Semiconductor laser element and method for manufacturing semiconductor laser element

Abstract

A semiconductor laser element (100) comprises: a semiconductor laminate (100S); a translucent electroconductive film (113) disposed above the semiconductor laminate (100S); and a metal layer (115) disposed above the translucent electroconductive film (113). The semiconductor laminate (100S) comprises an n-type cladding layer (104), an active layer (106) disposed above the n-type cladding layer (104), a p-type cladding layer (108) disposed above the active layer (106), and a contact layer (110) disposed above the p-type cladding layer (108). The contact layer (110) is an (Alx2Ga1-x2)y2In1-y2As layer or an (Alx3Ga1-x3)y3In1-y3P layer. The translucent electroconductive film (113) is in contact with the contact layer (110). The oscillation wavelength of the semiconductor laser element (100) is 610 nm or greater. The film thickness of the translucent electroconductive film (113) is 150 nm or less.

Description

Semiconductor laser element and method for manufacturing semiconductor laser element

[0001] The present disclosure relates to a semiconductor laser device and a method for manufacturing a semiconductor laser device.

[0002] Conventionally, semiconductor laser elements have been used as light sources for processing devices, etc. There is a demand for even higher efficiency in light sources for processing devices. To improve the efficiency of semiconductor laser elements, for example, a technique for reducing waveguide loss is known (see, for example, Patent Document 1).

[0003] International Publication No. 2023 / 153330

[0004] However, semiconductor laser devices are required to have even higher efficiency.

[0005] The present disclosure is intended to solve such problems, and has an object to provide a highly efficient semiconductor laser element and the like.

[0006] In order to solve the above problems, one aspect of a semiconductor laser device according to the present disclosure includes a semiconductor laminate, a first light-transmitting conductive film disposed above the semiconductor laminate, and a metal layer disposed above the first light-transmitting conductive film, wherein the semiconductor laminate has an n-type cladding layer, an active layer disposed above the n-type cladding layer, a p-type cladding layer disposed above the active layer, and a contact layer disposed above the p-type cladding layer, and the contact layer is made of (Al ｘ２ Ga １－ｘ２ ) ｙ２ In １－ｙ２ As (0≦x2≦1, 0≦y2≦1) layer, or (Al ｘ３ Ga １－ｘ３ ) ｙ３ In １－ｙ３ P(0≦x3≦1, 0≦y3≦1) layer, the first translucent conductive film is in contact with the contact layer, the oscillation wavelength of the semiconductor laser element is 610 nm or more, and the film thickness of the first translucent conductive film is 150 nm or less.

[0007] In order to solve the above-described problems, another aspect of the semiconductor laser device according to the present disclosure includes a semiconductor laminate, a first light-transmitting conductive film disposed above the semiconductor laminate, and a metal layer disposed above the first light-transmitting conductive film, wherein the semiconductor laminate has an n-type cladding layer, an active layer disposed above the n-type cladding layer, a p-type cladding layer disposed above the active layer, and a contact layer disposed above the p-type cladding layer, and the contact layer is made of Al ｘ１ In ｙ１ Ga １－ｘ１－ｙ１ N (0≦x1≦1, 0≦y1≦1, 0≦x1+y1≦1) layer, the first translucent conductive film is in contact with the contact layer, the oscillation wavelength of the semiconductor laser element is 350 nm or more and 550 nm or less, and the film thickness of the first translucent conductive film is less than 100 nm.

[0008] In order to solve the above-described problems, one aspect of a method for manufacturing a semiconductor laser device according to the present disclosure includes a semiconductor laminate formation step of forming a semiconductor laminate on a substrate, a first light-transmitting conductive film formation step of forming a first light-transmitting conductive film above the semiconductor laminate, and a metal layer formation step of forming a metal layer above the first light-transmitting conductive film, wherein the semiconductor laminate has an n-type cladding layer, an active layer disposed above the n-type cladding layer, a p-type cladding layer disposed above the active layer, and a contact layer disposed above the p-type cladding layer, and the contact layer is made of (Al ｘ２ Ga １－ｘ２ ) ｙ２ In １－ｙ２ As (0≦x2≦1, 0≦y2≦1) layer, or (Al ｘ３ Ga １－ｘ３ ) ｙ３ In １－ｙ３ P(0≦x3≦1, 0≦y3≦1) layer, the first translucent conductive film is in contact with the contact layer, the oscillation wavelength of the semiconductor laser element is 610 nm or more, and the film thickness of the first translucent conductive film is 150 nm or less.

[0009] In order to solve the above-described problems, another aspect of a method for manufacturing a semiconductor laser device according to the present disclosure includes a semiconductor laminate formation step of forming a semiconductor laminate on a substrate, a first light-transmitting conductive film formation step of forming a first light-transmitting conductive film above the semiconductor laminate, and a metal layer formation step of forming a metal layer above the first light-transmitting conductive film, wherein the semiconductor laminate has an n-type cladding layer, an active layer disposed above the n-type cladding layer, a p-type cladding layer disposed above the active layer, and a contact layer disposed above the p-type cladding layer, and the contact layer is made of Al ｘ１ In ｙ１ Ga １－ｘ１－ｙ１ The semiconductor laser element has an oscillation wavelength of 350 nm or more and 550 nm or less, and the first translucent conductive film has a thickness of less than 100 nm.

[0010] According to the present disclosure, a highly efficient semiconductor laser element and the like can be provided.

[0011] 1 is a schematic plan view showing the overall configuration of a semiconductor laser device according to a first embodiment. FIG. 2 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device according to the first embodiment. FIG. 3 is a schematic cross-sectional view showing the configuration of an active layer included in the semiconductor laser device according to the first embodiment. FIG. 4 is a schematic cross-sectional view showing the configuration of a p-type barrier relaxation layer included in the semiconductor laser device according to the first embodiment. FIG. 5 is a schematic cross-sectional view showing a semiconductor stack formation step in a method for manufacturing a semiconductor laser device according to the first embodiment. FIG. 6 is a schematic cross-sectional view showing a ridge formation step in a method for manufacturing a semiconductor laser device according to the first embodiment. FIG. 7 is a schematic cross-sectional view showing a current blocking layer formation step in a method for manufacturing a semiconductor laser device according to the first embodiment. FIG. 8 is a schematic cross-sectional view showing a first translucent conductive film formation step in a method for manufacturing a semiconductor laser device according to the first embodiment. FIG. 9 is a schematic cross-sectional view showing a metal layer formation step in a method for manufacturing a semiconductor laser device according to the first embodiment. 1 is a schematic cross-sectional view showing an electrode formation step in a method for manufacturing a semiconductor laser device according to a first embodiment; FIG. 2 is a schematic cross-sectional view showing a polishing step in a method for manufacturing a semiconductor laser device according to a first embodiment; FIG. 3 is a schematic diagram showing an energy band near the interface between a contact layer and a translucent conductive film according to the first embodiment; FIG. 4 is a diagram showing the work function of a semiconductor material; FIG. 5 is a diagram showing the work function of a conductive film material; FIG. 6 is a diagram explaining a model used in calculating reflectance; FIG. 7 is a diagram showing the relationship between the film thickness of a translucent layer and the reflectance for light with a wavelength of 380 nm; FIG. 8 is a diagram showing the relationship between the film thickness of a translucent layer and the reflectance for light with a wavelength of 450 nm; FIG. 9 is a diagram showing the relationship between the film thickness of a translucent layer and the reflectance for light with a wavelength of 630 nm; FIG. 10 is a diagram showing the relationship between the film thickness of a translucent layer and the reflectance for light with a wavelength of 980 nm; FIG. 11 is a graph showing the maximum film thickness of a translucent conductive film that can make the reflectance of the translucent conductive film and the metal layer 80% or more; and FIG. 12 is a schematic diagram for explaining the influence of roughness of the upper surface of the translucent conductive film on the reflectance.1 is a schematic cross-sectional view of a surface illustrating the definition of surface roughness Rz. FIG. 2 is a diagram illustrating the relationship between the film thickness of a translucent conductive film and the reflectance when the metal layer is made of Ag. FIG. 3 is a diagram illustrating the relationship between the film thickness of a translucent conductive film and the reflectance when the metal layer is made of Au. FIG. 4 is a diagram illustrating the relationship between the film thickness of a translucent conductive film and the reflectance when the metal layer is made of Cu. FIG. 5 is a diagram illustrating the refractive index and extinction coefficient of each of ITO, Ag, Cu, and Au for light having a wavelength of 380 nm. FIG. 6 is a diagram illustrating the refractive index and extinction coefficient of each of ITO, Ag, Cu, and Au for light having a wavelength of 450 nm. FIG. 7 is a diagram illustrating the refractive index and extinction coefficient of each of ITO, Ag, Cu, and Au for light having a wavelength of 635 nm. FIG. 8 is a diagram illustrating the refractive index and extinction coefficient of each of ITO, Ag, Cu, and Au for light having a wavelength of 980 nm. FIG. 9 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser element according to a second embodiment. FIG. 10 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser element according to a third embodiment. 35 is an enlarged view of the inside of the dashed frame shown in FIG. 35; ...

[0012] 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.

[0013] 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.

[0014] In this specification, the terms "above" and "below" do not refer to vertically above and below in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. The terms "above" and "below" are used not only when two components are arranged with a gap between them and another component is present between them, but also when two components are arranged in contact with each other.

[0015] Furthermore, in this specification, terms indicating the relationship between elements, such as parallel, terms indicating the shape of elements, such as flat plate and uniform film thickness, and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about several percent.

[0016] First Embodiment A semiconductor laser device according to a first embodiment will be described.

[0017] [1-1. Overall Configuration] First, the overall configuration of the semiconductor laser device according to this embodiment will be described with reference to FIGS. 1 to 4. FIGS. 1 and 2 are a schematic plan view and a cross-sectional view, respectively, showing the overall configuration of the semiconductor laser device 100 according to this embodiment. FIG. 2 shows a cross section taken along line II-II in FIG. 1. FIGS. 3 and 4 are schematic cross-sectional views, respectively, showing the configuration of the active layer 106 and the p-type barrier buffer layer 109 included in the semiconductor laser device 100 according to this embodiment. FIG. 3 shows an enlarged view of only the cross section of the active layer 106 among the cross sections shown in FIG. 2. FIG. 4 shows an enlarged view of only a portion of the cross section of the p-type barrier buffer layer 109 among the cross sections shown in FIG. 2. Note that each figure shows an X-axis, a Y-axis, and a Z-axis, which are orthogonal to one another. The X-axis, the Y-axis, and the Z-axis are in a right-handed Cartesian coordinate system. The stacking direction of the semiconductor laser device 100 is parallel to the Z-axis, and the main emission direction of light (laser light) is parallel to the Y-axis.

[0018] As shown in FIG. 2 , the semiconductor laser device 100 includes a semiconductor stack 100S including a plurality of stacked semiconductor layers, and emits light from a facet 100F (see FIG. 1 ) perpendicular to the stacking direction (i.e., the Z-axis direction) of the semiconductor stack 100S. In this embodiment, the semiconductor laser device 100 is a semiconductor laser device having two facets 100F and 100R that form a cavity. For example, if the semiconductor laser device 100 is a high-power laser device, the facet 100F may be a front facet from which laser light is emitted, and the facet 100R may be a rear facet having a higher reflectivity than the facet 100F. The reflectivities of the facets are not limited thereto. For example, if the semiconductor laser device 100 is a low-power laser device, the reflectivity of the facet 100F may be equal to the reflectivity of the facet 100R.

[0019] In this embodiment, the oscillation wavelength of the semiconductor laser element 100, i.e., the peak wavelength of the laser light emitted by the semiconductor laser element 100, may be 350 nm or more and 550 nm or less, or 610 nm or more and 2000 nm or less, or 610 nm or more and 10 μm or less.

[0020] 2, the semiconductor laser device 100 includes a substrate 101, a semiconductor stack 100S, a current blocking layer 112, a light-transmitting conductive film 113, a metal layer 115, a barrier metal layer 117, a cover electrode 118, and an n-side electrode 119. The semiconductor stack 100S is disposed above the substrate 101 and includes a plurality of stacked semiconductor layers. In the example shown in FIG. 2, the semiconductor stack 100S includes a buffer layer 102, an n-type barrier buffer layer 103, an n-type cladding layer 104, an n-side guide layer 105, an active layer 106, a p-side guide layer 107, a p-type cladding layer 108, a p-type barrier buffer layer 109, and a contact layer 110.

[0021] The substrate 101 is a plate-like member that serves as a base for the semiconductor laser device 100. In this embodiment, the substrate 101 is an n-type substrate.

[0022] The buffer layer 102 is a semiconductor layer disposed between the substrate 101 and the n-type cladding layer 104 .

[0023] The n-type barrier buffer layer 103 is a semiconductor layer disposed between the substrate 101 and the n-type cladding layer 104. In this embodiment, the n-type barrier buffer layer 103 is disposed between the buffer layer 102 and the n-type cladding layer 104. The n-type barrier buffer layer 103 is a layer for mitigating the potential barrier in the conduction band between the substrate 101 and the n-type cladding layer 104. The band gap energy of the n-type barrier buffer layer 103 is larger than the band gap energy of the substrate 101 and smaller than the band gap energy of the n-type cladding layer 104. In this embodiment, the band gap energy of the n-type barrier buffer layer 103 is larger than the band gap energy of the buffer layer 102 and smaller than the band gap energy of the n-type cladding layer 104.

[0024] The n-type cladding layer 104 is an n-type cladding layer disposed above the substrate 101. The n-type cladding layer 104 has a smaller refractive index than the active layer 106 and a larger band gap energy.

[0025] The n-side guide layer 105 is an optical guide layer disposed above the n-type cladding layer 104. The n-side guide layer 105 is disposed between the n-type cladding layer 104 and the active layer 106. The n-side guide layer 105 has a higher refractive index and a smaller band gap energy than the n-type cladding layer 104.

[0026] The active layer 106 is a light-emitting layer disposed above the n-type cladding layer 104. In this embodiment, the active layer 106 is disposed above the n-side guide layer 105 and has a quantum well structure. As shown in FIG. 3 , the active layer 106 has a well layer 106 b and barrier layers 106 a and 106 c.

[0027] The barrier layer 106a is disposed above the n-side guide layer 105 and functions as a barrier for the quantum well structure.

[0028] The well layer 106b is disposed above the barrier layer 106a and functions as a well of the quantum well structure. The well layer 106b is disposed between the barrier layer 106a and the barrier layer 106c.

[0029] The barrier layer 106c is disposed above the well layer 106b and functions as a barrier for the quantum well structure.

[0030] In this embodiment, the active layer 106 has a single quantum well structure including a single well layer 106b, but the active layer 106 may have a multiple quantum well structure including a plurality of well layers.

[0031] The p-side guide layer 107 is an optical guide layer disposed above the active layer 106. The p-side guide layer 107 is disposed between the active layer 106 and the p-type cladding layer 108. The p-side guide layer 107 has a higher refractive index and a smaller band gap energy than the p-type cladding layer 108.

[0032] The p-type cladding layer 108 is a p-type cladding layer disposed above the active layer 106. In this embodiment, the p-type cladding layer 108 is disposed between the p-side guide layer 107 and the contact layer 110. The p-type cladding layer 108 has a lower refractive index and a larger band gap energy than the active layer 106. In this embodiment, the p-type cladding layer 108 includes a first p-type cladding layer 108a and a second p-type cladding layer 108b disposed above the first p-type cladding layer 108a. The impurity concentration of the second p-type cladding layer 108b is higher than the impurity concentration of the first p-type cladding layer 108a.

[0033] The p-type barrier buffer layer 109 is a semiconductor layer disposed between the p-type cladding layer 108 and the contact layer 110. The p-type barrier buffer layer 109 is a layer for buffering the potential barrier in the valence band between the p-type cladding layer 108 and the contact layer 110. The band gap energy of the p-type barrier buffer layer 109 is smaller than the band gap energy of the p-type cladding layer 108 and larger than the band gap energy of the contact layer 110.

[0034] The detailed configuration of the p-type barrier buffer layer 109 according to this embodiment will be described with reference to Fig. 4. As shown in Fig. 4, the p-type barrier buffer layer 109 has a first layer 109a, a second layer 109b disposed above the first layer 109a, and a third layer 109c disposed above the second layer 109b. The bandgap energy of the second layer 109b is smaller than that of the first layer 109a, and the bandgap energy of the third layer 109c is smaller than that of the second layer 109b.

[0035] The contact layer 110 is a p-type semiconductor layer disposed above the p-type cladding layer 108. In this embodiment, the contact layer 110 is disposed at the upper end of the semiconductor stack 100S and is in contact with the light-transmitting conductive film 113. The contact layer 110 is disposed at least on the upper end of the ridge 110R of the semiconductor stack 100S. The bandgap energy of the contact layer 110 is larger than the bandgap energy of the active layer 106. In other words, the bandgap energy of the contact layer 110 is larger than the bandgap energy of the well layer 106b.

[0036] As shown in FIGS. 1 and 2 , the semiconductor stack 100S has a ridge 110R that protrudes upward. The ridge 110R extends in the Y-axis direction. The semiconductor stack 100S also has two grooves 110T that are arranged along the ridge 110R and extend in the Y-axis direction, and two protruding portions 110P that protrude upward. A groove 110T is formed between each of the two protruding portions 110P and the ridge 110R. In this embodiment, the ridge 110R, the protruding portions 110P, and the groove 110T are formed in the p-type cladding layer 108, the p-type barrier buffer layer 109, and the contact layer 110. The lower ends of the ridge 110R and the protruding portions 110P are located in the second p-type cladding layer 108b.

[0037] The current blocking layer 112 is an electrical insulating layer disposed above the semiconductor laminate 100S. In this embodiment, the current blocking layer 112 is transparent to light having the oscillation wavelength of the semiconductor laser device 100. In the example shown in FIG. 2, the current blocking layer 112 is disposed on the upper surface of the semiconductor laminate 100S in a region other than the upper surface 110Ru of the ridge 110R. That is, the current blocking layer 112 is disposed on the side surface of the ridge 110R (i.e., the end surface of the ridge 110R in the X-axis direction), the bottom of the groove 110T (i.e., the portion of the upper surface of the semiconductor laminate 100S that is located lowest in the groove 110T), the side surface of the protrusion 110P on the groove 110T side (i.e., the end surface of the protrusion 110P on the groove 110T side of the two end surfaces in the X-axis direction), and the upper surface of the protrusion 110P. In this embodiment, the current blocking layer 112 is formed of SiO ２ It is a layer.

[0038] The translucent conductive film 113 is an example of a first translucent conductive film disposed above the semiconductor stack 100S, and is a conductive oxide film or a conductive nitride film. The translucent conductive film 113 is translucent to light having the oscillation wavelength of the semiconductor laser device 100. In this embodiment, the translucent conductive film 113 is disposed on the upper surface 110Ru of the ridge 110R and is in contact with the contact layer 110. The translucent conductive film 113 above the ridge 110R has a uniform film thickness above the center of the ridge 110R in the width direction of the ridge 110R (the X-axis direction in FIG. 2 ). The translucent conductive film 113 is disposed continuously (i.e., without interruption) in the width direction of the ridge 110R in a cross section parallel to the width direction and stacking direction of the ridge 110R. In this embodiment, the translucent conductive film 113 is also disposed in regions facing the side surfaces of the ridge 110R and in regions facing the bottoms of the grooves 110T. That is, the transparent conductive film 113 is disposed continuously from a region facing the bottom of one groove 110T to a region facing the bottom of the other groove 110T.

[0039] The metal layer 115 is a metal film disposed above the translucent conductive film 113. The metal layer 115 has a high reflectivity for light having the oscillation wavelength of the semiconductor laser device 100. In this embodiment, the reflectivity of the metal layer 115 for light having the oscillation wavelength is higher than the reflectivity of Pd for the oscillation wavelength. In this embodiment, the metal layer 115 is in contact with the translucent conductive film 113. The metal layer 115 is disposed in a region facing the upper surface 110Ru of the ridge 110R, a region facing the side surface of the ridge 110R, and a region facing the bottom of the groove 110T. In other words, the metal layer 115 is disposed continuously from a region facing the bottom of one groove 110T to a region facing the bottom of the other groove 110T. As shown in FIG. 2 , the position of an end of the metal layer 115 in the X-axis direction may coincide with the position of an end of the translucent conductive film 113 in the X-axis direction.

[0040] The barrier metal layer 117 is a metal film disposed above the metal layer 115. In this embodiment, the barrier metal layer 117 is disposed between the metal layer 115 and the cover electrode 118, and prevents metal atoms diffusing in the cover electrode 118 from reaching the metal layer 115. The barrier metal layer 117 covers the upper surface of the metal layer 115. In this embodiment, the barrier metal layer 117 is disposed above the metal layer 115 and the current blocking layer 112. In addition, the barrier metal layer 117 covers the entire upper surface of the semiconductor stack 100S.

[0041] In this embodiment, the barrier metal layer 117 is, for example, a single layer film of Pt, Ti, Cr, or the like, or a film made of a compound containing these metals. The barrier metal layer 117 may be, for example, a TiW film or a TiN film. The barrier metal layer 117 may also be a single layer film or a multilayer film of a conductive oxide containing at least one metal selected from Zn, In, Sn, Ga, and Ni. The conductive oxide may be, for example, ITO (In ２ O ３Alternatively, the barrier metal layer 117 may be made of, for example, Sn, IZO, GZO, or nickel oxide. When the cover electrode 118 is mounted on a submount or the like via AuSn solder or the like, the barrier metal layer 117 can prevent Sn diffusing in the cover electrode 118 from reaching the metal layer 115. This can prevent changes in the characteristics of the metal layer 115.

[0042] The cover electrode 118 is an electrode that covers the metal layer 115. In this embodiment, the cover electrode 118 is electrically connected to the metal layer 115 via the barrier metal layer 117. The cover electrode 118 covers the upper surface of the metal layer 115 via the barrier metal layer 117. In this embodiment, the cover electrode 118 is disposed above the metal layer 115 and the current blocking layer 112. The cover electrode 118 also covers the entire upper surface of the semiconductor stack 100S. In this embodiment, the cover electrode 118 is made of Au with a film thickness of 3000 nm.

[0043] The n-side electrode 119 is a conductive layer disposed on the lower surface of the substrate 101 (i.e., on the main surface of the substrate 101 opposite to the main surface on which the semiconductor stack 100S is disposed). The n-side electrode 119 is, for example, a single layer film formed of at least one of Cr, Ti, Ni, Pd, Pt, Ge, and Au, or a compound or multilayer film containing these metals.

[0044] [1-2. Manufacturing Method of Semiconductor Laser Device] A manufacturing method of the semiconductor laser device 100 according to this embodiment will be described with reference to Figs. 5 to 14 and the above-mentioned Fig. 2. Figs. 5 to 14 are schematic cross-sectional views showing each step of the manufacturing method of the semiconductor laser device 100 according to this embodiment. Figs. 5 to 14 show the same cross section as Fig. 2.

[0045] 5, first, a semiconductor stack 100S is formed on a substrate 101 (semiconductor stack formation step). More specifically, each semiconductor layer is epitaxially grown on the substrate 101. In forming the semiconductor stack 100S, for example, a metal organic chemical vapor deposition (MOCVD) method is used.

[0046] 6, in the semiconductor stack formation step, a ridge 110R is formed in the semiconductor stack 100S (ridge formation step). In this embodiment, the ridge 110R, two grooves 110T, and two protrusions 110P are formed in the semiconductor stack 100S. More specifically, a SiO 2 film is formed in regions corresponding to the upper surfaces of the ridge 110R and the protrusions 110P by photolithography. ２ A mask made of, for example, a silicon dioxide film is formed, and regions not covered by the mask are dry-etched to form the ridge 110R, the groove 110T, and the protrusion 110P. After the ridge 110R and the like are formed, the mask is removed by wet etching.

[0047] 7, a current blocking layer 112 is formed above the semiconductor stack 100S (current blocking layer formation process). In this embodiment, the current blocking layer 112 is formed in an area other than the upper surface 110Ru of the ridge 110R. That is, the current blocking layer 112 is formed on the side surface of the ridge 110R, the bottom of the groove 110T, the side surface of the protrusion 110P facing the groove 110T, and the upper surface of the protrusion 110P. The current blocking layer 112 is formed, for example, by low-pressure CVD (Chemical Vapor Deposition). The current blocking layer 112 may also be formed by atmospheric pressure CVD, plasma CVD, or the like.

[0048] Next, as shown in FIG. 8 , a translucent conductive film 113 is formed above the semiconductor stack 100S (first translucent conductive film formation process). In this embodiment, the translucent conductive film 113 is formed over the entire upper surface of the semiconductor stack 100S. That is, the translucent conductive film 113 is formed above the upper surface 110Ru of the ridge 110R and the current blocking layer 112. The translucent conductive film 113 contacts the contact layer 110 on the upper surface 110Ru of the ridge 110R. The translucent conductive film 113 may be formed by, for example, ECR (Electron Cyclotron Resonance) sputtering. This reduces the roughness of the upper surface of the translucent conductive film 113. That is, the flatness of the upper surface of the translucent conductive film 113 can be improved.

[0049] 9 , a metal layer 115 is formed above the translucent conductive film 113 (metal layer formation process). In this embodiment, the metal layer 115 is formed on the entire upper surface of the translucent conductive film 113. That is, the metal layer 115 is formed above the upper surface 110Ru of the ridge 110R and the current blocking layer 112. The metal layer 115 is in contact with the translucent conductive film 113. The metal layer 115 is formed by, for example, ECR sputtering.

[0050] Next, a portion of the translucent conductive film 113 and the metal layer 115 is removed (removal process). Specifically, as shown in FIG. 10 , a resist 190 is formed above the metal layer 115. The resist 190 is disposed at least in a region facing the upper surface 110Ru of the ridge 110R. In this embodiment, the resist 190 is disposed in positions facing the upper surface 110Ru and side surfaces of the ridge 110R, as well as in a region facing the bottom of the groove 110T. Next, as shown in FIG. 11 , regions of the translucent conductive film 113 and the metal layer 115 that are not covered with the resist 190 shown in FIG. 10 are removed by, for example, dry etching. After the dry etching, the resist 190 is removed using a remover or the like.

[0051] 12, the metal layer 115 is heated to perform a heat treatment of the metal layer 115 (heat treatment step), which stabilizes the state of the metal layer 115 and reduces the contact resistance between the translucent conductive film 113 and the semiconductor stack 100S.

[0052] 13, a barrier metal layer 117 and a cover electrode 118 are formed above the metal layer 115 (electrode formation process). In this embodiment, the barrier metal layer 117 is formed on the entire upper surface of the semiconductor stack 100S. The cover electrode 118 is formed so as to cover a portion of the upper surface of the barrier metal layer 117. The cover electrode 118 does not have to cover the entire upper surface of the semiconductor stack 100S. The barrier metal layer 117 and the cover electrode 118 are formed using, for example, electron beam evaporation or electrolytic plating.

[0053] 14, the lower surface of the substrate 101 (i.e., the main surface of the substrate 101 opposite to the main surface on which the semiconductor stack 100S is disposed) is polished (polishing step). This reduces the thickness of the substrate 101.

[0054] 2, an n-side electrode 119 is formed below the substrate 101 (n-side electrode forming step). The n-side electrode 119 is formed by, for example, electron beam evaporation.

[0055] Through the steps described above, the semiconductor laser device 100 according to this embodiment can be manufactured.

[0056] [1-3. Effects] The effects of the semiconductor laser device 100 according to this embodiment will be described.

[0057] [1-3-1. Contact Resistance] First, the contact resistance between the contact layer 110 and the transparent conductive film 113 of the semiconductor laser device 100 according to this embodiment will be described with reference to FIGS. 15 to 17. FIG. 15 is a schematic diagram showing an energy band near the interface between the contact layer 110 and the transparent conductive film 113 according to this embodiment. In FIG. 15, the Fermi level E Ｆ , vacuum rank E Ｓ , the energy at the bottom of the conduction band E Ｃ , and the energy of the top of the valence band E Ｖ 15 also shows the work function Φ of the contact layer 110. Ｓ , electron affinity χ, and work function Φ of the transparent conductive film 113 Ｍ , and the barrier height Φ in the valence band between the contact layer 110 and the transparent conductive film 113 Ｂ 16 and 17 are diagrams showing the work functions of semiconductor materials and conductive film materials, respectively.

[0058] The work function Φ of the transparent conductive film 113 shown in FIG. Ｍ is the work function Φ of the contact layer 110 Ｓ If the thickness is larger than the thickness of the contact layer 110, the junction between the contact layer 110 and the transparent conductive film 113 becomes an ohmic junction, and in this case, the contact resistance between the contact layer 110 and the transparent conductive film 113 can be reduced.

[0059] In this embodiment, when a GaAs layer is used as the contact layer 110, as shown in FIG. 16, the work function Φ Ｓ is about 4.1 eV. Therefore, the transparent conductive film 113 is preferably made of ITO, ZnO, IGZO (In ｘ Ga ｙ Zn １－ｘ－ｙ By using a conductive oxide film such as nickel oxide (ZnO:Ga) (0<x<1, 0<y<1), the junction between the contact layer 110 and the translucent conductive film 113 becomes an ohmic junction. When GZO (ZnO:Ga) is used as the translucent conductive film 113, the junction between the contact layer 110 and the translucent conductive film 113 becomes an ohmic junction, just as when ZnO is used. When a nickel oxide other than NiO is used as the translucent conductive film 113, the junction between the contact layer 110 and the translucent conductive film 113 becomes an ohmic junction, just as when NiO is used.

[0060] Therefore, the contact layer 110 is preferably a GaAs layer or a GaAs layer having a work function Φ Ｓ When a semiconductor layer having this structure is used, it is possible to reduce the contact resistance between the contact layer 110 and the light-transmitting conductive film 113. This allows the efficiency of the semiconductor laser device 100 to be increased.

[0061] 17, when a GaAs layer is used as the contact layer 110 and a conductive nitride film such as HfN, ZrN, TaN, or TiN is used as the translucent conductive film 113, the work function of these conductive nitride films is slightly lower than that of GaAs, and therefore the junction between the contact layer 110 and the translucent conductive film 113 is not a perfect ohmic junction, resulting in a slightly higher contact resistance. On the other hand, by arranging these conductive nitride films between the metal layer 115 made of, for example, Ag and the contact layer 110, it is possible to suppress the diffusion of Ag into the contact layer 110.

[0062] When a GaN layer is used as the contact layer 110, the work function Φ of GaN is Ｓis about 7 eV, the work function Φ of the contact layer 110 Ｓ is larger than the work function Φ of the transparent conductive film 113. Ｍ Therefore, the junction between the contact layer 110 and the light-transmitting conductive film 113 becomes a Schottky junction. However, when the metal layer 115 has a work function Φ Ｍ When an Ag layer having a work function Φ of 4.3 eV is used, a layer having a work function Φ of 4.3 eV is formed between the metal layer 115 and the contact layer 110. Ｍ By inserting the light-transmitting conductive film 113 having a large thickness, the contact resistance can be reduced compared to when the metal layer 115 and the contact layer 110 are directly bonded to each other. This enables the efficiency of the semiconductor laser device 100 to be increased.

[0063] [1-3-2. Reflection of Spontaneous Emission Light] The effect of reflecting spontaneous emission light in the light-transmitting conductive film 113 and the metal layer 115 of the semiconductor laser device 100 according to this embodiment will be described with reference to FIG.

[0064] The active layer 106 of the semiconductor laser device 100 emits stimulated emission light and spontaneous emission light. The stimulated emission light amplifies the laser light oscillated in the semiconductor laser device 100. That is, the stimulated emission light is emitted in the same direction as the laser light. On the other hand, the spontaneous emission light is emitted in an unspecified direction, and therefore most of it does not contribute to the oscillation and amplification of the laser light. That is, most of the spontaneous emission light is lost without being effectively utilized.

[0065] The semiconductor laser device 100 according to this embodiment includes a metal layer 115 having a high reflectivity. This makes it possible to increase the proportion of spontaneously emitted light L1 incident on the metal layer 115 that is reflected by the metal layer 115, as shown in FIG. 2 . At least a portion of the spontaneously emitted light L2 reflected by the metal layer 115 returns to the active layer 106. Therefore, by increasing the proportion of spontaneously emitted light L1 incident on the metal layer 115 that is reflected by the metal layer 115, it is possible to increase the amount of spontaneously emitted light L2 that is reabsorbed in the active layer 106. This makes it possible to increase the quantum efficiency of the semiconductor laser device 100. This makes it possible to improve the efficiency of the semiconductor laser device 100.

[0066] Furthermore, in this embodiment, as described above, the translucent conductive film 113 and the metal layer 115 are continuously disposed from the region facing the bottom of one groove 110T to the region facing the bottom of the other groove 110T. This allows not only spontaneous emission light traveling from near the center of the active layer 106 in the X-axis direction toward the top surface of the ridge 110R, but also spontaneous emission light traveling toward the side surface of the ridge 110R to be reflected by the translucent conductive film 113 and the metal layer 115 and returned to the active layer 106. This makes it possible to increase the amount of spontaneous emission light reabsorbed in the active layer 106. This therefore makes it possible to further improve the efficiency of the semiconductor laser device 100.

[0067] The relationship between the reflectance of the light-transmitting conductive film 113 and the metal layer 115 according to this embodiment and the thickness of the light-transmitting conductive film 113 will be described with reference to FIGS. 18 to 23. FIG. 18 is a diagram illustrating a model used in calculating the reflectance. FIGS. 19, 20, 21, and 22 are diagrams illustrating the relationship between the film thickness of the light-transmitting layer and the reflectance for light with wavelengths of 380 nm, 450 nm, 630 nm, and 980 nm, respectively. FIGS. 19 to 22 show the reflectance of the light-transmitting layer and the metal layer 115 when the metal layer 115 is made of Ag, Au, or Cu. FIGS. 19 to 22 also show the reflectance when the light-transmitting conductive film 113 is made of ITO. FIG. 23 is a graph showing the maximum film thickness of the light-transmitting conductive film 113 that can achieve a reflectance of 80% or more for the light-transmitting conductive film 113 and the metal layer 115. The vertical axis of FIG. 23 indicates the maximum film thickness of the light-transmitting conductive film 113 that can make the reflectance 80% or more.

[0068] The reflectance of the light-transmitting conductive film 113 and the metal layer 115 of the semiconductor laser device 100 according to this embodiment was calculated using the model shown in Fig. 18. In the model used in the calculation, as shown in Fig. 18, the light-transmitting conductive film 113 as a light-transmitting layer and the metal layer 115 are stacked on a semiconductor layer. Note that in this model, it is assumed that there is air above the metal layer 115, but the structure above the metal layer 115 has almost no effect on the reflectance. As the semiconductor layer of the model shown in Fig. 18, an AlGaN layer was used when the wavelength was 550 nm or less, and an AlGaAs layer was used when the wavelength was 610 nm or more.

[0069] In this calculation, the reflectance is calculated when incident light is incident from the semiconductor layer perpendicularly to the interface between the semiconductor layer and the light-transmitting conductive film 113. The reflectance is calculated based on the complex refractive index of the semiconductor layer, the complex refractive index and film thickness of the light-transmitting conductive film 113, and the complex refractive index and film thickness of the metal layer 115.

[0070] 18 , light is reflected at the interface between the semiconductor layer and the light-transmitting conductive film 113, and at the interface between the light-transmitting conductive film 113 and the metal layer 115. The reflected light used to calculate the reflectance in this calculation includes light reflected at both of these interfaces. In other words, the reflectance at the light-transmitting conductive film 113 and the metal layer 115 means the reflectance of a stacked film formed by combining the light-transmitting conductive film 113 and the metal layer 115.

[0071] 19 and 20 , for light having a wavelength of 350 nm or more and 550 nm or less, high reflectance can be achieved by using a metal layer 115 made of Ag. Specifically, a reflectance of 80% or more can be achieved. Furthermore, when using a metal layer 115 made of Ag, high reflectance can be obtained by setting the film thickness of the translucent conductive film 113 to 50 nm or less.

[0072] As shown in Figures 19 and 20, high reflectivity can be achieved when the film thickness of the translucent conductive film 113 is 0, but in this embodiment, from the perspective of the contact resistance described above, the film thickness of the translucent conductive film 113 is set to a value greater than 0.

[0073] 21 and 22 , for light having a wavelength of 610 nm or more, high reflectance can be achieved by using a metal layer 115 made of Ag, Cu, or Au. Specifically, a reflectance of 80% or more can be achieved. Furthermore, when using a metal layer 115 made of Ag, Cu, or Au, high reflectance can be obtained by setting the film thickness of the translucent conductive film 113 to 150 nm or less.

[0074] 19 to 22, the reflectance tends to decrease while oscillating as the film thickness of the translucent conductive film 113 increases. Therefore, a high reflectance can be achieved by setting the film thickness of the translucent conductive film 113 to a predetermined maximum film thickness or less. For example, the film thickness of the translucent conductive film 113 may be 150 nm or less. This allows a high reflectance to be achieved. Furthermore, the film thickness of the translucent conductive film 113 may be less than 100 nm. This allows an even higher reflectance to be achieved. In particular, a higher reflectance can be achieved when a metal layer 115 made of Ag is used.

[0075] Therefore, when a metal layer 115 made of Ag is used, the maximum film thickness of the translucent conductive film 113 at each wavelength where a reflectance of 80% or more can be obtained was calculated and plotted on the graph shown in FIG. 23 . As shown in FIG. 21 , when there are multiple ranges of film thickness of the translucent conductive film 113 where the reflectance is 80% or more, the maximum film thickness is defined as the maximum value in the smallest film thickness range (i.e., the range including a film thickness near 0). A curve obtained by approximating the plotted points using the least squares method is shown by a dashed line in FIG. 23 . This curve indicates the maximum film thickness of the translucent conductive film 113 at which the reflectance of the translucent conductive film 113 and the metal layer 115 can be 80% or more. This curve, where the wavelength is expressed in λ [nm], represents the maximum film thickness F of the translucent conductive film 113 at which a reflectance of 80% or more can be obtained. ＭＡＸ [nm] is expressed by the following formula:

[0076] F ＭＡＸ = 3.54 x 10 －９ λ ４ -9.97 x 10 －６ λ ３ +9.74 x 10 －３ λ ２-3.61λ+448

[0077] 23, the hatched area with dashed diagonal lines indicates the range of the film thickness of the light-transmitting conductive film 113 that can achieve a reflectance of 80% or more at each wavelength. Therefore, when the film thickness of the light-transmitting conductive film 113 is expressed as F(λ) [nm], the following inequality may hold:

[0078] F(λ)≦3.54×10 －９ λ ４ -9.97 x 10 －６ λ ３ +9.74 x 10 －３ λ ２ -3.61λ+448

[0079] This increases the reflectance of the transparent conductive film 113 and the metal layer 115. This allows more spontaneously emitted light to be returned to the active layer 106, thereby increasing the efficiency of the semiconductor laser device 100. ４ The factor 3.54 x 10 is multiplied by －９ The unit is [nm －３ ] and λ ３ Coefficient to be multiplied by -9.97 x 10 －６ The unit is [nm －２ ] and λ ２ The factor multiplied by 9.74 x 10 －３ The unit is [nm －１ ], the coefficient −3.61 multiplied by λ is a dimensionless number, and the unit of the constant 448 is [nm].

[0080] Note that the above inequality is an inequality obtained using the results calculated based on an example in which a metal layer 115 made of Ag is used. However, when the above inequality holds true even when a metal layer 115 made of another metal is used, the reflectance of the translucent conductive film 113 and the metal layer 115 can be increased compared to when the above inequality does not hold true.

[0081] Although FIG. 23 does not show the case where the wavelength is longer than 1000 nm, the above inequality is also applicable to the case where the wavelength is longer than 1000 nm.

[0082] The thickness of the light-transmitting conductive film 113 may be smaller than the thickness of the metal layer 115. By reducing the thickness of the light-transmitting conductive film 113 in this manner, the reflectance of the light-transmitting conductive film 113 and the metal layer 115 can be increased.

[0083] Next, the relationship between the roughness of the upper surface of the light-transmitting conductive film 113 and the reflectance of the light-transmitting conductive film 113 and the metal layer 115 will be described. It has been experimentally confirmed that when the upper surface of the light-transmitting conductive film 113 is rough (i.e., when the surface roughness of the upper surface is large), the reflectance of the light-transmitting conductive film 113 and the metal layer 115 decreases. The mechanism of such a decrease in reflectance will be described with reference to Fig. 24. Fig. 24 is a schematic diagram for explaining the effect of the roughness of the upper surface of the light-transmitting conductive film 113 on the reflectance.

[0084] 24 , when the flatness of the upper surface of the translucent conductive film 113 is poor (i.e., the upper surface is rough), it is presumed that free electrons in the metal layer 115 disposed on the upper surface of the translucent conductive film 113 localize in recesses formed on the upper surface of the translucent conductive film 113, causing plasma oscillation. It is presumed that the spontaneous emission light L1 incident on the translucent conductive film 113 is absorbed by the free electrons causing plasma oscillation in this manner, thereby reducing the intensity of the spontaneous emission light L2 reflected by the metal layer 115. It is presumed that this reduces the reflectance of the translucent conductive film 113 and the metal layer 115.

[0085] Experiments have confirmed that a decrease in reflectance occurs when the roughness Rz of the upper surface of the translucent conductive film 113 is greater than 2.0 nm. Therefore, the roughness Rz of the upper surface of the translucent conductive film 113 according to this embodiment may be 0.2 nm or more and 2.0 nm or less. This can suppress a decrease in reflectance at the translucent conductive film 113 and the metal layer 115. Note that, for example, when an ITO film is deposited as the translucent conductive film 113, it is expected that a step of approximately 0.2 nm to 0.3 nm, equivalent to the thickness of one atomic layer of ITO, will be formed on the surface of the ITO film. For this reason, the lower limit of the roughness Rz of the upper surface of the translucent conductive film 113 is set to 0.2 nm.

[0086] Here, the surface roughness Rz will be described with reference to FIG. 25 . FIG. 25 is a schematic cross-sectional view of a surface illustrating the definition of the surface roughness Rz. The surface roughness Rz is defined as the maximum height of the irregularities on the surface as shown in FIG. 25 . The roughness Rz of the upper surface of the translucent conductive film 113 is measured by measuring the maximum height of the irregularities in a cross section of the upper surface of the translucent conductive film 113. The cross section of the surface of the translucent conductive film 113 may be formed, for example, by cutting the translucent conductive film 113 along the thickness direction.

[0087] In the above-described method for manufacturing the semiconductor laser device 100, the roughness Rz of the upper surface of the formed light-transmitting conductive film 113 may be 0.2 nm or more and 2.0 nm or less. The roughness Rz of the upper surface of the light-transmitting conductive film 113 may be measured based on the height of the irregularities in a cross section of the upper surface of the light-transmitting conductive film 113.

[0088] Furthermore, as the thickness of the translucent conductive film 113 increases, the upper surface of the translucent conductive film 113 tends to become rougher. For example, when the thickness of the translucent conductive film 113 is 20 nm, the roughness Rz of the upper surface of the translucent conductive film 113 is 0.4 nm, and when the thickness of the translucent conductive film 113 is 200 nm, the roughness Rz of the upper surface of the translucent conductive film 113 is 2.0 nm. Therefore, the thickness of the translucent conductive film 113 may be 200 nm or less. This can reduce the roughness of the upper surface of the translucent conductive film 113.

[0089] The transparent conductive film 113 may also be formed by ECR sputtering, which can reduce the roughness of the upper surface of the transparent conductive film 113 compared to when the transparent conductive film 113 is formed by RF sputtering, for example.

[0090] Next, the relationship between the reflectance and refractive index of the translucent conductive film 113 and the metal layer 115 will be described with reference to FIGS. 26 to 32. FIGS. 26, 27, and 28 are diagrams showing the relationship between the film thickness of the translucent conductive film 113 and the reflectance when the metal layer 115 is made of Ag, Au, and Cu, respectively. FIGS. 26 to 28 show the reflectance of the translucent conductive film 113 and the metal layer 115 for light of wavelengths of 380 nm to 1000 nm. FIGS. 26 to 28 also show the reflectance when the translucent conductive film 113 is made of ITO. The reflectances shown in FIGS. 26 to 28 are calculated using a model similar to that shown in FIG. 18. The reflectances shown in FIGS. 26 to 28 are calculated assuming the film thickness of the metal layer 115 is 100 nm. Fig. 29 is a diagram showing the refractive index and extinction coefficient of each of ITO, Ag, Cu, and Au for light having a wavelength of 380 nm. Fig. 30 is a diagram showing the refractive index and extinction coefficient of each of ITO, Ag, Cu, and Au for light having a wavelength of 450 nm. Fig. 31 is a diagram showing the refractive index and extinction coefficient of each of ITO, Ag, Cu, and Au for light having a wavelength of 635 nm. Fig. 32 is a diagram showing the refractive index and extinction coefficient of each of ITO, Ag, Cu, and Au for light having a wavelength of 980 nm.

[0091] As shown in Figure 26, when using a metal layer 115 made of Ag, by appropriately setting the film thickness of the translucent conductive film 113, it is possible to achieve a reflectance of 80% or more in the range of 380 nm or more and 1000 nm or less.

[0092] As shown in Figure 27, when using a metal layer 115 made of Au, by appropriately setting the film thickness of the translucent conductive film 113, it is possible to achieve a reflectance of 80% or more in the range of 600 nm or more and 1000 nm or less.

[0093] As shown in Figure 28, when using a metal layer 115 made of Cu, by appropriately setting the film thickness of the translucent conductive film 113, it is possible to achieve a reflectance of 80% or more in the range of 600 nm or more and 1000 nm or less.

[0094] As described above, the reflectance varies depending on the wavelength of light and the material of the metal layer 115. These differences in reflectance depending on the wavelength of light and the material of the metal layer 115 are due to the differences in the refractive index of the metal layer 115 and the translucent conductive film 113 at each wavelength, as shown in FIGS. 29 to 31 . For example, as shown in FIGS. 29 and 30 , a high reflectance can be obtained when the refractive index of the metal layer 115 made of Ag is 0.5 or less and the difference in refractive index between the translucent conductive film 113 made of ITO and the metal layer 115 made of Ag is 1.4 or more. Similarly, as shown in FIGS. 31 and 32 , a high reflectance can be obtained when the refractive index of the metal layer 115 made of Ag, Cu, or Au is 0.5 or less and the difference in refractive index between the translucent conductive film 113 made of ITO and the metal layer 115 made of Ag, Cu, or Au is 1.4 or more.

[0095] Therefore, the difference in refractive index between the translucent conductive film 113 and the metal layer 115 may be 1.4 or more, and the refractive index of the metal layer 115 may be 0.5 or less, thereby making it possible to increase the reflectance of the translucent conductive film 113 and the metal layer 115.

[0096] [1-4. Configuration Example 1] Configuration example 1 of the semiconductor laser device 100 according to the present embodiment will be described. In configuration example 1, the oscillation wavelength is 610 nm or more. Each component of configuration example 1 of the semiconductor laser device 100 will be described below.

[0097] The substrate 101 is an n-type GaAs substrate.

[0098] The buffer layer 102 is an n-type GaAs layer with a thickness of 0.400 μm.

[0099] The n-type barrier buffer layer 103 is made of n-type Al ｘ４ Ga １－ｘ４The Al composition ratio x4 of the n-type barrier buffer layer 103 monotonically increases as it approaches the n-type cladding layer 104. Here, the configuration in which the Al composition ratio x4 of the n-type barrier buffer layer 103 monotonically increases as it approaches the n-type cladding layer 104 also includes a configuration in which the n-type barrier buffer layer 103 has a region in which the Al composition ratio x4 does not change depending on the distance from the n-type cladding layer 104. For example, it also includes a configuration in which the Al composition ratio of the n-type barrier buffer layer 103 increases stepwise as it approaches the n-type cladding layer 104.

[0100] The n-type cladding layer 104 is an n-type AlInP layer having a thickness of 1.3 μm.

[0101] The n-side guide layer 105 is made of Al ０．５６ Ga ０．４４ ) ０．５１０ In ０．４９０ This is the P layer.

[0102] Each of the barrier layers 106a and 106c is an undoped (Al ０．５６ Ga ０．４４ ) ０．５０８ In ０．４９２ This is the P layer.

[0103] The well layer 106b is an undoped GaInP layer with a thickness of 0.0125 μm. The composition of the well layer 106b may be adjusted appropriately depending on the oscillation wavelength of the semiconductor laser device 100, etc.

[0104] The p-side guide layer 107 is made of (Al ０．５６ Ga ０．４４ ) ０．５１０ In ０．４９０ This is the P layer.

[0105] The p-type cladding layer 108 is a p-type AlInP layer with a thickness of 0.910 μm. The p-type cladding layer 108 includes a first p-type cladding layer 108 a, which is a p-type AlInP layer with a thickness of 0.290 μm, and a second p-type cladding layer 108 b, which is a p-type AlInP layer with a thickness of 0.620 μm and is disposed above the first p-type cladding layer 108 a.

[0106] The p-type barrier buffer layer 109 is a p-type (Al ０．７０ Ga０．３０ ) ０．５１ In ０．４９ The first layer 109a is a P layer, and a p-type (Al ０．４０ Ga ０．６０ ) ０．５１ In ０．４９ The second layer 109b is a P layer, and a p-type (Al ０．１２ Ga ０．８８ ) ０．５１ In ０．４９ and a third layer 109c which is a P layer.

[0107] The contact layer 110 is made of (Al ｘ２ Ga １－ｘ２ ) ｙ２ In １－ｙ２ As (0≦x2≦1, 0≦y2≦1) layer, or (Al ｘ３ Ga １－ｘ３ ) ｙ３ In １－ｙ３ The contact layer 110 is, for example, a p-type (Al ０．２０ Ga ０．８０ ) ０．５１ In ０．４９ The contact layer 110 is, for example, a p-type Ga ０．４３ In ０．５７ As layer, p-type (Al ０．４３ Ga ０．５７ ) ０．９７ In ０．０３ The contact layer 110 may be an As layer or the like. ｘ２ Ga １－ｘ２ ) ｙ２ In １－ｙ２ As layer or (Al ｘ３ Ga １－ｘ３ ) ｙ３ In １－ｙ３ The contact layer 110 may be a P layer having the same lattice constant as the substrate 101. By making the lattice constant of the contact layer 110 equal to that of the substrate 101, strain of the semiconductor stack 100S relative to the substrate 101 can be reduced.

[0108] Furthermore, since the contact layer 110 contains Al and In, the bandgap energy of the contact layer 110 can be made larger than the bandgap energy of GaAs, thereby reducing light absorption in the contact layer 110. Therefore, the efficiency of the semiconductor laser device 100 can be improved.

[0109] The transparent conductive film 113 is made of at least one of GZO, AZO, ITO, IGZO, nickel oxide, HfN, ZrN, TaN, and TiN. The transparent conductive film 113 is, for example, an ITO film with a film thickness of 0.050 μm.

[0110] The main component of the metal layer 115 is at least one of Ag, Au, and Cu. The metal layer 115 is, for example, an Ag layer with a film thickness of 0.100 μm.

[0111] The barrier metal layer 117 has a Ti layer with a thickness of 0.05 μm, a Pt layer with a thickness of 0.15 μm arranged above the Ti layer, and an Au layer with a thickness of 0.05 μm arranged above the Pt layer.

[0112] The cover electrode 118 is an Au film with a thickness of 3 μm.

[0113] The n-side electrode has, arranged in this order from the substrate 101 side, an AuGe film with a thickness of 0.09 μm, a Ni film with a thickness of 0.02 μm, an Au film with a thickness of 0.05 μm, a Ti film with a thickness of 0.10 μm, a Pt film with a thickness of 0.05 μm, a Ti film with a thickness of 0.10 μm, a Pt film with a thickness of 0.05 μm, and an Au film with a thickness of 0.5 μm.

[0114] Such configuration example 1 achieves the effects of the semiconductor laser device 100 described above. Specifically, the oscillation wavelength of the semiconductor laser device 100 is 610 nm or more, and the reflectance of the light of the oscillation wavelength at the transparent conductive film 113 and the metal layer 115 is 80% or more. This makes it possible to increase the amount of spontaneous emission light that is reflected at the transparent conductive film 113 and the metal layer 115 and returns to the active layer 106. This makes it possible to increase the quantum efficiency of the semiconductor laser device 100. This makes it possible to improve the efficiency of the semiconductor laser device 100.

[0115] Furthermore, since the contact resistance between the contact layer 110 and the light-transmitting conductive film 113 can be reduced, the efficiency of the semiconductor laser device 100 can be improved.

[0116] [1-5. Configuration Example 2] Configuration Example 2 of the semiconductor laser device 100 according to the present embodiment will be described. In Configuration Example 2, the oscillation wavelength is 350 nm or more and 550 nm or less. Each component of Configuration Example 2 of the semiconductor laser device 100 will be described below.

[0117] The substrate 101 is an n-type GaN substrate.

[0118] The n-type cladding layer 104 is made of n-type Al ０．０２６ Ga ０．９７４ This is the N layer.

[0119] The n-side guide layer 105 is an undoped In layer having a thickness of 280 nm. ０．０３ Ga ０．９７ This is the N layer.

[0120] The barrier layer 106a is an undoped In layer having a thickness of 7 nm. ０．０４ Ga ０．９６ This is the N layer.

[0121] The well layer 106b is an undoped In layer having a thickness of 3 nm. ０．１８ Ga ０．８２ This is the N layer.

[0122] The barrier layer 106c is an undoped In layer having a thickness of 5 nm. ０．０４ Ga ０．９６ This is the N layer.

[0123] The p-side guide layer 107 is an undoped In layer having a thickness of 160 nm. ０．０３ Ga ０．９７ This is the N layer.

[0124] The p-type cladding layer 108 is made of a nitride semiconductor containing Al. The p-type cladding layer 108 is made of a p-type Al ０．０２６ Ga ０．９７４ The first p-type cladding layer 108a is an N layer, and a p-type Al layer having a thickness of 150 nm is disposed above the first p-type cladding layer 108a. ０．０２６ Ga ０．９７４ and a second p-type cladding layer 108b which is an N layer.

[0125] The contact layer 110 is made of Al ｘ１ In ｙ１ Ga １－ｘ１－ｙ１ The contact layer 110 is, for example, a p-type GaN layer having a thickness of 10 nm. The contact layer 110 is, for example, an AlN (0≦x1≦1, 0≦y1≦1, 0≦x1+y1≦1) layer. ｘ１ In ｙ１ Ga １－ｘ１－ｙ１ The contact layer 110 may be an N (0≦x1≦1, 0≦y1≦1, 0≦x1+y1≦1) layer having the same lattice constant as the substrate 101. By making the lattice constant of the contact layer 110 equal to that of the substrate 101, the strain of the semiconductor stack 100S relative to the substrate 101 can be reduced.

[0126] Furthermore, since the contact layer 110 contains Al and In, the bandgap energy of the contact layer 110 can be made larger than the bandgap energy of GaN, thereby reducing light absorption in the contact layer 110. As a result, the efficiency of the semiconductor laser device 100 can be improved.

[0127] In Configuration Example 2, the semiconductor stack 100S does not necessarily have to include the buffer layer 102, the n-type barrier buffer layer 103, and the p-type barrier buffer layer 109. The semiconductor stack 100S may also include an electron barrier layer disposed between the active layer 106 and the p-type cladding layer 108 and having a band gap energy greater than that of the p-type cladding layer 108.

[0128] The transparent conductive film 113 is a conductive oxide film. Specifically, the transparent conductive film 113 is made of at least one of GZO, AZO, ITO, IGZO, and nickel oxide. The transparent conductive film 113 is, for example, an ITO film with a film thickness of 0.050 μm.

[0129] The main component of the metal layer 115 is Ag, and the metal layer 115 is, for example, an Ag layer with a film thickness of 0.100 μm.

[0130] The barrier metal layer 117 has a Ti layer with a thickness of 0.05 μm, a Pt layer with a thickness of 0.15 μm arranged above the Ti layer, and an Au layer with a thickness of 0.05 μm arranged above the Pt layer.

[0131] The cover electrode 118 is an Au film with a thickness of 3 μm.

[0132] The n-side electrode has, arranged in this order from the substrate 101 side, an AuGe film with a thickness of 0.09 μm, a Ni film with a thickness of 0.02 μm, an Au film with a thickness of 0.05 μm, a Ti film with a thickness of 0.10 μm, a Pt film with a thickness of 0.05 μm, a Ti film with a thickness of 0.10 μm, a Pt film with a thickness of 0.05 μm, and an Au film with a thickness of 0.5 μm.

[0133] Such configuration example 2 achieves the effects of the semiconductor laser device 100 described above. Specifically, the oscillation wavelength of the semiconductor laser device 100 is 350 nm or more and 550 nm or less, and the reflectance of the light of the oscillation wavelength at the translucent conductive film 113 and the metal layer 115 is 80% or more. This makes it possible to increase the amount of spontaneous emission light that is reflected at the translucent conductive film 113 and the metal layer 115 and returns to the active layer 106. This makes it possible to increase the quantum efficiency of the semiconductor laser device 100. This makes it possible to improve the efficiency of the semiconductor laser device 100.

[0134] Furthermore, since the contact resistance between the contact layer 110 and the light-transmitting conductive film 113 can be reduced, the efficiency of the semiconductor laser device 100 can be improved.

[0135] (Embodiment 2) A semiconductor laser device according to embodiment 2 will be described. The semiconductor laser device according to this embodiment differs from the semiconductor laser device 100 according to embodiment 1 in that a light-transmitting conductive film is provided above the metal layer 115. The semiconductor laser device according to this embodiment will be described below with reference to FIG. 33, focusing on the differences from the semiconductor laser device 100 according to embodiment 1. FIG. 33 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device 100a according to this embodiment. Like FIG. 2, FIG. 33 shows a cross section perpendicular to the main emission direction of laser light from the semiconductor laser device 100a.

[0136] As shown in FIG. 33 , the semiconductor laser device 100 a according to this embodiment includes a substrate 101, a semiconductor stack 100S, a current blocking layer 112, a light-transmitting conductive film 113, a metal layer 115, a light-transmitting conductive film 116, a barrier metal layer 117, a cover electrode 118, and an n-side electrode 119.

[0137] The translucent conductive film 116 according to this embodiment is an example of a second translucent conductive film disposed above the metal layer 115, and is a conductive oxide film or a conductive nitride film. In this embodiment, the translucent conductive film 116 contacts the metal layer 115 and covers the entire upper surface of the metal layer 115. The translucent conductive film 116 is disposed in a region facing the upper surface 110Ru of the ridge 110R, a region facing the side surface of the ridge 110R, and a region facing the bottom of the groove 110T. That is, the translucent conductive film 116 is disposed continuously from a region facing the bottom of one groove 110T to a region facing the bottom of the other groove 110T. As shown in FIG. 33 , the position of the end of the translucent conductive film 116 in the X-axis direction may coincide with the position of the end of the metal layer 115 in the X-axis direction.

[0138] The transparent conductive film 116 is made of at least one of, for example, GZO, AZO, ITO, IGZO, nickel oxide, HfN, ZrN, TaN, and TiN. The thickness of the transparent conductive film 116 is, for example, 3 nm or more and 300 nm or less.

[0139] The translucent conductive film 116 is formed above the metal layer 115, for example, after the metal layer formation step in the manufacturing method for the semiconductor laser device 100 according to the first embodiment (second translucent conductive film formation step). In this embodiment, the translucent conductive film 116 is formed on the entire upper surface of the metal layer 115. That is, the translucent conductive film 116 is formed above the upper surface 110Ru of the ridge 110R and the current blocking layer 112. The translucent conductive film 116 is in contact with the metal layer 115. The translucent conductive film 116 is formed by, for example, ECR sputtering. A portion of the translucent conductive film 116 may be removed together with the translucent conductive film 113 and the metal layer 115 in the removal step.

[0140] The semiconductor laser device 100a according to the present embodiment also achieves the same effects as the semiconductor laser device 100 according to the first embodiment. Furthermore, in the semiconductor laser device 100a according to the present embodiment, the metal layer 115 can be protected by the translucent conductive film 116 disposed above the metal layer 115. The translucent conductive film 116 covering the metal layer 115 can suppress aggregation of the metal layer 115. Furthermore, the translucent conductive film 116 covering the metal layer 115 can suppress alteration of the metal layer 115 in a removal step or the like after the second translucent conductive film formation step. For example, when a resist 190 is formed above the metal layer 115 or when the resist 190 is removed, the metal layer 115 can be prevented from being sulfurized by a chemical solution or the like. These effects are particularly significant when the metal layer 115 contains Ag.

[0141] (Embodiment 3) A semiconductor laser device according to embodiment 3 will be described. The semiconductor laser device according to this embodiment differs from the semiconductor laser device 100 according to embodiment 1 in that an adhesive layer is provided between the light-transmitting conductive film 113 and the metal layer 115. The semiconductor laser device according to this embodiment will be described below with reference to FIG. 34 , focusing on the differences from the semiconductor laser device 100 according to embodiment 1. FIG. 34 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device 100b according to this embodiment. Like FIG. 2, FIG. 34 shows a cross section perpendicular to the main emission direction of laser light from the semiconductor laser device 100b.

[0142] As shown in FIG. 34 , the semiconductor laser element 100b according to this embodiment includes a substrate 101, a semiconductor stack 100S, a current blocking layer 112, a light-transmitting conductive film 113, an adhesion layer 114, a metal layer 115, a barrier metal layer 117, a cover electrode 118, and an n-side electrode 119.

[0143] The adhesion layer 114 according to this embodiment is a conductive layer disposed above the translucent conductive film 113. That is, the adhesion layer 114 is disposed between the translucent conductive film 113 and the metal layer 115. The adhesion layer 114 has a function of increasing the adhesion between the translucent conductive film 113 and the metal layer 115.

[0144] In this embodiment, the adhesion layer 114 is in contact with the translucent conductive film 113 and the metal layer 115 and covers the entire upper surface of the translucent conductive film 113. The adhesion layer 114 is disposed in a region facing the upper surface 110Ru of the ridge 110R, a region facing the side surface of the ridge 110R, and a region facing the bottom of the groove 110T. That is, the adhesion layer 114 is disposed continuously from a region facing the bottom of one groove 110T to a region facing the bottom of the other groove 110T. As shown in FIG. 34 , the position of the end of the adhesion layer 114 in the X-axis direction may coincide with the position of the end of the translucent conductive film 113 in the X-axis direction. The average film thickness of the adhesion layer 114 is, for example, 0.3 nm or more and 5 nm or less. Here, if the average film thickness of the adhesion layer 114 is 0.3 nm or more and 1 nm or less, it may not be possible to form the adhesion layer 114 with a uniform film thickness. For example, when the average film thickness of the adhesion layer 114 is 0.3 nm or more and 1 nm or less, the adhesion layer 114 may have a mesh shape in plan view, or may have an island (or dot) shape, etc. In this way, when the average film thickness of the adhesion layer 114 is 0.3 nm or more and 1 nm or less and the film thickness of the adhesion layer 114 is non-uniform, the average film thickness of the adhesion layer 114 is defined as the average value of the film thickness at each position on the adhesion layer 114.

[0145] A first example of the adhesion layer 114 is made of an oxide containing metal atoms contained in the metal layer 115 and metal atoms contained in the translucent conductive film 113. For example, when the translucent conductive film 113 contains In and the metal layer 115 contains Ag, the adhesion layer 114 may be made of an oxide containing Ag and In. Specifically, the adhesion layer 114 may be made of AgInO ｘ５ Furthermore, when the transparent conductive film 113 contains In and the metal layer 115 contains Cu, the adhesive layer 114 may be made of an oxide containing Cu and In. Specifically, the adhesive layer 114 may be made of CuInO ２ It may consist of:

[0146] A first example of the adhesion layer 114 may be formed above the translucent conductive film 113 after the first translucent conductive film forming step (adhesion layer forming step). The adhesion layer 114 may be formed by, for example, ECR sputtering or the like, or may be formed at the interface between the translucent conductive film 113 and the metal layer 115 by forming a metal layer 115 on the translucent conductive film 113 and then performing a heat treatment.

[0147] The first example of the adhesion layer 114 can improve the adhesion between the translucent conductive film 113 and the metal layer 115. In particular, the first example of the adhesion layer 114 can form a mixed crystal between the translucent conductive film 113 and the metal layer 115. This can further improve the adhesion between the translucent conductive film 113 and the metal layer 115. Therefore, peeling of the metal layer 115 can be suppressed. Furthermore, the first example of the adhesion layer 114 can realize an adhesion layer 114 with high transmittance for light having the oscillation wavelength of the semiconductor laser device 100b. Therefore, a decrease in the efficiency of the semiconductor laser device 100b can be suppressed.

[0148] A second example of the adhesion layer 114 is made of a metal having a higher ionization tendency than the metal layer 115. Such an adhesion layer 114 is made of at least one of Ni, Ti, and Al, for example. In this case, for example, the translucent conductive film 113 may be made of ITO, and the main component of the metal layer 115 may be Ag.

[0149] The second example of the adhesion layer 114 may be formed above the translucent conductive film 113 after the first translucent conductive film forming step (adhesion layer forming step). The adhesion layer 114 may be formed by, for example, ECR sputtering.

[0150] The second example of the adhesion layer 114 can improve the adhesion between the translucent conductive film 113 and the metal layer 115. In particular, the second example of the adhesion layer 114 can improve the ionic bonding between the adhesion layer 114 and the translucent conductive film 113 and between the adhesion layer 114 and the translucent conductive film 113 and the metal layer 115. This can further improve the adhesion between the translucent conductive film 113 and the metal layer 115. Therefore, peeling of the metal layer 115 can be suppressed.

[0151] Furthermore, a part of the adhesion layer 114 made of Ni, Ti, Al, or the like bonds with oxygen contained in the translucent conductive film 113 to become an oxide having translucency (i.e., a band gap energy greater than the energy corresponding to photons having the oscillation wavelength of the semiconductor laser element 100b), thereby suppressing the loss of light in the adhesion layer 114.

[0152] A third example of the adhesion layer 114 is made of an oxide containing a metal having a higher ionization tendency than the metal layer 115. Such an adhesion layer 114 is made of, for example, an oxide containing at least one of Ni, Ti, and Al. In this case, for example, the translucent conductive film 113 may be made of ITO, the adhesion layer 114 may be made of titanium oxide, nickel oxide, or aluminum oxide, and the metal layer 115 may be mainly composed of Ag. Furthermore, when the oscillation wavelength of the semiconductor laser device 100b is 610 nm or longer (i.e., when the contact layer 110 is made of a GaAs-based material), the translucent conductive film 113 may be made of nickel oxide, the adhesion layer 114 may be made of TiN, and the metal layer 115 may be mainly composed of Ag.

[0153] The third example of the adhesion layer 114 may be formed above the translucent conductive film 113 after the first translucent conductive film forming step (adhesion layer forming step). The adhesion layer 114 may be formed by, for example, ECR sputtering.

[0154] The third example of the adhesion layer 114 can improve the adhesion between the translucent conductive film 113 and the metal layer 115. Therefore, peeling of the metal layer 115 can be suppressed. Furthermore, the third example of the adhesion layer 114 can realize the adhesion layer 114 with high transmittance for light having the oscillation wavelength of the semiconductor laser element 100b. Therefore, a decrease in the efficiency of the semiconductor laser element 100b can be suppressed.

[0155] Fourth Embodiment A semiconductor laser device according to the fourth embodiment will be described. The semiconductor laser device according to this embodiment differs from the semiconductor laser device 100 according to the first embodiment mainly in the configuration of the translucent conductive film. The semiconductor laser device according to this embodiment will be described below with reference to FIGS. 35 and 36 , focusing on the differences from the semiconductor laser device 100 according to the first embodiment. FIG. 35 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device 100c according to this embodiment. As with FIG. 2 , FIG. 35 shows a cross section perpendicular to the main emission direction of laser light from the semiconductor laser device 100c. FIG. 36 is an enlarged view of the interior of the dashed-line frame XXXVI shown in FIG. 35. FIG. 36 also shows, with dashed arrows, examples of propagation paths of the spontaneously emitted light L1 and L2.

[0156] As shown in FIG. 35, the semiconductor laser element 100c according to this embodiment includes a substrate 101, a semiconductor stack 100S, a current blocking layer 112, a light-transmitting conductive film 113c, a metal layer 115c, a barrier metal layer 117, a cover electrode 118, and an n-side electrode 119.

[0157] The translucent conductive film 113c according to this embodiment is an example of a first translucent conductive film arranged above the semiconductor stack 100S, and is a conductive oxide film or a conductive nitride film. Like the translucent conductive film 113 according to the first embodiment, the translucent conductive film 113c according to this embodiment is also arranged on the upper surface 110Ru of the ridge 110R and is in contact with the contact layer 110. As shown in FIGS. 35 and 36 , the translucent conductive film 113c according to this embodiment is arranged on the upper surface 110Ru of the ridge 110R, and is not arranged in a region facing the side surface of the ridge 110R or in a region facing the bottom of the groove 110T.

[0158] The translucent conductive film 113c is disposed continuously and without interruption in the width direction of the ridge 110R (i.e., the X-axis direction) on the upper surface 110Ru of the ridge 110R. The translucent conductive film 113c has a uniform film thickness above the center of the ridge 110R in the width direction of the ridge 110R. On the other hand, above the ends of the ridge 110R in the width direction of the ridge 110R, the film thickness of the translucent conductive film 113c decreases as one approaches the ends of the ridge 110R. The positions of the ends of the translucent conductive film 113c in the X-axis direction may coincide with the positions of the ends of the upper surface 110Ru of the ridge 110R in the X-axis direction.

[0159] 36 , the translucent conductive film 113c has an upper surface 113cu. The upper surface 113cu has a central portion 113ca located at the center of the width of the ridge 110R, and an inclined portion 113cb located between the end of the upper surface 113cu and the central portion 113ca in the width direction of the ridge 110R. The inclined portion 113cb is inclined with respect to the upper surface 110Ru of the ridge 110R. The film thickness of the portion of the translucent conductive film 113c located below the inclined portion 113cb decreases with increasing distance from the center of the width of the ridge 110R. The central portion 113ca may be parallel to the upper surface 110Ru of the ridge 110R.

[0160] The light-transmitting conductive film 113c according to this embodiment can be formed by, for example, a lift-off method. Specifically, a resist is formed on the upper surfaces of the semiconductor stack 100S and the current blocking layer 112, except for the upper surface 110Ru of the ridge 110R, and then the light-transmitting conductive film 113c is formed at least above the upper surface 110Ru of the ridge 110R. The resist is then removed, thereby forming the light-transmitting conductive film 113c according to this embodiment.

[0161] The metal layer 115c according to the present embodiment is a metal film disposed above the light-transmitting conductive film 113c. In the present embodiment, as in the first embodiment, the metal layer 115c is disposed in a region facing the upper surface 110Ru of the ridge 110R, a region facing the side surface of the ridge 110R, and a region facing the bottom of the groove 110T. In other words, the metal layer 115c is disposed continuously from a region facing the bottom of one groove 110T to a region facing the bottom of the other groove 110T.

[0162] In this embodiment, the metal layer 115c contacts the light-transmitting conductive film 113 above the upper surface 110Ru of the ridge 110R. The metal layer 115c also contacts the current blocking layer 112 in a region facing the side surface of the ridge 110R and a region facing the bottom of the groove 110T.

[0163] The metal layer 115c is disposed above the upper surface 110Ru of the ridge 110R and along the upper surface 113cu of the translucent conductive film 113c. In this embodiment, the upper and lower surfaces of the metal layer 115c are inclined with respect to the upper surface 110Ru of the ridge 110R in a region facing the inclined portion 113cb of the translucent conductive film 113c. The upper and lower surfaces of the metal layer 115c may be parallel to the upper surface 110Ru of the ridge 110R in a region facing the central portion 113ca of the translucent conductive film 113c.

[0164] The effects of the semiconductor laser device 100c according to this embodiment will be described with reference to Fig. 37 and Fig. 38. Fig. 37 and Fig. 38 are enlarged cross-sectional views each showing a schematic view of the central portion 113ca and the inclined portion 113cb of the light-transmitting conductive film 113c according to this embodiment. Fig. 37 and Fig. 38 show enlarged views of the same cross section as Fig. 36.

[0165] In this embodiment, the thickness of the translucent conductive film 113c is not uniform. As described in the first embodiment, the thicker the translucent conductive film 113c, the rougher the upper surface 113cu of the translucent conductive film 113c tends to be. In other words, the thinner the translucent conductive film 113c, the less rough the upper surface 113cu becomes (i.e., the flatter the upper surface 113cu becomes). Therefore, the average roughness (e.g., arithmetic mean roughness Ra) of the inclined portion 113cb of the upper surface 113cu of the translucent conductive film 113c, which corresponds to the thinner portion of the translucent conductive film 113c, is smaller than the average roughness of the central portion 113ca. 37 and 38, the upper surface 113cu of the translucent conductive film 113c has microscopic irregularities, and the average size of the irregularities in the inclined portions 113cb is smaller than the average size of the irregularities in the central portion 113ca. The average roughness of the inclined portions 113cb may be 1 / 100 or less of the oscillation wavelength of the semiconductor laser device 100c.

[0166] Therefore, the reflectance of the metal layer 115c for the spontaneous emission light L1 incident on the inclined portion 113cb is greater than the reflectance of the metal layer 115c for the spontaneous emission light L1 incident on the central portion 113ca, thereby increasing the amount of the spontaneous emission light L2 reflected by the metal layer 115c that is reabsorbed in the active layer 106.

[0167] Furthermore, due to the inclination of the inclined portion 113cb, as shown in FIG. 36 , the spontaneous emission light L2 reflected by the metal layer 115c on the inclined portion 113cb is reflected toward the central portion of the active layer 106 in the X-axis direction, thereby reducing the propagation of the spontaneous emission light L2 outside the ridge 110R. Therefore, the amount of the spontaneous emission light L2 reabsorbed can be increased near the central portion of the active layer 106 in the X-axis direction, which contributes most to the amplification of laser light. This further increases the quantum efficiency of the semiconductor laser device 100c. This further increases the efficiency of the semiconductor laser device 100c.

[0168] Fifth Embodiment A semiconductor laser device according to a fifth embodiment will be described. The semiconductor laser device according to this embodiment differs from the semiconductor laser device 100 according to the first embodiment mainly in the positional relationship between the light-transmitting conductive film, the metal layer, and the current blocking layer. The semiconductor laser device according to this embodiment will be described below with reference to FIG. 39 , focusing on the differences from the semiconductor laser device 100 according to the first embodiment. FIG. 39 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device 100d according to this embodiment. Similar to FIG. 2, FIG. 39 shows a cross section perpendicular to the main emission direction of laser light from the semiconductor laser device 100d.

[0169] As shown in FIG. 39, the semiconductor laser element 100d according to this embodiment includes a substrate 101, a semiconductor stack 100S, a current blocking layer 112d, a light-transmitting conductive film 113, a metal layer 115, a barrier metal layer 117, a cover electrode 118, and an n-side electrode 119.

[0170] The translucent conductive film 113 is in contact with the contact layer 110. In this embodiment, the translucent conductive film 113 continuously covers the bottom of one groove 110T, one side surface of the ridge 110R, the upper surface 110Ru of the ridge 110R, the other side surface of the ridge 110R, and the bottom of the other groove 110T, and is in contact with the bottom of one groove 110T, one side surface of the ridge 110R, the upper surface 110Ru of the ridge 110R, the other side surface of the ridge 110R, and the bottom of the other groove 110T. The translucent conductive film 113 is in contact with the p-type cladding layer 108 at the bottom of the groove 110T, and is in contact with the p-type cladding layer 108, the p-type barrier buffer layer 109, and the contact layer 110 at the side surface of the ridge 110R. In this manner, the current blocking layer 112d is not disposed between the light-transmitting conductive film 113 and the semiconductor laminate 100S according to this embodiment.

[0171] The metal layer 115 is disposed above the translucent conductive film 113. In this embodiment, the metal layer 115 covers the entire upper surface of the translucent conductive film 113.

[0172] The current blocking layer 112d is an electrical insulating layer disposed above the semiconductor laminate 100S. A light-transmitting conductive film 113 and a metal layer 115 are disposed between the current blocking layer 112d according to this embodiment and the semiconductor laminate 100S. An opening 112da is formed in the current blocking layer 112d at a position corresponding to the upper surface 110Ru of the ridge 110R. In this embodiment, the opening 112da is located above the upper surface 110Ru of the ridge 110R. In the example shown in FIG. 39 , the width W112da of the opening 112da in the width direction of the ridge 110R is greater than the width WRu of the upper surface 110Ru of the ridge 110R in the width direction of the ridge 110R. This reduces the electrical resistance of the semiconductor laser device 100d, thereby reducing the operating voltage of the semiconductor laser device 100d.

[0173] The width W112da of the opening 112da in the width direction of the ridge 110R may be smaller than the width WRu of the top surface 110Ru of the ridge 110R in the width direction of the ridge 110R. This prevents the current passing through the opening 112da from flowing along the side surface of the ridge 110R, concentrating the current within the ridge 110R. A layer damaged during the formation of the ridge 110R is formed on the side surface of the ridge 110R. If a current flows along the side surface of the ridge 110R, current loss may occur in this damaged layer. However, by reducing the width W112da of the opening 112da, the current flowing along the side surface of the ridge 110R can be suppressed, thereby suppressing current loss and the resulting deterioration of the semiconductor laser device 100d.

[0174] The barrier metal layer 117 is a metal film disposed above the metal layer 115. In this embodiment, the barrier metal layer 117 covers the entire upper surface of the current blocking layer 112d. The barrier metal layer 117 also contacts the metal layer 115 at the opening 112da of the current blocking layer 112d.

[0175] In this embodiment, the current blocking layer 112d is not disposed between the translucent conductive film 113 and the semiconductor stack 100S. Therefore, the translucent conductive film 113 is in contact with the p-type cladding layer 108 and the p-type barrier buffer layer 109. However, when the translucent conductive film 113 made of ITO is formed on the surface of an Al-containing semiconductor layer such as the p-type cladding layer 108 or the p-type barrier buffer layer 109, the surface of the Al-containing semiconductor layer is oxidized. As a result, the electrical resistance between the Al-containing semiconductor layer and the translucent conductive film 113 increases. Therefore, it is possible to suppress current flow from the translucent conductive film 113 to semiconductor layers other than the contact layer 110.

[0176] Furthermore, in this embodiment, the opening 112da is located above the upper surface 110Ru of the ridge 110R, which allows the current flowing to the opening 112da via the cover electrode 118 and the barrier metal layer 117 to be concentrated within the ridge 110R.

[0177] Sixth Embodiment A semiconductor laser device according to the sixth embodiment will be described. The semiconductor laser device according to the sixth embodiment differs from the semiconductor laser device 100d according to the fifth embodiment mainly in the positional relationship between the light-transmitting conductive film, the metal layer, and the current blocking layer. The semiconductor laser device according to the sixth embodiment will be described below with reference to FIG. 40 , focusing on the differences from the semiconductor laser device 100d according to the fifth embodiment. FIG. 40 is a schematic cross-sectional view showing the overall configuration of the semiconductor laser device 100e according to the sixth embodiment. Similar to FIG. 2, FIG. 40 shows a cross section perpendicular to the main emission direction of laser light from the semiconductor laser device 100e.

[0178] As shown in FIG. 40, the semiconductor laser element 100e according to this embodiment includes a substrate 101, a semiconductor stack 100S, a current blocking layer 112e, a light-transmitting conductive film 113, a metal layer 115, a barrier metal layer 117, a cover electrode 118, and an n-side electrode 119.

[0179] The transparent conductive film 113 is in contact with the contact layer 110 in the same manner as in the fifth embodiment.

[0180] The current blocking layer 112e is an electrical insulating layer disposed above the semiconductor stack 100S. A translucent conductive film 113 is disposed between the current blocking layer 112e according to this embodiment and the semiconductor stack 100S. An opening 112ea is formed in the current blocking layer 112e at a position corresponding to the upper surface 110Ru of the ridge 110R. In this embodiment, the opening 112ea is located above the upper surface 110Ru of the ridge 110R. In the example shown in FIG. 40 , the width W112ea of ​​the opening 112ea in the width direction of the ridge 110R is larger than the width WRu of the upper surface 110Ru of the ridge 110R in the width direction of the ridge 110R. Note that the width W112ea of ​​the opening 112ea in the width direction of the ridge 110R may be smaller than the width WRu of the upper surface 110Ru of the ridge 110R in the width direction of the ridge 110R.

[0181] The metal layer 115 is disposed above the translucent conductive film 113. In this embodiment, the current blocking layer 112e is disposed between the metal layer 115 and the translucent conductive film 113. The metal layer 115 contacts the translucent conductive film 113 at the opening 112ea of ​​the current blocking layer 112e.

[0182] In the present embodiment, as in the fifth embodiment, it is possible to suppress current from flowing from the translucent conductive film 113 to semiconductor layers other than the contact layer 110. In particular, in the present embodiment, when current is concentrated in the ridge 110R by the opening 112ea in the current blocking layer 112e, the electrical resistance of the translucent conductive film 113 made of ITO or the like below the opening 112ea is greater than the electrical resistance of the metal layer 115 made of Ag or the like, and therefore it is possible to reduce the current flowing outside the ridge 110R.

[0183] In this embodiment, the opening 112ea is located above the upper surface 110Ru of the ridge 110R, which allows the current flowing to the opening 112ea via the cover electrode 118, the barrier metal layer 117, and the metal layer 115 to be concentrated within the ridge 110R.

[0184] In this embodiment, in the region near the widthwise end of the ridge 110R, a current blocking layer 112e is disposed between the light-transmitting conductive film 113 and the metal layer 115. The reflectance of spontaneous emission light in such a region will be described with reference to the above-mentioned FIGS.

[0185] For example, SiO ２ The current blocking layer 112e, which is made of, for example, a material having light-transmitting properties, can be treated substantially as part of the light-transmitting layer shown in Figures 19 to 22. The reflectance of the spontaneously emitted light in the metal layer 115 and the like when the spontaneously emitted light of the semiconductor laser device 100e includes ultraviolet light (light having a wavelength in the 380 nm band) will be described with reference to Figure 19. As shown in Figure 19, when the film thickness of the light-transmitting conductive film 113 is 15 nm, the reflectance of the spontaneously emitted light in the region where the light-transmitting conductive film 113 and the metal layer 115 contact each other (in other words, the region corresponding to the opening 112ea) is about 80%.

[0186] Furthermore, if the thickness of the transparent conductive film 113 is 15 nm and the thickness of the current blocking layer 112e is 80 nm, the thickness of the transparent layer in the region where the current blocking layer 112e is disposed between the transparent conductive film 113 and the metal layer 115 is 95 nm (=15 nm+80 nm). In this case, as shown in Fig. 19 , the reflectance of the spontaneously emitted light in this region is about 72%.

[0187] In this way, by adjusting the film thicknesses of the translucent conductive film 113 and the current blocking layer 112e, it is possible to obtain a high reflectance for spontaneous emission light including ultraviolet light in both the region where the translucent conductive film 113 and the metal layer 115 contact each other and the region where the current blocking layer 112e is disposed between the translucent conductive film 113 and the metal layer 115.

[0188] Next, the reflectance of the spontaneous emission light in the metal layer 115 and the like when the spontaneous emission light of the semiconductor laser device 100e includes blue light (light with a wavelength in the 450 nm band) will be described with reference to Fig. 20. As shown in Fig. 20, when the film thickness of the translucent conductive film 113 is 40 nm, the reflectance of the spontaneous emission light in the region where the translucent conductive film 113 and the metal layer 115 contact each other is about 80%.

[0189] Furthermore, if the thickness of the transparent conductive film 113 is 40 nm and the thickness of the current blocking layer 112e is 80 nm, the thickness of the transparent layer in the region where the current blocking layer 112e is disposed between the transparent conductive film 113 and the metal layer 115 is 120 nm (=40 nm+80 nm). In this case, as shown in Fig. 20 , the reflectance of the spontaneously emitted light in this region is about 70%.

[0190] In this way, by adjusting the film thicknesses of the translucent conductive film 113 and the current blocking layer 112e, a high reflectance can be obtained for spontaneously emitted light including blue light in both the region where the translucent conductive film 113 and the metal layer 115 contact each other and the region where the current blocking layer 112e is disposed between the translucent conductive film 113 and the metal layer 115.

[0191] Next, the reflectance of the spontaneous emission light in the metal layer 115 and the like when the spontaneous emission light of the semiconductor laser device 100e includes red light (light with a wavelength in the 630 nm band) will be described with reference to Fig. 21. As shown in Fig. 21, when the film thickness of the translucent conductive film 113 is 115 nm, the reflectance of the spontaneous emission light in the region where the translucent conductive film 113 and the metal layer 115 contact each other is about 80%.

[0192] Furthermore, if the thickness of the translucent conductive film 113 is 115 nm and the thickness of the current blocking layer 112e is 50 nm, the thickness of the translucent layer in the region where the current blocking layer 112e is disposed between the translucent conductive film 113 and the metal layer 115 is 165 nm (=115 nm+50 nm). In this case, as shown in Figure 21, the reflectance for spontaneous emission in this region is approximately 80%. Note that by setting the thickness of the current blocking layer 112e to 85 nm, the reflectance for spontaneous emission in the region where the current blocking layer 112e is disposed between the translucent conductive film 113 and the metal layer 115 can be increased to approximately 85%.

[0193] In this way, by adjusting the film thicknesses of the translucent conductive film 113 and the current blocking layer 112e, it is possible to obtain a high reflectance for spontaneously emitted light including red light in both the region where the translucent conductive film 113 and the metal layer 115 contact each other and the region where the current blocking layer 112e is disposed between the translucent conductive film 113 and the metal layer 115.

[0194] Next, the reflectance of the metal layer 115 and the like when the spontaneous emission light of the semiconductor laser device 100e includes infrared light (light having a wavelength in the 980 nm band) will be described with reference to Fig. 22. As shown in Fig. 22, when the film thickness of the translucent conductive film 113 is 155 nm, the reflectance of the spontaneous emission light in the region where the translucent conductive film 113 and the metal layer 115 contact each other is about 80%.

[0195] Furthermore, if the thickness of the transparent conductive film 113 is 155 nm and the thickness of the current blocking layer 112e is 220 nm, the thickness of the transparent layer in the region where the current blocking layer 112e is disposed between the transparent conductive film 113 and the metal layer 115 is 375 nm (=155 nm+220 nm). In this case, as shown in Fig. 22 , the reflectance of the spontaneously emitted light in this region is about 70%.

[0196] In this way, by adjusting the film thicknesses of the translucent conductive film 113 and the current blocking layer 112e, it is possible to obtain a high reflectance for spontaneously emitted light including infrared light in both the region where the translucent conductive film 113 and the metal layer 115 contact each other and the region where the current blocking layer 112e is disposed between the translucent conductive film 113 and the metal layer 115.

[0197] As described above, in this embodiment, the efficiency of the semiconductor laser device 100e can be improved by increasing the reflectance of the transparent conductive film 113, the current blocking layer 112e, and the metal layer 115 for spontaneously emitted light in the ultraviolet to infrared range.

[0198] Seventh Embodiment A semiconductor laser device according to a seventh embodiment will be described. The semiconductor laser device according to this embodiment differs from the semiconductor laser device 100c according to the fourth embodiment mainly in the configuration of the current blocking layer. The semiconductor laser device according to this embodiment will be described below with reference to FIG. 41 , focusing on the differences from the semiconductor laser device 100c according to the fourth embodiment. FIG. 41 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device 100f according to this embodiment. Similar to FIG. 2, FIG. 41 shows a cross section perpendicular to the main emission direction of laser light from the semiconductor laser device 100f.

[0199] As shown in FIG. 41, the semiconductor laser element 100f according to this embodiment includes a substrate 101, a semiconductor stack 100S, a current blocking layer 112f, a light-transmitting conductive film 113c, a metal layer 115f, a barrier metal layer 117, a cover electrode 118, and an n-side electrode 119.

[0200] The current blocking layer 112f according to this embodiment is arranged not only in an area of ​​the upper surface of the semiconductor stack 100S other than the upper surface 110Ru of the ridge 110R, but also in a part of the upper surface 113cu of the light-transmitting conductive film 113c arranged above the upper surface 110Ru. As shown in Fig. 41 , the current blocking layer 112f is also arranged near the end of the upper surface 113cu in the width direction of the ridge 110R.

[0201] An opening 112fa is formed in the current blocking layer 112f at a position corresponding to the upper surface 110Ru of the ridge 110R. In this embodiment, the opening 112fa is located above the upper surface 110Ru of the ridge 110R and above the upper surface 113cu of the translucent conductive film 113c. In the example shown in Fig. 41 , the width W112fa of the opening 112fa in the width direction of the ridge 110R is smaller than the width of the translucent conductive film 113c in the width direction of the ridge 110R (and the width of the upper surface 110Ru of the ridge 110R in the width direction of the ridge 110R).

[0202] The metal layer 115f is a metal film disposed above the translucent conductive film 113c. In this embodiment, the metal layer 115f covers the entire upper surface of the current blocking layer 112f. The metal layer 115f contacts the upper surface 113cu of the translucent conductive film 113c at the opening 112fa of the current blocking layer 112f. The metal layer 115f is disposed in a region facing the upper surface 110Ru of the ridge 110R, a region facing the side surface of the ridge 110R, a region facing the bottom of the groove 110T, a region facing the side surface of the protrusion 110P on the groove 110T side, and a region facing the upper surface of the protrusion 110P.

[0203] The present embodiment also achieves the same effects as those of the fourth embodiment. Furthermore, in the present embodiment, there is a region in which the current blocking layer 112f is disposed between the light-transmitting conductive film 113c and the metal layer 115f. Even in this configuration, as described in the sixth embodiment, the reflectance of the light-transmitting conductive film 113c, the current blocking layer 112f, and the metal layer 115f for spontaneous emission can be increased by adjusting the film thicknesses of the light-transmitting conductive film 113c and the current blocking layer 112f. Therefore, in the present embodiment, the efficiency of the semiconductor laser device 100e can be improved by increasing the reflectance of the light-transmitting conductive film 113c, the current blocking layer 112f, and the metal layer 115f for spontaneous emission.

[0204] Eighth Embodiment A semiconductor laser device according to the eighth embodiment will be described. The semiconductor laser device according to this embodiment differs from the semiconductor laser device 100 according to the first embodiment mainly in the configuration of the contact layer. The semiconductor laser device according to this embodiment will be described below with reference to FIGS. 42 and 43 , focusing on the differences from the semiconductor laser device 100 according to the first embodiment. FIG. 42 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device 200 according to this embodiment. FIG. 43 is an enlarged view of the inside of the dashed-line frame XXXXIII shown in FIG. 42 . Similar to FIG. 2 , FIGS. 42 and 43 show cross sections perpendicular to the main emission direction of laser light from the semiconductor laser device 200. FIG. 43 also shows examples of propagation paths of the spontaneously emitted light L1 and L2 with dashed arrows.

[0205] As shown in FIG. 42 , the semiconductor laser element 200 according to this embodiment includes a substrate 101, a semiconductor stack 200S, a current blocking layer 112, a light-transmitting conductive film 113, a metal layer 115, a barrier metal layer 117, a cover electrode 118, and an n-side electrode 119.

[0206] The semiconductor laminate 200S according to this embodiment includes a plurality of semiconductor layers that are disposed above the substrate 101. The semiconductor laminate 200S includes a buffer layer 102, an n-type barrier buffer layer 103, an n-type cladding layer 104, an n-side guide layer 105, an active layer 106, a p-side guide layer 107, a p-type cladding layer 208, a p-type barrier buffer layer 109, and a contact layer 210.

[0207] The semiconductor stack 200S has a ridge 210R that protrudes upward. The ridge 210R extends in the Y-axis direction. The semiconductor stack 200S also has two grooves 210T that are arranged along the ridge 210R and extend in the Y-axis direction, and two protruding portions 210P that protrude upward. A groove 210T is formed between each of the two protruding portions 210P and the ridge 210R. In this embodiment, the ridge 210R, the protruding portions 210P, and the groove 210T are formed in the p-type cladding layer 208, the p-type barrier buffer layer 109, and the contact layer 210. The lower ends of the ridge 210R and the protruding portions 210P are located in the etching stop layer 208c of the p-type cladding layer 208.

[0208] The p-type cladding layer 208 according to this embodiment is a p-type cladding layer disposed above the active layer 106. In this embodiment, the p-type cladding layer 208 is disposed between the p-side guide layer 107 and the p-type barrier buffer layer 109. The p-type cladding layer 208 includes a first p-type cladding layer 108a and a second p-type cladding layer 108b disposed above the first p-type cladding layer 108a. In this embodiment, the p-type cladding layer 208 further includes an etching stop layer 208c disposed between the first p-type cladding layer 108a and the second p-type cladding layer 108b.

[0209] The etching stop layer 208c is a layer that has a lower etching rate than the second p-type cladding layer 108b with respect to the etchant used when forming the ridge 210R by etching. The etching stop layer 208c according to this embodiment is a p-type (Al ０．６０ Ga ０．４０ ) ０．５１ In ０．４９ The p-type cladding layer 208 has such an etching stop layer 208c, so that the position of the bottom end of the ridge 210R can be controlled with high precision. Note that the p-type cladding layer 208 does not necessarily have to have the etching stop layer 208c.

[0210] The p-type barrier buffer layer 109 is disposed between the p-type cladding layer 208 and the contact layer 210. As shown in FIG. 42 , the p-type barrier buffer layer 109 may protrude from the p-type cladding layer 208 in the X-axis direction toward the groove 210T. By having the p-type barrier buffer layer 109 protrude in this manner, the contact area between the semiconductor stack 200S and the current blocking layer 112 can be increased. Therefore, the adhesion between the semiconductor stack 200S and the current blocking layer 112 can be improved.

[0211] The contact layer 210 is a p-type semiconductor layer disposed above the p-type cladding layer 208. The contact layer 210 is disposed on the upper end of the ridge 210R. The contact layer 210 according to this embodiment is a p-type Al layer having a thickness of 0.100 μm or more. ０．６０ Ga ０．４０The contact layer 210 according to the present embodiment is an As layer. As such, the contact layer 210 according to the present embodiment has a larger thickness than the contact layer 110 according to the first embodiment. The thickness of the contact layer 210 may be less than 0.400 μm. This makes it possible to suppress the series resistance in the contact layer 210. Furthermore, the contact layer 210 according to the present embodiment has a larger band gap energy than the contact layer 110 according to the first embodiment. In this embodiment, since the contact layer 210 has a large thickness, when the band gap energy of the contact layer 210 is small, the absorption of laser light and spontaneous emission light in the contact layer 210 becomes more pronounced. In this embodiment, by increasing the band gap energy of the contact layer 210, it is possible to suppress the absorption of laser light and spontaneous emission light in the contact layer 210 having a large thickness.

[0212] 43, the contact layer 210 located on the ridge 210R has a central region 210a and an inclined region 210b. The central region 210a is a region of the contact layer 210 located at the center in the width direction of the ridge 210R. The thickness of the central region 210a is uniform. The thickness of the inclined region 210b decreases toward the ends in the width direction of the ridge 210R.

[0213] The upper surface of the contact layer 210 is the upper surface 210Ru of the ridge 210R. The upper surface 210Ru has a central portion 210Ra located at the center of the width direction of the ridge 210R, and an inclined portion 210Rb located between the end of the upper surface 210Ru and the central portion 210Ra in the width direction of the ridge 210R. The inclined portion 210Rb is inclined with respect to the upper surface 210Ru of the ridge 210R. The central portion 210Ra may be parallel to the width direction of the ridge 210R. As described above, by using a contact layer 210 with a large thickness, it becomes easier to form the inclined portion 210Rb when forming the ridge 210R by wet etching.

[0214] Furthermore, the contact layer 210 located in the protruding portion 210P of the semiconductor laminate 200S may have a region whose film thickness decreases toward the groove 210T.

[0215] The semiconductor laser device 200 according to this embodiment includes a semiconductor stack 200S having the above-described configuration. Furthermore, the light-transmitting conductive film 113 and the metal layer 115 are disposed above the inclined region 210b of the contact layer 210. Therefore, the light-transmitting conductive film 113 and the metal layer 115 are inclined. Therefore, as shown in FIG. 43 , when spontaneous emission light L1 is incident on the metal layer 115 above the inclined region 210b, the spontaneous emission light L2 is reflected toward the central portion of the active layer 106 in the X-axis direction, thereby reducing propagation of the spontaneous emission light L2 outside the ridge 210R. This increases the amount of spontaneous emission light L2 reabsorbed near the central portion of the active layer 106 in the X-axis direction, which contributes most to the amplification of laser light. This further increases the quantum efficiency of the semiconductor laser device 200. This further increases the efficiency of the semiconductor laser device 200.

[0216] Ninth Embodiment A semiconductor laser device according to a ninth embodiment will be described. The semiconductor laser device according to this embodiment differs from the semiconductor laser device 200 according to the eighth embodiment mainly in the positional relationship between the light-transmitting conductive film, the metal layer, and the current blocking layer. The semiconductor laser device according to this embodiment will be described below with reference to FIG. 44, focusing on the differences from the semiconductor laser device 200 according to the eighth embodiment. FIG. 44 is a schematic cross-sectional view showing the overall configuration of a semiconductor laser device 200a according to this embodiment. Similar to FIG. 2, FIG. 44 shows a cross section perpendicular to the main emission direction of laser light from the semiconductor laser device 200a.

[0217] As shown in FIG. 44, the semiconductor laser element 200a according to this embodiment includes a substrate 101, a semiconductor stack 200S, a current blocking layer 112, a light-transmitting conductive film 113, a metal layer 115, a barrier metal layer 117, a cover electrode 118, and an n-side electrode 119.

[0218] In this embodiment, a light-transmitting conductive film 113 and a metal layer 115 are disposed below the current blocking layer 112. The light-transmitting conductive film 113 is in contact with the semiconductor stack 200S not only at the upper surface 210Ru of the ridge 210R but also at the side surfaces of the ridge 210R and the bottom of the groove 210T. The metal layer 115 is disposed above the light-transmitting conductive film 113. In this embodiment, the metal layer 115 covers the entire upper surface of the light-transmitting conductive film 113. The current blocking layer 112 may be disposed above a portion of the upper surface 210Ru of the ridge 210R.

[0219] The semiconductor laser device 200a according to the present embodiment also achieves the same effects as the semiconductor laser device 200 according to the eighth embodiment. Furthermore, in the present embodiment, similar to the fifth embodiment, the current blocking layer 112 is not disposed between the translucent conductive film 113 and the semiconductor stack 200S. Therefore, the translucent conductive film 113 is in contact with the p-type cladding layer 208 and the p-type barrier buffer layer 109. However, similar to the fifth embodiment, it is possible to suppress current from flowing from the translucent conductive film 113 to semiconductor layers other than the contact layer 210.

[0220] (Modifications, etc.) Although the semiconductor laser device according to the present disclosure has been described above based on the embodiments, the present disclosure is not limited to the above-described embodiments.

[0221] For example, in each of the above embodiments, the semiconductor laser element has a single ridge, but the semiconductor laser element may have a plurality of ridges.

[0222] Furthermore, although the semiconductor laser elements according to the first to fourth embodiments include the buffer layer 102, the n-type barrier buffer layer 103, the n-side guide layer 105, the p-side guide layer 107, the p-type barrier buffer layer 109, the current blocking layer 112, the barrier metal layer 117, and the cover electrode 118, these components are not necessarily required.

[0223] The semiconductor stack 100S of the semiconductor laser devices according to the first to fourth embodiments may include semiconductor layers other than the above-described semiconductor layers. For example, the semiconductor stack 100S may include an electron barrier layer that is disposed between the active layer 106 and the p-type cladding layer 108 and is a semiconductor layer having a bandgap energy larger than that of the p-type cladding layer 108.

[0224] 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.

[0225] For example, the semiconductor laser devices according to the second and fourth embodiments may include the adhesion layer 114 according to the third embodiment.

[0226] The semiconductor laser device 100c according to the fourth embodiment may also include the translucent conductive film 116 according to the second embodiment (that is, the second translucent conductive film).

[0227] The semiconductor laser device of the present disclosure can be applied to light sources for various purposes, for example, as a high-output and highly efficient light source.

[0228] 100, 100a, 100b, 100c, 100d, 100e, 100f, 200, 200a Semiconductor laser element 100F, 100R Facet 100S, 200S Semiconductor laminate 101 Substrate 102 Buffer layer 103 N-type barrier relaxation layer 104 N-type cladding layer 105 N-side guide layer 106 Active layer 106a, 106c Barrier layer 106b Well layer 107 P-side guide layer 108, 208 P-type cladding layer 108a First p-type cladding layer 108b Second p-type cladding layer 109 P-type barrier relaxation layer 109a First layer 109b Second layer 109c Third layer 110, 210 Contact layer 110P, 210P Protruding portion 110R, 210R Ridge 110Ru, 113cu, 210Ru Upper surface 110T, 210T Groove 112, 112d, 112e, 112f Current blocking layer 112da, 112ea, 112fa Opening 113, 113c, 116 Light-transmitting conductive film 113ca, 210Ra Central portion 113cb, 210Rb Inclined portion 114 Adhesion layer 115, 115c, 115f Metal layer 117 Barrier metal layer 118 Cover electrode 119 N-side electrode 190 Resist 208c Etching stop layer 210a Central region 210b Inclined region L1, L2 Spontaneous emission light

Claims

1. A semiconductor laser element comprising: a semiconductor laminate; a first light-transmitting conductive film disposed above the semiconductor laminate; and a metal layer disposed above the first light-transmitting conductive film, wherein the semiconductor laminate has an n-type cladding layer, an active layer disposed above the n-type cladding layer, a p-type cladding layer disposed above the active layer, and a contact layer disposed above the p-type cladding layer, and the contact layer is made of (Al ｘ２ Ga １－ｘ２ ) ｙ２ In １－ｙ２ As (0≦x2≦1, 0≦y2≦1) layer, or (Al ｘ３ Ga １－ｘ３ ) ｙ３ In １－ｙ３ P(0≦x3≦1, 0≦y3≦1) layer, the first translucent conductive film is in contact with the contact layer, the oscillation wavelength of the semiconductor laser element is 610 nm or more, and the film thickness of the first translucent conductive film is 150 nm or less.

2. The semiconductor laser device according to claim 1, wherein the reflectance of said metal layer to light of said oscillation wavelength is higher than the reflectance of Pd to light of said oscillation wavelength.

3. The semiconductor laser device according to claim 1 or 2, wherein the reflectance of the first translucent conductive film and the metal layer for light of the oscillation wavelength is 80% or more.

4. The semiconductor laser device according to any one of claims 1 to 3, wherein the first translucent conductive film is made of at least one of GZO, AZO, ITO, IGZO, nickel oxide, HfN, ZrN, TaN, and TiN.

5. When the oscillation wavelength is expressed as λ [nm] and the film thickness of the first translucent conductive film is expressed as F(λ) [nm], the following inequality holds: F(λ)≦3.54×10 －９ λ ４ -9.97 x 10 －６ λ ３ +9.74 x 10 －３ λ ２ -3.61λ+448 The semiconductor laser device according to any one of claims 1 to 4.

6. The semiconductor laser device according to any one of claims 1 to 5, wherein the roughness Rz of the upper surface of the first translucent conductive film is 0.2 nm or more and 2.0 nm or less.

7. The semiconductor laser device according to any one of claims 1 to 6, wherein the difference in refractive index between said first translucent conductive film and said metal layer is 1.4 or more, and the refractive index of said metal layer is 0.5 or less.

8. The semiconductor laser device according to claim 7, wherein the main component of the metal layer is at least one of Ag, Au, and Cu.

9. The semiconductor laser device according to any one of claims 1 to 8, further comprising a second light-transmitting conductive film disposed above the metal layer.

10. The semiconductor laser device according to any one of claims 1 to 9, wherein the band gap energy of said contact layer is larger than the band gap energy of said active layer.

11. The semiconductor laser device according to any one of claims 1 to 10, further comprising an adhesion layer disposed between the first translucent conductive film and the metal layer, the adhesion layer being made of an oxide containing metal atoms contained in the metal layer and metal atoms contained in the first translucent conductive film.

12. The semiconductor laser device according to claim 11, wherein the oxide contains Ag and In.

13. The semiconductor laser device according to claim 11 or 12, wherein the band gap energy of the oxide is greater than the energy of photons having the oscillation wavelength.

14. A semiconductor laser element according to any one of claims 1 to 13, wherein a ridge is formed in the semiconductor laminate, and the top surface of the first translucent conductive film has a central portion located at the center of the width of the ridge, and an inclined portion located between an end of the top surface in the width direction of the ridge and the central portion, the film thickness of the first translucent conductive film located below the inclined portion decreases with increasing distance from the center of the width direction of the ridge, and the average roughness of the inclined portion is smaller than the average roughness of the central portion.

15. A semiconductor laser device according to any one of claims 1 to 13, wherein a ridge protruding upward is formed in the semiconductor laminate, the contact layer is disposed at the upper end of the ridge, the contact layer has a sloped region whose thickness decreases toward the end of the ridge in the width direction, and the first translucent conductive film and the metal layer are disposed above the sloped region.

16. A semiconductor laser element comprising: a semiconductor laminate; a first light-transmitting conductive film disposed above the semiconductor laminate; and a metal layer disposed above the first light-transmitting conductive film, wherein the semiconductor laminate has an n-type cladding layer, an active layer disposed above the n-type cladding layer, a p-type cladding layer disposed above the active layer, and a contact layer disposed above the p-type cladding layer, and the contact layer is made of Al ｘ１ In ｙ１ Ga １－ｘ１－ｙ１ N (0≦x1≦1, 0≦y1≦1, 0≦x1+y1≦1) layer, the first translucent conductive film is in contact with the contact layer, the oscillation wavelength of the semiconductor laser element is 350 nm or more and 550 nm or less, and the film thickness of the first translucent conductive film is less than 100 nm.

17. The semiconductor laser device according to claim 16, wherein the reflectance of said metal layer to light of said oscillation wavelength is higher than the reflectance of Pd to light of said oscillation wavelength.

18. The semiconductor laser device according to claim 16 or 17, wherein the reflectance of the first translucent conductive film and the metal layer for light of the oscillation wavelength is 80% or more.

19. The semiconductor laser device according to any one of claims 16 to 18, wherein the first translucent conductive film is made of at least one of GZO, AZO, ITO, IGZO, and nickel oxide.

20. When the oscillation wavelength is expressed as λ [nm] and the film thickness of the first translucent conductive film is expressed as F(λ) [nm], the following inequality holds: F(λ)≦3.54×10 －９ λ ４ -9.97 x 10 －６ λ ３ +9.74 x 10 －３ λ ２ -3.61λ+448 The semiconductor laser device according to any one of claims 16 to 19.

21. The semiconductor laser device according to any one of claims 16 to 19, wherein the roughness Rz of the upper surface of the first translucent conductive film is 0.2 nm or more and 2.0 nm or less.

22. The semiconductor laser device according to any one of claims 16 to 21, wherein the difference in refractive index between said first translucent conductive film and said metal layer is 1.4 or more, and the refractive index of said metal layer is 0.5 or less.

23. The semiconductor laser device according to claim 22, wherein the metal layer is mainly composed of Ag.

24. The semiconductor laser device according to any one of claims 16 to 23, further comprising a second light-transmitting conductive film disposed above the metal layer.

25. The semiconductor laser device according to any one of claims 16 to 24, wherein the band gap energy of the contact layer is larger than the band gap energy of the active layer.

26. A method for manufacturing a semiconductor laser device, comprising: a semiconductor laminate formation step of forming a semiconductor laminate on a substrate; a first light-transmitting conductive film formation step of forming a first light-transmitting conductive film above the semiconductor laminate; and a metal layer formation step of forming a metal layer above the first light-transmitting conductive film, wherein the semiconductor laminate has an n-type cladding layer, an active layer disposed above the n-type cladding layer, a p-type cladding layer disposed above the active layer, and a contact layer disposed above the p-type cladding layer, and the contact layer is made of (Al ｘ２ Ga １－ｘ２ ) ｙ２ In １－ｙ２ As (0≦x2≦1, 0≦y2≦1) layer, or (Al ｘ３ Ga １－ｘ３ ) ｙ３ In １－ｙ３ P(0≦x3≦1, 0≦y3≦1) layer, the first translucent conductive film is in contact with the contact layer, the oscillation wavelength of the semiconductor laser element is 610 nm or more, and the film thickness of the first translucent conductive film is 150 nm or less.

27. The method for manufacturing a semiconductor laser device according to claim 26, wherein the roughness Rz of the upper surface of the first translucent conductive film is 0.2 nm or more and 2.0 nm or less, and the roughness Rz of the upper surface of the first translucent conductive film is measured based on the height of irregularities in a cross section of the upper surface of the first translucent conductive film.

28. A method for manufacturing a semiconductor laser device, comprising: a semiconductor laminate formation step of forming a semiconductor laminate on a substrate; a first light-transmitting conductive film formation step of forming a first light-transmitting conductive film above the semiconductor laminate; and a metal layer formation step of forming a metal layer above the first light-transmitting conductive film, wherein the semiconductor laminate has an n-type cladding layer, an active layer disposed above the n-type cladding layer, a p-type cladding layer disposed above the active layer, and a contact layer disposed above the p-type cladding layer, and the contact layer is Al ｘ１ In ｙ１ Ga １－ｘ１－ｙ１ an N layer, the first translucent conductive film being in contact with the contact layer, an oscillation wavelength of the semiconductor laser element being 350 nm or more and 550 nm or less, and a film thickness of the first translucent conductive film being less than 100 nm.

29. The method for manufacturing a semiconductor laser device according to claim 28, wherein the roughness Rz of the upper surface of the first translucent conductive film is 0.2 nm or more and 2.0 nm or less, and the roughness Rz of the upper surface of the first translucent conductive film is measured based on the height of irregularities in a cross section of the upper surface of the first translucent conductive film.

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