably reduced, and the adverse effect on the shape of the laser beam is suppressed. The
Therefore, in the laser elements of the third and fourth embodiments, as a material for the first protective film and the second protective film, a condition that at least the transmittance of the first protective film is larger than the transmittance of the second protective film. It is possible to select various materials so as to satisfy the above.

(First protective film)
Preferred materials for the first protective film are selected from compounds such as oxides, nitrides, and fluorides of Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, B, and Ti. Any one of these, or a multilayer film can be used. These may be used alone or in combination. Preferred materials are materials using Si, Mg, Al, Hf, Zr, Y, and Ga. As the semiconductor material, AlN, AlGaN, BN, or the like can be used. As the insulator material, compounds such as oxides, nitrides, and fluorides of Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, and B can be used.

Further, by forming the first protective film with a material having a refractive index between the refractive index in the atmosphere and the refractive index of the semiconductor, an antireflection (AR) film can be formed, thereby preventing light reflection. can do. In the case of the AR film, the relationship between the refractive index n _AR of the first protective film and the refractive index n _S of the semiconductor element that is a stacked structure is 0.75 n _S ^1/2 ≦ n _AR ≦ 1.25 n. It is preferable to satisfy _S ^1/2 . Preferably, 0.85 n _S ^1/2 ≦ n _AR ≦ 1.15 n _S ^1/2 , and most preferably 0.93 n _S ^1/2 ≦ n _AR ≦ 1.07. Examples of the material having such a refractive index include Al ₂ O ₃ , MgO, Y ₂ O ₃ , SiO ₂ and MgF ₂ . Using these materials, the AR film is formed by controlling the film thickness. In order to obtain an AR film, the film thickness is λ × (2m _AR −1) / 4n _AR or λ × m _AR / 2n + λ × (2m _AR −1) / 4n _AR (m _AR = 1, 2, 3 ,...) Are preferable, and more preferably λ / 4n _AR or λ / 2n + λ / 4n _AR (λ: wavelength of light generated from the active layer). An AR film can be easily formed by forming a protective film so as to satisfy such a condition.

In the case where a conductive material such as a metal material is used, an insulating layer can be formed on the surface of the laminated structure and can be formed on the insulating layer. Thereby, it is a material with poor adhesiveness to the laminated structure and can be used as the material of the first protective film.
In the present invention, when the main focus is on protecting the exit surface, the first protective film is preferably formed using a material having a refractive index difference within ± 10% of the refractive index of the laminated structure. Further, by forming the first protective film with a material having a refractive index close to the refractive index of the semiconductor layer (mainly the active layer) constituting the waveguide region, the thickness of the first protective film is slightly changed. Even if it is made, it can be set as the film | membrane (absent layer) whose light reflectance and transmittance | permeability do not change.

For example, when the laminated structure is a nitride semiconductor element, the refractive index of the active layer set so that the wavelength is about 400 nm is about 2.5 (however, in practice, the impurity concentration and composition ratio) Depending on the refractive index). In this case, the preferable refractive index of the first protective film is 2.25 to 2.75 which is ± 10% of 2.5. Specific examples of the refractive index within this range include Nb ₂ O ₅ . If the refractive index is within ± 10% of the laminated structure, the laminated structure can be protected with almost no change in the characteristics of the emitted light. If the refractive index is higher than the refractive index of the laminated structure by more than 10%, the threshold can be lowered, but the slope efficiency is deteriorated, and if the refractive index is lower than 10%, the slope efficiency is improved. Is not preferable.

Here, FIG. 19A to FIG. 19C show electric field intensity distributions when the first protective film is not formed on the emission surface of the resonator surface and when it is formed. As the stacked structure, a semiconductor element made of gallium nitride (GaN) is used. FIG. 19A shows a case where a protective film is not formed. FIG. 19B shows a first protective film, mainly for the purpose of preventing reflection. a case of forming a ₂ O _3, FIG. 19C is a case of forming the _Nb 2 _{O 5} for the purpose of mainly emitting end face protection. The broken line indicates the refractive index distribution, and the solid line indicates the electric field strength (optical power distribution).
As can be seen from FIG. 19A, when the first protective film is not formed, the electric field strength is maximized at the element end face. This is because the end face of the element is in contact with a layer having a low refractive index (air layer: refractive index 1). In such a case, the electric field strength is maximized at the interface. Therefore, an excessive load is applied to the resonator surface, resulting in a problem that COD is likely to occur.

On the other hand, when Al ₂ O ₃ is formed as the first protective film, the electric field strength is smaller than that when the first protective film is not formed as shown in FIG. 19B. . Such a protective film can reduce the load on the resonator surface by controlling the film thickness so that it becomes an AR film, but conversely the RIN (relative noise intensity) characteristics deteriorate and noise is reduced. A phenomenon of a slight increase occurs. Therefore, it can be used for specific applications such as those that are not easily affected by RIN, such as for high output.

Further, when Nb ₂ O ₅ is used as the first protective film formed on the resonator surface, the electric field strength at the element end face can be reduced as shown in FIG. 19C. Can be prevented. In addition, since the refractive index of Nb ₂ O ₅ is almost the same as that of GaN, the reflectivity of the end face (the surface of the first protective film) does not decrease like Al ₂ O ₃ , and the RIN characteristics are deteriorated. Can be prevented. Therefore, it is preferably used for applications in which stability is important, such as fields related to optical disks such as DVR.
Further, since the protective film has various characteristics depending on the refractive index and the film thickness, it is preferable that the film thickness of the first protective film is λ / 4n and an odd multiple thereof. Damage can be reduced. As described above, the AR film can be formed by taking the refractive index into consideration, but the film thickness is preferably λ / 4n regardless of the refractive index. In the case of a single layer, λ / 4n may be used, but in the case of a multilayer film, λ / 2n + λ / 4n or a real number multiple thereof may be used. As a result, the thickness of the electric field strength of the standing wave can be reduced to the minimum value at the interface between the end face of the laminated structure and the protective film (see FIG. 19C), so that the resonator end face is prevented from being damaged. In addition, the device life can be improved.

  Controlling the thickness of the protective film in this way can be applied not only to the resonator surface on the light emitting side, but also to the protective film (mirror) formed on the light reflecting side (monitor side). In order to emit laser light, even if only one of the resonators deteriorates, the characteristics deteriorate. Therefore, as with the light emitting side, the light reflecting side is not damaged by the light from the active layer. Further, by controlling the thickness of the protective film (mirror), deterioration can be prevented and the element life can be improved.

(Second protective film)
Preferred materials for the second protective film include Ni, Cr, Ti, Cu, Fe, Zr, Hf, Nb, W, Rh, Ru, Mg, Ga, Pt, Au, Si, Pd, V, Ta, Mo, A material using C or the like, more preferably a material using Ni, Cr, Ti, or Si. As the semiconductor material, Si, InGaN, GaAs, InP, or the like can be used. As the insulator material, TiO ₂ , CrO ₂ or the like can be used. It is preferable to use these to form an opaque film that hardly transmits light. Specific preferred materials include Ti, TiO ₂ , SiO ₂ , RhO, ZrO _{2 and the} like, and these can be formed as a single layer film or a multilayer film. Various methods such as vapor deposition and sputtering can be used to form these at desired positions.

  Here, in the present invention, the light transmittance is a relative value with respect to the output when the protective film is not formed on the laser light emitted from the waveguide region. The higher the numerical value, the higher the light transmittance. It shows that. In addition, a light-transmitting film is used if the light transmittance is close to 0% and is almost blocked. This light transmittance varies depending on the film thickness even with the same material, and even if it has a different refractive index, the light transmittance may be approximately the same in balance with the film thickness.

Further, the thickness of the second protective film varies depending on the material, but is preferably 200 mm or more when a conductive material is used. Since this second protective film is a film for making it difficult to emit light to the outside, it can be easily formed by increasing the film thickness, but it does not block the light emitted from the emission surface and allows light to pass through. In order to avoid this, the film thickness is preferably about 1500 to 3000 mm. However, when a conductive material is used as the second protective film, an insulating film needs to be formed between the element and the second protective film. In this case, the thickness of the insulating film is not particularly limited as long as the insulating property can be maintained. Further, the light transmittance is not particularly limited. When a dielectric multilayer film is used as the second protective film, a film having a low refractive index is formed with a film thickness of λ / 4n, and a film with a high refractive index is stacked thereon to have a film thickness of λ / 4n. The light transmittance can be controlled.
Further, as a preferred combination of the first protective film and the second protective film, Nb ₂ O ₅ is used as the first protective film on the emission surface of the resonator surface, and the second surface is formed in the vicinity of the resonator surface excluding the emission surface. An opaque film is used as the protective film. As the opaque film, a metal material or a compound thereof is preferable. As specific materials, Ti, TiO ₂ , SiO ₂ , RhO, ZrO _{2 and the} like are preferable, and these can be formed as a single layer film or a multilayer film. By selecting such a material, it is possible to suppress the deterioration of the resonator surface and to obtain a semiconductor laser element with little ripple.
The waveguide region can be formed in the same manner as in the first embodiment.

  In addition, in order to set the longitudinal direction of the stripe-shaped convex portion as the resonance direction, the pair of resonator surfaces provided on the end faces are flat surfaces formed by cleavage or etching. The method of forming the resonator surface differs depending on the type of substrate described later. In the case of using the same kind of substrate, for example, when a laminated structure made of a gallium nitride compound semiconductor layer is formed on a gallium nitride substrate, the resonator surface can be easily formed by cleavage. However, when forming a laminated structure on a heterogeneous substrate, for example, when forming a gallium nitride compound semiconductor layer on a sapphire substrate, depending on the main surface of the substrate, the cleavage surface of the substrate may be a cleavage surface of the semiconductor layer above it. Does not coincide with the surface of the resonator. In such a case, it is preferable to form the resonator surface by etching. In addition, when the resonator surface is formed by etching, if the substrate is exposed deeply until the substrate is exposed, the surface may be roughened. Therefore, a good resonator surface can be obtained by etching at least to the depth at which the waveguide region is exposed. It is done. However, in order to facilitate the division of the element, it is preferable to perform etching until the substrate is exposed. However, when the end face is processed by etching, the end face is not a single flat face like the cleaved resonator face, but a step is generated as shown in FIG. In particular, as the number of times of etching increases, the level difference increases accordingly. In this case, it is necessary to process the portion protruding from the resonator surface so as not to block the emitted light. Further, both of the resonator surfaces may be formed by the same method such as cleaving or etching, or may be formed by different methods such as cleaving only one and etching the other, and these may be appropriately selected according to the purpose. You can choose.

Further, the stripe-shaped convex portions can be formed in the same manner as in the first embodiment, and various substrates shown in the first to third embodiments can be applied to the substrate.
Furthermore, various structures such as those described in Embodiment Mode 1 can be used as the stacked structure body and the semiconductor layer forming the stacked structure body.
Furthermore, when the same structure on the emission end face side as in the first embodiment is applied, the method described in the first to third embodiments can be applied to the method for forming the non-resonator face and the second side face. .

In the present invention, various layer structures can be used as the structure of each of the first conductivity type semiconductor layer, the active layer, and the second conductivity type semiconductor layer constituting the stacked structure. As a specific structure of the device, for example, a device structure described in Examples described later can be given. Moreover, an electrode, an insulating film (protective film), etc. are not specifically limited, A various thing can be used. In the case of a nitride semiconductor laser device, nitride semiconductor growth methods include MOVPE, MOCVD (metal organic chemical vapor deposition), HVPE (halide vapor deposition), MBE (molecular beam vapor deposition), etc. All methods known to grow physical semiconductors can be applied.
Hereinafter, a semiconductor laser device using a nitride semiconductor will be described as an example. However, the semiconductor laser device of the present invention is not limited to this, and can be applied to various semiconductor laser devices in the technical idea of the present invention. Yes.

In the first embodiment, a different substrate different from the nitride semiconductor is used as the substrate. However, in the present invention, a substrate made of a nitride semiconductor such as a GaN substrate may be used. Here, as the dissimilar substrate, for example, an oxide that lattice-matches with sapphire, spinel, ZnS, ZnO, GaAs, Si, SiC, and a nitride semiconductor whose main surface is any one of the C-plane, R-plane, and A-plane. A substrate material capable of growing a nitride semiconductor, such as a substrate, can be used. Preferred examples of the different substrate include sapphire and spinel. Further, the heterogeneous substrate may be off-angle, and in this case, it is preferable to use a step-off-angle substrate because the underlayer made of gallium nitride can be grown with good crystallinity. Further, when a heterogeneous substrate is used, a nitride semiconductor as a base layer before forming the element structure is grown on the heterogeneous substrate, and then the heterogeneous substrate is removed by a method such as polishing to obtain a single substrate of the nitride semiconductor The element structure may be formed as follows, or the heterogeneous substrate may be removed after the element structure is formed. When a heterogeneous substrate is used, a nitride semiconductor with good crystallinity can be grown by forming an element through a buffer layer and an underlayer.
Hereinafter, the semiconductor laser device of Example 1 will be described in the order of manufacturing steps.
(Buffer layer)
A heterogeneous substrate made of sapphire with a 2-inch φ and C-plane as the main surface is set in a MOVPE reaction vessel and the temperature is set to 500 ° C., and a buffer layer made of GaN is formed using trimethyl gallium (TMG) and ammonia (NH ₃ ). Grow with a thickness of 200 mm.

(Underlayer)
After forming the buffer layer, the temperature is set to 1050 ° C., and a nitride semiconductor layer made of undoped GaN is grown to a thickness of 4 μm using TMG and ammonia. This layer acts as a base layer (growth substrate) in the growth of each layer forming the element structure. In addition, if a nitride semiconductor grown by ELOG (Epitaxially Lateral Overgrowth) is used as the growth substrate, an underlayer (growth substrate) with good crystallinity can be obtained. Specific examples of the ELOG growth layer include the following methods.

Specific example of ELOG growth layer
A nitride semiconductor layer is grown on a heterogeneous substrate, and a protective film made of a material that does not grow nitride semiconductor at all or almost on the surface thereof is provided, for example, in stripes so that openings are formed at regular intervals. A mask region in which a mask is formed in this manner and a non-mask region in which the surface of the nitride semiconductor is exposed to grow a nitride semiconductor are alternately provided, and the nitride semiconductor is grown from the non-mask region. Thus, in addition to the growth in the film thickness direction, the growth in the lateral direction is performed so as to cover the mask, so that the nitride semiconductor is also grown in the mask region so as to cover the whole.

Specific Example of ELOG Growth Layer 2.
Openings are provided at regular intervals in a nitride semiconductor layer grown on a different kind of substrate, and a nitride semiconductor layer covering the whole is formed by growing laterally from the nitride semiconductor on the side surface of the opening.
Next, each layer constituting the multilayer structure is formed on the base layer made of the nitride semiconductor.
(N-type contact layer)
An n-type contact layer made of GaN doped with Si at 1 × 10 ¹⁸ / cm ³ at 1050 ° C. using TMG, ammonia, and silane gas as an impurity gas on the underlying layer (nitride semiconductor substrate) is 4.5 μm thick. Grow in.
(Crack prevention layer)
Next, a crack prevention layer made of In _0.06 Ga _0.94 N is grown to a thickness of 0.15 μm using TMG, TMI (trimethylindium), and ammonia at a temperature of 800 ° C. This crack prevention layer can be omitted.
(N-type cladding layer)
Next, the temperature is set to 1050 ° C., TMA (trimethylaluminum), TMG, and ammonia are used as source gases, and an A layer made of undoped AlGaN is grown to a thickness of 25 mm. A silane gas is used to grow a B layer made of GaN doped with Si at 5 × 10 ¹⁸ / cm ³ to a thickness of 25 mm. This operation is repeated 160 times, and the A layer and the B layer are alternately stacked to grow an n-type cladding layer made of a multilayer film (superlattice structure) having a total film thickness of 8000 mm. At this time, if the mixed crystal ratio of Al in the undoped AlGaN is in the range of 0.05 to 0.3, a refractive index difference that sufficiently functions as a cladding layer can be provided.

(N-type light guide layer)
Next, an n-type light guide layer made of undoped GaN is grown to a thickness of 0.1 μm using TMG and ammonia as source gases at the same temperature. This layer may be doped with n-type impurities.
(Active layer)
Next, the temperature is set to 800 ° C., TMI (trimethylindium), TMG, and ammonia are used as raw materials, silane gas is used as an impurity gas, and In _0.05 Ga _0.95 doped with Si at 5 × 10 ¹⁸ / cm ^3. A barrier layer made of N is grown to a thickness of 100 mm. Subsequently, silane gas is stopped and a well layer made of undoped In _0.1 Ga _0.9 N is grown to a thickness of 50 mm. This operation is repeated three times. Finally, a barrier layer is stacked to grow an active layer having a total quantum thickness of 550 mm and having a multiple quantum well structure (MQW).

(P-type cap layer)
Next, at the same temperature, TMA, TMG, and ammonia are used as source gases, Cp ₂ Mg (cyclopentadienylmagnesium) is used as an impurity gas, and p made of AlGaN doped with 1 × 10 ¹⁹ / cm ^{3 of} Mg. A type electron confinement layer is grown to a thickness of 100 mm.
(P-type light guide layer)
Next, the temperature is set to 1050 ° C., TMG and ammonia are used as source gases, and a p-type light guide layer made of undoped GaN is grown to a thickness of 750 mm. The p-type light guide layer is grown as undoped, but may be doped with Mg.

(P-type cladding layer)
Subsequently, a layer made of undoped Al _0.16 Ga _0.84 N is grown to a thickness of 25 mm at 1050 ° C., then TMG is stopped, and a layer made of Mg-doped GaN using Cp ₂ Mg is a thickness of 25 mm. A p-type cladding layer made of a superlattice layer having a total thickness of 0.6 μm is grown. When a p-type cladding layer is made of a superlattice in which at least one nitride semiconductor layer containing Al is included and nitride semiconductor layers having different bandgap energies are stacked, impurities are both highly doped in one layer. Although so-called modulation doping tends to improve the crystallinity, both may be doped in the same manner.
(P-type contact layer)
Finally, a p-type contact layer made of p-type GaN doped with 1 × 10 ²⁰ / cm ³ of Mg is grown on the p-type cladding layer at 1050 ° C. to a thickness of 150 mm. The p-type contact layer can be composed of p-type In _x Al _y Ga _1-xy N (x ≦ 0, y ≦ 0, x + y ≦ 1). Preferably, Mg-doped GaN is p. The most favorable ohmic contact with the electrode is obtained. After the completion of the reaction, the wafer is annealed at 700 ° C. in a nitrogen atmosphere in the reaction vessel to further reduce the resistance of the p-type layer.

(N-type layer exposure)
After the nitride semiconductor is grown as described above to form a laminated structure, the wafer is taken out of the reaction vessel, a protective film made of SiO ₂ is formed on the surface of the uppermost p-type contact layer, and RIE (reaction) is performed. The surface of the n-type contact layer for forming the n-electrode is exposed by etching with SiCl ₄ gas using a reactive ion etching. At this time, the active layer end face serving as the resonator face may be exposed and the etching end face may be used as the resonator face. As the etching gas, another gas, for example, Cl ₂ may be used instead of the SiCl ₄ gas.
(Formation of stripe-shaped convex part and light shielding layer forming surface)

Next, in order to form a striped waveguide region, a protective film made of Si oxide (mainly SiO ₂ ) is formed to a thickness of 0.5 μm on almost the entire surface of the uppermost p-type contact layer by a CVD apparatus. After the formation, a mask having a predetermined shape is put on the protective film, and a stripe-shaped protective film is formed by a photolithography technique using CHF ₃ gas by an RIE apparatus, and the stripe-shaped convex film is formed above the active layer. Part is formed. Thereafter, using the resist mask, only the vicinity of the resonator surface of the convex portion is further etched below the active layer so that the corners of the element are removed as shown in FIG. A non-resonator surface and a second side surface are formed.

(Light shielding layer)
The protective film and the resist mask are left as they are, and a light shielding layer that is continuous with the optical non-resonator surface, the second side surface, and the exposed surface of the n-type layer is formed by sputtering. The light shielding layer is made of Si and has a thickness of 4000 mm. This light shielding layer can also be formed after forming the first insulating film in a later step. Alternatively, after the ohmic electrode is formed, the second insulating film can be formed.
(First insulating film)
With the SiO ₂ mask attached, a first insulating film made of ZrO ₂ is formed on the surface of the p-type layer. The first insulating film may be provided on the entire surface of the semiconductor layer by masking the n-side ohmic electrode formation surface. Further, a portion where an insulating film is not formed is provided so that it can be easily divided later. This portion has a 10 μm stripe shape and is provided so as to be orthogonal to the convex portion. After the first insulating film is formed, it is immersed in a buffered solution to dissolve and remove SiO ₂ formed on the upper surface of the stripe-shaped convex portion, and on the p-type contact layer together with SiO ₂ by a lift-off method (further, n-type contact) ZrO ₂ on the layer) is removed. Thereby, the upper surface of the stripe-shaped convex portion is exposed, and the side surface of the convex portion is covered with ZrO ₂ .

(Ohmic electrode)
Next, a p-side ohmic electrode is formed on the first insulating film on the outermost surface of the convex portion on the p-type contact layer. This p-side ohmic electrode is made of Au and Ni. A striped n-side ohmic electrode is also formed on the surface of the n-type contact layer exposed by etching. The n-side ohmic electrode is made of Ti and Al. After forming these, each is annealed at 600 ° C. in an atmosphere of oxygen: nitrogen at a ratio of 80:20 to alloy the p-side and n-side ohmic electrodes to obtain good ohmic characteristics (first) 2 insulation film)
Next, a resist is applied to a part of the p-side ohmic electrode and the n-side ohmic electrode on the stripe-shaped convex part, and a second insulating film made of Si oxide (mainly SiO ₂ ) is formed on the entire surface excluding the division position. Then, a part of the p-side ohmic electrode and the n-side ohmic electrode is exposed by lift-off. The division position is a position between non-resonator surfaces formed so as to face each other and perpendicular to the stripe-shaped convex portion. The element is divided by cleaving this portion. By not forming the first and second insulating films and electrodes in the stripe-shaped range having a width of about 10 μm across this division position, it becomes easy to cleave and the resonator surface becomes a mirror surface. .

(Pad electrode)
Next, a p-side pad electrode and an n-side pad electrode are formed so as to cover the insulating film. The electrode is made of Ni-Ti-Au. The pad electrode is in contact with the exposed ohmic electrode in a stripe shape.
(Cleavage and resonator surface formation)
After polishing the sapphire substrate of the wafer to 70 μm, it is cleaved in a bar shape from the substrate side in a direction perpendicular to the stripe-shaped electrode, and corresponds to a cleaved surface (11-00 plane, hexagonal columnar crystal side surface) Resonator surface was prepared on the surface to be used (M surface). This resonator surface may be formed by etching.

(Mirror formation)
A dielectric multilayer film made of SiO ₂ and ZrO ₂ is formed as a mirror on the resonator surface formed as described above. A protective film made of ZrO ₂ was formed on the resonator surface on the light reflection side by using a sputtering apparatus, and then a highly reflective film was formed by alternately laminating three pairs of SiO ₂ and ZrO ₂ . Here, the thicknesses of the protective film and the SiO ₂ film and the ZrO ₂ film constituting the highly reflective film can be set to preferable thicknesses according to the emission wavelength from the active layer. Further, it is not necessary to provide a resonator surface on the light emission side, and a first low reflection film made of ZrO ₂ and a _second low reflection film made of SiO ₂ are formed by using a sputtering apparatus. Also good. At this time, a mirror may be formed on the non-resonator surface. Next, the bar is finally cut in a direction parallel to the stripe-shaped convex portion to obtain the semiconductor laser device of the present invention.
The semiconductor laser device obtained as described above was confirmed to have a threshold of 2.0 kA / cm ² at room temperature and a continuous oscillation with an oscillation wavelength of 405 nm at a high output of 30 mW. Obtained.

In Example 1, a nitride semiconductor substrate made of GaN formed on sapphire produced as follows is used as a substrate. First, as a heterogeneous substrate for growing a nitride semiconductor, a sapphire substrate having a thickness of 425 μm, 2 inches φ, a main surface being a C-plane, and an orientation flat surface (hereinafter referred to as an orientation flat surface) being an A-plane is prepared. The substrate (wafer) is set in Next, a temperature is set to 510 ° C., hydrogen is used as a carrier gas, ammonia and TMG (trimethyl gallium) are used as a source gas, and a low-temperature growth buffer layer made of GaN is grown on a sapphire substrate with a film thickness of about 200 mm. Next, the temperature is set to 1050 ° C., TMG and ammonia are used as source gases, and an underlayer made of undoped GaN is grown to a thickness of 2.5 μm. Subsequently, a plurality of masks made of striped SiO ₂ each having a width of 6 μm in a direction tilted by θ = 0.3 ° from a direction perpendicular to the orientation flat surface (A surface) of the sapphire substrate are arranged between the masks. They are formed in parallel so that the interval (mask opening) is 14 μm. Then, returning to the MOCVD apparatus, undoped GaN is grown to a thickness of 15 μm. In this case, GaN selectively grown from the mask opening grows mainly in the vertical direction (thickness direction) in the mask opening, and grows laterally on the mask to cover the mask and the mask opening. Are formed (ELOG growth). In such a grown base layer, the laterally grown nitride semiconductor layer can reduce threading dislocations. More specifically, the threading dislocations have a dislocation density as high as about 10 ¹⁰ / cm ² above the mask opening and near the center of the mask where the nitride semiconductor grown laterally from both sides of the mask joins. On the mask excluding the part, the dislocation density is as low as about 10 ⁸ / cm ² .

(Thick film layer)
Using the thus obtained substrate having a nitride semiconductor, the wafer is subsequently placed on an HVPE apparatus, and undoped GaN is further grown on the underlayer to a thickness of about 100 μm (this about 100 μm A layer grown with a thickness of 2 is called a thick film layer.)
(Underlayer)
A nitride semiconductor is grown on the nitride semiconductor substrate so as to be accompanied by lateral growth using a striped SiO ₂ mask in the same manner as the base layer used when the nitride semiconductor substrate is formed. Growing with a film thickness of
(Formation of light shielding layer forming surface)
Subsequent layers are stacked in the same manner as in Example 1 to stack semiconductor layers. After stacking up to the p-side contact layer, a stripe-shaped convex portion (ridge) having a width of 1.6 μm is formed after the n-type layer exposure step. Next, when forming the light shielding layer formation surface, a second side surface on a surface different from the ridge side surface can be formed by providing a mask wider than the ridge and etching to the n-type layer. Here, a resonator in which the width of the active layer on the resonator surface of the emission surface is about 7 μm is provided by providing a mask with a width of about 7 μm so that the ridge is approximately in the center and etching the n-type layer from the active layer. Form a surface. The etched surfaces thus formed are the non-resonator surface and the second side surface, and both are used as the light shielding layer forming surface.

(Light shielding layer)
A light shielding layer is formed by sputtering on the second side surface, non-resonator surface, and exposed surface of the n-type layer formed as described above. First, Rh oxide is formed with a thickness of 500 mm, and the same Rh oxide is formed thereon with a thickness of 1500 mm by changing the sputtering conditions. In this way, by stacking the same material under different sputtering conditions to form a multilayer film, a light-shielding layer excellent in both adhesion and light-shielding characteristics can be obtained. In Example 2, since the mask used when forming the light shielding layer forming surface is used as it is, the light shielding layer is formed on the second side surface, the non-resonator surface, and the exposed surface of the n-type layer. There is no problem even if it is provided so as to extend to the surface of the p-type layer by changing. By forming the light shielding layer up to a part of the surface (upper surface) of the p-type layer, it is possible to prevent light from leaking upward. In addition, the end of the light shielding layer may be easily formed by forming the edge of the light shielding layer at the edge between the end surface and the upper surface. Thus, the light shielding layer can be formed with good adhesion by being provided continuously on the upper surface. Therefore, stable beam characteristics can be obtained.

(Different substrate peeling)
Thereafter, the process is performed in the same manner as in Example 1 until the pad electrode is formed. Before the cleavage, a part of the sapphire substrate, the low-temperature growth buffer layer, the base layer, and the thick film layer is removed to obtain a GaN substrate. The GaN substrate has a thickness of about 80 μm. Here, a nitride film other than GaN may be used for the thick film layer by HVPE. However, in the present invention, GaN or AlN that has a good crystallinity and can easily grow a thick nitride semiconductor. Is preferably used. In addition, the dissimilar substrate or the like may be removed by removing a part of the thick film layer before forming the element structure as described above, or after forming the waveguide, It may be performed at the stage. Also. By removing the heterogeneous substrate before cutting the wafer into bars or chips, the nitride semiconductor cleavage plane ({11-00} M plane approximated in the hexagonal system, { 1010} A plane, (0001) C plane). Next, after forming a eutectic metal composed of Ti—Pt—Au on the back surface, a resonator surface is formed in a bar shape from the substrate side in the direction perpendicular to the stripe electrodes in the same manner as in Example 1. Then, a mirror is formed on the monitor side to obtain the semiconductor laser device of the present invention.
The semiconductor laser device obtained as described above has a threshold value of 2.0 kA / cm ² at room temperature, continuous oscillation at an oscillation wavelength of 405 nm is confirmed at a high output of 30 mW, and a good beam with no ripple is obtained in FFP. .

In Example 2, the same process as in Example 2 is performed except that a substrate manufactured as follows is used. First, a buffer layer made of GaN is formed by MOCVD using a sapphire substrate with the C plane as the main plane and the orientation flat plane as the A plane at a temperature of 510 ° C. using hydrogen as the carrier gas and ammonia and TMG as the source gases. Grow at 200mm thickness. Next, only the TMG gas is stopped and the temperature is increased to 1050 ° C. When the temperature reaches 1050 ° C., a nitride semiconductor made of undoped GaN is grown to a thickness of 2.5 μm using TMG, ammonia, and silane gas as source gases. Its CVD on the nitride semiconductor by a protective film made of SiO ₂ is grown to a thickness of 0.5 [mu] m, the stripe width 14μm by etching to form a stripe-shaped mask, the spacing between the stripes 6μm of SiO ₂ A protective film is formed. This stripe-shaped protective film has a direction perpendicular to the A-plane of sapphire.

Next, the first nitride semiconductor made of GaN is grown to a thickness of 2 μm by using MOMG with a temperature of 1050 ° C. under reduced pressure and using TMG, ammonia, silane gas, and Cp ₂ Mg as raw materials. At this time, the first nitride semiconductor grows from a portion where the SiO ₂ protective film is not formed, and grows laterally on the protective film. The gap between adjacent first nitride semiconductors that stops growing before the first nitride semiconductor completely covers the SiO ₂ protective film is about 2 μm.

Next, 0.3 μm of the SiO ₂ protective film is removed by isotropic etching which is dry etching at a temperature of 120 ° C. using oxygen and CF ₄ as etching gas.
Furthermore, from the side and top surfaces of the first nitride semiconductor grown in the lateral direction, the temperature is raised to 1050 ° C. by MOCVD at normal pressure, TMG, ammonia, silane gas, and Cp ₂ Mg are used as source gases, and the _second is made of GaN. The nitride semiconductor is grown to a thickness of 15 μm. Note that the second nitride semiconductor may be grown not under normal pressure but under reduced pressure. On the substrate thus obtained, growth is performed from the thick film layer to the p-side contact layer in the same manner as in Example 2, and then the respective steps are performed in the same manner to obtain the semiconductor laser device of the present invention. In the semiconductor laser device obtained as described above, continuous oscillation at an oscillation wavelength of 405 nm was confirmed at a high output of 30 mW with a threshold of 2.0 kA / cm ² at room temperature, and a good beam without ripples was obtained in FFP. It is done.

In Example 1, before exposing the n-type layer, the active layer in the vicinity of the light emission surface of the stripe-shaped convex portion is etched and removed so as to remain with a width of 2 μm to form a light shielding layer forming surface. The removed portion is laminated with a semiconductor layer made of GaN and grown to the same height as the upper surface of the p-contact layer. Thereafter, the semiconductor laser device according to the present invention is performed in the same manner as in Example 1 except that a stripe-shaped convex portion is formed so as to correspond to the remaining active layer having a width of 2 μm and the n-type layer is exposed. Get. The obtained semiconductor laser device was confirmed to have a continuous oscillation at an oscillation wavelength of 405 nm at a threshold of 2.0 kA / cm ² and a high output of 30 mW at room temperature. A beam is obtained.

In Example 1, the semiconductor layer stacking process is the same, and the process after the n-type layer exposure is performed as follows. In Example 1, the exit surface is a cleaved surface, whereas in Example 5, the exit surface is formed by etching. That is, the output surface side end surface is not at least a single plane, but has a shape provided with a step as shown in FIG.
(N-type layer exposure and resonator surface formation)
After forming the laminated structure, the wafer is taken out from the reaction vessel, a protective film made of SiO ₂ is formed on the surface of the uppermost p-type contact layer, and etched with SiCl ₄ gas using RIE (reactive ion etching). The n-type contact layer that forms the n-electrode is exposed, and the surface that becomes the resonator surface is also exposed. That is, in Example 1, the stripe-shaped convex portions are continuous over a plurality of elements on the wafer until the last cleaving, but in Example 2, the stripe-shaped convex portions are exposed when the n-type layer is exposed. The surface orthogonal to the convex portion is also etched to form the resonator surface at the same time. At this time, stripe-shaped convex portions for two elements may be continuous. As the etching gas, for example, other gas such as Cl ₂ may be used.

(Formation of stripe-shaped convex part and light shielding layer forming surface)
Next, in order to form a striped waveguide, a protective film made of SiO _{2 is formed} on the substantially front surface including the uppermost p-type contact layer and the resonator surface exposed in the previous step by using a CVD apparatus. After forming the film to a thickness of 5 μm, a mask having a predetermined shape is put on the protective film, and a stripe-shaped protective film is formed by a photolithography technique using CF ₄ gas by an RIE apparatus, so that Striped projections are formed on the top. The stripe-shaped convex portion is formed so as to be orthogonal to the resonator surface.
The second side surface and the non-resonator surface are formed by further etching the vicinity of the resonator surface, which is the end of the convex portion on the stripe, until the active layer is exposed. At this time, it is formed in the vicinity of the resonator surface which becomes the light emitting side resonator surface, but it may be formed in both.

(Light shielding layer)
The protective film is left as it is, and a light shielding layer is formed by sputtering on the optical non-resonator surface, the second side surface, and the exposed surface of the n-type layer by sputtering. The light shielding layer is made of Si and has a thickness of 5000 mm. This light shielding layer can also be formed after forming the first insulating film in a later step. Alternatively, after the ohmic electrode is formed, the second insulating film can be formed.
(First insulating film)
With the SiO ₂ mask attached, a first insulating film made of ZrO ₂ is formed on the surface of the p-type layer. After forming the first insulating film, it is immersed in a buffered solution to dissolve and remove SiO ₂ formed on the upper surface of the stripe-shaped convex portion, and ZrO ₂ on the p-type contact layer is removed together with SiO ₂ by a lift-off method. To do. Thus, the p-type layer is exposed on the upper surface of the stripe-shaped convex portion, and the upper surface of the p-type layer is covered with ZrO ₂ from the side surface of the convex portion.

(Ohmic electrode)
Next, a p-side ohmic electrode is formed on the p-type contact layer. The ohmic electrode is made of Au—Ni and is formed over the first insulating film on the p-type contact layer. An ohmic electrode is also formed on the upper surface of the n-type contact layer. The n-side ohmic electrode is made of Ti—Al, and is formed in a stripe shape parallel to the stripe-shaped convex portion and having the same length. After forming these, the p-side and n-side ohmic electrodes are alloyed by annealing at 600 ° C. in an oxygen / nitrogen ratio of 80:20 to obtain ohmic electrodes having good ohmic characteristics.

(Second insulating film)
Next, a resist is applied to a part of the p-side ohmic electrode and the n-side ohmic electrode on the stripe-shaped convex portion and the light-emitting side resonator surface, and the multilayer film made of SiO ₂ and ZrO _{2 is} subjected to the second insulation. A film is formed on almost the entire surface excluding the light emitting side resonator surface (two pairs of SiO ₂ and ZrO ₂ are laminated alternately), and a part of each electrode and the light emitting side resonator surface are exposed by lift-off. Let A second insulating film is also formed on the upper surface of the light shielding layer. Furthermore, since the resonator surface on the light reflecting side is also formed to be covered, the second insulating film functions as a light reflecting film (mirror). As described above, at least one of the resonator surfaces is formed by etching prior to the insulating film forming step, so that the light reflecting film (mirror) is formed so as to wrap around in the wafer state before being divided. be able to. As a result, the light emitting side resonator surface and the light reflecting side resonator surface can be formed of different materials or reflecting films having different film thicknesses.

(Pad electrode)
Next, a p-side pad electrode and an n-side pad electrode are formed so as to cover the second insulating film. The pad electrode is made of Ni—Ti—Au, and is in contact with the p-side ohmic electrode and the n-side ohmic electrode in a stripe shape through the second insulating film. In this example, as shown in FIG. 11, the p-side pad electrode 4 is also formed on the upper surface of the stripe-shaped convex portion sandwiched between the second side surfaces via the second insulating film.
(Division and formation of protective film on the light emission side)
The n-type layer exposed previously is further etched until the substrate is exposed. As a result, only the substrate remains at the dividing position, and as shown in FIG. 12, the resonator surface and the n-type layer end surface are formed by etching. Dividing into a bar shape from the substrate side in a direction perpendicular to the striped electrode. Next, ZrO ₂ is formed on the light emitting side resonator surface, and SiO ₂ is formed so as to cover it to form a protective film. Finally, the bar is cut in a direction parallel to the striped electrode to obtain the semiconductor laser device of the present invention. In this example, as shown in FIG. 12, the end face of the substrate protrudes from the resonator surface, but the protrusion length can be kept small enough not to affect the laser beam shape, so there is no problem. .
In the semiconductor laser device obtained as described above, continuous oscillation at an oscillation wavelength of 405 nm was confirmed at a high output of 30 mW with a threshold of 2.0 kA / cm ² at room temperature, and a good beam without ripples was obtained in FFP. It is done.

In Example 4, the same process as in Example 4 is performed except that Ti is used as the light shielding layer and SiO ₂ is used as the insulating film, thereby obtaining the semiconductor laser device of the present invention. First, by forming Ti after forming SiO ₂ , it is possible to provide a light-shielding layer that has excellent insulating properties and can effectively block stray light. Regarding the film thickness, Ti is 4500 mm and SiO ₂ is 1500 mm. The obtained semiconductor laser device was confirmed to have a continuous oscillation at an oscillation wavelength of 405 nm at a threshold of 2.0 kA / cm ² and a high output of 30 mW at room temperature. A beam is obtained.

The semiconductor laser device of the present invention is obtained in the same manner as in Example 6 except that a substrate having the same nitride semiconductor as in Example 3 is used. In the obtained semiconductor laser element, continuous oscillation at an oscillation wavelength of 405 nm was confirmed at a threshold of 2.0 kA / cm ² and a high output of 30 mW at room temperature, and a good beam without ripples was obtained in FFP.

The semiconductor laser device of Example 8 is manufactured in the same manner as in Example 1 except that the light-transmitting film 9a is formed below the light shielding layer 9 in the semiconductor laser device of Example 1 as described later ( 13A-13C).
(Translucent film 9a)
In the same manner as in Example 1, after forming the stripe-shaped convex portions and the light-shielding film forming surface, the optical non-resonator surface, the second side surface, and the n-type layer are left as they are. A translucent film continuous with the exposed surface is formed by sputtering. The translucent film 9a is made of Rh oxide and has a thickness of 500 mm.

(Light shielding film)
Further, a light shielding film is formed on the light transmitting film by sputtering. This light-shielding film is also made of Rh oxide and has a thickness of 1500 mm, like the light-transmitting film. This light-shielding film can be obtained by changing the composition ratio of Rh and oxygen by lowering the degree of vacuum as the sputtering conditions for forming the light-transmitting film. The apparatus can be used as it is, and only the degree of vacuum can be changed to form layers having different film quality, particularly light transmittance. The light-transmitting film and the light-shielding film can also be formed after forming the first insulating film in a later step. Alternatively, after the ohmic electrode is formed, the second insulating film can be formed.
Thereafter, from the formation of the first insulating film to the mirror formation, a semiconductor laser device is fabricated in the same manner as in Example 1.
The semiconductor laser device obtained as described above was confirmed to have a threshold of 2.0 kA / cm ² at room temperature and a continuous oscillation with an oscillation wavelength of 405 nm at a high output of 30 mW. Obtained.

In the same manner as the laser element of Example 2, the semiconductor laser element of Example 9 was laminated up to the p-side contact layer, and then formed with a light-shielding film and a light-transmitting film as follows. A film and a light shielding film are formed.
(Formation of light shielding film and translucent film forming surface)
After stacking up to the p-side contact layer, a stripe-shaped convex portion (ridge) having a width of 1.6 μm is formed after the n-type layer exposure step. Next, a mask having a width wider than that of the ridge is provided in the vicinity of the resonance end face on the emission side where the light-transmitting film is formed, and etching is performed up to the n-type layer, thereby forming a second side surface that is different from the ridge side surface. Although the width of the active layer can be controlled by a mask wider than this ridge, as shown in FIG. 13A, in order to remove only the active layer in the vicinity of the cavity surface on the emission side, By providing a mask on the entire surface and further providing a mask wider than the width of the ridge in the vicinity of the resonator surface, the active layer can be removed in a limited portion near the resonator surface. A mask wider than the ridge can also be provided over the entire ridge. Here, a resonator in which the width of the active layer on the resonator surface of the emission surface is about 7 μm is provided by providing a mask with a width of about 7 μm so that the ridge is approximately in the center and etching the n-type layer from the active layer. Form a surface. The etched surfaces thus formed are the non-resonator surface and the second side surface, and both the light transmitting film and the light shielding film are provided.

(Translucent film and light shielding film)
A translucent film is formed by sputtering on the second side surface, the non-resonator surface, and the exposed surface of the n-type layer formed as described above. First, an Rh oxide having a thickness of 500 mm is formed as a lower light-transmitting film, and an Rh oxide having the same thickness as the light-transmitting film is formed thereon with a thickness of 500 mm by changing sputtering conditions. Further, the same Rh oxide is formed thereon as an upper light-shielding film with a thickness of 1500 mm by changing the sputtering conditions. Sputtering conditions may be a three-layer structure in which the lower light-transmitting film, the intermediate film, and the upper light-shielding film are made constant, respectively. You may change so that it may become low gradually. Thereby, Rh oxides having different composition ratios can be easily formed. In Example 2, since the mask used when forming the light-transmitting film forming surface is used as it is, the light-transmitting film and the light shielding film are formed on the second side surface, the non-resonator surface, and the exposed surface of the n-type layer. However, there is no problem even if the mask is changed so as to extend to the surface of the p-type layer. By forming the light-transmitting film and the light-shielding film up to a part of the surface (upper surface) of the p-type layer, it is possible to prevent light from leaking upward. In addition, the end portion of the light shielding film may be easily peeled off at the edge between the end surface and the upper surface, but in this way, the light shielding film can be formed with good adhesion by providing it continuously on the upper surface. Therefore, stable beam characteristics can be obtained.

Thereafter, the semiconductor laser device of Example 9 is fabricated in the same manner as in Example 2.
In the semiconductor laser device of Example 9 obtained as described above, a continuous oscillation with an oscillation wavelength of 405 nm was confirmed at a threshold of 2.0 kA / cm ² and a high output of 30 mW at room temperature, and there was no ripple in the FFP. A beam is obtained.

A semiconductor laser device is manufactured in the same manner as in Example 9 except that a substrate manufactured in the same manner as in Example 3 is used and that substrate is used.
The semiconductor laser device of Example 10 fabricated as described above can obtain the same characteristics as the semiconductor laser device of Example 3.

In Example 9, the stacking process of the semiconductor layers is the same, and the processes after the n-type layer exposure are performed as follows. In Example 9, the exit surface is a cleaved surface, whereas in Example 11, the exit surface is formed by etching. That is, the exit surface side end surface as shown in FIG. 12 is not a single plane, but has a shape with a step. The formation of the emission surface by such etching is effective when a substrate that is difficult to cleave is used.
(N-type layer exposure and resonator surface formation)
After forming the laminated structure, the wafer is taken out from the reaction vessel, a protective film made of SiO ₂ is formed on the surface of the uppermost p-type contact layer, and etched with SiCl ₄ gas using RIE (reactive ion etching). The n-type contact layer that forms the n-electrode is exposed, and the surface that becomes the resonator surface is also exposed. That is, in Example 9, the stripe-shaped convex portions are continuous over a plurality of elements on the wafer until the last cleaving, but in Example 4, when the n-type layer is exposed, the stripe-shaped projections are continuous. The surface orthogonal to the convex portion is also etched to form the resonator surface at the same time. At this time, stripe-shaped convex portions for two elements may be continuous. As the etching gas, Cl ₂ or the like may be used.
(Formation of stripe-shaped convex part and light shielding layer forming surface)

Next, in order to form a striped waveguide, a protective film made of SiO _{2 is formed} on the substantially front surface including the uppermost p-type contact layer and the resonator surface exposed in the previous step by using a CVD apparatus. After forming the film to a thickness of 5 μm, a mask having a predetermined shape is put on the protective film, and a stripe-shaped protective film is formed by etching using CHF ₃ gas with an RIE apparatus, and above the active layer. Striped convex portions are formed. The stripe-shaped convex portion is formed so as to be orthogonal to the resonator surface.
The second side surface and the non-resonator surface are formed by further etching the vicinity of the resonator surface, which is the end of the convex portion on the stripe, until the active layer is exposed. At this time, it is formed in the vicinity of the resonator surface which becomes the light emitting side resonator surface, but it may be formed in both.

(Translucent film and light shielding film)
The protective film is left as it is, and a light-transmitting film and a light-shielding film are formed by sputtering on the optical non-resonator surface, the second side surface, and the exposed surface of the n-type layer. As a light-transmitting film, Rh oxide is formed with a thickness of 600 mm, and the same Rh oxide is formed with a thickness of 600 mm by changing the sputtering conditions, and further, the same Rh oxide is further changed with the sputtering conditions. It is formed with a film thickness of 2000 mm. Sputtering conditions are such that each layer is performed under a certain condition, and the degree of vacuum is lowered as it goes to the upper layer. Thereby, Rh oxides having different composition ratios can be easily formed. The light-transmitting film and the light-shielding film can also be formed after forming the first insulating film in a later step. Alternatively, after the ohmic electrode is formed, the second insulating film can be formed.

(First insulating film)
With the SiO ₂ mask attached, a first insulating film made of ZrO ₂ is formed on the surface of the p-type layer. After forming the first insulating film, it is immersed in a buffered solution to dissolve and remove SiO ₂ formed on the upper surface of the stripe-shaped convex portion, and ZrO ₂ on the p-type contact layer is removed together with SiO ₂ by a lift-off method. To do. Thus, the p-type layer is exposed on the upper surface of the stripe-shaped convex portion, and the upper surface of the p-type layer is covered with ZrO ₂ from the side surface of the convex portion.
(Ohmic electrode)

  Next, a p-side ohmic electrode is formed on the p-type contact layer. The ohmic electrode is made of Au—Ni and is formed over the first insulating film on the p-type contact layer. An ohmic electrode is also formed on the upper surface of the n-type contact layer. The n-side ohmic electrode is made of Ti—Al, and is formed in a stripe shape parallel to the stripe-shaped convex portion and having the same length. After forming these, the p-side and n-side ohmic electrodes are alloyed by annealing at 600 ° C. in an oxygen / nitrogen ratio of 80:20 to obtain ohmic electrodes having good ohmic characteristics.

(Second insulating film)
Next, a multilayer film composed of SiO ₂ and TiO ₂ is formed on almost the entire surface of the second insulating film except the light emitting side resonator surface. Two pairs of SiO ₂ and TiO ₂ are alternately laminated. A resist is applied to portions other than the p-side ohmic electrode and the n-side ohmic electrode on the stripe-shaped convex portion, and a part of each electrode is exposed by dry etching. A second insulating film is also formed on the upper surface of the light shielding layer. Furthermore, since the resonator surface on the light reflecting side is also formed to be covered, the second insulating film functions as a light reflecting film (mirror). As described above, at least one of the resonator surfaces is formed by etching prior to the insulating film forming step, so that the light reflecting film (mirror) is formed so as to wrap around in the wafer state before being divided. be able to. As a result, the light emitting side resonator surface and the light reflecting side resonator surface can be formed of different materials or reflecting films having different film thicknesses.

(Pad electrode)
Next, a p-side pad electrode and an n-side pad electrode are formed so as to cover the second insulating film. The pad electrode is made of Ni—Ti—Au, and is in contact with the p-side ohmic electrode and the n-side ohmic electrode in a stripe shape through the second insulating film. It is also formed on the upper surface of the stripe-shaped convex portion sandwiched between the second side surfaces.

(Division and formation of light exit side mirror)
The n-type layer exposed previously is further etched until the substrate is exposed. As a result, only the substrate remains at the dividing position, and the resonator face and the n-type layer end face are formed by etching. Dividing into a bar shape from the substrate side in a direction perpendicular to the striped electrode. Next, SiO ₂ is formed on the resonator surface on the light emitting side, and ZrO ₂ is formed so as to cover it to form a mirror. Finally, the bar is cut in a direction parallel to the striped electrode to obtain the semiconductor laser device of the present invention.
The semiconductor laser device of Example 11 obtained as described above was confirmed to have a threshold of 2.0 kA / cm ² at room temperature and a continuous oscillation with an oscillation wavelength of 405 nm at a high output of 30 mW. A simple beam can be obtained.

In the semiconductor laser device of Example 12, a buffer layer and an underlayer are grown on the substrate in the same manner as in Example 1, and TMG, TMA, ammonia, and silane gas as impurity gas are formed on the underlayer (nitride semiconductor substrate). An n-type contact layer made of AlGaN doped with Si at 1 × 10 ¹⁸ / cm ³ at 1050 ° C. is grown to a thickness of 4.5 μm.
Then, on the n-type contact layer made of AlGaN, a crack prevention layer, an n-type cladding layer, an n-type light guide layer active layer, a p-type cap layer, and a p-type light guide layer are formed in the same manner as in Example 1. A p-type cladding layer and a p-type contact layer are grown. Further, in the same manner as in Example 1, the n-type layer is exposed to form a resonator surface, and a convex portion is formed as follows.

(Striped convex formation)
In Example 12, in order to form a stripe-shaped waveguide region, a protective film made of Si oxide (mainly SiO ₂ ) is formed on almost the entire surface of the uppermost p-type contact layer by a CVD apparatus with a thickness of 0.5 μm. After forming the film thickness, a mask having a predetermined shape is put on the protective film, a stripe-shaped protective film is formed by a photolithography technique using CF4 gas by an RIE apparatus, and the stripe-shaped protective film is formed above the active layer. Are formed. In the RIE apparatus, CHF ₃ can be used instead of CF ₄ gas.
After forming the convex portion, the first insulating film and the p and n-side ohmic electrodes are formed in the same manner as in Example 1, and a semiconductor laser device is manufactured through the following steps.

(Second insulating film)
Next, a resist is applied to a part of the p-side ohmic electrode and the n-side ohmic electrode on the stripe-shaped convex portion, and a second insulating film made of Si oxide (mainly SiO ₂ ) is formed on the entire surface excluding the division position. Then, lift-off exposes part of the p-side ohmic electrode and the n-side ohmic electrode.
(Pad electrode)
Next, a p-side pad electrode and an n-side pad electrode are formed so as to be in contact with the p-side ohmic electrode and the n-side ohmic electrode through the opening of the second insulating film. The electrode is made of Ni-Ti-Au. The pad electrode is in contact with the exposed ohmic electrode in a stripe shape.

(Substrate exposure)
Next, after forming SiO2 on the front surface of the wafer, a resist film is formed thereon except for the exposed surface of the n-type contact layer, and etching is performed until the substrate is exposed. Since the resist film is also formed on the side surface such as the resonator surface, the side surface (p-type layer, active layer, and part of the n-type layer) formed on the resonator surface is formed after etching. And an n-type layer between the resonator surface and the substrate are formed.
(Second protective film)
Next, a second protective film is formed. A second protective film made of SiO ₂ (1350 Å) / Ti (2250 Å) is formed by sputtering on the light emitting side resonator surface with a resist film or the like. The transmittance of the second protective film is about 0.01%, and a light shielding effect of about 100% can be obtained.
(Divided into bars)
After the p-side ohmic electrode and the n-side ohmic electrode were formed as described above, the substrate was polished to a total film thickness including the substrate of 200 μm, and a back metal made of Ti—Pt—Au was formed on the back surface. Thereafter, the substrate is divided into bars from the substrate side in a direction perpendicular to the striped electrodes. At this time, if scribing is performed from the back surface side of the substrate corresponding to the dividing position before dividing into bars, it becomes easier to divide in a subsequent process.

(Light reflection side mirror and first protective film)
In the semiconductor divided into bars as described above, the light emitting side resonator surfaces are arranged on one side of the bar, and the light reflecting side resonator surfaces are arranged on the opposite side. The angle of these several bars is changed so that the light emitting side resonator surface and the light reflecting side resonator surface face the same direction. Subsequently, it arrange | positions on a film-forming jig | tool so that there may be no clearance gap between each bar through a spacer. By using the spacer in this way, a protective film can be prevented from being formed on the electrode or the like formed on the element. First, 6 pairs of ZrO ₂ and (SiO ₂ / ZrO ₂ ) are formed on the resonator surface on the light reflection side to form a mirror. Next, Nb ₂ O _{5 is formed} to a thickness of 400 mm as a first protective film on the light emitting side. This Nb ₂ O ₅ is provided over the light emitting surface of the resonator surface and the second protective film provided in the vicinity of the light emitting surface.
The light transmittance of the second protective film made of Nb ₂ O ₅ is about 82%.
Finally, the bar is cut in a direction parallel to the stripe-shaped convex portion to obtain the semiconductor laser device of the present invention.
The semiconductor laser device obtained as described above was confirmed to have a continuous oscillation with an oscillation wavelength of 405 nm at a threshold of 2.0 kA / cm ² and a high output of 30 mW at room temperature. Obtained.

In Example 13, a nitride semiconductor substrate formed by forming GaN on sapphire is used as a substrate (produced in the same manner as in Example 2), and a semiconductor laser as shown in FIG. 17 is produced.
Specifically, it is as follows.
(Buffer layer)
First, a buffer layer made of undoped AlGaN having an Al mixed crystal ratio of 0.01 is formed on the underlying layer of the nitride semiconductor substrate. This buffer layer can be omitted, but when the substrate using lateral growth is GaN, or when the underlying layer formed by lateral growth is GaN, a nitride having a smaller thermal expansion coefficient than that. Since a pit can be reduced by using a buffer layer made of _a semiconductor, that is, Al _a Ga _1-a N (0 <a ≦ 1) or the like, the buffer layer is preferably formed. That is, when another nitride semiconductor is grown on the nitride semiconductor layer formed with lateral growth like the underlayer, pits are likely to be generated, but this buffer layer prevents the generation of pits. effective.

  Further, the Al mixed crystal ratio a of the buffer layer is preferably 0 <a <0.3, whereby a buffer layer with good crystallinity can be formed. The buffer layer may be formed as a layer that also functions as an n-side contact layer. After forming the buffer layer, an n-side contact layer represented by the same composition formula as the buffer layer is formed. Thus, the n-side contact layer may also have a buffer effect. That is, this buffer layer is provided between the lateral growth layer (GaN substrate) and the nitride semiconductor layer constituting the device structure, or between the active layer in the device structure and the lateral growth layer (GaN substrate). More preferably, by providing at least one layer between the substrate side in the device structure, the lower cladding layer and the lateral growth layer (GaN substrate), pits can be reduced and device characteristics can be improved. . Further, when the buffer layer having the function of the n-side contact layer is used, the Al mixed crystal ratio a is preferably 0.1 or less so that a good ohmic contact with the electrode can be obtained. The buffer layer formed on the base layer may be grown at a low temperature of 300 ° C. or higher and 900 ° C. or lower as in the case of the buffer layer provided on the above-mentioned different substrate, but preferably at a temperature of 800 ° C. or higher and 1200 ° C. or lower. When the single crystal is grown, the above-mentioned pit reduction effect tends to be obtained more effectively. Furthermore, this buffer layer may be doped with n-type and p-type impurities, or may be undoped, but is preferably formed undoped in order to improve the crystallinity. Furthermore, when two or more buffer layers are provided, the n-type, p-type impurity concentration, and Al mixed crystal ratio can be changed.

(N-side contact layer)
On the buffer layer, an n-side contact layer made of Al _0.01 Ga _0.99 N doped with 4 μm in thickness and 3 × 10 ¹⁸ / cm ^{3 of} Si is formed.
(Crack prevention layer)
A crack preventing layer made of In _0.06 Ga _0.94 N having a thickness of 0.15 μm is formed on the n-side contact layer.
(N-side cladding layer)
An n-side cladding layer having a superlattice structure with a total film thickness of 1.2 μm is formed on the crack prevention layer.
Specifically, an undoped Al _0.05 Ga _0.95 N layer having a thickness of 25 mm and a GaN layer having a thickness of 25 mm and doped with Si of 1 × 10 ¹⁹ / cm ³ are alternately stacked to form n A side cladding layer is formed.
(N-side light guide layer)
An n-side light guide layer made of undoped GaN having a thickness of 0.15 μm is formed on the n-side cladding layer.

(Active layer)
An active layer having a multi-quantum well structure with a total film thickness of 550 mm is formed on the n-side light guide layer.
Specifically, a barrier layer (B) made of Si-doped In _0.05 Ga _0.95 N with a thickness of 140 mm doped with 5 × 10 ¹⁸ / cm ³ of Si, and an undoped In _0.13 Ga film with a thickness of 50 mm. _An active layer is formed by laminating a well layer (W) of _0.87 N in the order of (B)-(W)-(B)-(W)-(B).
(P-side electron confinement layer)
On the active layer, a p-side electron confinement layer made of p-type Al _0.3 Ga _0.7 N with a thickness of 100 mm and Mg doped at 1 × 10 ²⁰ / cm ³ is formed.
(P-side light guide layer)
A p-side light guide layer made of p-type GaN doped with 1 × 10 ¹⁸ / cm ³ of Mg having a thickness of 0.15 μm is formed on the p-side electron confinement layer.
(P-side cladding layer)
A superlattice p-side cladding layer having a total film thickness of 0.45 μm is formed on the p-side light guide layer.
Specifically, by alternately laminating undoped Al _0.05 Ga _0.95 N with a film thickness of 25 mm and p-type GaN doped with 1 × 10 ²⁰ / cm ³ of Mg with a film thickness of 25 mm, A p-side cladding layer is formed.

(P-side contact layer)
On the p-side cladding layer, a p-side contact layer made of p-type GaN having a thickness of 150 mm and Mg doped at 2 × 10 ²⁰ / cm ³ is formed.
(N-type layer exposure, stripe-shaped convex part formation)
As described above, after forming the element structure from the n-side contact layer to the p-side contact layer, after exposing the n-type contact layer in the same manner as in Example 12, the stripe-shaped convex portions (ridges) are formed. It is formed by etching.
(Second side surface and non-resonator surface formation)
Next, a second side surface and a non-resonator surface, which are surfaces on which the second protective film is formed, are formed. A second side surface and a non-resonator surface are formed by forming a mask on the surface other than the end surface near the resonator surface and performing etching. Here, since the second side surface is formed so as to be closer to the end surface of the element than the ridge side surface, as shown in FIG. 17, the width of the active layer is the width of the ridge at the end surface in the direction perpendicular to the ridge. It is wider than.

(Second protective film)
Next, a second protective film is formed on the second side surface and the non-resonator surface formed as described above. Using the mask as it is, a multilayer film made of SiO ₂ / Ti is formed as a _second protective film by sputtering.
(First insulating film to second insulating film)
Next, similarly to Example 12, a first insulating film made of ZrO ₂ , an ohmic electrode, and a _second insulating film made of SiO ₂ / TiO ₂ are formed.
(Pad electrode)
Next, RhO—Pt—Au is formed as a p-side pad electrode, and Ni—Ti—Au is formed as an n-side pad electrode.
(Different substrate peeling)
Subsequently, a part of the sapphire substrate, the low temperature growth buffer layer, the base layer, and the thick film layer is removed to form only the thick film layer (single unit), and the film thickness of the GaN substrate is set to 80 μm. Here, the nitride film other than GaN may be used for the HVPE thick film layer. However, in the present invention, GaN or AlN that has good crystallinity and can easily grow a thick nitride semiconductor is used. It is preferable to use it. In addition, the dissimilar substrate or the like may be removed by removing a part of the thick film layer before forming the element structure as described above, or after forming the waveguide, It may be done at this stage. Further, by removing the heterogeneous substrate or the like before cutting the wafer into bars or chips, the nitride semiconductor cleavage plane ({11-00} M approximated in a hexagonal system) is cut into chips. Surface, {1010} A surface, (0001) C surface).

(Cavity plane formation)
Next, after forming a eutectic metal composed of Ti—Pt—Au on the back surface, it was divided into bars from the substrate side in the direction perpendicular to the striped electrodes in the same manner as in Example 1 to form the resonator surface. To do.
(Light reflection side mirror and first protective film)
Next, a mirror composed of six pairs of ZrO ₂ and (SiO ₂ / ZrO ₂ ) is formed on the light reflection side resonator surface, and Nb ₂ O ₅ is formed as a first protective film on the light emission side. Let This Nb ₂ O ₅ is provided on the light emitting side resonator surface and on the second protective film provided in the vicinity of the resonator surface. Further, the bar is cleaved in parallel with the cavity direction on the A plane perpendicular to the M plane cleaved between the elements to obtain a laser chip.
The laser element obtained as described above has a threshold current density of 2.5 kA / cm ² at room temperature, a threshold voltage of 4.5 V, an oscillation wavelength of 405 nm, and an aspect ratio of the emitted laser beam of 1.5 It is. In addition, a high-power laser element having a long lifetime of 1000 hours or longer with a continuous oscillation of 30 mW can be obtained. The laser element can continuously oscillate in an output range of 5 mW to 80 mW, and has a beam characteristic suitable as a light source for an optical disc system in the output range.

In Example 12, a semiconductor light emitting device as shown in FIG. 18 is obtained in the same manner as in Example 12 except that the steps are changed as follows.
(N-type layer exposure)
The n-type layer is exposed as in Example 12, but at this time, the resonator surface is not formed.
(Stripe-shaped projection formation, non-resonator surface and second side surface formation)
After the formation of the stripe-shaped protrusion, the side surface of the stripe-shaped protrusion near the element dividing surface is further etched below the active layer using the same mask so that the corner of the element is removed as shown in FIG. Forming a non-resonator surface and a second side surface. A second protective film is formed on this surface. ZrO ₂ / RhO is used as the second protective film.

(Division and resonator surface formation)
Before forming the exit side mirror, the sapphire substrate of the wafer is polished to 70 μm and then cleaved in a bar shape from the substrate side in the direction perpendicular to the striped electrode. The plane corresponding to the side surface of the crystal = M plane), and the resonator plane is formed. Next, a first protective film is provided on the resonator surface on the emission side of the resonator surface. Nb ₂ O ₅ is used as the first protective film.
In the semiconductor laser device obtained as described above, continuous oscillation at an oscillation wavelength of 405 nm was confirmed at room temperature with a threshold of 2.0 kA / cm ² and a high output of 30 mW, and the spread angle was wider than that of the example. A good beam without ripples can be obtained.

  As described above, since a semiconductor laser device having a good far field pattern (FFP) can be provided, it can be used in various devices such as electronic devices such as DVDs, medical devices, processing devices, and light sources for optical fiber communication.

FIG. 1 is a perspective view showing the outer shape of the semiconductor laser device according to the first embodiment of the present invention. 2 is a cross-sectional view taken along the line II-II in FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a perspective view showing the shape of the light shielding layer in the semiconductor laser device of the first embodiment. FIG. 5 is a perspective view of a semiconductor laser device according to a modification of the first embodiment. FIG. 6 is a perspective view of a semiconductor laser device according to a modification of the first embodiment. FIG. 7 is a perspective view of a semiconductor laser device according to a modification of the first embodiment. FIG. 8 is a perspective view of a semiconductor laser device according to a modification of the first embodiment. FIG. 9 is a cross-sectional view of another modification of the semiconductor laser device according to the first embodiment in which the emission end portion has a shape different from that of FIG. 10 is a cross-sectional view of another modification of the semiconductor laser device according to the first embodiment in which the emission end portion has a shape further different from that of FIG.

FIG. 11 is a cross-sectional view of the semiconductor laser device according to Example 4 of the present invention. FIG. 12 is a perspective view of the semiconductor laser device according to the fourth embodiment. FIG. 13A is a perspective view of a semiconductor laser device according to Example 9 of the present invention. 13B is a cross-sectional view taken along line XIIIB-XIIIB in FIG. 13A. 13C is a cross-sectional view taken along line XIIIC-XIIIC in FIG. 13A. FIG. 14A is a perspective view of the semiconductor laser element according to Embodiment 3 of the present invention. FIG. 14B is a perspective view showing the first and second protective films of the third embodiment. 14C is a cross-sectional view taken along the line XIVC-XIVC in FIG. 14A. FIG. 15 is a perspective view of a semiconductor laser device according to a modification of the third embodiment. FIG. 16 is a perspective view of a semiconductor laser device according to another modification of the third embodiment. FIG. 17A is a perspective view of the semiconductor laser device according to the fourth embodiment of the present invention. FIG. 17B is a perspective view of the semiconductor laser element according to Embodiment 4 of the present invention. FIG. 18A is a perspective view of the semiconductor laser device according to the fourth embodiment of the present invention. FIG. 18B is a perspective view of the semiconductor laser element according to Embodiment 4 of the present invention. FIG. 19A is a graph showing a refractive index distribution and an electric field strength distribution in the case where the first protective film is not formed on the emission surface, shown for comparison with the semiconductor laser device of the fourth embodiment. FIG. 19B is a graph showing the refractive index distribution and the electric field strength distribution when the first protective film made of Al ₂ O ₃ is formed on the emission surface in the semiconductor laser device of the fourth embodiment. FIG. 19C is a graph showing a refractive index distribution and an electric field strength distribution when the first protective film made of Nb ₂ O ₅ is formed on the emission surface in the semiconductor laser device of the fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st conductivity type semiconductor layer 2 2nd conductivity type semiconductor layer 3 Active layer 4 p-type pad electrode 5, 7 Ohmic electrode 6 n-type pad electrode 8 Striped convex part (ridge)
9, 103 Light-shielding layer 9a Translucent film 10, 11 Insulating film 71, 72 Rectangular groove 100 Laminated structure 101a Resonator surface 101b, 101c, 101d Non-resonator surface 102a, 102e Second side surface 109, 110 Protective film

Claims (17)

A stacked structure in which a semiconductor layer of a first conductivity type, an active layer, and a semiconductor layer of a second conductivity type different from the first conductivity type are sequentially stacked, and the stacked structure is unidirectional in the semiconductor laser device possess a cavity surface of the laser resonator in the waveguide region and both ends for guiding light, and one light emitting surface of the cavity surface of the both ends,
The laminated structure is formed on the light emitting surface side so as to include an active layer cross section separately from the resonator surface, and has a non-resonator surface perpendicular to the light guiding direction ,
The resonator surface that is the light emitting surface protrudes from the non-resonator surface,
A semiconductor laser device, wherein a light shielding layer is formed on the non-resonator surface . The side surface of the stacked structure has a first side surface including an active layer cross section, and a second side surface located closer to the waveguide region than the first side surface and including the active layer cross section, The semiconductor laser device according to claim 1, wherein a light shielding layer is formed on a side surface of the semiconductor laser device. 3. The semiconductor laser device according to claim 2, wherein the non-resonator surface and the second side surface are continuous . In the laminated structure, a stripe-shaped convex portion is formed, and the waveguide region is formed by the stripe-shaped convex portion,
4. The semiconductor laser device according to claim 2, wherein the second side surface is located on a different surface from the side surface of the convex portion and is formed outside the convex portion . 5. The non-resonator surface is a surface provided by removing both corners of the laminated structure in the vicinity of the light emitting surface to below the active layer. The semiconductor laser device described. The non-resonator surface is a surface in which a rectangular groove is formed so as to sandwich a stripe-shaped convex portion, and the surface is orthogonal to the resonance direction of the groove. The semiconductor laser device described. The light-shielding layer, a semiconductor laser device according to any one of claims 1 to 6 is formed in contact with said laminate structure. The light-shielding layer, a semiconductor laser device according to any one of claims 1 to 6 is formed on the laminated structure provided in the insulating layer. The light-shielding layer, the conductor, a semiconductor, a semiconductor laser device according to any one of claims 1 to 8 made of any insulator. The semiconductor laser device according to the light shielding layer, any one of claims 1 to 9 comprising a dielectric multilayer film. The first conductive type semiconductor layer, the active layer, the second conductive type semiconductor layer, a semiconductor laser device according to any one of claims 1 to 10 nitride semiconductor is used. 12. The semiconductor laser device according to claim 11 , wherein the first conductivity type semiconductor layer has an n-type nitride semiconductor, and the second conductivity type semiconductor layer has a p-type nitride semiconductor. The light shielding layer is a conductive material, and is Ni, Cr, Ti, Cu, Fe, Zr, Hf, Nb, W, Rh, Ru, Mg, Al, Sc, Y, Mo, Ta, Co, Pd, Ag 13. The semiconductor laser according to claim 1, wherein the semiconductor laser is any one selected from the group consisting of a simple substance of Au, Au, Pt, and Ga, an alloy, a multilayer film, or an oxide or nitride thereof. element. The light shielding layer is a conductive material, Ni, Cr, Ti, Cu, Fe, Zr, Hf, Nb, W, Rh, Ru, Mg, Ga alone, an alloy, a multilayer film, or an oxide thereof. 14. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is any one selected from nitrides . The semiconductor laser device according to claim 1 , wherein the light shielding layer is a semiconductor material and is any one of Si, In, GaN, GaAs, and InP . The light blocking layer is an insulating material, a semiconductor laser device according to any one of claims 1 to 12, characterized in that either TiO _2, CrO _2. The light-shielding layer, a semiconductor laser device according to any one of claims 1 to 12 comprising at least Rh oxide.

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