JP2007311616A - Surface-emitting light source and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-emitting light source capable of obtaining a laser beam having a radiation pattern of a narrow radiation angle, and a manufacturing method thereof. <P>SOLUTION: This surface-emitting laser 100 includes a first mirror 102, an active layer 103 formed on the upper part of the first mirror, a second mirror 104 formed on the upper part of the active layer, and a thermal lens layer 110 formed on the upper part of the second mirror. The temperature distribution of the thermal lens layer is set to be low from the center axis of a light to be incident on the thermal lens layer toward the outside. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface emitting laser and a manufacturing method thereof.

In general, surface-emitting lasers emit laser light perpendicular to the substrate, are easier to handle than edge-emitting lasers, and have a circular radiation pattern, which is expected as a light source for various sensors and optical communications. Has been. When a surface emitting laser is actually used for various sensors and optical communication, it is desirable to obtain a laser beam having a radiation pattern with a narrow radiation angle.
JP 2002-26452 A

  An object of the present invention is to provide a surface emitting laser capable of obtaining a laser beam having a radiation pattern with a narrow radiation angle and a method for manufacturing the same.

The surface emitting laser according to the present invention is
A first mirror;
An active layer formed above the first mirror;
A second mirror formed above the active layer;
A thermal lens layer formed above the second mirror;
Including
The temperature distribution of the thermal lens layer is lower from the central axis of the light incident on the thermal lens layer toward the outside.

  In the present invention, the thermal lens layer refers to a semiconductor layer that provides a thermal lens effect. By providing such a thermal lens layer above the second mirror, the radiation angle of the oscillating light can be narrowed and the coupling efficiency with an optical fiber or the like can be improved.

In the surface emitting laser according to the present invention,
The thermal lens layer may include a high resistance semiconductor layer made of a material having higher resistance than the second mirror.

In the surface emitting laser according to the present invention,
The impurity concentration of the high resistance semiconductor layer may be lower than the impurity concentration of the second mirror.

In the surface emitting laser according to the present invention,
The high resistance semiconductor layer may be made of an intrinsic semiconductor.

In the surface emitting laser according to the present invention,
The high-resistance semiconductor layer can be made of a material that does not absorb light having a design wavelength of the surface-emitting laser.

In the surface emitting laser according to the present invention,
The high-resistance semiconductor layer can be made of a semiconductor having an energy band gap larger than that of light having a design wavelength of the surface emitting laser.

In the surface emitting laser according to the present invention,
A first electrode connected to the first mirror;
A second electrode connected to the second mirror;
A third electrode connected to the thermal lens layer;
Further including
The first electrode and the second electrode are electrodes for driving the surface emitting laser,
The second electrode and the third electrode may be electrodes for flowing a current through the thermal lens layer.

In the surface emitting laser according to the present invention,
The thermal lens layer may be made of a semiconductor having an energy band gap smaller than that of light having a design wavelength of the surface emitting laser.

In the surface emitting laser according to the present invention,
An electrode formed above the second mirror;
The electrode has an opening;
The thermal lens layer may be formed inside the opening and not in contact with the electrode.

In the surface emitting laser according to the present invention,
The thermal lens layer may have an oxidized constricting layer at the periphery.

In the surface emitting laser according to the present invention,
And further comprising another oxidized constriction layer formed on the second mirror,
The inner diameter of the oxidized constricting layer may be larger than the inner diameter of the other oxidized constricting layer.

The surface emitting laser according to the present invention is
A first mirror;
An active layer formed above the first mirror;
A second mirror formed above the active layer;
A thermal lens layer formed above the second mirror;
A thermal lens layer electrode connected to the thermal lens layer;
Including
The thermal lens layer includes a high-resistance semiconductor layer made of a material having higher resistance than the second mirror.

In the surface emitting laser according to the present invention,
The thermal lens layer is composed of a diode,
The electrode for the thermal lens layer may be an electrode for applying a forward voltage to the thermal lens layer.

The surface emitting laser according to the present invention is
A first mirror;
An active layer formed above the first mirror;
A second mirror formed above the active layer;
A thermal lens layer formed above the second mirror;
Including
The thermal lens layer is made of a semiconductor having an energy band gap smaller than that of the light having the design wavelength of the surface emitting laser.

A method for manufacturing a surface emitting laser according to the present invention includes:
Laminating a semiconductor multilayer film for constituting the first mirror, the active layer, the second mirror, and the thermal lens layer from the substrate side above the substrate;
Forming a first columnar portion including an active layer and a second mirror by patterning the semiconductor multilayer film;
Forming a second columnar portion including a thermal lens layer by patterning the semiconductor multilayer film;
including.

  Thus, in the method for manufacturing a surface emitting laser according to the present invention, the thermal lens layer can be obtained by patterning the semiconductor multilayer film. Therefore, the number of steps can be reduced as compared with the case where a lens is added after the laser is formed.

In the method for manufacturing the surface emitting laser according to the present invention,
After the patterning process,
At least one of the semiconductor layers constituting the second mirror and at least one of the semiconductor layers constituting the thermal lens layer are simultaneously oxidized from the side surface, whereby the first mirror is The method may further include forming an oxidized constricting layer and forming a second oxidized constricting layer in the thermal lens layer.

In the method for manufacturing the surface emitting laser according to the present invention,
The thickness of the first oxidized constricting layer may be larger than the thickness of the second oxidized constricting layer.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1. 1. First embodiment 1.1. Configuration of Surface Emitting Laser FIGS. 1 and 2 are sectional views schematically showing a surface emitting laser 100 according to a first embodiment to which the present invention is applied. FIG. 3 is a plan view schematically showing the surface emitting laser 100 shown in FIGS. 1 and 2. 1 is a diagram showing a cross section taken along line II of FIG. 3, and FIG. 2 is a diagram showing a cross section taken along line II-II of FIG.

  The surface emitting laser 100 is provided on a semiconductor substrate (in this embodiment, an n-type GaAs substrate) 101. The surface emitting laser 100 has a vertical resonator. Further, the surface emitting laser 100 may include a columnar semiconductor deposited body (hereinafter referred to as “columnar portion”) 130.

The surface-emitting laser 100 includes, for example, 40 pairs of distributed reflection type multilayer mirrors (hereinafter, referred to as “n-type Al _0.9 Ga _0.1 As layers” and “n-type Al _0.15 Ga _0.85 As layers”). , Called a “first mirror”) 102, an active layer 103 comprising a GaAs well layer and an Al _0.3 Ga _0.7 As barrier layer, the well layer comprising three layers, and a p-type 25 pairs of distributed reflective multilayer mirrors (hereinafter referred to as “second mirrors”) 104 in which Al _0.9 Ga _0.1 As layers and p-type Al _0.15 Ga _0.85 As layers are alternately stacked; Are sequentially laminated.

The uppermost layer 14 of the second mirror 104 can be composed of a semiconductor layer with a low Al composition or a GaAs layer. Specifically, the uppermost layer 14 is formed so as to be the one having the smaller Al composition of the second mirror 104, that is, a p-type Al _0.15 Ga _0.85 As layer or a p-type GaAs layer.

  The second mirror 104 is made p-type by doping carbon (C), for example, and the first mirror 102 is made n-type by doping silicon (Si), for example. Therefore, a pin diode is formed by the p-type second mirror 104, the active layer 103 not doped with impurities, and the n-type first mirror 102.

  In addition, a portion of the surface emitting laser 100 from the second mirror 104 to the middle of the first mirror 102 is etched into a circular shape as viewed from the upper surface of the second mirror 104 to form the first columnar portion 130. Yes. In the present embodiment, the planar shape of the first columnar portion 130 is circular, but this shape can be any shape.

Further, the surface emitting laser 100 further includes a first oxidation confinement layer 105 above the active layer 103. Specifically, the first oxidation confinement layer 105 oxidizes the Al _x Ga _1-x As (x> 0.95) layer in the region close to the active layer 103 among the layers constituting the second mirror 104 from the side surface. Can be obtained. The first oxidized constricting layer 105 is formed in a ring shape, for example. That is, the first oxidized constriction layer 105 has a cross-sectional shape when cut along a plane parallel to the surface 101a of the semiconductor substrate 101 shown in FIGS. It can be a concentric circular ring. When light confinement is performed by the first oxidation confinement layer 105, the diameter of the first oxidation confinement layer 105 is preferably designed so that single-mode light is oscillated from the surface emitting laser 100. .

The surface emitting laser 100 further includes a thermal lens layer 110 on the upper surface of the first columnar section 130. The thermal lens layer 110 includes a high resistance semiconductor layer 112 made of a material having higher resistance than the second mirror 104 and a contact layer 113 formed on the upper surface of the high resistance semiconductor layer 112. The high-resistance semiconductor layer 112 may be made of a semiconductor containing impurities lower than the impurity concentration of the second mirror 104 or an intrinsic semiconductor. For example, when the carrier concentration of the second mirror 104 is about 1 × 10 ¹⁸ cm ⁻³ , the carrier concentration of the high-resistance semiconductor layer 112 is preferably less than 1 × 10 ¹⁸ cm ⁻³ .

  Thereby, the resistance of the high-resistance semiconductor layer 112 can be increased, the temperature in the thermal lens layer 110 can be raised, and the temperature distribution can be made non-uniform. That is, in the thermal lens layer 110, since current flows easily in the center, the high resistance semiconductor layer 112 is formed of a material having high resistance, so that the temperature around the central axis of the laser light oscillated by the surface emitting laser 100 is increased. The temperature can be lowered mainly towards the outside. That is, the temperature distribution in the thermal lens layer 110 can be convex. Thereby, a refractive index distribution can be provided in the thermal lens layer 110, and the thermal lens layer 110 can function as a lens. Specifically, the thermal lens layer 110 can function as a convex lens because the semiconductor has a characteristic that the refractive index increases as the temperature rises. Therefore, the radiation angle of the laser light oscillated by the surface emitting laser 100 can be narrowed.

The high resistance semiconductor layer 112 is preferably made of a material that does not absorb light having the design wavelength of the surface emitting laser 100. That is, the high resistance semiconductor layer 112 is preferably made of a semiconductor having an energy band gap larger than the energy of the light having the design wavelength of the surface emitting laser 100. Examples of the material that does not absorb the light having the design wavelength of the surface emitting laser 100 include Al _x Ga _1-x As (x satisfies 0 <x ≦ 1), In _x Ga _1-x P (x = 0.0). 5), In _x Ga _1-x As (x satisfies 0 <x <0.4), and the like can be applied.

  Thereby, when the surface emitting laser 100 oscillates the laser beam, it is possible to prevent the temperature from rising due to the high resistance semiconductor layer 112 absorbing the light. Therefore, the refractive index distribution of the thermal lens layer can be precisely controlled by adjusting the current flowing through the high resistance semiconductor layer 112.

  The contact layer 113 can be made of, for example, an n-type GaAs layer, and the high-resistance semiconductor layer 112 can be made of, for example, an AlGaAs layer into which no impurity is introduced. Specifically, the contact layer 113 is made n-type by doping silicon (Si), for example. Therefore, a pin diode is formed by the uppermost layer 14 of the p-type second mirror 104, the high-resistance semiconductor layer 112 that is not doped with impurities, and the n-type contact layer 113.

  In the surface emitting laser 100, the second columnar portion 140 is formed by etching the portion of the thermal lens layer 110 into a circular shape when viewed from the upper surface of the thermal lens layer 110, thereby forming the second columnar portion 140. Yes. In the present embodiment, the planar shape of the second columnar section 140 is circular, but this shape can be any shape.

  The surface emitting laser 100 further includes a first electrode 107, a second electrode 109, and a third electrode 114. The first electrode 107 and the second electrode 109 are used for driving the surface emitting laser 100. The second electrode 109 and the third electrode 114 are used for passing a current through the thermal lens layer 110.

  The first electrode 107 is provided on the lower surface of the substrate 101 as shown in FIG. The first electrode 107 is electrically connected to the first mirror 102 via the substrate 101. The second electrode 109 is provided on the upper surface of the surface emitting laser 100. As shown in FIG. 3, the second electrode 109 includes, for example, a connecting portion 109a having a ring-shaped planar shape, a lead portion 109b having a linear planar shape, a pad portion 109c having a circular planar shape, Have The second electrode 109 is electrically connected to the second mirror 104 at the connection portion 109a. The lead portion 109b of the second electrode 109 connects the connection portion 109a and the pad portion 109c. The pad portion 109c of the second electrode can be used as an electrode pad. The connecting portion 109 a of the second electrode 109 is provided so as to mainly surround the thermal lens layer 110. In other words, the thermal lens layer 110 is provided inside the second electrode 109.

  As shown in FIG. 1, the third electrode 114 is provided on the upper surface of the thermal lens layer 110. As shown in FIG. 3, the third electrode 114 includes, for example, a connection portion 114a having a ring-like planar shape, a lead portion 114b having a linear planar shape, a pad portion 114c having a circular planar shape, Have The third electrode 114 is electrically connected to the thermal lens layer 110 at the connection portion 114a. The lead portion 114b of the third electrode 114 connects the connection portion 114a and the pad portion 114c. The pad portion 114c of the third electrode 114 can be used as an electrode pad. Further, the inner diameter of the connection portion 114 a of the third electrode 114 is preferably larger than the inner diameter of the first oxidized constricting layer 105. As a result, the amount of light emitted from the oscillated laser beam by the third electrode 114 can be reduced.

  The first electrode 107 is made of a laminated film of, for example, an alloy of gold (Au) and germanium (Ge) and gold (Au). The second electrode 109 is made of, for example, a laminated film of platinum (Pt), titanium (Ti), and gold (Au). The third electrode 114 is made of a laminated film of, for example, an alloy of gold (Au) and germanium (Ge) and gold (Au). A current is injected into the active layer 103 by the first electrode 107 and the second electrode 109. A current is injected into the thermal lens layer 110 by the second electrode 109 and the third electrode 114. Note that the materials for forming the first electrode 107, the second electrode 109, and the third electrode 114 are not limited to those described above. For example, an alloy of gold (Au) and zinc (Zn), etc. Is available.

  Note that although the case where the first electrode 107 is provided on the lower surface of the substrate 101 is described in this embodiment mode, the first electrode 107 may be provided on the upper surface of the first mirror 102. The first electrode 107 can have a ring-shaped planar shape so as to surround the first columnar portion 130, for example.

  The surface emitting laser 100 includes a first insulating layer 30 and a second insulating layer 40. The first insulating layer 30 is formed on the upper surface of the first mirror 102 so as to mainly surround the first columnar portion 130. The first insulating layer 30 is formed under the lead portion 109b and the pad portion 109c of the second electrode 109. Furthermore, the first insulating layer 30 is formed under the second insulating layer 40 described later. The second insulating layer 40 is formed on the upper surface of the second mirror 104 so as to surround the thermal lens layer 110. The second insulating layer 40 may be formed on the second electrode 109. The second insulating layer 40 is formed below the lead portion 114b and the pad portion 114c of the third electrode 114. The first insulating layer 30 and the second insulating layer 40 are made of an insulating material, for example, polyimide.

  In the surface emitting laser 100 according to the present embodiment, the case where an AlGaAs-based material is used has been described. However, the present invention is not limited to this.

  Further, although the surface emitting laser 100 according to the present embodiment has a three-terminal electrode structure, a four-terminal electrode structure may be used instead. That is, the second electrode 109 functions as a common electrode for flowing a current to the thermal lens layer 110 and the active layer 103, but for example, functions only to flow a current to the active layer 103. A fourth electrode electrically connected to the thermal lens layer 110 may be further provided. At this time, a separation layer for insulating from the second mirror 104 may be provided under the thermal lens layer 110.

1.2. Driving Method of Surface Emitting Laser The operation of the surface emitting laser 100 according to the present embodiment is described below. The following method for driving the surface emitting laser 100 is merely an example, and various modifications can be made without departing from the spirit of the present invention.

  The thermal lens layer 110 can narrow the radiation angle of light oscillated from the upper surface of the second mirror 104. First, when a forward voltage is applied to the pin diode between the first electrode 107 and the second electrode 109, recombination of electrons and holes occurs in the active layer 103, and light emission due to the recombination occurs. Stimulated emission occurs when the generated light reciprocates between the second mirror 104 and the first mirror 102, and the light intensity is amplified. When the optical gain exceeds the optical loss, laser oscillation occurs, and laser light is emitted from the upper surface of the second mirror 104 and enters the high-resistance semiconductor layer 112 of the thermal lens layer 110.

  Here, a forward voltage is applied to the pin diode by the first electrode 107 and the second electrode 109, and simultaneously, a voltage is applied to the pin diode constituted by the thermal lens layer 110 by the second electrode 109 and the third electrode 114. Apply. The light incident on the high resistance semiconductor layer 112 is emitted from the upper surface 115 of the contact layer 113 with a radiation angle narrowed while passing through the high resistance semiconductor layer 112 and the contact layer 113. Here, the voltage applied to the thermal lens layer 110 is preferably a forward voltage. As a result, a large current can be passed efficiently.

1.3. Method for Manufacturing Surface Emitting Laser Next, an example of a method for manufacturing the surface emitting laser 100 according to the embodiment to which the present invention is applied will be described with reference to FIGS. 4 to 6 are cross-sectional views schematically showing one manufacturing process of the surface-emitting laser 100 shown in FIGS. 1, 2, and 3, and each correspond to the cross-sectional view shown in FIG.

(1) First, as shown in FIG. 4, a semiconductor multilayer film 150 is formed on the surface 101a of an n-type GaAs layer by epitaxial growth while modulating the composition. Here, the semiconductor multilayer film 150 is, for example, a 38.5 pair of first mirrors 102a in which n-type Al _0.9 Ga _0.1 As layers and n-type Al _0.1 Ga _0.9 As layers are alternately stacked. , An active layer 103a including a quantum well structure composed of a GaAs well layer and an Al _0.3 Ga _0.7 As barrier layer, and the well layer comprising three layers, a p-type Al _0.9 Ga _0.1 As layer, 24 pairs of second mirrors 104a alternately stacked with p-type Al _0.1 Ga _0.9 As layers, high-resistance semiconductor layer 112a made of an AlGaAs layer not doped with impurities, and contact layer made of a p-type GaAs layer 113a. By laminating these layers on the semiconductor substrate 101 in order, the semiconductor multilayer film 150 is formed.

  When the second mirror 104a is grown, at least one layer in the vicinity of the active layer 103a can be formed as an AlAs layer or an AlGaAs layer that is oxidized later and becomes the first oxide constriction layer 105. The Al composition of the AlGaAs layer that becomes the first oxide constriction layer 105 is, for example, 0.95 or more. In the present embodiment, the Al composition of the AlGaAs layer is the composition of aluminum (Al) with respect to the group 3 element. The Al composition of the AlGaAs layer is from 0 to 1. That is, the AlGaAs layer includes a GaAs layer (when the Al composition is 0) and an AlAs layer (when the Al composition is 1). It is desirable that the outermost layer of the second mirror 104a has a high carrier density and facilitates ohmic contact with the second electrode 109.

  The temperature at which the epitaxial growth is performed is appropriately determined depending on the growth method and raw material, the type of the semiconductor substrate 101, or the type, thickness, and carrier density of the semiconductor multilayer film 150 to be formed. Preferably there is. Further, the time required for performing the epitaxial growth is also appropriately determined in the same manner as the temperature. As a method for epitaxial growth, a metal-organic vapor phase epitaxy (MOVPE) method, an MBE method (Molecular Beam Epitaxy) method, or an LPE method (Liquid Phase Epitaxy) can be used.

  (2) Next, the semiconductor multilayer film 150 is patterned using a known lithography technique and etching technique. Thereby, as shown in FIG. 5, the 1st columnar part 130 and the 2nd columnar part 140 are formed.

  In this patterning step, the order of forming the first columnar portion 130 and the second columnar portion 140 is not particularly limited.

  (3) Next, the above-described second mirror 104 is introduced by introducing the semiconductor substrate 101 on which the first columnar portion 130 and the second columnar portion 140 are formed by the above-described process in a water vapor atmosphere at about 400 ° C. A layer having a high Al composition is oxidized from the side surface to form a first oxidized constricting layer 105 (see FIG. 6).

  The oxidation rate depends on the furnace temperature, the amount of steam supplied, the Al composition of the layer to be oxidized and the film thickness. In the surface emitting laser 100 including the first oxidized constricting layer 105 formed by oxidation, current is applied only to a portion where the first oxidized constricting layer 105 is not formed (a portion not oxidized). Flowing. Therefore, in the step of forming the first oxidized constricting layer 105 by oxidation, the current density can be controlled by controlling the range of the first oxidized constricting layer 105 to be formed.

  Further, the circular portion of the portion where the first oxidized constricting layer 105 is not formed (the portion that is not oxidized) so that most of the light emitted from the upper surface of the second mirror 104 enters the high-resistance semiconductor layer 112. It is desirable to adjust the diameter. Specifically, as illustrated in FIG. 6, it is preferable that the inner diameter of the first oxidized constricting layer 105 is smaller than the diameter of the high-resistance semiconductor layer 112.

  (4) Next, as shown in FIG. 1, a first insulating layer 30 is formed. As the first insulating layer 30, for example, a material obtained by curing a liquid material (for example, an ultraviolet curable resin or a precursor of a thermosetting resin) that can be cured by energy such as heat or light can be used. Examples of the ultraviolet curable resin include an ultraviolet curable acrylic resin and an epoxy resin. Examples of the thermosetting resin include thermosetting polyimide resins. For the insulating layer 106, for example, an inorganic dielectric film such as a silicon oxide film or a silicon nitride film can be used. The first insulating layer 30 can also be formed as a stacked film using a plurality of the above materials, for example.

  Here, a case where a polyimide resin precursor is used as a material for forming the first insulating layer 30 will be described. First, a precursor (polyimide resin precursor) is applied onto the semiconductor substrate 101 using, for example, a spin coating method to form a precursor layer. As a method for forming the precursor layer, known techniques such as a dipping method, a spray coating method, and a droplet discharge method can be used in addition to the spin coating method described above.

  Next, the semiconductor substrate 101 is heated using, for example, a hot plate to remove the solvent, and then placed in a furnace at, for example, about 400 ° C. for about several hours to imidize the precursor layer, thereby almost completely. A cured polyimide resin layer is formed. Subsequently, as shown in FIG. 7, the first insulating layer 30 is formed by patterning the polyimide resin layer using a known lithography technique. As an etching method used for patterning, a dry etching method or the like can be used. Dry etching can be performed by plasma of oxygen or argon, for example.

  In the above-described method for forming the first insulating layer 30, the example in which the polyimide resin precursor layer is cured and then patterned is shown. However, the patterning is performed before the polyimide resin precursor layer is cured. It can also be done. As an etching method used in the patterning, a wet etching method or the like can be used. The wet etching can be performed using, for example, an alkali solution or an organic solution.

For example, when silicon nitride is used as the first insulating layer 30, the first insulating layer 30 can be formed by a plasma CVD method, for example. More specifically, the first insulating layer 30 is formed in a plasma using silane (SiH ₄ ), ammonia (NH ₃ ), and nitrogen (N ₂ ) as source gases at a temperature of about 350 ° C. can do.

  (5) Next, as shown in FIG. 1, the second electrode 109 is formed on the upper surface of the second mirror 104. First, before the second electrode 109 is formed, the upper surface of the second mirror 104 is cleaned using a plasma processing method or the like as necessary. Thereby, an element having more stable characteristics can be formed.

  Next, a laminated film (not shown) of, for example, titanium (Ti), platinum (Pt), and gold (Au) is formed by, for example, a vacuum deposition method. Next, the second electrode 109 is formed by removing the laminated film other than the predetermined position by a lift-off method. In this step, ohmic contact can be obtained between the second electrode 109 and the uppermost surfaces of the second mirror 104 without performing heat treatment.

  (6) Next, as shown in FIG. 1, the second insulating layer 40 is formed. The formation process of the 2nd insulating layer 40 can be formed by the method similar to the formation process of the 1st insulating layer 30 mentioned above.

  (7) Next, as shown in FIG. 1, the first electrode 107 is formed on the lower surface of the substrate 101, and the third electrode 114 is formed on the contact layer 113. First, before forming the first electrode 107 and the third electrode 114, the lower surface of the substrate 101 and the upper surface of the contact layer 111 are cleaned using a plasma treatment method or the like as necessary. Thereby, an element having more stable characteristics can be formed.

  Next, a laminated film (not shown) of, for example, an alloy of gold (Au) and germanium (Ge), nickel (Ni), and gold (Au) is formed by, for example, a vacuum deposition method. Next, the first electrode 107 is formed on the lower surface of the substrate 101 and the third electrode 114 is formed on the contact layer 113 by removing the laminated film other than the predetermined position using a known lift-off technique. .

  Next, annealing is performed in, for example, a nitrogen atmosphere. The annealing temperature is about 400 ° C., for example. The annealing process is performed for about 3 minutes, for example.

  Through the above steps, the surface emitting laser 100 of the present embodiment is obtained as shown in FIGS.

2. Second Embodiment FIG. 7 is a cross-sectional view schematically showing a surface emitting laser 200 according to a second embodiment to which the present invention is applied.

  The surface emitting laser 200 differs from the surface emitting laser 100 described above in that it does not have the third electrode 114 and in the material of the thermal lens layer.

The thermal lens layer 210 of the surface emitting laser 200 is made of a semiconductor having an energy band gap smaller than the energy of the light having the design wavelength of the surface emitting laser 200. That is, the thermal lens layer 210 is made of a material that can absorb light having a design wavelength of the surface emitting laser 200. For example, when a GaAs layer and an AlGaAs layer are applied as the material of the active layer 103, the laser wavelength is 780 nm to 860 nm. Therefore, as a material that can absorb light of the design wavelength of the surface emitting laser 200, for example, Al _x Ga _{1 -x} As (x _is. satisfying _{0 ≦ x ≦ 0.1), in} x Ga 1-x As (x is 0 satisfy <x <0.4.) and the like can be applied. For example, when an InGaAs layer and a GaAs layer are applied as the material of the active layer 103, the laser wavelength is 900 nm to 1200 nm. Therefore, as a material that can absorb light having the design wavelength of the surface emitting laser 200, for example, In _x Ga _{1 -x} As (x satisfies 0.1 ≦ x ≦ 0.5.) can be applied or the like.

  The thermal lens layer 210 absorbs part of the light emitted from the second mirror 104, thereby increasing the temperature in the thermal lens layer 210 and making the temperature distribution non-uniform. That is, since the amount of laser light near the central axis of the laser light oscillated by the surface emitting laser 100 is large, the temperature at the center of the thermal lens layer 210 can be mainly increased to lower the device temperature toward the outside. That is, the temperature distribution in the thermal lens layer 210 can be convex. Accordingly, a refractive index distribution can be provided in the thermal lens layer 210, and the thermal lens layer 210 can function as a convex lens. Therefore, the radiation angle of the laser light oscillated by the surface emitting laser 200 can be narrowed.

  The thermal lens layer 210 is formed on the inner side of the second electrode 109 so as not to contact the second electrode 109, like the thermal lens layer 110 described above.

  Since the other configuration and manufacturing method of the surface emitting laser 200 according to the second embodiment are the same as those of the surface emitting laser 100 according to the first embodiment described above, description thereof will be omitted.

3. Third embodiment 3.1. Configuration of Surface Emitting Laser FIG. 8 is a cross-sectional view schematically showing a surface emitting laser 300 according to a third embodiment to which the present invention is applied. The surface emitting laser 300 is different from the surface emitting laser 100 described above in that it further includes a second oxidation constriction layer 318. The second oxidized constricting layer 318 is formed on the periphery of the high resistance semiconductor layer 312 as shown in FIG. Specifically, the second oxidized constricting layer 318 is obtained by oxidizing one of the layers constituting the high-resistance semiconductor layer 312 from the side surface. The second oxidized constricting layer 318 is formed in a ring shape, for example. The second oxidation confinement layer 318 has a cross-sectional shape when cut along a plane parallel to the surface 101a of the semiconductor substrate 101 shown in FIGS. It can be ring-shaped.

  By providing the second oxidized constricting layer 318 in this way, the current flowing through the thermal lens layer 310 can be concentrated in the central portion, so that the temperature near the central axis of light can be dramatically increased. Therefore, the refractive index distribution can be remarkably provided in the thermal lens layer 310, and the thermal lens layer 310 can function as a higher performance convex lens. Therefore, the radiation angle of the laser light oscillated by the surface emitting laser 300 can be narrowed.

  The inner diameter B of the second oxidized constricting layer 318 is preferably larger than the inner diameter A of the first oxidized constricting layer 105 (another oxidized constricting layer). Thereby, the mode number of the light emitted from the surface emitting laser 300 can be controlled by adjusting the inner diameter of the first oxidized constricting layer 105.

  The other configuration of the surface-emitting laser 300 according to the third embodiment is the same as that of the surface-emitting laser 100 according to the first embodiment described above, and a description thereof will be omitted.

3.2. Method for Manufacturing Surface Emitting Laser The second oxidized constricting layer 318 can be formed simultaneously with the formation of the first oxidized constricting layer 105 in the step (3) described above. Specifically, when the semiconductor multilayer film 150 is formed by epitaxial growth in the above-described step (1), a part or all of the layers for forming the thermal lens layer 310 are changed to an AlAs layer or an AlGaAs layer having a high Al composition. Form. The AlGaAs layer having a high Al composition is, for example, an AlGaAs layer having an Al composition of 0.95 or more, for example. As shown in FIG. 8, a part of the high-resistance semiconductor layer 312 can be an AlAs layer or an AlGaAs layer having a high Al composition. At this time, the thickness of the AlAs layer or the AlGaAs layer having a high Al composition is preferably smaller than the thickness of the layer constituting the first oxide constriction layer 105. Thereby, the inner diameter B of the second oxidized constricting layer 318 can be made larger than the inner diameter A of the first oxidized constricting layer 105.

  Further, the Al composition of the AlGaAs layer for the second oxidized constricting layer 318 is preferably smaller than the Al composition of the AlAs layer or the AlGaAs layer for the first oxidized constricting layer 105. Thereby, the inner diameter B of the second oxidized constricting layer 318 can be made larger than the inner diameter A of the first oxidized constricting layer 105.

  Thereafter, through the patterning step described above, in step (3), the AlAs layer or the AlGaAs layer having a high Al composition is oxidized from the side surface. Subsequent steps of the surface emitting laser 300 according to the third embodiment are the same as those of the method of manufacturing the surface emitting laser 100 according to the first embodiment described above, and thus the description thereof is omitted.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, in the embodiment, even if the p-type and n-type in each semiconductor layer are interchanged, it does not depart from the spirit of the present invention. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and results). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  For example, in the above-described embodiment, the AlGaAs type is mainly described. However, other material types such as a GaInP type, a ZnSSe type, an InGaN type, an AlGaN type, an InGaAs type, and a GaInNAs type depending on the oscillation wavelength. It is also possible to use a GaAsSb-based semiconductor material.

1 is a cross-sectional view schematically showing a surface emitting laser according to a first embodiment. 1 is a cross-sectional view schematically showing a surface emitting laser according to a first embodiment. The top view which shows typically the surface emitting laser concerning 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting laser concerning 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting laser concerning 1st Embodiment. Sectional drawing which shows typically the manufacturing process of the surface emitting laser concerning 1st Embodiment. Sectional drawing which shows typically the surface emitting laser concerning 2nd Embodiment. Sectional drawing which shows typically the surface emitting laser concerning 3rd Embodiment.

Explanation of symbols

100 surface emitting laser, 101 substrate, 102 first mirror, 103 active layer, 104 second mirror, 105 first oxidation constriction layer, 107 first electrode, 109 second electrode, 110 thermal lens layer, 112 high resistance semiconductor layer , 113 contact layer, 114 third electrode, 115 emitting surface, 150 semiconductor multilayer film, 200 surface emitting laser, 210 thermal lens layer, 300 surface emitting laser, 310 thermal lens layer

Claims (17)

A first mirror;
An active layer formed above the first mirror;
A second mirror formed above the active layer;
A thermal lens layer formed above the second mirror;
Including
The surface emitting laser, wherein a temperature distribution of the thermal lens layer is lowered outward from a central axis of light incident on the thermal lens layer. In claim 1,
The thermal lens layer is a surface emitting laser including a high-resistance semiconductor layer made of a material having a higher resistance than the second mirror. In claim 2,
A surface emitting laser in which an impurity concentration of the high-resistance semiconductor layer is lower than an impurity concentration of the second mirror. In claim 2,
The high-resistance semiconductor layer is a surface emitting laser made of an intrinsic semiconductor. In any of claims 2 to 4,
The high resistance semiconductor layer is a surface emitting laser made of a material that does not absorb light having a design wavelength of the surface emitting laser. In claim 5,
The high resistance semiconductor layer is a surface emitting laser made of a semiconductor having an energy band gap larger than the energy of light having a design wavelength of the surface emitting laser. In any one of Claims 1 thru | or 6.
A first electrode connected to the first mirror;
A second electrode connected to the second mirror;
A third electrode connected to the thermal lens layer;
Further including
The first electrode and the second electrode are electrodes for driving the surface emitting laser,
The surface emitting laser, wherein the second electrode and the third electrode are electrodes for passing a current through the thermal lens layer. In claim 1,
The thermal lens layer is a surface emitting laser made of a semiconductor having an energy band gap smaller than that of light having a design wavelength of the surface emitting laser. In claim 8,
An electrode formed above the second mirror;
The electrode has an opening;
The surface-emitting laser in which the thermal lens layer is formed inside the opening and not in contact with the electrode. In any one of Claim 1 thru | or 9,
The thermal lens layer is a surface emitting laser having an oxidized constriction layer on the periphery. In claim 10,
And further comprising another oxidized constriction layer formed on the second mirror,
The surface-emitting laser in which an inner diameter of the oxidized constricting layer is larger than an inner diameter of the other oxidized constricting layer. A first mirror;
An active layer formed above the first mirror;
A second mirror formed above the active layer;
A thermal lens layer formed above the second mirror;
A thermal lens layer electrode connected to the thermal lens layer;
Including
The thermal lens layer is a surface emitting laser including a high-resistance semiconductor layer made of a material having a higher resistance than the second mirror. In claim 12,
The thermal lens layer is composed of a diode,
The surface emitting laser, wherein the thermal lens layer electrode is an electrode for applying a forward voltage to the thermal lens layer. A first mirror;
An active layer formed above the first mirror;
A second mirror formed above the active layer;
A thermal lens layer formed above the second mirror;
Including
The thermal lens layer is a surface emitting laser made of a semiconductor having an energy band gap smaller than that of light having a design wavelength of the surface emitting laser. Laminating a semiconductor multilayer film for constituting the first mirror, the active layer, the second mirror, and the thermal lens layer from the substrate side above the substrate;
Forming a first columnar portion including an active layer and a second mirror by patterning the semiconductor multilayer film;
Forming a second columnar portion including a thermal lens layer by patterning the semiconductor multilayer film;
A method of manufacturing a surface emitting laser, comprising: In claim 15,
After the patterning process,
At least one of the semiconductor layers constituting the second mirror and at least one of the semiconductor layers constituting the thermal lens layer are simultaneously oxidized from the side surface, whereby the first mirror is A method of manufacturing a surface emitting laser, further comprising forming an oxidized constricting layer and forming a second oxidized constricting layer in the thermal lens layer. In claim 16,
The method of manufacturing a surface emitting laser, wherein the film thickness of the first oxide confinement layer is larger than the film thickness of the second oxide confinement layer.

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