KR20070080695A - Semiconductor laser device and method for manufacturing the same having structure of non-absorbing mirror - Google Patents

Abstract

A semiconductor laser device having a non-absorbing mirror structure and a fabrication method thereof are provided to reduce a fabrication cost by removing an edge pattern forming process and a re-growth process for forming a non-absorbing mirror structure by using a seed pattern structure with different see width according to a region. A fabrication method of a semiconductor laser device having a non-absorbing mirror structure includes the steps of: preparing a substrate(10); forming wing in a vertical direction to cavity or seed patterns(20) having different widths; forming a base layer(30) having a vertical growth step difference on the substrate(10) where the seed patterns(20) are formed; forming a lamination of a semiconductor layer(40) on the base layer(30); and completing a fabrication of the semiconductor laser device by forming a ridge-type contact layer(50) on the lamination of the semiconductor layer(40).

Description

Semiconductor laser device and method for manufacturing the same having structure of non-absorbing mirror

1 to 4 schematically show a process of manufacturing a semiconductor laser device having a non-absorbing mirror structure according to the present invention.

5 and 6 schematically show a semiconductor laser device according to embodiments of the present invention.

7 and 8 illustrate embodiments of a seed pattern that may be applied to fabricate a semiconductor laser device according to the present invention of FIGS. 5 and 6.

9 is an enlarged view of a slope formed at a boundary area between a window area and a cavity area.

Figure 10 is a laser beam is non-absorbing mirror (NAM) structure that goes through the defined window area naohmyeonseo P toward _two of the window region a quantum well (QW: quantum well) light intensity (intensity spanning the side P ₁ of the cavity area in which the position ) Ratio, that is, the relationship between the intensity aspect ratio and the tilt angle (degree) of the slope.

FIG. 11 shows an embodiment of a stacked structure of a semiconductor laser device having a non-absorbing mirror (NAM) structure according to the present invention.

<Description of the symbols for the main parts of the drawings>

10 ... substrate 20 ... seed pattern

30 ... base layer 40 ... semiconductor layer

50,310 ... Contact layer 100,200,300 ... Semiconductor laser device

305 ... active layer

The present invention relates to a semiconductor laser device having a non-absorbing mirror (NAM) structure and a method of manufacturing the same. More specifically, a separate etching pattern and a regrowth process for forming the non-absorbing mirror structure are unnecessary. A semiconductor laser device and a method of manufacturing the same.

A nitride semiconductor laser device, such as a GaN semiconductor laser device, is used for recording and / or playing back a high density optical information storage medium such as a BD (Blu-ray Disc) and an HD DVD (High Definition Digital Versatile Disc) following a current DVD. Not only is it attracting attention as a light source for optical systems, it is also attracting attention as a new semiconductor laser light source of blue and green in the field of laser display.

In order to be used as a light source of such an optical system, the semiconductor laser device (LD) has a long life under high temperature and high power conditions, which increases the optical power threshold value at which catastrophic optical damage (COD) occurs. It is necessary.

In general, a method of reducing the photon density per unit area by increasing the size of the optical mode by designing a semiconductor laser device structure that reduces the optical confinement factor to increase the COD level is proposed. However, there is a limit to the fundamental COD solution at high wattage. Accordingly, there is a need for a technique of increasing a COD level by introducing a non-absorbing mirror (NAM) structure in a window region of a semiconductor laser device.

US Patent 5,280, 535 discloses a semiconductor laser device to which the NAM structure is applied. The semiconductor laser device disclosed in U.S. Patent No. 5,280,535 has a pattern etching of window and ridge regions selectively on a GaAs (or InP) substrate, and then grows a semiconductor laser device structure on the substrate, thereby forming a band. A clad region having a relatively large gap has a one-dimensional structure in which a clad region is set as a semiconductor laser device facet. Such a structure is a structure generally used to solve COD in the case of a watt-class high power semiconductor laser device.

Conventionally, as in US Pat. No. 5,280,535, in order to manufacture a semiconductor laser device to which a NAM structure is applied, a process of selectively etching a substrate and regrowing the semiconductor laser device structure thereon is additionally required.

However, in the case of a GaN substrate, selective substrate etching is difficult due to the high temperature growth of GaN, and regrowth may cause various crystal defects. In addition, regrowth itself tends to be unstable depending on the etch plane direction and shape. In particular, the strain, crack, and leakage caused by regrowth after etching on the AlGaN layer used as the clad layer have a high possibility of causing problems in terms of performance and mass production of semiconductor laser devices. .

The present invention has been made in view of the above, and a semiconductor laser device capable of forming a non-absorbing mirror (NAM) structure without etching the substrate and regrowth on the etched substrate and its manufacture The purpose is to provide a method.

In order to achieve the above object, the present invention provides a method for manufacturing a semiconductor laser device, comprising the steps of: preparing a substrate; Forming a seed pattern on the substrate, the seed pattern having a width of a wing or seed in a direction perpendicular to a cavity of a semiconductor laser device according to a region; Forming a base layer on the substrate on which the seed pattern is formed, wherein the cavity region and the window region of the semiconductor laser device are stepped by a growth rate difference due to a difference in wings or widths of seeds in each region of the seed pattern; And forming a stacked structure of a semiconductor layer constituting the semiconductor laser device on the base layer having the step difference.

The semiconductor laser device according to the present invention for achieving the above object is, by the growth rate difference due to the difference in the width of the wing or seed for each region of the seed pattern in the direction perpendicular to the substrate and the cavity of the semiconductor laser device A base layer formed to step between the cavity region and the window region of the semiconductor laser device; And a laminated structure of a semiconductor layer constituting a semiconductor laser device formed on the base layer having the step difference.

The seed pattern may be a modified PENDEO or ELO seed pattern.

The seed pattern may be made of any one of GaN, Al _x Ga _1-x N (0 <x≤1), and In _y Al _x Ga _1-yx N (0 <x≤1, 0 <y≤1). .

An area corresponding to the boundary between the window area and the cavity area may have a length of 0.1-30 μm.

A growth step of about 10 μm to about 5 μm may be formed in the stacking direction of the semiconductor layer.

An area corresponding to a boundary between the window area and the cavity area may be formed to have an inclination of 10 ° or more due to a growth step.

The seed pattern may have a wing width of 0.1-5 μm narrower or wider than a wing width of a region corresponding to the window region.

The semiconductor layer includes an active layer, and the maximum output center of the laser beam may be formed to oscillate through the window region at least out of the layer region adjacent to the active layer.

The substrate may be any one of a nitride based substrate and a sapphire substrate, and the base layer may be formed of a nitride based semiconductor material.

The semiconductor layer may include a nitride-based semiconductor layer.

Hereinafter, a semiconductor laser device having a non-reflective mirror (NAM) structure and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

1 to 4 schematically show a process of manufacturing a semiconductor laser device having a non-absorbing mirror structure according to the present invention.

Referring to FIG. 1, first, a substrate 10 is prepared to manufacture a semiconductor laser device according to the present invention, and on the substrate 10 in a direction perpendicular to the cavity direction of the semiconductor laser device. The width of the wing or seed forms a seed pattern 20 that varies with the area.

When the semiconductor laser device according to the present invention is to form a nitride semiconductor laser device, the substrate 10 may include a sapphire substrate or a nitride substrate such as GaN.

The seed pattern 20 may be formed of any one of GaN, Al _x Ga _1-x N (0 <x≤1), and In _y Al _x Ga _1-yx N (0 <x≤1, 0 <y≤1). Can be done. The seed pattern 20 may be formed as a modified PENDEO or ELO seed pattern. Here, the reason for using the expression “modified” in the modified Pdeo or ELO seed pattern is that the conventional FENDO or ELO seed pattern has a constant seed or wing width, whereas the seed or wing width varies depending on the region. Because it is formed.

After forming the seed pattern 20 on the substrate 10, as shown in FIG. 2, the base layer 30 is formed on the substrate 10 on which the seed pattern 20 is formed. In this case, when the lateral growth, the base layer 30 is vertical due to the growth rate difference caused by the difference in wing width or seed width of each region of the seed pattern 20. growth step in the vertical direction occurs.

As can be seen from Figs. 1 and 2, the larger the seed width area (the smaller wing width area) 20a is faster in the vertical direction than the smaller the seed width area 20b. The growth step may occur in which the base layer 30 is thicker in the seed width region 20a than in the seed width region 20b.

When the substrate 10 is any one of a nitride based substrate such as GaN and a sapphire substrate, the base layer 30 may be formed of a nitride based semiconductor material.

After the stepped base layer 30 is formed, a stacked structure of the semiconductor layers 40 constituting the semiconductor laser device is formed on the base layer 30 as shown in FIG. 3. The semiconductor layer 40 constituting the semiconductor laser device includes an active layer as in the embodiment described later. For example, the semiconductor layer 40 may include an n-type cladding layer, an n-type optical waveguide layer, an active layer, a p-type optical waveguide layer, and a p-type cladding layer, as in the following embodiments.

In the semiconductor laser device according to the present invention, the growth step in the vertical direction is such that the maximum output center of the laser beam generated in the cavity region is at least adjacent to the active layer in the window region, for example, the n-type cladding layer. It is preferably formed to oscillate through the window area.

When the substrate 10 is any one of a nitride based substrate such as GaN and a sapphire substrate, and the base layer 30 is formed of a nitride based semiconductor material, the semiconductor layer 40 may include a nitride based semiconductor layer. have. In this case, the semiconductor laser device according to the present invention becomes a nitride semiconductor laser device.

Next, as illustrated in FIG. 4, a ridge type contact layer 50 or the like is formed on the stacked structure of the semiconductor layer to complete fabrication of the semiconductor laser device. 4 illustrates an example in which the contact layer 50 is formed in both the cavity region and the window region. The contact layer 50 may be formed only in the cavity region.

The semiconductor laser device according to the present invention manufactured through the above manufacturing process includes a cavity region and a cavity region due to a growth step according to a seed width (or wing width) according to a region when the base layer 30 is formed. The window region has a stepped non-absorbing mirror (NAM) structure. Here, the cavity region represents a region where lasing is performed by resonance.

5 and 6 schematically show semiconductor laser devices 100 and 200 according to embodiments of the present invention.

As shown in FIG. 5, the semiconductor laser device 100 or 200 according to the present invention may be formed to have a stepped structure such that a window region protrudes above a cavity region, or FIG. As shown in FIG. 6, the cautter region may be formed to have a stepped structure to protrude upward from the window region.

7 and 8 illustrate embodiments of the seed pattern 20 that may be applied to fabricate the semiconductor laser device 100, 200 according to the present invention. 7 is a cross-sectional view of the semiconductor laser device according to an embodiment of the present invention, in which the cavity area and the window area of the semiconductor laser device and the seed width (wing width) of the seed pattern 20 are formed. Show the relationship. FIG. 8 is a cross-sectional view of the cavity region and the window region of the semiconductor laser device and the seed width (wing width) of the seed pattern 20 when the semiconductor laser device according to the present invention is to have a stepped structure as shown in FIG. 6. Show the relationship. Dotted lines between the two seed patterns 20 in FIGS. 7 and 8 represent the coalescence boundary upon growth of the base layer 30. As can be seen in FIGS. 7 and 8, the wing width corresponds to the distance from the coalescing boundary to the boundary of the seed pattern 20. The seed width corresponds to a distance to both boundaries of the seed pattern 20.

5 and 7, when the seed width of the seed pattern 20 is larger in the window area than in the cavity area (the wing width between the seed patterns 20 is smaller in the window area than in the cavity area). In this case, the base layer 30 may be formed such that the window region portion grows thicker than the cavity region portion and protrudes upward as shown in FIG. 5. Thereby, the semiconductor laser element 100 of the structure which the window area protruded compared with the cavity area is obtained.

6 and 8, when the seed width of the seed pattern 20 is smaller in the window area than in the cavity area (the wing width between the seed patterns 20 is smaller in the window area than in the cavity area). If larger), the base layer 30 is formed such that the cavity region portion grows thicker than the window region portion and protrudes upward. As a result, the semiconductor laser device 200 having a structure in which the cavity region protrudes compared to the window region is obtained.

Here, in manufacturing the semiconductor laser device according to the present invention, the wing width (or seed width) of the seed pattern 20 in the window region is larger than the wing width (or seed width) of the seed pattern 20 in the cavity region. It may be formed 0.1 to 5μm narrow or wide.

As described above, when the seed pattern 20 is formed such that the seed width (or the wing width between the seed patterns 20) is different from each other in the window region and the cavity region, and the base layer 30 is grown, the seed pattern 20 is formed in a horizontal or vertical direction. Due to the difference in the growth rates of the semiconductor laser devices, the height difference in the cavity area and the window area of the semiconductor laser device is different from each other, thereby forming a stepped structure. In this case, the area 41 corresponding to the boundary between the window area and the cavity area is formed. 9, the slope s in FIG. 9 may have a length of 0.1 to 30 μm.

In addition, the growth step in the vertical direction of the cavity region and the window region may be formed in a range of 10 μm to 5 μm. As described above, due to the growth step due to the difference in growth rate, the stepped window area has a non-absorbing mirror (NAM) structure compared to the cavity area.

Meanwhile, due to the growth step in the vertical direction formed at the boundary between the window region and the cavity region of the seed pattern 20, the boundary region 41 between the window region and the cavity region may be, for example, shown in FIGS. 5 and 6. As can be seen, a slope is formed, the slope of which can be approximately 10 degrees or more. 9 shows an enlarged view of the slope s formed in the boundary region 41 between the window region and the cavity region. 9 shows, for example, a case where a growth step is formed such that the window area protrudes more than the cavity area. In FIG. 9, P ₁ represents an active layer present position having, for example, a quantum well (QW) in the cavity region, and P ₂ represents an active layer present position in the window region.

Figure 10 is a laser beam is non-absorbing mirror (NAM) structure that goes through the defined window area naohmyeonseo P toward _two of the window region a quantum well (QW: quantum well) light intensity (intensity spanning the side P ₁ of the cavity area in which the position ) Ratio, that is, the relationship between the intensity aspect ratio and the tilt angle (degree) of the slope. FIG. 10 shows the relationship between the tilt angle and the light intensity aspect ratio of the slope s when the length s of the slope s shown in FIG. 9 is 1 μm.

Referring to FIG. 10, as the tilt angle increases, the aspect ratio increases, and when the tilt angle is 10 degrees, the aspect ratio becomes about 1.6, and when the tilt angle becomes larger than that, the aspect ratio becomes larger. This means that when the tilt angle is 10 degrees or more, the beam intensity is distributed 1.6 times or more on the P2 side compared to the P1 side, and the effect of increasing the COD level is sufficient. In particular, when the tilt angle is 15 degrees or more, the beam intensity is more than 2.5 times more distributed on the P2 side than on the P1 side, thereby exhibiting an effect of rapidly increasing the COD level.

As described above, a slope s is formed at the boundary between the window region and the cavity region due to the growth step of the window region and the cavity region, and the aspect ratio may vary according to the tilt angle of the slope s. In the tilt angle range (5 ° to 15 ° range) shown in Fig. 10, the larger the tilt angle, the larger the aspect ratio. The larger the aspect ratio, the higher the COD level.

According to the present invention as described above, a semiconductor laser device, for example, a nitride-based semiconductor laser device having a cavity region and a window region having a stepped non-absorptive mirror (NAM) structure due to a growth step. It can be realized.

FIG. 11 shows an embodiment of a stacked structure of a semiconductor laser device having a non-absorbing mirror (NAM) structure according to the present invention.

Referring to FIG. 11, a semiconductor laser device 300 having a non-absorption mirror (NAM) structure according to an embodiment of the present invention has a substrate 10 and a base layer 30 having a stepped structure formed on the substrate. And a lamination structure of the semiconductor layer 40 constituting the semiconductor laser device 300 on the base layer 30. As illustrated in FIG. 11, the semiconductor layer 40 includes n-type cladding layers 301, n-waveguide layers 303, active layers 305, p-waveguide layers 307, and p-type stacked sequentially. The cladding layer 309 may be included. In addition, a ridge type contact layer 310 may be provided on the p-type cladding layer 309.

The stacked structure of the semiconductor layer 40 also has a structure in which the window area and the cavity area are stepped with each other according to the stepped structure of the base layer 30. 11 illustrates an embodiment of a structure that protrudes from the cavity area of the window area.

In the semiconductor laser device 300 according to the present invention, the maximum output center of the laser beam generated in the cavity region is moved to at least the layer region adjacent to the active layer 305, for example, the n-type cladding layer 301, in the window region. It is desirable to have a growth step in the vertical direction to oscillate through the window area.

The n-type cladding layer 301 and the p-type cladding layer 309 have a refractive index smaller than that of the active layer 305. In particular, the n-type cladding layer 301 has a larger energy bandgap width than the active layer 305. It is preferably formed of a material.

According to the semiconductor laser device 300 having a non-absorptive mirror (NAM) structure according to an embodiment of the present invention, the refractive index is higher than that of the n-type cladding layer 301, for example, in the stepped window region to protrude more than the cavity region. This relatively high active layer 305 is present around the n-type cladding layer 301 through which the laser light passes, which gives the effect of expanding the optical mode vertically and horizontally, thereby improving beam quality and facet. At lower photon density, the COD level can be increased.

More specifically, since the window region through which the laser light generated from the active layer 305 passes protrudes above the cavity region, the n-type cladding layer 301 and the active layer 305 and p sequentially stacked on the window region are sequentially formed. The type cladding layer 309 is disposed at a relatively higher position than the n-type cladding layer 301 and the active layer 305 and the p-type cladding layer 309 sequentially stacked in the cavity region, and thus the active layer of the cavity region. The laser light generated from 305 may be emitted through the n-type cladding layer 301 in the window region. In this structure, since the laser light is emitted through the region of the n-type cladding layer 301 having a band gap higher than that of the active layer 305, catatrophic optical damage at the facet. Occurrence can be reduced.

Meanwhile, the embodiment of the structure in which the window area protrudes from the cavity area has been described with reference to FIG. 11, but the structure in which the cavity area protrudes from the window area is also possible. The laminated structure of FIG. 11 may also be applied to a structure in which the cavity area protrudes above the window area. For an embodiment of the structure in which the cavity area protrudes above the window area, it is sufficiently described from FIG. 11 and the above description. Since it can be inferred, the illustration and description are abbreviate | omitted.

Here, in the case of the structure where the cavity region protrudes more than the window region, as can be inferred, the active layer 305 is present around the p-type cladding layer 301 through which the laser light passes, and in this case, This has the effect of expanding the mode vertically and horizontally.

In this case, the n-type cladding layer 301 and the active layer 305 and the p-type cladding layer 309 sequentially stacked in the window region are the n-type cladding layer 301 and the active layer (sequentially stacked in the cavity region). 305) and the laser light generated from the active layer 305 of the cavity region is emitted at a position lower than that of the p-type cladding layer 309 and exits through the window region, for example, the p-type cladding layer 309. Can be. Therefore, in this case, the n-type cladding layer 301 and the p-type cladding layer 309 have a smaller refractive index than the active layer 305, and in particular, the p-type cladding layer 309 has a higher energy bandgap width than the active layer 305. It is preferred to be formed of a larger material.

In the above, an embodiment of a semiconductor laser device having a non-absorptive mirror (NAM) structure according to the present invention has been described with reference to FIG. 11, but the present invention is not limited to this embodiment, and the technical spirit of the claims is defined. Various modifications and equivalent other embodiments are possible within the scope.

According to the present invention as described above, by introducing a seed pattern structure having a different seed width (or wing width) depending on the region, a separate etching pattern for forming a non-absorbing mirror (NAM) structure and the process of regrowth is unnecessary Process costs can be reduced.

In addition, defects and nonuniformities in crystal growth due to etching and regrowth can be solved compared to the conventional non-absorbing mirror (NAM) structure fabrication method, which requires an additional process such as selective substrate etching and regrowth of semiconductor laser devices. have.

In addition, it is possible to arbitrarily adjust the far field pattern shape by adjusting the seed pattern.

Claims (17)

In the method of manufacturing a semiconductor laser device, Preparing a substrate; Forming a seed pattern on the substrate, the seed pattern having a width of a wing or seed in a direction perpendicular to a cavity of a semiconductor laser device according to a region; Forming a base layer on the substrate on which the seed pattern is formed, wherein the cavity region and the window region of the semiconductor laser device are stepped by a growth rate difference due to a difference in wings or widths of seeds in each region of the seed pattern; And forming a stacked structure of a semiconductor layer constituting the semiconductor laser device on the base layer having the step difference. The method of claim 1, wherein the seed pattern is a modified PENDEO or ELO seed pattern. The material of claim 1, wherein the seed pattern is formed of GaN, Al _x Ga _1-x N (0 <x ≦ 1), and In _y Al _x Ga _1-yx N (0 <x ≦ 1, 0 <y ≦ 1) material. Method for manufacturing a semiconductor laser device, characterized in that made of any one. The method of claim 1, wherein a region corresponding to a boundary between the window region and the cavity region has a length of 0.1-30 μm. The method of manufacturing a semiconductor laser device according to claim 1, wherein a growth step of 10 mW-5 m is formed in the stacking direction of the semiconductor layer. The method of claim 1, wherein a region corresponding to a boundary between the window region and the cavity region is formed at an inclination of 10 ° or more due to a growth step. The method of claim 1, wherein the seed pattern has a wing width of an area corresponding to the window area being 0.1 to 5 μm narrower or wider than a wing width of an area corresponding to the cavity area. The method of claim 1, wherein the semiconductor layer comprises an active layer, And the maximum output center of the laser beam is oscillated through the window region at least out of the layer region adjacent to the active layer. The substrate according to any one of claims 1 to 8, wherein the substrate is any one of a nitride based substrate and a sapphire substrate. The base layer is a semiconductor laser device manufacturing method, characterized in that made of a nitride-based semiconductor material. The method of claim 9, wherein the semiconductor layer comprises a nitride-based semiconductor layer. Substrate, A base layer formed such that the cavity region and the window region of the semiconductor laser device are stepped by a growth rate difference caused by a difference in wings or seeds of each region of the seed pattern in a direction perpendicular to the cavity of the semiconductor laser device; And a stacked structure of semiconductor layers constituting a semiconductor laser element formed on the base layer having the step difference. The semiconductor laser device of claim 11, wherein a region corresponding to a boundary between the window region and the cavity region has a length of 0.1-30 μm. The semiconductor laser device according to claim 11, wherein a growth step of 10 mW-5 m is formed in the stacking direction of the semiconductor layer. 12. The semiconductor laser device according to claim 11, wherein a region corresponding to a boundary between the window region and the cavity region is formed at an inclination of 10 degrees or more by a growth step. The method of claim 11, wherein the semiconductor layer comprises an active layer, And the maximum output center of the laser beam is oscillated through the window region at least out of the layer region adjacent to the active layer. The method according to any one of claims 11 to 15, wherein the substrate is any one of a nitride based substrate and a sapphire substrate, The base layer is a semiconductor laser device, characterized in that made of a nitride-based semiconductor material. The semiconductor laser device according to claim 9, wherein the semiconductor layer comprises a nitride-based semiconductor layer.

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