semiconductor laser element

Abstract

This semiconductor laser element (10) comprises a substrate (21) and a semiconductor laminate (10S). The semiconductor laminate (10S) has an N-side semiconductor layer (22), an active layer (23), a P-side semiconductor layer (24), and a P-type contact layer (25). The semiconductor laminate (10S) has two end surfaces. A laser beam resonates between the two end surfaces. The semiconductor laminate (10S) has a ridge part (20r) extending in a resonance direction, and a bottom part (20b) surrounding the periphery of the ridge part (20r) in a top view of the semiconductor laminate (10S). The ridge part (20r) protrudes upward from the bottom part (20b), is spaced apart from the two end surfaces, and includes at least a portion of the P-type contact layer (25). A current injection window (25a), which is a region into which current is injected, is formed only on the ridge part (20r) of the upper surface of the semiconductor laminate (10S). The distance from the upper surface of the active layer (23) to the bottom part (20b) is uniform.

Description

[Technical Field]

[0001] The present disclosure relates to a semiconductor laser device. [Background technology]

[0002] Conventionally, semiconductor laser elements that generate laser light in a resonator have been known (see, for example, Patent Document 1). The semiconductor laser element described in Patent Document 1 includes a semiconductor laminate including an N-type cladding layer, an active layer, a P-type cladding layer, and a P-type contact layer; an insulating film having an opening and disposed on the semiconductor laminate; and a P-side electrode disposed on the insulating film. An opening is formed in the insulating film, and current is supplied from the P-side electrode to the semiconductor laminate through the opening. The opening is not formed near the end face that forms the resonator of the semiconductor laser element. As a result, the semiconductor laser element described in Patent Document 1 attempts to suppress current supply near the end face, thereby suppressing COD (catastrophic optical damage) near the end face. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 206012 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the semiconductor laser device described in Patent Document 1, the P-type contact layer extends from one facet to the other facet, so that a current can be supplied from the P-side electrode disposed in the opening of the insulating film to the vicinity of the facet via the P-type contact layer. Therefore, in the semiconductor laser device described in Patent Document 1, COD can occur near the facet.

[0005] The present disclosure is intended to solve such problems, and has an object to provide a semiconductor laser element that can suppress COD near the facet. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the semiconductor laser element according to the present disclosure is a semiconductor laser element that emits laser light in multiple transverse modes, comprising: a substrate; and a semiconductor laminate disposed above the substrate, the semiconductor laminate having an N-side semiconductor layer disposed above the substrate, an active layer disposed above the N-side semiconductor layer, a P-side semiconductor layer disposed above the active layer, and a P-type contact layer disposed above the P-side semiconductor layer, the semiconductor laminate having two end faces facing each other, and the laser light resonating between the two end faces. The semiconductor laminate has a ridge portion extending in the resonance direction of the laser light, and a bottom portion which is part of the upper surface of the semiconductor laminate and surrounds the ridge portion when viewed from above, the ridge portion protruding upward from the bottom portion and spaced apart from the two end faces, the ridge portion including at least a part of the P-type contact layer, a current injection window which is a region into which current is injected is formed only on the ridge portion of the upper surface of the semiconductor laminate, and the distance from the upper surface of the active layer to the bottom portion is uniform.

[0007] In order to solve the above-described problems, one aspect of the semiconductor laser element according to the present disclosure is a semiconductor laser element that emits laser light in multiple transverse modes, comprising: a substrate; and a semiconductor laminate disposed above the substrate, the semiconductor laminate having an N-side semiconductor layer disposed above the substrate, an active layer disposed above the N-side semiconductor layer, a P-side semiconductor layer disposed above the active layer, and a P-type contact layer disposed above the P-side semiconductor layer, the semiconductor laminate having two end faces facing each other, and the laser light is emitted in a common direction between the two end faces. The semiconductor laminate has a ridge portion extending in the resonance direction of the laser light, and a bottom portion which is a part of the upper surface of the semiconductor laminate and surrounds the periphery of the ridge portion in a top view of the semiconductor laminate, the ridge portion protruding upward from the bottom portion and being spaced apart from the two end faces, the ridge portion including at least a part of the P-type contact layer, a current injection window which is a region into which current is injected is formed only above the ridge portion on the upper surface of the semiconductor laminate, and the P-type contact layer is exposed at the bottom portion. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a semiconductor laser device that can suppress COD near the facet. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic plan view showing the overall configuration of a semiconductor laser device according to an embodiment. [Figure 2] FIG. 2 is a first cross-sectional view schematically illustrating the overall configuration of a semiconductor laser device according to an embodiment. [Figure 3] FIG. 3 is a second cross-sectional view schematically illustrating the overall configuration of the semiconductor laser device according to the embodiment. [Figure 4] FIG. 4 is a third cross-sectional view schematically illustrating the overall configuration of the semiconductor laser device according to the embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing a configuration example of an N-side semiconductor layer according to the embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing an example of the configuration of an active layer according to the embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing a configuration example of a P-side semiconductor layer according to the embodiment. [Figure 8] FIG. 8 is a cross-sectional view showing the structure of a model used in a simulation of the semiconductor laser device according to the embodiment. [Figure 9] FIG. 9 is a graph showing a simulation result of current spreading in the lateral direction of the semiconductor laser device according to the embodiment. [Figure 10] FIG. 10 is a graph showing an enlarged portion of FIG. [Figure 11] FIG. 11 is a graph showing a simulation result of the lateral width of the near-field pattern (NFP) of the semiconductor laser device according to the embodiment. [Figure 12] FIG. 12 is a graph showing a simulation result of current spreading in the resonance direction of the semiconductor laser device according to the embodiment. [Figure 13] FIG. 13 is a graph showing the relationship between the distance from the top surface to the bottom of the active layer and the effective refractive index difference. [Figure 14] FIG. 14 is a schematic cross-sectional view showing a first step of a method for manufacturing a semiconductor laser device according to the embodiment. [Figure 15] FIG. 15 is a schematic cross-sectional view showing a second step of the method for manufacturing the semiconductor laser device according to the embodiment. [Figure 16] FIG. 16 is a first cross-sectional view schematically illustrating a third step of the method for manufacturing the semiconductor laser device according to the embodiment. [Figure 17] FIG. 17 is a second cross-sectional view schematically illustrating a third step of the method for manufacturing the semiconductor laser device according to the embodiment. [Figure 18] FIG. 18 is a first cross-sectional view schematically illustrating a fourth step of the method for manufacturing the semiconductor laser device according to the embodiment. [Figure 19]FIG. 19 is a second cross-sectional view schematically illustrating a fourth step of the method for manufacturing the semiconductor laser device according to the embodiment. [Figure 20] FIG. 20 is a first cross-sectional view schematically illustrating a fifth step of the method for manufacturing the semiconductor laser device according to the embodiment. [Figure 21] FIG. 21 is a second cross-sectional view schematically illustrating a fifth step of the method for manufacturing the semiconductor laser device according to the embodiment. [Figure 22] FIG. 22 is a first cross-sectional view schematically illustrating a sixth step of the method for manufacturing the semiconductor laser device according to the embodiment. [Figure 23] FIG. 23 is a second cross-sectional view schematically illustrating a sixth step of the method for manufacturing the semiconductor laser device according to the embodiment. [Figure 24] FIG. 24 is a schematic plan view showing the overall configuration of a semiconductor laser device according to the fourth modification. [Figure 25] FIG. 25 is a schematic plan view showing the overall configuration of a semiconductor laser device according to Modification 5. As shown in FIG. [Figure 26] FIG. 26 is a schematic plan view showing the overall configuration of a semiconductor laser device according to Modification 6. As shown in FIG. [Figure 27] FIG. 27 is a schematic plan view showing the overall configuration of a semiconductor laser device according to the seventh modification. [Figure 28] FIG. 28 is a schematic plan view showing the overall configuration of a semiconductor laser device according to Modification 8. As shown in FIG. [Figure 29] FIG. 29 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device according to Modification 8. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, and the arrangement and connection of the components shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0011] Furthermore, each figure is a schematic diagram and is not necessarily an exact representation. Therefore, the scales and the like do not necessarily match in each figure. In each figure, the same reference numerals are used to denote substantially the same components, and redundant explanations will be omitted or simplified.

[0012] In this specification, the terms "above" and "below" do not refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. Furthermore, the terms "above" and "below" are applied not only to cases where two components are arranged with a gap between them and another component exists between the two components, but also to cases where two components are arranged in contact with each other.

[0013] (Embodiment) A semiconductor laser device according to an embodiment will be described.

[0014] [1. Overall structure] The overall configuration of a semiconductor laser device according to this embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic plan view showing the overall configuration of a semiconductor laser device 10 according to this embodiment. FIGS. 2 to 4 are schematic cross-sectional views showing the overall configuration of the semiconductor laser device 10 according to this embodiment. FIGS. 2, 3, and 4 show cross sections taken along lines II-II, III-III, and IV-IV in FIG. 1, respectively. Each drawing shows an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other. The X-axis, the Y-axis, and the Z-axis form a right-handed Cartesian coordinate system. The stacking direction of the semiconductor laser device 10 is parallel to the Z-axis direction, and the main emission direction of light (laser light in this embodiment) is parallel to the Y-axis direction.

[0015] The semiconductor laser device 10 is a device that emits multi-transverse mode laser light. As shown in FIG. 2, the semiconductor laser device 10 includes a substrate 21 and a semiconductor laminate 10S. The semiconductor laminate 10S has two end faces 10F and 10R that are perpendicular to the stacking direction (i.e., the Z-axis direction) and face each other (see FIG. 1). The two end faces 10F and 10R form a resonator, and the semiconductor laminate 10S emits laser light from the end face 10F. In this embodiment, the semiconductor laminate 10S includes an optical waveguide located between the two end faces 10F and 10R that guides the laser light. In this embodiment, the semiconductor laser device 10 has a gain-guided waveguide characteristic. In this embodiment, the resonator length of the semiconductor laser device 10 (i.e., the distance between the end face 10F and the end face 10R) is 2 mm or more. The resonator length of the semiconductor laser device 10 may be 4 mm or more or less than 2 mm. The end face 10F is a front end face from which laser light is emitted, and the end face 10R is a rear end face having a higher reflectance than the end face 10F.

[0016] A first facet coating film 71 is disposed on the facet 10F, and a second facet coating film 72 is disposed on the facet 10R. The first facet coating film 71 and the second facet coating film 72 are films for adjusting the reflectance of laser light at each facet. In this embodiment, the first facet coating film 71 and the second facet coating film 72 are multilayer films composed of dielectric multilayer films. For example, the first facet coating film 71 is a multilayer film including one or more Al2O3 films and one or more Ta2O5 films, and the second facet coating film 72 is a multilayer film including one or more Al2O3 films, one or more SiO2 films, and one or more Ta2O5 films. As an example, the reflectance of the first facet coating film 71 is 2%, and the reflectance of the second facet coating film 72 is 95%. Note that in this embodiment, the two facets of the substrate 21 in the resonance direction are coplanar with the facets 10F and 10R of the semiconductor laminate 10S (see FIG. 4). A first facet coating film 71 and a second facet coating film 72 are also disposed on the two facets of the substrate 21 in the resonance direction, respectively. The reflectances of the first facet coating film 71 and the second facet coating film 72 are not limited to those described above. For example, when the semiconductor laser device 10 is disposed in an external resonator, the reflectance of the first facet coating film 71 may be 0.2% or less. This can prevent problems such as kink occurrence caused by competition between the laser oscillation mode between the two facets 10F and 10R of the semiconductor laser device 10 and the laser oscillation mode of the external resonator. Here, a kink is a phenomenon in which the power of the output laser light changes discontinuously with changes in the current supplied to the semiconductor laser device 10. In other words, a kink is a phenomenon in which a discontinuous change occurs in a graph showing the relationship between the current supplied to the semiconductor laser device 10 and the power of the output laser light.

[0017] The semiconductor laser device 10 according to this embodiment emits laser light having a wavelength of 900 nm or more and 980 nm or less. A semiconductor laminate 10S of the semiconductor laser device 10 is made of, for example, a III-V group compound semiconductor made of an AlGaInAs-based material. The semiconductor laser device 10 emits laser light having a wavelength of, for example, 976 nm. As will be described in detail later, the semiconductor laser device 10 has an end face window structure. That is, as shown in FIG. 4, the semiconductor laminate 10S of the semiconductor laser device 10 has a window region 10w adjacent to the end face 10F (i.e., the front end face) from which laser light is emitted, out of the two end faces. In this embodiment, the window region 10w is in contact with the end face 10F. The semiconductor laminate 10S may further have a window region 10w adjacent to the end face 10R. In this embodiment, the semiconductor laminate 10S has a window region 10w adjacent to the end face 10R.

[0018] As shown in FIG. 2, the semiconductor laser device 10 includes a substrate 21, a semiconductor laminate 10S, an insulating film 30, a first P-side electrode 41, a pad electrode 50, a second P-side electrode 42, and an N-side electrode 60.

[0019] The substrate 21 is a plate-like member that serves as a base for the semiconductor laser device 10. The substrate 21 is a flat member having a uniformly flat main surface. The substrate 21 is a semiconductor substrate such as a GaAs substrate or an insulating substrate such as a sapphire substrate. In this embodiment, the substrate 21 is an N-type GaAs substrate.

[0020] The semiconductor laminate 10S is a laminate disposed above the substrate 21. The semiconductor laminate 10S has multiple semiconductor layers stacked in a stacking direction (i.e., the Z-axis direction in each drawing). In this embodiment, the semiconductor laminate 10S has an N-side semiconductor layer 22, an active layer 23, a P-side semiconductor layer 24, and a P-type contact layer 25. As shown in FIG. 1, the semiconductor laminate 10S has a ridge portion 20r extending in the resonance direction of the laser light and a bottom portion 20b surrounding the ridge portion 20r in a top view of the semiconductor laminate 10S. Here, the bottom portion 20b is a part of the top surface of the semiconductor laminate 10S. As shown in FIG. 2, the ridge portion 20r protrudes upward from the bottom portion 20b and includes at least a part of the P-type contact layer 25. Furthermore, as shown in FIGS. 1 and 4, the ridge portion 20r is spaced apart from the two end faces 10F and 10R. The ridge portion 20r of the semiconductor laminate 10S forms the optical waveguide of the semiconductor laser device 10. In this embodiment, the width of the ridge portion 20r (that is, the dimension in the X-axis direction) is 230 μm.

[0021] As shown in FIGS. 2 to 4, in this embodiment, the distance Db from the top surface of the active layer 23 to the bottom 20b in the stacking direction is uniform. In other words, the bottom 20b is on a plane perpendicular to the stacking direction. This allows the entire bottom 20b to be formed simultaneously by etching or the like. Note that a configuration in which the distance Db is uniform includes not only a configuration in which the distance Db is uniform at any position on the bottom 20b, but also a configuration in which the distance Db is substantially uniform. For example, a configuration in which the error in the distance Db is 5% or less is also included in the configuration in which the distance Db is uniform. In this embodiment, as shown in FIGS. 2 to 4, the P-side semiconductor layer 24 is exposed at the bottom 20b. That is, the distance Db is equal to or less than the film thickness of the P-side semiconductor layer 24. Note that the configuration of the bottom 20b according to this embodiment is not limited to this. That is, the distance Db from the top surface of the active layer 23 to the bottom 20b in the stacking direction does not have to be uniform. For example, the bottom portion 20b may have a region that is inclined with respect to the XY plane, or may have a step portion.

[0022] 1, 2, and 4, a current injection window 25a, which is a region into which current is injected, is formed only on the ridge portion 20r of the upper surface of the semiconductor laminate 10S. The current injection window 25a is a region where the P-type contact layer 25 of the semiconductor laminate 10S and the first P-side electrode 41 come into contact.

[0023] As shown in FIG. 1, the semiconductor laminate 10S includes a portion of the P-type contact layer 25 and has two wing portions 20w extending in the resonance direction. At least a portion of the ridge portion 20r is disposed between the two wing portions 20w when viewed from above the semiconductor laminate 10S. Each of the two wing portions 20w is adjacent to the ridge portion 20r via the bottom portion 20b. As shown in FIGS. 2 and 3, the two wing portions 20w protrude upward from the bottom portion 20b. The heights of the two wing portions 20w from the bottom portion 20b are equal to the height of the ridge portion 20r from the bottom portion 20b. This allows, for example, stress applied to the semiconductor laser element 10 during mounting to be dispersed among the wing portions 20w, thereby preventing stress from concentrating solely on the ridge portion 20r. This prevents damage to the ridge portion 20r.

[0024] The configuration in which the heights of the two wing portions 20w from the bottom 20b are equal to the height of the ridge portion 20r from the bottom 20b includes not only a configuration in which the heights are completely equal, but also a configuration in which the heights are substantially equal. For example, a configuration in which the error in the heights is 5% or less is also included in the configuration in which the heights are equal.

[0025] Each of the two wing portions 20w extends to the two end faces 10F and 10R. In this embodiment, each of the two wing portions 20w extends from the end face 10F to the end face 10R. This reduces the stress applied to the ridge portion 20r near the end faces 10F and 10R, where stress tends to concentrate, when mounting the semiconductor laser device 10. This prevents the ridge portion 20r from being damaged.

[0026] The width of the bottom 20b between the ridge 20r and the wing 20w (i.e., the dimension in the X-axis direction) may be 5 μm or more and 30 μm or less. This reduces shear stress outside the ridge 20r. If the width of the bottom 20b is too large, the weight during mounting will be concentrated on the ridge 20r, which serves as the current injection region. Therefore, the width of the bottom 20b between the ridge 20r and the wing 20w may be 10 μm or more and 20 μm or less. This effectively suppresses rotation of the polarization plane due to shear stress and reduces the effect of shear stress on the laser light propagating through the optical waveguide.

[0027] Furthermore, separation grooves 20t are formed at both ends of the semiconductor laminate 10S in the X-axis direction. The separation grooves 20t are grooves used when dividing the semiconductor laminate 10S into individual pieces.

[0028] The N-side semiconductor layer 22 is an example of a first conductivity-type first semiconductor layer disposed above the substrate 21 and below the active layer 23. Hereinafter, a configuration example of the N-side semiconductor layer 22 according to this embodiment will be described with reference to FIG. 5 . FIG. 5 is a schematic cross-sectional view showing a configuration example of the N-side semiconductor layer 22 according to this embodiment. As shown in FIG. 5 , in this embodiment, the N-side semiconductor layer 22 includes an N-type buffer layer 22a, a first N-type compositionally graded layer 22b, an N-type cladding layer 22c, and a second N-type compositionally graded layer 22d. The N-type buffer layer 22a, the first N-type compositionally graded layer 22b, the N-type cladding layer 22c, and the second N-type compositionally graded layer 22d are N-type semiconductor layers intentionally doped with impurities, such as an N-type GaAs layer or an N-type AlGaAs layer. The impurity doped into each layer of the N-side semiconductor layer 22 can be, for example, silicon (Si).

[0029] The N-type buffer layer 22a is an N-type semiconductor layer having a thickness of, for example, 1.0 μm or less. By reducing the thickness in this manner, when the window region 10w is formed by thermal diffusion, the amount of energy shift in the window region 10w is reduced by the amount of energy shift in the N-type buffer layer 22a. 22aThis can suppress a decrease in the energy density due to the influence of impurities contained in the N-type buffer layer 22a. To increase the amount of energy shift in the window region 10w, the thickness of the N-type buffer layer 22a may be set to 0.5 μm or less. In this embodiment, the N-type buffer layer 22a is an N-type GaAs layer with a thickness of 0.50 μm.

[0030] The N-type cladding layer 22c is disposed above the first N-type composition gradient layer 22b and is an N-type semiconductor layer having a lower refractive index than the active layer 23. In this embodiment, the N-type cladding layer 22c is an N-type Al 0.32 Ga 0.68 This is the As layer.

[0031] The first N-type compositionally graded layer 22b is disposed above the N-type buffer layer 22a and has a composition that varies depending on the position in the stacking direction. The bandgap energy of the first N-type compositionally graded layer 22b is between the bandgap energy of the N-type buffer layer 22a and the bandgap energy of the N-type cladding layer 22c. The bandgap energy of the first N-type compositionally graded layer 22b approaches the bandgap energy of the N-type cladding layer 22c as the position in the stacking direction approaches the N-type cladding layer 22c, and approaches the bandgap energy of the N-type buffer layer 22a as the position in the stacking direction approaches the N-type buffer layer 22a. The presence of the first N-type compositionally graded layer 22b in the N-side semiconductor layer 22 alleviates the abrupt change in bandgap energy between the N-type buffer layer 22a and the N-type cladding layer 22c. This reduces the device resistance of the semiconductor laser device 10. In this embodiment, the first N-type compositionally graded layer 22b is a 0.05 μm-thick N-type Al x1 Ga 1-x1 The Al composition ratio x1 of the first N-type composition gradient layer 22b is 0.15 near the interface with the N-type buffer layer 22a, and 0.32 near the interface with the N-type cladding layer 22c, and increases with increasing distance from the N-type cladding layer 22c.

[0032] The second N-type compositionally graded layer 22d is disposed above the N-type cladding layer 22c and has a composition that changes depending on the position in the stacking direction. The bandgap energy of the second N-type compositionally graded layer 22d is between the bandgap energy of the N-type cladding layer 22c and the bandgap energy at the lower end (N-type guide layer 23a) of the active layer 23. The bandgap energy of the second N-type compositionally graded layer 22d approaches the bandgap energy of the N-type cladding layer 22c as the position in the stacking direction approaches the N-type cladding layer 22c, and approaches the bandgap energy at the lower end of the active layer 23 as the position in the stacking direction approaches the active layer 23. The presence of the second N-type compositionally graded layer 22d in the N-side semiconductor layer 22 alleviates the abrupt change in bandgap energy between the N-type cladding layer 22c and the active layer 23. Therefore, the device resistance of the semiconductor laser device 10 can be reduced. In this embodiment, the second N-type composition gradient layer 22d is an N-type AlN layer having a thickness of 0.03 μm. x2 Ga 1-x2 The Al composition ratio x2 of the second N-type composition gradient layer 22d is 0.32 near the interface with the N-type cladding layer 22c, and 0.285 near the interface with the active layer 23. The Al composition ratio x2 decreases with increasing distance from the active layer 23 in the stacking direction.

[0033] The N-side semiconductor layer 22 does not necessarily have to include the N-type buffer layer 22a, the first N-type compositionally graded layer 22b, and the second N-type compositionally graded layer 22d. The N-side semiconductor layer 22 may also include other semiconductor layers. For example, the N-side semiconductor layer 22 may include an undoped semiconductor layer.

[0034] The active layer 23 is a light-emitting layer disposed above the N-side semiconductor layer 22. In this embodiment, the active layer 23 in the region other than the window region 10w has a quantum well structure. The active layer 23 may have a single quantum well or multiple quantum wells. Here, the active layer 23 in the window region 10w will be described. The bandgap energy measured by photoluminescence in the gain region, which is the region of the active layer 23 other than the window region 10w, is defined as Eg1. The bandgap energy measured by photoluminescence in the region of the active layer 23 where the window region 10w is formed is defined as Eg2. If the difference between Eg1 and Eg2 is defined as ΔEg, the window region 10w is formed so that, for example, ΔEg = Eg2 - Eg1 = 100 meV. In other words, the bandgap energy of the active layer 23 in the window region 10w is greater than the bandgap energy of the active layer 23 in the region other than the window region 10w (i.e., the region having the quantum well structure). This makes it possible to suppress absorption of laser light in the active layer 23 near the end faces 10F and 10R of the semiconductor laminate 10S, thereby suppressing the occurrence of COD near the end faces 10F and 10R.

[0035] Furthermore, when window region 10w is formed, if the bandgap energy measured by photoluminescence in the boundary region between the gain region and the region where window region 10w is formed is Eg3, then the relationship Eg2 > Eg3 > Eg1 may hold. Specifically, the bandgap energy of active layer 23 near facets 10F and 10R may be larger than the bandgap energy measured by photoluminescence in the boundary region between the gain region and the region where window region 10w is formed, and the bandgap energy measured by photoluminescence in the boundary region between the region where window region 10w is not formed and the region where window region 10w is formed may be larger than the bandgap energy of active layer 23 in the center in the resonance direction.

[0036] 2 and 3, a pair of side surfaces of the active layer 23 (both end surfaces in the X-axis direction in FIGS. 2 and 3) are inclined with respect to the stacking direction. This makes it possible to prevent stray light traveling from a region of the active layer 23 located below the ridge portion 20r toward the side surfaces of the active layer 23 from returning to the region located below the ridge portion 20r. This makes it possible to prevent competition between the laser light resonating between the end faces 10F and 10R and the stray light, thereby stabilizing the operation of the semiconductor laser device 10.

[0037] A configuration example of the active layer 23 according to this embodiment will be described below with reference to FIG. 6. FIG. 6 is a schematic cross-sectional view showing a configuration example of the active layer 23 according to this embodiment. As shown in FIG. 6, in this embodiment, the active layer 23 has an N-type guide layer 23a, a second N-side barrier layer 23b, a first N-side barrier layer 23c, a well layer 23d, a first P-side barrier layer 23e, a second P-side barrier layer 23f, and a P-type guide layer 23g. In this way, the active layer 23 has a single quantum well structure having a single quantum well.

[0038] The N-type guide layer 23a is a layer disposed above the N-side semiconductor layer 22 and has a higher refractive index than the N-side semiconductor layer 22. In this embodiment, the N-type guide layer 23a is an N-type Al 1N 0.15 μm thick layer. 0.285 Ga 0.715 The N-type guide layer 23a is an As layer. The N-type guide layer 23a is doped with silicon as an impurity.

[0039] The second N-side barrier layer 23b is disposed above the N-type guide layer 23a and functions as a barrier of the quantum well. The second N-side barrier layer 23b may have a doped region intentionally doped with impurities and an undoped region not doped with impurities. In this embodiment, the second N-side barrier layer 23b has an N-type layer disposed above the N-type guide layer 23a and an undoped layer disposed above the N-type layer. The N-type layer is an N-type Al 0.0268 μm thick layer. 0.15 Ga 0.85 The N-type layer is doped with silicon as an impurity. The undoped layer is an Al layer with a thickness of 0.0083 μm.0.15 Ga 0.85 This is the As layer.

[0040] The first N-side barrier layer 23c is disposed above the second N-side barrier layer 23b and functions as a quantum well barrier. The first N-side barrier layer 23c may have a doped region intentionally doped with impurities and an undoped region not doped with impurities. In this case, the undoped region is disposed closer to the well layer 23d than the doped region. The thickness of the undoped region of the first N-side barrier layer 23c is, for example, 5 nm or more. Doping the region of the first N-side barrier layer 23c near the well layer 23d with impurities reduces the series resistance of the semiconductor laser device 10, but increases the waveguide loss due to free carrier loss. On the other hand, increasing the thickness of the undoped region increases the series resistance of the semiconductor laser device 10. To suppress an increase in the series resistance of the semiconductor laser device 10 while suppressing an increase in free carrier loss, the thickness of the undoped region may be set to 5 nm or more and 40 nm or less. When the doping concentration of impurities in the N-type guide layer 23a gradually increases with increasing distance from the well layer 23d, the increase in waveguide loss can be suppressed even if the thickness of the undoped region in the first N-side barrier layer 23c is 20 nm or less. In this embodiment, the first N-side barrier layer 23c is an undoped Al 0.50 Ga 0.32 In 0.18 This is the As layer.

[0041] The well layer 23d is disposed above the first N-side barrier layer 23c and functions as a quantum well. The well layer 23d is disposed between the first N-side barrier layer 23c and the first P-side barrier layer 23e, and is in contact with both the first N-side barrier layer 23c and the first P-side barrier layer 23e. The thickness of the well layer 23d may be 0.0060 nm or more. In this embodiment, the well layer 23d is an undoped In layer having a thickness of 0.0090 μm. 0.135 Ga 0.865 This is the As layer.

[0042] The first P-side barrier layer 23e is disposed above the well layer 23d and functions as a quantum well barrier. The first P-side barrier layer 23e may have a doped region intentionally doped with impurities and an undoped region not doped with impurities. In this case, the undoped region is disposed closer to the well layer 23d than the doped region. The thickness of the undoped region of the first P-side barrier layer 23e is, for example, 5 nm or more. Doping the region of the first P-side barrier layer 23e near the well layer 23d with impurities reduces the series resistance of the semiconductor laser device 10, but increases the waveguide loss due to free carrier loss. On the other hand, increasing the thickness of the undoped region increases the series resistance of the semiconductor laser device 10. To suppress an increase in the series resistance of the semiconductor laser device 10 while suppressing an increase in free carrier loss, the thickness of the undoped region may be set to 5 nm or more and 40 nm or less. When the doping concentration of impurities in the P-type guide layer 23g gradually increases with increasing distance from the well layer 23d, the increase in waveguide loss can be suppressed even if the thickness of the undoped region in the first P-side barrier layer 23e is set to 20 nm or less. In this embodiment, the first P-side barrier layer 23e is an undoped Al 0.50 Ga 0.32 In 0.18 This is the As layer.

[0043] The second P-side barrier layer 23f is a layer disposed above the first P-side barrier layer 23e and functions as a barrier of the quantum well. The second P-side barrier layer 23f may have a doped region intentionally doped with impurities and an undoped region not doped with impurities. In this embodiment, the second P-side barrier layer 23f has an undoped layer disposed above the first P-side barrier layer 23e and a P-type layer disposed above the undoped layer. The undoped layer is an Al 0.0083 μm thick layer. 0.15 Ga 0.85 The P-type layer is a 0.025 μm thick P-type Al 0.15 Ga 0.85 The P-type layer is doped with carbon (C) as an impurity.

[0044] The P-type guide layer 23g is a layer disposed above the second P-side barrier layer 23f, and has a refractive index higher than that of the P-side semiconductor layer 24. In this embodiment, the P-type guide layer 23g is a P-type Al 0.22 μm thick layer. 0.28 Ga 0.72 The p-type guide layer 23g is an As layer. The p-type guide layer 23g is doped with carbon as an impurity.

[0045] The P-side semiconductor layer 24 is an example of a second semiconductor layer of a second conductivity type disposed above the active layer 23. Hereinafter, a configuration example of the P-side semiconductor layer 24 according to this embodiment will be described with reference to FIG. 7. FIG. 7 is a schematic cross-sectional view showing a configuration example of the P-side semiconductor layer 24 according to this embodiment. As shown in FIG. 7, in this embodiment, the P-side semiconductor layer 24 has a first P-type compositional gradient layer 24a, a P-type cladding layer 24b, and a second P-type compositional gradient layer 24c. The first P-type compositional gradient layer 24a, the P-type cladding layer 24b, and the second P-type compositional gradient layer 24c are P-type semiconductor layers intentionally doped with impurities, such as P-type AlGaAs layers. Carbon, for example, can be used as the impurity doped into each layer of the P-side semiconductor layer 24. The impurity concentration of the P-side semiconductor layer 24 is, for example, 1.0×10 19 cm -3 is less than.

[0046] As described above, the P-side semiconductor layer 24 is exposed at the bottom 20b of the semiconductor laminate 10S. At the bottom 20b, the second P-type composition gradient layer 24c or the P-type cladding layer 24b may be exposed. The bottom 20b may be located on the top surface of the second P-type composition gradient layer 24c, or may be located between the bottom and top surfaces of the second P-type composition gradient layer 24c. Furthermore, the bottom 20b may be located on the top surface of the P-type cladding layer 24b, or may be located between the bottom and top surfaces of the P-type cladding layer 24b.

[0047] The P-type cladding layer 24b is disposed above the first P-type composition gradient layer 24a and is a P-type semiconductor layer having a lower refractive index than the active layer 23. In this embodiment, the P-type cladding layer 24b is a P-type Al 0.70 Ga0.30 This is the As layer.

[0048] The first P-type composition gradient layer 24a is disposed above the active layer 23 and has a different composition depending on the position in the stacking direction. The band gap energy of the first P-type composition gradient layer 24a is 23 The band gap energy of the first P-type composition gradient layer 24a is between the band gap energy at the upper end (P-type guide layer 23g) of the active layer 23 and the band gap energy of the P-type cladding layer 24b. The band gap energy of the first P-type composition gradient layer 24a approaches the band gap energy of the P-type cladding layer 24b as the layer stacking direction position approaches the P-type cladding layer 24b, and approaches the band gap energy of the upper end of the active layer 23 as the layer stacking direction position approaches the active layer 23. The P-side semiconductor layer 24 has the first P-type composition gradient layer 24a, which alleviates the abrupt change in band gap energy between the active layer 23 and the P-type cladding layer 24b. Therefore, the device resistance of the semiconductor laser device 10 can be reduced. In this embodiment, the first P-type composition gradient layer 24a is a 0.05 μm-thick P-type Al y1 Ga 1-y1 The Al composition ratio y1 of the first P-type composition gradient layer 24a is 0.28 near the interface with the active layer 23, and 0.70 near the interface with the P-type cladding layer 24b, and increases with increasing distance from the P-type cladding layer 24b in the stacking direction.

[0049] The second P-type compositional gradient layer 24c is disposed above the P-type cladding layer 24b and has a different composition depending on the position in the stacking direction. The bandgap energy of the second P-type compositional gradient layer 24c is between the bandgap energy of the P-type cladding layer 24b and the bandgap energy of the P-type contact layer 25. The bandgap energy of the second P-type compositional gradient layer 24c approaches the bandgap energy of the P-type cladding layer 24b as the layering direction position approaches the P-type cladding layer 24b, and approaches the bandgap energy of the P-type contact layer 25 as the layering direction position approaches the P-type contact layer 25. The P-side semiconductor layer 24 has the second P-type compositional gradient layer 24c, which alleviates the abrupt change in bandgap energy between the P-type cladding layer 24b and the P-type contact layer 25. Therefore, the device resistance of the semiconductor laser device 10 can be reduced. In this embodiment, the second P-type compositional gradient layer 24c is a 0.05 μm-thick P-type Al y2 Ga 1-y2 The Al composition ratio y2 of the second P-type composition gradient layer 24c is 0.70 near the interface with the P-type cladding layer 24b, and 0.15 near the interface with the P-type contact layer 25. The Al composition ratio y2 decreases with increasing distance from the P-type contact layer 25 in the stacking direction.

[0050] The P-type contact layer 25 is a layer disposed above the P-side semiconductor layer 24. The P-type contact layer 25 is disposed below the first P-side electrode 41 and is in contact with the first P-side electrode 41. The P-type contact layer 25 is a P-type semiconductor layer intentionally doped with impurities, for example, P-type GaAs. The impurity doped into the P-type contact layer 25 can be, for example, carbon. The doping concentration in the P-type contact layer 25 is, for example, 1.0×10 19 cm -3 In this embodiment, the P-type contact layer 25 is a P-type GaAs layer with a film thickness of 0.25 μm.

[0051] The insulating film 30 is an electrically insulating film disposed above the semiconductor laminate 10S and functions as a current blocking film. As shown in FIGS. 1, 2, and 4, the insulating film 30 covers a pair of side surfaces of the active layer 23 (i.e., both end surfaces in the X-axis direction of the active layer 23 shown in FIGS. 2 and 3). In this embodiment, the insulating film 30 covers the side surfaces of the N-side semiconductor layer 22, the active layer 23, the P-side semiconductor layer 24, and the P-type contact layer 25. The insulating film 30 also covers the entire upper surface of the semiconductor laminate 10S except for the current injection window 25a. As shown in FIGS. 1, 2, and 4, the insulating film 30 also covers the periphery of the current injection window 25a on the upper surface of the ridge portion 20r. The insulating film 30 has an opening 30a in a region corresponding to the current injection window 25a. The opening 30a is an opening formed in a portion of the insulating film 30 disposed above the ridge portion 20r. A current injection window 25a is formed on the upper surface of the ridge portion 20r by disposing the first p-side electrode 41 in the opening 30a of the insulating film 30. The insulating film 30 is made of an insulating material such as SiN or SiO2.

[0052] As shown in FIGS. 2 to 4, the insulating film 30 is disposed on the bottom 20b of the semiconductor laminate 10S. The region of the bottom 20b where the insulating film 30 is disposed (i.e., the interface between the bottom 20b and the insulating film 30) may be oxidized. In other words, the oxygen concentration in the bottom 20b may be higher than the oxygen concentration inside the semiconductor laminate 10S. The inside of the semiconductor laminate 10S refers to, for example, the region below the bottom 20b, which is part of the upper surface of the semiconductor laminate 10S. Oxidizing the bottom 20b improves the adhesion between the insulating film 30 and the bottom 20b. Therefore, it is possible to prevent the semiconductor laser device 10 from being damaged due to peeling of the insulating film 30.

[0053] Methods for promoting oxidation of the bottom 20b include forming an oxygen-containing film such as SiO2 as the insulating film 30, performing oxygen plasma treatment on the bottom 20b before forming the insulating film 30, and treating with a chemical solution that promotes oxidation, such as a mixture of tartaric acid and hydrogen peroxide.

[0054] The first P-side electrode 41 is a P-side electrode in contact with the P-type contact layer 25. The first P-side electrode 41 is disposed above the ridge portion 20r of the semiconductor laminate 10S and in contact with the current injection window 25a of the P-type contact layer 25 through the opening 30a in the insulating film 30. In this embodiment, as shown in FIGS. 1 to 4, the first P-side electrode 41 is also disposed above the bottom portion 20b and the wing portions 20w of the semiconductor laminate 10S through the insulating film 30. The first P-side electrode 41 contains at least one metal selected from the group consisting of Pt, Ti, Cr, Ni, Mo, and Au. In this embodiment, the first P-side electrode 41 includes a Ti layer in contact with the P-type contact layer 25, a Pt layer stacked on the Ti layer, and an Au layer stacked on the Pt layer.

[0055] The pad electrode 50 is a pad-shaped electrode disposed above the first P-side electrode 41. In this embodiment, both ends of the pad electrode 50 in the resonance direction are located between the two end faces 10F and 10R and the ridge portion 20r, respectively. In this manner, the pad electrode 50 is not disposed on the two end faces 10F and 10R. The pad electrode 50 is formed of, for example, an Au film.

[0056] The second p-side electrode 42 is a p-side electrode disposed above the pad electrode 50. In the present embodiment, the second p-side electrode 42 covers the pad electrode 50. The second p-side electrode 42 includes at least one metal selected from the group consisting of Pt, Ti, Cr, Ni, Mo, and Au. In the present embodiment, the second p-side electrode 42 includes a Ti layer, a Pt layer stacked on the Ti layer, and an Au layer stacked on the Pt layer.

[0057] The N-side electrode 60 is an electrode disposed on the lower main surface of the substrate 21 (i.e., the main surface on which the semiconductor laminate 10S is not disposed, out of the two opposing main surfaces of the substrate 21). The N-side electrode 60 includes, for example, an AuGe film, a Ni film, an Au film, a Ti film, a Pt film, and an Au film, which are laminated in this order from the substrate 21 side.

[0058] In the semiconductor laser device 10 having the above-described configuration, the peak position of the light intensity distribution in the stacking direction is located in the N-side semiconductor layer 22. This minimizes free carrier loss and maximizes the utilization efficiency of carriers injected into the active layer 23. As a result, the semiconductor laser device 10 can be operated with low driving voltage, low threshold current, and high slope efficiency, and an optical output of several tens of watts can be achieved with high efficiency and low driving current.

[0059] [2.Effects] The effects of the semiconductor laser device 10 according to this embodiment will be described. As described above, the semiconductor laser device 10 according to this embodiment includes a semiconductor stack 10S having a ridge portion 20r. As shown in FIG. 1, the bottom portion 20b surrounds the periphery of the ridge portion 20r. The P-side semiconductor layer 24 is exposed at the bottom portion 20b. The effects of this configuration according to this embodiment will be described with reference to FIGS. 8 to 12. FIG. 8 is a cross-sectional view showing the structure of a model used in a simulation of the semiconductor laser device 10 according to this embodiment. FIG. 9 is a graph showing simulation results of current spreading in the lateral direction (i.e., the X-axis direction) of the semiconductor laser device 10 according to this embodiment. FIG. 10 is a graph showing an enlarged view of a portion of FIG. 9. The horizontal axis in FIGS. 9 and 10 indicates the lateral position, and the vertical axis indicates a normalized value of the current flowing in the active layer 23. FIG. 11 is a graph showing simulation results of the lateral width of the near-field pattern (NFP) of the semiconductor laser device 10 according to this embodiment. 11, the horizontal axis represents the remaining thickness of the P-type contact layer 25 at the bottom 20b, and the vertical axis represents the NFP width in the horizontal direction. Fig. 12 is a graph showing the simulation results of current spreading in the resonance direction (i.e., the Y-axis direction) of the semiconductor laser device 10 according to this embodiment.

[0060] As shown in Fig. 8, the remaining thickness of the P-type contact layer 25 at the bottom 20b of the semiconductor laser device 10 is denoted as Tr. The remaining thickness of the P-type contact layer 25 is the distance from the lower surface of the P-type contact layer 25 to the bottom 20b. Figs. 9 and 10 show simulation results when the remaining thickness Tr of the P-type contact layer 25 is set to 0 nm, 10 nm, 20 nm, and 30 nm. In the simulation, the width of the ridge portion 20r (i.e., the dimension in the X-axis direction) is set to 230 µm, and the entire upper surface of the ridge portion 20r is used as the current injection window region.

[0061] As shown in FIGS. 9 and 10 , providing the bottom 20b around the ridge 20r, including in the lateral direction, can suppress current leakage from the ridge 20r in the lateral direction. Furthermore, as the remaining thickness of the P-type contact layer 25 decreases, the current leakage from the ridge 20r in the lateral direction decreases. In this embodiment, the P-side semiconductor layer 24 is exposed at the bottom 20b. That is, the remaining thickness of the P-type contact layer 25 is zero, so that the current leakage from the ridge 20r in the lateral direction can be minimized. Therefore, the semiconductor laser device 10 according to this embodiment can reduce the reactive current during laser oscillation, thereby improving the light emission efficiency and suppressing a decrease in laser light output. Note that the configuration of the semiconductor laser device 10 according to this embodiment is not limited thereto. The remaining thickness Tr of the P-type contact layer 25 at the bottom 20b of the semiconductor laser device 10 may be greater than zero. That is, the P-type contact layer 25 may be exposed at the bottom 20b. Even in such a configuration, by providing the bottom portion 20b around the ridge portion 20r as shown in FIGS. 9 and 10, it is possible to suppress current leaking from the ridge portion 20r to the outside of the ridge portion 20r.

[0062] 11, as the residual thickness of the P-type contact layer 25 is reduced, the NFP width of the semiconductor laser device 10 is reduced. That is, the NFP width can be reduced by providing the bottom 20b around the ridge portion 20r, including in the lateral direction, and reducing the residual thickness of the P-type contact layer 25. In this embodiment, the residual thickness of the P-type contact layer 25 is zero, so that the NFP width can be reduced to a value close to the width (230 μm) of the ridge portion 20r, and the divergence angle of the laser light can be suppressed.

[0063] 12 shows simulation results for the cases where a P-type contact layer 25 is present at the bottom 20b located between the ridge portion 20r and the end faces 10F and 10R, and for the cases where it is not present. When the P-type contact layer 25 is present at the bottom 20b, the remaining thickness Tr of the P-type contact layer 25 is 50 nm. The distance between the ridge portion 20r and the end faces 10F and 10R is 80 μm, and the length of the window region 10w (i.e., the dimension in the Y-axis direction) is 70 μm.

[0064] As shown in FIG. 12 , providing the bottom 20b between the ridge portion 20r and the end faces 10F and 10R can suppress the current flowing from the ridge portion 20r to the vicinity of the end faces 10F and 10R. Furthermore, eliminating the P-type contact layer 25 at the bottom 20b can further suppress the current flowing from the ridge portion 20r to the vicinity of the end faces 10F and 10R. In this embodiment, the P-side semiconductor layer 24 is exposed at the bottom 20b located between the ridge portion 20r and the end faces 10F and 10R. In other words, since the P-type contact layer 25 is not present at the bottom 20b located between the ridge portion 20r and the end faces 10F and 10R, the current flowing from the ridge portion 20r to the vicinity of the end faces 10F and 10R can be minimized. Therefore, the semiconductor laser device 10 according to this embodiment can suppress carrier diffusion into the window regions 10w formed near the end faces 10F and 10R, thereby suppressing the occurrence of COD. Furthermore, in this embodiment, it is possible to reduce carrier injection into the window region 10w that does not contribute to the amplification of the laser light, thereby increasing the light emission efficiency and the laser light output.

[0065] Furthermore, like the bottom 20b according to the present embodiment, the distance Db from the upper surface of the active layer 23 to the bottom 20b may be less than the film thickness of the P-side semiconductor layer 24. That is, at the bottom 20b, a part of the P-side semiconductor layer 24 may be removed. This further suppresses the current flowing from the ridge portion 20r to the vicinity of the end faces 10F and 10R.

[0066] As the distance Db decreases, the effective refractive index difference (Δn) between the inside and outside of the ridge portion 20r increases, as shown in FIG. 13. When the effective refractive index difference increases, the semiconductor laser device 10 oscillates as an index guided type rather than a gain guided type, and the horizontal divergence angle increases. Therefore, when the semiconductor laser device 10 is used in a system that uses an optical lens, this causes a decrease in the light capture efficiency. Therefore, the distance Db of the bottom portion 20b inside the resonator is set within a range that can suppress an increase in the effective refractive index difference. For example, the distance Db may be set to a value within a range in which the change in the effective refractive index difference is small (0.4 μm or more and 0.6 μm or less). Furthermore, when the effective refractive index difference is 2.0×10 -4 The distance Db may be set to 0.15 μm or more so that the following holds: This makes it possible to suppress current spread while suppressing an increase in the horizontal spread angle of the laser light.

[0067] If the length of the window region 10w in the resonance direction is greater than the length of the bottom portion 20b located between the facet 10F and the ridge portion 20r in the resonance direction, a window region 10w is also formed directly below the ridge portion 20r. Because the window region 10w located directly below the ridge portion 20r is located relatively far from the facets 10F and 10R, it is not very effective in suppressing COD at the facets 10F and 10R. Furthermore, because a relatively large current flows through the window region 10w located directly below the ridge portion 20r, the laser beam increases carrier injection into the window region 10w, which does not contribute to the amplification of the laser beam. Therefore, the length of the window region 10w in the resonance direction may be shorter than the length of the bottom portion 20b located between the facet 10F and the ridge portion 20r in the resonance direction. This reduces carrier injection into the window region 10w, thereby improving the light emission efficiency and laser beam output. The length in the resonance direction of the bottom portion 20b located between the end face 10F and the ridge portion 20r may be 80 μm or more.

[0068] The length of the window region 10w in the resonance direction may be, for example, 70 μm or more, which reduces the thermal load when forming the window region 10w, thereby preventing deterioration of the crystallinity of the active layer 23 in the region outside the window region 10w.

[0069] 4, both ends of the pad electrode 50 in the resonance direction are located between the two end faces 10F and 10R and the ridge portion 20r. In other words, since the pad electrode 50 is not located on the end faces, it is possible to reduce the mounting stress applied to the vicinity of the end faces 10F and 10R when mounting the upper surface of the P-side semiconductor layer 24 on a mounting base via solder. Furthermore, since a part of the pad electrode 50 is located on the bottom 20b near the end faces 10F and 10R, the pad electrode 50 can cover the upper surface and side surfaces of the ridge portion 20r, as well as the bottom 20b near the ridge portion 20r. This reduces the stress on the ridge portion 20r due to current injection. 20r Heat generated by Joule heat and non-radiative recombination of carriers in the semiconductor device can be effectively dissipated via the pad electrode 50.

[0070] Furthermore, by bringing the resonance direction end of the pad electrode 50 close to the facets 10F and 10R, the heat dissipation of the facets 10F and 10R can be improved. This makes it possible to suppress deterioration of the semiconductor laser device 10 due to heat. The distance between the resonance direction end of the pad electrode 50 and the facets 10F and 10R may be 15 μm or less. This further improves heat dissipation.

[0071] [3. Manufacturing method] A method for manufacturing the semiconductor laser device 10 according to this embodiment will be described with reference to Figs. 2 and 3, and Figs. 14 to 23. Figs. 14 to 23 are schematic cross-sectional views showing each step of the method for manufacturing the semiconductor laser device 10 according to this embodiment. Figs. 14, 16, 18, 20, and 22 show cross sections of the semiconductor laser device 10 taken along line II-II in Fig. 1 during the manufacturing process. Figs. 15, 17, 19, 21, and 23 show cross sections of the semiconductor laser device 10 taken along line III-III in Fig. 1 during the manufacturing process.

[0072] First, as shown in FIG. 14, an N-side semiconductor layer 22 is formed on the upper surface of a substrate 21, an active layer 23 is formed above the N-side semiconductor layer 22, a P-side semiconductor layer 24 is formed above the active layer 23, and a P-type contact layer 25 is formed above the P-side semiconductor layer 24.

[0073] In this embodiment, an N-side semiconductor layer 22, an active layer 23, a P-side semiconductor layer 24, and a P-type contact layer 25 are sequentially grown by crystal growth on a substrate 21, which is an N-type GaAs wafer, using a crystal growth technique based on metalorganic chemical vapor deposition (MOCVD).

[0074] As the N-side semiconductor layer 22, an N-type buffer layer 22a, a first N-type compositionally graded layer 22b, an N-type cladding layer 22c, and a second N-type compositionally graded layer 22d are grown sequentially on the substrate 21 by crystal growth.

[0075] As the active layer 23, an N-type guide layer 23a, a second N-side barrier layer 23b, a first N-side barrier layer 23c, a well layer 23d, a first P-side barrier layer 23e, a second P-side barrier layer 23f, and a P-type guide layer 23g are sequentially grown by crystal growth on the N-side semiconductor layer 22.

[0076] As the P-side semiconductor layer 24, a first P-type compositionally graded layer 24a, a P-type cladding layer 24b, and a second P-type compositionally graded layer 24c are grown in this order on the active layer 23 by crystal growth.

[0077] Next, as shown in FIG. 15 , window regions 10w are formed near the end faces 10F and 10R. Specifically, the window regions 10w are formed on the end faces 10F and 10R of the semiconductor laminate 10S. Methods for forming the window regions 10w generally include impurity diffusion and vacancy diffusion. In this embodiment, the window regions are formed by vacancy diffusion. This is because, in an ultra-high-power semiconductor laser device 10 exceeding 10 W per emitter, reducing the amount of light absorption by reducing loss is important. For example, if the window regions 10w are formed by impurity diffusion, the impurities increase light absorption, making it difficult to reduce light absorption loss. On the other hand, since the vacancy diffusion method does not use impurities, forming the window regions 10w by vacancy diffusion can reduce light absorption loss due to the introduction of impurities.

[0078] In the vacancy diffusion method, the window region 10w can be formed by subjecting the semiconductor laminate 10S to rapid high-temperature treatment. For example, a protective film that generates Ga vacancies during high-temperature treatment is formed by forming the window region. Uhan Conductor laminate 10S AreaAfter forming the active layer 23, the active layer 23 is exposed to extremely high temperatures of 750°C to 950°C, which is close to the crystal growth temperature, to diffuse the Ga vacancies. This allows the vacancies and Group III elements to interdiffuse, resulting in disordering of the quantum well structure of the active layer 23 and the formation of windows (transparent regions). As a result, the band gap of the active layer 23 can be increased, and the region where the quantum well structure is disordered can function as the window region 10w. Furthermore, in the region other than the window region 10w, a protective film that suppresses the generation of Ga vacancies during high-temperature treatment can be formed to suppress disordering of the quantum well structure. In this embodiment, the window region 10w is formed by the vacancy diffusion method, but it may also be formed by other methods, such as impurity diffusion.

[0079] Next, as shown in FIG. 16, recesses for defining the ridge portion 20r and the wing portions 20w are formed in the P-type contact layer 25. The bottom surfaces of the formed recesses are the bottom portions 20b. Specifically, a mask made of SiO2 or the like is formed in a predetermined pattern on the P-type contact layer 25 by photolithography, and then the recesses are formed by wet etching, thereby forming the ridge portion 20r and the wing portions 20w. Meanwhile, as shown in FIG. 17, bottom portions 20b are formed in place of the ridge portion 20r near the end face 10F of the semiconductor laser device 10. Note that recesses may be formed at positions where separation grooves 20t for singulation are to be formed at both ends of the semiconductor laser device 10 in the X-axis direction. The recesses extend in the resonance direction.

[0080] 18 and 19, separation grooves 20t having inclined surfaces are formed at both ends in the X-axis direction of the semiconductor laminate 10S. Specifically, a mask made of SiO2 or the like is formed in a predetermined pattern on the P-side semiconductor layer 24 using photolithography, and then wet etching is performed from the P-side semiconductor layer 24 to partway through the N-side semiconductor layer 22, thereby forming the separation grooves 20t that are inclined at both ends in the X-axis direction of the semiconductor laminate 10S. The separation grooves 20t are used when singulating the semiconductor laser elements 10, and extend in the resonance direction.

[0081] The etching solution used to form the separation grooves 20t may be, for example, a sulfuric acid-based etching solution. In this case, an etching solution containing sulfuric acid, hydrogen peroxide, and water in a ratio of 1:1:10 may be used. The etching solution is not limited to sulfuric acid-based etching solutions, and may be an organic acid-based etching solution or an ammonia-based etching solution.

[0082] The isolation trench 20t is formed by isotropic wet etching. This allows for the formation of inclined surfaces on the side surfaces of the semiconductor layers, thereby forming a constricted structure (i.e., an overhang structure) in the semiconductor layers. The inclination angle of the side surface of the isolation trench 20t varies depending on the Al composition ratio of the AlGaAs material in each of the semiconductor layers. Increasing the Al composition ratio of the AlGaAs material can increase the etching rate. Therefore, to form the inclined side surfaces in the semiconductor stack 10S shown in FIGS. 18 and 19, the Al composition ratio of the P-side semiconductor layer 24 is maximized, thereby maximizing the etching rate of the P-side semiconductor layer 24 in the lateral direction (X-axis direction) of the semiconductor stack 10S. This allows for the formation of the narrowest portion (the portion with the narrowest width in the horizontal direction) of the semiconductor stack 10S near the P-side semiconductor layer 24.

[0083] Next, the mask used to form the isolation trench 20t is removed with a hydrofluoric acid-based etching solution, and then a SiN film is deposited as the insulating film 30 over the entire surface above the substrate 21, as shown in Figures 20 and 21. After that, photolithography and etching are used to remove the insulating film 30 from the portion corresponding to the current injection window 25a, thereby forming an opening 30a. Note that the insulating film 30 from the portion corresponding to the non-current injection region is not removed.

[0084] The insulating film 30 can be etched by wet etching using a hydrofluoric acid-based etching solution or dry etching using reactive ion etching (RIE). The insulating film 30 is not limited to a SiN film, but may be a SiO2 film or the like. The insulating film 30 may be formed by plasma-enhanced chemical vapor deposition (hereinafter referred to as PCVD) in this embodiment. The source gas for forming the insulating film 30 may be a mixed gas of SiH4, CF4, NH3, NO, N2, or the like.

[0085] In this embodiment, the deposition technique is the PCVD method, and the source gas is a mixed gas of SiH4, NH3, and N2. The deposition conditions can be, but are not limited to, a SiH4 volume content in the mixed gas of 5% to 18%, a temperature of the lower electrode on which the semiconductor substrate is placed of 150°C to 350°C, a pressure in the chamber of 50 Pa to 200 Pa, and an RF power of 100 W to 400 W.

[0086] When a SiN film is used as the insulating film 30, the source gas does not contain O, so the surface of the bottom portion 20b is less likely to be oxidized. When a SiO film is used as the insulating film 30, a mixed gas of SiH, N, O, and N is used as the source gas.

[0087] 22 and 23, a P-side electrode is formed on the semiconductor laminate 10S. In the present embodiment, a first P-side electrode 41, a pad electrode 50, and a second P-side electrode 42 are formed in this order on the P-type contact layer 25 as the P-side electrodes.

[0088] Specifically, a first P-side electrode 41 made of a laminated film of Ti, Pt, and Au films is formed as a base electrode by electron beam evaporation. Then, a pad electrode 50 made of an Au-plated film is formed by electrolytic plating. Then, the pad electrode 50 near the end faces is selectively removed using photolithography, etching, and lift-off techniques. An iodine solution can be used as an etchant for etching the pad electrode 50 made of the Au-plated film. Then, a second P-side electrode 42 made of a laminated film of Ti, Pt, and Au films is formed on the pad electrode 50 by electron beam evaporation. In this way, the first P-side electrode 41 and the second P-side electrode 42 are formed over almost the entire length in the resonance direction, but the pad electrode 50 is not formed near the end faces 10F and 10R.

[0089] 2 and 3, an N-side electrode 60 is formed on the lower main surface of the substrate 21. Specifically, the N-side electrode 60 is formed by depositing an AuGe film, a Ni film, an Au film, a Ti film, a Pt film, and an Au film in this order from the substrate 21 side.

[0090] Thereafter, although not shown, the substrate 21 on which the semiconductor laminate 10S is formed is separated into bars by dicing or cleaving using a blade, and then further separated into chips by cutting along the separation grooves 20t, thereby manufacturing individual semiconductor laser elements 10.

[0091] [4. Modifications] Semiconductor laser elements according to modifications 1 to 8 To the childThe semiconductor laser devices according to Modifications 1 to 3 have a semiconductor laminate 10S similar to that of the semiconductor laser device 10 according to the embodiment, but the layer configuration of part of the semiconductor laminate 10S is different. The semiconductor laser devices according to Modifications 4 to 8 differ from the semiconductor laser device 10 according to the embodiment in the configurations of the ridge portion 20r, the wing portions 20w, and the bottom portion 20b of the semiconductor laminate 10S. The following will mainly describe the configurations of the semiconductor laser devices according to Modifications 1 to 8 that are different from the semiconductor laser device 10 according to the embodiment.

[0092] [4-1. Variation 1] The configuration of the semiconductor laser device according to the first modification will be described.

[0093] The first N-type composition gradient layer 22b of the semiconductor laser device according to the first modification is an N-type Al x1 Ga 1-x1 The Al composition ratio x1 of the first N-type composition gradient layer 22b is 0.15 near the interface with the N-type buffer layer 22a, and 0.353 near the interface with the N-type cladding layer 22c, and increases with increasing distance from the N-type cladding layer 22c.

[0094] The N-type cladding layer 22c of the semiconductor laser device according to the first modification is made of N-type Al 0.353 Ga 0.647 This is the As layer.

[0095] The second N-type composition gradient layer 22d of the semiconductor laser device according to the first modification is an N-type Al x2 Ga 1-x2 The Al composition ratio x2 of the second N-type composition gradient layer 22d is 0.353 near the interface with the N-type cladding layer 22c, and 0.323 near the interface with the active layer 23. The Al composition ratio x2 decreases with increasing distance from the active layer 23 in the stacking direction.

[0096] The N-type guide layer 23a of the semiconductor laser device according to the first modification is an N-type AlN layer having a thickness of 0.95 μm. 0.323 Ga 0.677This is the As layer.

[0097] The second N-side barrier layer 23b of the semiconductor laser device according to the first modification includes an N-type layer disposed above the N-type guide layer 23a and an undoped layer disposed above the N-type layer. The N-type layer is an N-type Al 0.0250 μm thick layer. 0.18 Ga 0.82 The N-type layer is doped with silicon as an impurity. The undoped layer is an Al layer with a thickness of 0.0065 μm. 0.18 Ga 0.82 This is the As layer.

[0098] The first N-side barrier layer 23c of the semiconductor laser device according to the first modification is an undoped AlN layer having a thickness of 0.0035 μm. 0.35 Ga 0.55 In 0.10 This is the As layer.

[0099] The well layer 23d of the semiconductor laser device according to the first modification is an undoped In layer having a thickness of 0.0060 μm. 0.11 Ga 0.89 This is the As layer.

[0100] The first P-side barrier layer 23e of the semiconductor laser device according to the first modification is an undoped Al 0.35 Ga 0.55 In 0.10 This is the As layer.

[0101] The second P-side barrier layer 23f of the semiconductor laser device according to the first modification has an undoped layer disposed above the first P-side barrier layer 23e and a P-type layer disposed above the undoped layer. The undoped layer is an Al 0.18 Ga 0.82 The P-type layer is a 0.025 μm thick P-type Al 0.18 Ga 0.82 The P-type layer is doped with carbon (C) as an impurity.

[0102] The P-type guide layer 23g of the semiconductor laser device according to the first modification is a P-type Al0.32 Ga 0.68 This is the As layer.

[0103] The first p-type composition gradient layer 24a of the semiconductor laser device according to the first modification is a p-type Al y1 Ga 1-y1 The Al composition ratio y1 of the first P-type composition gradient layer 24a is 0.32 near the interface with the active layer 23, and 0.70 near the interface with the P-type cladding layer 24b, and increases with increasing distance from the P-type cladding layer 24b in the stacking direction.

[0104] The semiconductor laser device according to the first modification having the above-described configuration also exhibits the same effects as the semiconductor laser device 10 according to the embodiment. The semiconductor laser device according to the first modification can obtain laser light with a wavelength in the 915 nm band.

[0105] [4-2. Variation 2] The configuration of the semiconductor laser device according to the second modification will be described.

[0106] The N-type buffer layer 22a of the semiconductor laser device according to the second modification is an N-type GaAs layer with a thickness of 0.10 μm.

[0107] The first N-type composition gradient layer 22b of the semiconductor laser device according to the second modification is an N-type Al x1 Ga 1-x1 The Al composition ratio x1 of the first N-type composition gradient layer 22b is 0.15 near the interface with the N-type buffer layer 22a, 0.25 near the interface with the N-type cladding layer 22c, and increases with increasing distance from the N-type cladding layer 22c.

[0108] The N-type cladding layer 22c of the semiconductor laser device according to the second modification is made of N-type AlN.sub.2O.sub.3 and has a thickness of 1.80 .mu.m. 0.25 Ga 0.75 This is the As layer.

[0109] The N-side semiconductor layer 22 of the semiconductor laser device according to Modification 2 does not have the second N-type composition gradient layer 22d. On the other hand, the N-type guide layer 23a of the active layer 23 of the semiconductor laser device according to Modification 2 has a third N-type guide layer, a second N-type guide layer arranged above the third N-type guide layer, and a first N-type guide layer arranged above the second N-type guide layer. The third N-type guide layer is an N-type Al 0.20 μm thick layer. 0.25 Ga 0.75 The second N-type guide layer is an N-type Al layer with a thickness of 0.60 μm. 0.23 Ga 0.77 The first N-type guide layer is an N-type Al layer with a thickness of 0.46 μm. 0.21 Ga 0.79 This is the As layer.

[0110] The second N-side barrier layer 23b of the semiconductor laser device according to the second modification includes an N-type layer disposed above the N-type guide layer 23a and an undoped layer disposed above the N-type layer. The N-type layer is an N-type Al 0.0268 μm thick layer. 0.16 Ga 0.84 The N-type layer is doped with silicon as an impurity. The undoped layer is an Al layer with a thickness of 0.0083 μm. 0.16 Ga 0.84 This is the As layer.

[0111] The second P-side barrier layer 23f of the semiconductor laser device according to the second modification is an Al 0.16 Ga 0.84 This is the As layer.

[0112] The P-type guide layer 23g of the semiconductor laser device according to the second modification is a P-type Al z1 Ga 1-z1 The Al composition ratio of the p-type guide layer 23g is z 1 is 0.19 near the interface with the second P-side barrier layer 23f, 0.21 near the interface with the P-side semiconductor layer 24, and increases as the position in the stacking direction approaches the P-side semiconductor layer 24.

[0113] The first P-type composition gradient layer 24a of the semiconductor laser device according to the second modification is a P-type Al y1 Ga 1-y1 The Al composition ratio y1 of the first P-type composition gradient layer 24a is 0.21 near the interface with the active layer 23, and 0.70 near the interface with the P-type cladding layer 24b, and increases with increasing distance from the P-type cladding layer 24b in the stacking direction.

[0114] The P-type cladding layer 24b of the semiconductor laser device according to the second modification is a P-type Al 0.70 Ga 0.30 This is the As layer.

[0115] The semiconductor laser device according to the second modification having the above-described configuration also achieves the same effects as those of the semiconductor laser device 10 according to the embodiment.

[0116] [4-3. Variation 3] The configuration of the semiconductor laser device according to the third modification will be described.

[0117] The N-type buffer layer 22a of the semiconductor laser device according to the third modification is an N-type GaAs layer with a thickness of 0.10 μm.

[0118] The first N-type composition gradient layer 22b of the semiconductor laser device according to the third modification is an N-type Al x1 Ga 1-x1 The Al composition ratio x1 of the first N-type composition gradient layer 22b is 0.15 near the interface with the N-type buffer layer 22a, and 0.24 near the interface with the N-type cladding layer 22c, and increases with increasing distance from the N-type cladding layer 22c.

[0119] The N-type cladding layer 22c of the semiconductor laser device according to the third modification is made of N-type AlN.sub.2O.sub.3 and has a thickness of 1.80 .mu.m. 0.24 Ga 0.76 This is the As layer.

[0120] The second N-type composition gradient layer 22d of the semiconductor laser device according to the third modification is an N-type Al x2 Ga 1-x2 The Al composition ratio x2 of the second N-type composition gradient layer 22d is 0.24 near the interface with the N-type cladding layer 22c, and 0.22 near the interface with the active layer 23. The Al composition ratio x2 decreases with increasing distance from the active layer 23 in the stacking direction.

[0121] The N-type guide layer 23a of the semiconductor laser device according to the third modification includes a second N-type guide layer and a first N-type guide layer disposed above the second N-type guide layer. The second N-type guide layer is an N-type Al 1N 2O 3 layer having a thickness of 0.40 μm. z2 Ga 1-z2 The Al composition ratio z2 of the second N-type guide layer is 0.22 near the interface with the N-side semiconductor layer 22, and the Al composition ratio z2 of the first N-type guide layer is 0.22 near the interface with the N-side semiconductor layer 22. Type The thickness is 0.19 near the interface with the guide layer, and the thickness is 0.19 near the interface with the guide layer. Type The first N-type guide layer is an N-type Al layer with a thickness of 0.09 μm. 0.19 Ga 0.81 This is the As layer.

[0122] The second N-side barrier layer 23b of the semiconductor laser device according to the third modification includes an N-type layer disposed above the N-type guide layer 23a and an undoped layer disposed above the N-type layer. The N-type layer is an N-type Al 0.0268 μm thick layer. 0.16 Ga 0.84 The N-type layer is doped with silicon as an impurity. The undoped layer is an Al layer with a thickness of 0.0083 μm. 0.16 Ga 0.84 This is the As layer.

[0123] The second P-side barrier layer 23f of the semiconductor laser device according to the third modification is an Al 0.16 Ga 0.84 This is the As layer.

[0124] The P-type guide layer 23g of the semiconductor laser device according to the third modification includes a first P-type guide layer and a second P-type guide layer disposed above the first P-type guide layer. The first P-type guide layer is a P-type Al 0.01 μm thick layer. 0.19 Ga 0.81 The second P-type guide layer is a P-type Al layer with a thickness of 0.28 μm. z1 Ga 1-z1 The Al composition ratio z1 of the second P-type guide layer is 0.19 near the interface with the first P-side guide layer, and 0.21 near the interface with the P-side semiconductor layer 24, and increases as the position in the stacking direction approaches the P-side semiconductor layer 24.

[0125] The first P-type composition gradient layer 24a of the semiconductor laser device according to the third modification is a P-type Al y1 Ga 1-y1 The Al composition ratio y1 of the first P-type composition gradient layer 24a is 0.21 near the interface with the active layer 23, and 0.70 near the interface with the P-type cladding layer 24b, and increases with increasing distance from the P-type cladding layer 24b in the stacking direction.

[0126] The P-type cladding layer 24b of the semiconductor laser device according to the third modification is a P-type Al 0.70 Ga 0.30 This is the As layer.

[0127] The semiconductor laser device according to the third modification having the above-described configuration also achieves the same effects as those of the semiconductor laser device 10 according to the embodiment.

[0128] [4-4. Variation 4] The semiconductor laser device according to Modification 4 will be described with reference to FIG. 24. FIG. 24 is a schematic plan view showing the overall configuration of a semiconductor laser device 110 according to Modification 4. As shown in FIG. 24, the semiconductor laser device 110 according to Modification 4 differs from the semiconductor laser device 10 according to the embodiment in that it does not have wing portions 20w. The region where the wing portions 20w are arranged in the semiconductor laser device 10 according to the embodiment is different from the region where the wing portions 20w are arranged in the semiconductor laser device according to Modification 4.110 In the example shown in FIG.

[0129] The semiconductor laser device 110 according to the fourth modification having the above-described configuration also exhibits the same effects as the semiconductor laser device 10 according to the embodiment, except for the effects provided by the wing portions 20w.

[0130] [4-5. Variation 5] The semiconductor laser device according to Modification 5 will be described with reference to Fig. 25. Fig. 25 is a schematic plan view showing the overall configuration of a semiconductor laser device 210 according to Modification 5. As shown in Fig. 25, the semiconductor laser device 210 according to Modification 5 differs from the semiconductor laser device 10 according to the embodiment in that it has bottom portions 20b on the outer sides of the wing portions 20w in the lateral direction.

[0131] The semiconductor laser device 210 according to the fifth modification having the above-described configuration also achieves the same effects as the semiconductor laser device 10 according to the embodiment. Furthermore, according to the semiconductor laser device 210 according to the fifth modification, the bottom portions 20b are disposed on both lateral sides of the wing portions 20w, thereby improving the adhesion of the insulating film 30 to the semiconductor laminate 10S.

[0132] [4-6. Variation 6] A semiconductor laser device according to Modification 6 will be described with reference to FIG. 26. FIG. 26 is a schematic plan view showing the overall configuration of a semiconductor laser device 310 according to Modification 6. As shown in FIG. 26, in the semiconductor laser device 310 according to Modification 6, the bottom portion 20b surrounds the periphery of the wing portion 20w. That is, the bottom portion 20b is disposed on the lateral outer side of the wing portion 20w and between the wing portion 20w and the end faces 10F and 10R. In Modification 6, the wing portion 20w is spaced apart from the end faces 10F and 10R. Furthermore, the distances from the wing portion 20w to the end faces 10F and 10R may be greater than the distances from the ridge portion 20r to the end faces 10F and 10R.

[0133] The semiconductor laser device 310 according to the sixth modification having the above-described configuration also achieves the same effects as the semiconductor laser device 10 according to the embodiment. Furthermore, according to the semiconductor laser device 310 according to the sixth modification, the bottom portion 20b is disposed around the periphery of the wing portion 20w, thereby improving the adhesion of the insulating film 30 to the semiconductor laminate 10S.

[0134] [4-7. Variation 7] A semiconductor laser device according to Modification 7 will be described with reference to FIG. 27. FIG. 27 is a schematic plan view showing the overall configuration of a semiconductor laser device 410 according to Modification 7. The semiconductor laser device 410 according to Modification 7 differs from the semiconductor laser device 10 according to the embodiment in that dummy ridges 420r are arranged between the ridge 20r and each of the end faces 10F and 10R. The dummy ridges 420r are portions that protrude upward from the bottom 20b, similar to the ridge 20r. The dummy ridges 420r are adjacent to the ridge 20r via the bottom 20b. In Modification 7, the height of the dummy ridges 420r from the bottom 20b is equal to the height of the ridge 20r from the bottom 20b. The width of the dummy ridges 420r (i.e., the dimension in the X-axis direction) is equal to the width of the ridge 20r, and the dummy ridges 420r have a rectangular shape in top view. The dummy ridge portion 420r contacts the end face 10F or 10R.

[0135] The semiconductor laser device 410 according to the seventh modification having the above-described configuration also achieves the same effects as the semiconductor laser device 10 according to the embodiment. 410 According to the present invention, by providing the dummy ridge portion 420r, for example, a semiconductor laser element 410When mounting the semiconductor laser element 410, stress applied to the semiconductor laser element 410 is dispersed to the dummy ridge portion 420r, thereby preventing the stress from concentrating only on the ridge portion 20r. Therefore, damage to the ridge portion 20r can be prevented. Furthermore, when the AlGaAs layer is exposed at the bottom portion 20b, the insulating film 30 is likely to peel off in the region where the insulating film 30 contacts the bottom portion 20b due to poor adhesion between the insulating film 30 and the bottom portion 20b. With the semiconductor laser element 410 according to the seventh modification, a portion of the region where the AlGaAs layer is exposed between the end faces 10F and 10R and the ridge portion 20r can be replaced with a dummy ridge portion 420r made of GaAs, thereby improving adhesion between the insulating film 30 and the semiconductor laminate 10S.

[0136] [4-8. Variation 8] A semiconductor laser device according to Modification 8 will be described with reference to FIGS. 28 and 29 . FIGS. 28 and 29 are a schematic plan view and a cross-sectional view, respectively, showing the overall configuration of a semiconductor laser device 510 according to Modification 8. FIG. 29 shows a cross section taken along line XXIX-XXIX in FIG. 28 near the facet 10F. As shown in FIGS. 28 and 29 , the semiconductor laser device 510 according to Modification 8 differs from the semiconductor laser device 10 according to the embodiment in that dummy ridges 520r are disposed between the ridge 20r and each of the facets 10F and 10R, similar to Modification 7. The dummy ridges 520r according to Modification 8 are integrated with the wing portions 20w. In other words, the regions of the bottom 20b between the dummy ridges 420r and the wing portions 20w according to Modification 7, adjacent to the facets 10F and 10R, are replaced with the dummy ridges 520r. That is, the bottom portion 20b does not contact the end faces 10F and 10R (see FIG. 29).

[0137] The semiconductor laser device according to Modification 8 having the above-described configuration 510 In this case, the same effects as those of the semiconductor laser device 10 according to the embodiment can be achieved. 510 According to the present invention, by providing the dummy ridge portion 520r, for example, a semiconductor laser element 510When mounting the semiconductor laser element 510, the stress applied to the semiconductor laser element 510 is dispersed to the dummy ridge portion 520r, so that the stress can be prevented from concentrating only on the ridge portion 20r. Therefore, the ridge portion 20r can be prevented from being damaged. Furthermore, when the AlGaAs layer is exposed at the bottom portion 20b, the adhesion between the insulating film 30 and the bottom portion 20b is poor, so peeling of the insulating film 30 is likely to occur in the region where the insulating film 30 contacts the bottom portion 20b. Modified Example 8 Semiconductor laser element related to 510 According to this modification, a part of the region where the AlGaAs layer is exposed between the end faces 10F and 10R and the ridge portion 20r can be replaced with a dummy ridge portion 520r made of GaAs, thereby improving the adhesion between the insulating film 30 and the semiconductor laminate 10S. Furthermore, in the semiconductor laser device 510 according to the eighth modification, the bottom portion 20b does not contact the end faces 10F and 10R, so the contact surface between the insulating film 30 and the bottom portion 20b, which has poor adhesion, is not exposed from the end faces 10F and 10R. Therefore, peeling of the insulating film 30 can be further suppressed.

[0138] (Variations, etc.) Although the semiconductor laser device according to the present disclosure has been described above based on the respective embodiments, the present disclosure is not limited to the above-described respective embodiments.

[0139] For example, in the above-described Modifications 1 to 8, the distance Db from the top surface of the active layer 23 to the bottom 20b may be equal to or greater than the film thickness of the P-side semiconductor layer 24, or may be less than the film thickness of the P-side semiconductor layer 24. In other words, either the P-type contact layer 25 or the P-side semiconductor layer 24 may be exposed at the bottom 20b.

[0140] This disclosure also includes forms obtained by applying various modifications to the above-mentioned embodiments that a person skilled in the art would conceive, and forms realized by arbitrarily combining the components and functions of the above-mentioned embodiments within the scope of the present disclosure. [Industrial Applicability]

[0141] The semiconductor laser element and the like of the present disclosure can be applied, for example, as a highly efficient light source for a processing machine. [Explanation of symbols]

[0142] 10, 110, 210, 310, 410, 510 Semiconductor laser element 10F, 10R end face 10S Semiconductor laminate 10w window area 20b bottom 20r Ridge 20t separation groove 20w wing part 21 PCB 22 N-side semiconductor layer 22a N-type buffer layer 22b First N-type composition gradient layer 22c N-type cladding layer 22d Second N-type composition gradient layer 23 Active layer 23a N-type guide layer 23b Second N-side barrier layer 23c First N-side barrier layer 23d Well layer 23e First P-side barrier layer 23f Second P-side barrier layer 23g P-type guide layer 24 P-side semiconductor layer 24a First P-type compositionally graded layer 24b P-type cladding layer 24c Second P-type compositionally graded layer 25 P-type contact layer 25a Current injection window 30 insulating film 30a opening 41 First P side electrode 42 Second P side electrode 50 pad electrodes 60 N side electrode 71 First facet coating film 72 Second end face coating film 420r, 520r dummy ridge section

Claims

1. A semiconductor laser element that emits multi-transverse mode laser light, A substrate; a semiconductor stack disposed above the substrate, The semiconductor laminate is an N-side semiconductor layer disposed above the substrate; an active layer disposed above the N-side semiconductor layer; a P-side semiconductor layer disposed above the active layer; a P-type contact layer disposed above the P-side semiconductor layer, the semiconductor laminate has two end faces facing each other, the laser light resonates between the two end faces, the semiconductor laminate has a ridge portion extending in a resonance direction of the laser light, and a bottom portion that is a part of an upper surface of the semiconductor laminate and surrounds the ridge portion in a top view of the semiconductor laminate, The ridge portion protrudes upward from the bottom portion, the ridge portion is spaced apart from the two end faces, the ridge portion includes at least a part of the P-type contact layer, a current injection window, which is a region into which current is injected, is formed only on the ridge portion of the upper surface of the semiconductor laminate; The distance from the top surface of the active layer to the bottom surface is uniform. Semiconductor laser element.

2. The P-side semiconductor layer is exposed at the bottom.

2. The semiconductor laser device according to claim 1.

3. A semiconductor laser element that emits multi-transverse mode laser light, A substrate; a semiconductor stack disposed above the substrate, The semiconductor laminate is an N-side semiconductor layer disposed above the substrate; an active layer disposed above the N-side semiconductor layer; a P-side semiconductor layer disposed above the active layer; a P-type contact layer disposed above the P-side semiconductor layer, the semiconductor laminate has two end faces facing each other, the laser light resonates between the two end faces, the semiconductor laminate has a ridge portion extending in a resonance direction of the laser light, and a bottom portion that is a part of an upper surface of the semiconductor laminate and surrounds the ridge portion in a top view of the semiconductor laminate, The ridge portion protrudes upward from the bottom portion, the ridge portion is spaced apart from the two end faces, the ridge portion includes at least a part of the P-type contact layer, a current injection window, which is a region into which current is injected, is formed only on the ridge portion of the upper surface of the semiconductor laminate; The P-type contact layer is exposed at the bottom. Semiconductor laser element.

4. A semiconductor laser element that emits multi-transverse mode laser light, comprising: A substrate; a semiconductor stack disposed above the substrate, The semiconductor laminate is an N-side semiconductor layer disposed above the substrate; an active layer disposed above the N-side semiconductor layer; a P-side semiconductor layer disposed above the active layer; a P-type contact layer disposed above the P-side semiconductor layer, the semiconductor laminate has two end faces facing each other, the laser light resonates between the two end faces, the semiconductor laminate has a ridge portion extending in a resonance direction of the laser light, and a bottom portion that is a part of an upper surface of the semiconductor laminate and surrounds the ridge portion in a top view of the semiconductor laminate, The ridge portion protrudes upward from the bottom portion, the ridge portion is spaced apart from the two end faces, the ridge portion includes at least a part of the P-type contact layer, a current injection window, which is a region into which current is injected, is formed only on the ridge portion of the upper surface of the semiconductor laminate; the semiconductor laminate has a window region adjacent to a front end face, which is one of the two end faces and is an end face from which the laser light is emitted, The band gap energy of the active layer in the window region is greater than the band gap energy of the active layer in the region other than the window region. Semiconductor laser element.

5. the semiconductor laminate includes a part of the P-type contact layer and has two wing portions extending in the resonance direction; at least a part of the ridge portion is disposed between the two wing portions in a top view of the semiconductor laminate; Each of the two wing portions is adjacent to the ridge portion via the bottom portion, The two wing portions protrude upward from the bottom portion, The height of the two wing portions from the bottom is equal to the height of the ridge portion from the bottom.

5. The semiconductor laser device according to claim 1.

6. Each of the two wing portions extends to the two end faces.

6. The semiconductor laser device according to claim 5.

7. the semiconductor laminate has a window region adjacent to a front end face, which is one of the two end faces and is an end face from which the laser light is emitted, The band gap energy of the active layer in the window region is greater than the band gap energy of the active layer in the region other than the window region.

4. The semiconductor laser device according to claim 1.

8. The active layer in the region other than the window region has a quantum well structure.

8. The semiconductor laser device according to claim 7.

9. the window region is in contact with the front end surface; The length of the window region in the resonance direction is smaller than the length of the bottom portion located between the front end face and the ridge portion in the resonance direction.

8. The semiconductor laser device according to claim 7.

10. further comprising an insulating film disposed above the semiconductor laminate; The insulating film has an opening in a region corresponding to the current injection window.

10. The semiconductor laser device according to claim 1.

11. The oxygen concentration at the bottom is higher than the oxygen concentration inside the semiconductor laminate.

11. The semiconductor laser device according to claim 1.

12. a P-side electrode in contact with the P-type contact layer, and a pad electrode disposed above the P-side electrode; Both ends of the pad electrode in the resonance direction are located between the two end faces and the ridge portion.

12. The semiconductor laser device according to claim 1.

13. The semiconductor laser element has a gain-guided waveguide characteristic.

13. The semiconductor laser device according to claim 1.

14. The active layer in a region other than the window region has a quantum well structure.

5. The semiconductor laser device according to claim 4.

15. The window region is in contact with the front end surface, The length of the window region in the resonance direction is smaller than the length of the bottom portion located between the front end face and the ridge portion in the resonance direction.

5. The semiconductor laser device according to claim 4.

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