Semiconductor laser element and method for producing semiconductor laser element

Abstract

A semiconductor laser element (1) having a plurality of light-emitting regions (1a), said semiconductor laser element (1) comprising a substrate (10), an N-side semiconductor layer (21) positioned above the substrate (10), a light-emitting layer (22) positioned above the N-side semiconductor layer (21), a P-side semiconductor layer (23) positioned above the light-emitting layer (22), a plurality of P-side contact layers (24) positioned above the P-side semiconductor layer (23) and provided for each of the plurality of light-emitting regions (1a), and a first p-electrode (41) provided for each of the plurality of P-side contact layers (24) so as to be in contact with each of the plurality of P-side contact layers (24), wherein one of at least two first p-electrodes (41) among the plurality of first p-electrodes (41) includes a first electrode material, and another of the at least two first p-electrodes (41) includes a second electrode material having a refractive index different from that of the first electrode material.

Description

Semiconductor laser element and method of manufacturing the same

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

[0002] 2. Description of the Related Art Semiconductor laser elements have advantages such as long life, high efficiency, and small size, and are therefore used as light sources for a variety of products such as projectors, optical discs, vehicle headlamps, lighting devices, and laser processing devices.

[0003] In order to reduce speckle noise, semiconductor laser elements that emit multiple laser beams with different wavelengths have been proposed. Speckle noise is an interference phenomenon that occurs when coherent laser beams are irradiated onto a rough surface. For example, if speckle noise occurs when a semiconductor laser element is used as the light source of a projector, it will cause glare when an image is projected onto a screen, resulting in a degradation of image quality.

[0004] As a semiconductor laser element that emits multiple laser beams with different wavelengths, Patent Document 1 discloses a multi-beam semiconductor laser that emits multiple laser beams with different wavelengths by varying the film thickness of a dielectric film on each of multiple ridge portions.

[0005] Japanese Patent Application Laid-Open No. 2019-175955

[0006] However, in the multi-beam semiconductor laser disclosed in Patent Document 1, the thickness of the dielectric film on one of the two ridges is thin, which increases the lateral spread of light within the device and allows light leaking from the dielectric film to reach the bottom of the ridge. Since the ridge is formed by dry etching or other methods, damage may remain at the bottom of the ridge during its formation. Therefore, if light reaches the bottom of the ridge where damage remains, defects may extend to the active layer, potentially reducing reliability.

[0007] The present disclosure has been made to solve such problems, and aims to provide a semiconductor laser element and a method for manufacturing a semiconductor laser element that can reduce speckle noise using a novel method not previously available.

[0008] In order to achieve the above object, one aspect of the semiconductor laser element according to the present disclosure is a semiconductor laser element having a plurality of light-emitting regions, comprising: a substrate; an N-side semiconductor layer located above the substrate; a light-emitting layer located above the N-side semiconductor layer; a P-side semiconductor layer located above the light-emitting layer; a plurality of P-side contact layers located above the P-side semiconductor layer and provided for each of the plurality of light-emitting regions; and a first p-electrode provided for each of the plurality of P-side contact layers so as to be in contact with each of the plurality of P-side contact layers, wherein one of at least two of the plurality of first p-electrodes contains a first electrode material and the other contains a second electrode material having a refractive index different from that of the first electrode material.

[0009] One aspect of a method for manufacturing a semiconductor laser element according to the present disclosure is a method for manufacturing a semiconductor laser element having a plurality of light-emitting regions, the method including the steps of: forming an N-side semiconductor layer, a light-emitting layer, a P-side semiconductor layer, and a P-side contact layer above a substrate; patterning the P-side contact layer to form a plurality of P-side contact layers for each of the plurality of light-emitting regions; and forming a first p-electrode for each of the plurality of P-side contact layers so as to be in contact with each of the plurality of P-side contact layers, wherein the plurality of P-side contact layers include a first P-side contact layer and a second P-side contact layer. the first p-electrodes include a first first p-electrode located on the first P-side contact layer and a second first p-electrode located on the second P-side contact layer, and the step of forming the first p-electrodes includes a step of forming a first first p-electrode made of a first electrode material on the first P-side contact layer, and then a step of forming an electrode layer made of a second electrode material having a refractive index different from that of the first electrode material on the first first p-electrode, and a step of forming a second first p-electrode made of the second electrode material on the second P-side contact layer.

[0010] According to the present disclosure, a semiconductor laser device capable of reducing speckle noise can be obtained.

[0011] FIG. 1 is a cross-sectional view of a semiconductor laser element according to an embodiment. FIG. 2 is a cross-sectional view of a semiconductor laser device according to an embodiment. FIG. 3 is a diagram showing a model structure of a semiconductor laser element according to an embodiment. FIG. 4 is a diagram showing IL characteristics and IV characteristics of the semiconductor laser element according to an embodiment. FIG. 5 is a diagram showing waveguide loss dependence at an operating point of 2.2A in a semiconductor laser element according to an embodiment. FIG. 6 is a diagram showing groupings of materials that can be used as electrode materials for a first p-electrode. FIG. 7A is a diagram showing the relationship between the refractive index difference between the first p-electrode and the second p-electrode and the wavelength difference between two laser beams when the thickness of the convex portion of the P-side semiconductor layer is 0.3 μm. FIG. 7B is a diagram showing the relationship between the refractive index difference between the first p-electrode and the second p-electrode and the wavelength difference between two laser beams when the thickness of the convex portion of the P-side semiconductor layer is 0.43 μm. FIG. 7C is a diagram showing the relationship between the refractive index difference between the first p-electrode and the second p-electrode and the wavelength difference between two laser beams when the thickness of the convex portion of the P-side semiconductor layer is 0.6 μm. FIG. 8 is a diagram illustrating the relationship between the thickness of the convex portion of the P-side semiconductor layer and the waveguide loss for ten types of electrode materials that can be used for the first p-electrode. FIG. 9 is a diagram illustrating the relationship between the thickness of the convex portion of the P-side semiconductor layer and the wavelength difference between two laser beams for ten types of electrode materials that can be used for the first p-electrode. FIG. 10A is a diagram illustrating a step of forming a semiconductor stacked structure in a method for manufacturing a semiconductor laser device according to an embodiment. FIG. 10B is a diagram illustrating a step of forming a resist in a step of forming a plurality of P-side contact layers in a method for manufacturing a semiconductor laser device according to an embodiment. FIG. 10C is a diagram illustrating a step of forming an opening in the resist in a step of forming a plurality of P-side contact layers in a method for manufacturing a semiconductor laser device according to an embodiment. FIG. 10D is a diagram illustrating a step of etching the semiconductor stacked structure to form a ridge portion in a step of forming a plurality of P-side contact layers in a method for manufacturing a semiconductor laser device according to an embodiment. FIG. 10E is a diagram illustrating a step of removing the resist in a step of forming a plurality of P-side contact layers in a method for manufacturing a semiconductor laser device according to an embodiment.10F is a diagram for explaining a step of forming a resist in the step of forming a separation trench in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 10G is a diagram for explaining a step of forming an opening in the resist in the step of forming a separation trench in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 10H is a diagram for explaining a step of etching the semiconductor stacked structure to form the separation trench in the step of forming a separation trench in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 10I is a diagram for explaining a step of removing the resist in the step of forming the separation trench in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 10J is a diagram for explaining a step of forming an insulating film in the step of forming an insulating film having an opening in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 10K is a diagram for explaining a step of forming a resist in the step of forming an insulating film having an opening in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 10L is a diagram for explaining a step of forming an opening in the resist in the step of forming an insulating film having an opening in the method for manufacturing a semiconductor laser device according to the embodiment. FIG. 10M is a diagram for explaining a step of forming an opening in the insulating film in the step of forming an insulating film having an opening in the method for manufacturing a semiconductor laser device according to the embodiment. 10N is a diagram for explaining a step of removing a resist in a step of forming an insulating film having an opening in a manufacturing method for a semiconductor laser device according to an embodiment. FIG. 10O is a diagram for explaining a step of forming a resist having an opening in a step of forming a first p-electrode in a manufacturing method for a semiconductor laser device according to an embodiment. FIG. 10P is a diagram for explaining a step of forming a first p-electrode by depositing an electrode film in a step of forming a first p-electrode in a manufacturing method for a semiconductor laser device according to an embodiment. FIG. 10Q is a diagram for explaining a step of removing a resist in the step of forming a first p-electrode in a manufacturing method for a semiconductor laser device according to an embodiment.10R is a diagram for explaining a step of forming an adhesion layer on a first first p-electrode and forming a second first p-electrode in a step of forming a first p-electrode in a manufacturing method of a semiconductor laser device according to an embodiment. FIG. 10S is a diagram for explaining a step of forming a second p-electrode in a manufacturing method of a semiconductor laser device according to an embodiment. FIG. 10T is a diagram for explaining a step of forming a pad electrode in a manufacturing method of a semiconductor laser device according to an embodiment. FIG. 10U is a diagram for explaining a step of forming an n-electrode in a manufacturing method of a semiconductor laser device according to an embodiment. FIG. 11 is a cross-sectional view of a semiconductor laser device of Modification 1. FIG. 12 is a diagram showing an example combination of electrode materials for the first p-electrode in the semiconductor laser device of Modification 1. FIG. 13 is a cross-sectional view of a semiconductor laser device of Modification 2. FIG. 14 is a diagram showing an example combination of electrode materials for the first p-electrode in the semiconductor laser device of Modification 2. FIG. 15 is a diagram showing an example combination of electrode materials for the first p-electrode in a semiconductor laser device of Modification 2 having four light-emitting regions. FIG. 16 is a diagram showing an example combination of electrode materials for the first p-electrode in a semiconductor laser device of Modification 2 having five light-emitting regions. Fig. 17 is a cross-sectional view of a semiconductor laser device of Modification 3. Fig. 18 is a diagram showing the relationship between the film thickness of the first electrode layer of the first p-electrode and the waveguide loss when the first electrode layer is used as an adhesive layer in the semiconductor laser device of Modification 3. Fig. 19 is a cross-sectional view of a semiconductor laser device of Modification 4.

[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, the arrangement and connection of the components, steps (processes), and the order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concept of the present disclosure will be described as optional components.

[0013] Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. 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 the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. Furthermore, the terms "above" and "below" are used not only when two components are arranged with a gap between them and another component is present between the two components, but also when two components are arranged in contact with each other.

[0015] (Embodiment) [Semiconductor Laser Device] First, the configuration of a semiconductor laser device 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view of the semiconductor laser device 1 according to the embodiment.

[0016] The semiconductor laser element 1 is a semiconductor laser that emits laser light. Specifically, the semiconductor laser element 1 is a multi-emitter laser having multiple light-emitting regions 1 a (emitters), and emits multiple laser beams. In this embodiment, the multiple laser beams emitted by the semiconductor laser element 1 have different wavelengths.

[0017] 1, the semiconductor laser device 1 has a substrate 10 and a semiconductor laminated structure 20 located on the substrate 10. The semiconductor laminated structure 20 is formed on one surface, that is, the upper surface, of the substrate 10.

[0018] The semiconductor stacked structure 20 is a structure in which a plurality of semiconductor layers are stacked. In this embodiment, a plurality of semiconductor stacked structures 20 are provided on one substrate 10. Specifically, two semiconductor stacked structures 20 are provided on the substrate 10. One of the two semiconductor stacked structures 20 is a first semiconductor stacked structure 20a, and the other of the two semiconductor stacked structures 20 is a second semiconductor stacked structure 20b.

[0019] A light emitting region 1a exists in each of the plurality of semiconductor stacked structures 20. In this embodiment, the semiconductor laser device 1 has two semiconductor stacked structures 20, and therefore has two light emitting regions 1a.

[0020] As an example, the semiconductor laser element 1 emits laser light in the 635 nm wavelength band. That is, the multiple laser beams emitted from the semiconductor laser element 1 are all laser beams in the 635 nm wavelength band, but there is a difference in wavelength. As an example, the difference in wavelength between the two laser beams emitted from the semiconductor laser element 1 is greater than 0 nm and not more than 5 nm. The semiconductor stacked structure 20 is made of, for example, a III-V group compound semiconductor made of an AlGaInAs-based semiconductor material. Note that a window region may or may not be formed at the front end of the semiconductor stacked structure 20.

[0021] When the semiconductor laminated structure 20 is made of an AlGaInAs-based semiconductor material, a semiconductor substrate such as a GaAs substrate can be used as the substrate 10. In this embodiment, an n-type GaAs substrate is used as the substrate 10. A buffer layer may be formed between the substrate 10 and the semiconductor laminated structure 20. Specifically, the buffer layer is formed between the substrate 10 and the N-side semiconductor layer 21. The buffer layer is, for example, an n-type GaAs layer, and is laminated on the substrate 10.

[0022] Each of the multiple semiconductor laminated structures 20 has, in this order, an N-side semiconductor layer 21, a light-emitting layer 22, a P-side semiconductor layer 23, and a P-side contact layer 24 on the substrate 10. Specifically, the first semiconductor laminated structure 20a has a first N-side semiconductor layer 21a, a first light-emitting layer 22a, a first P-side semiconductor layer 23a, and a first P-side contact layer 24a. The second semiconductor laminated structure 20b has a second N-side semiconductor layer 21b, a second light-emitting layer 22b, a second P-side semiconductor layer 23b, and a second P-side contact layer 24b.

[0023] The layer configurations of the multiple semiconductor laminate structures 20 are the same. That is, the composition of each semiconductor layer in the first semiconductor laminate structure 20a and the second semiconductor laminate structure 20b is the same. In this embodiment, not only the composition of each semiconductor layer in the first semiconductor laminate structure 20a and the second semiconductor laminate structure 20b but also the film thickness of each semiconductor layer are the same. Therefore, the first N-side semiconductor layer 21a and the second N-side semiconductor layer 21b have the same composition and film thickness, the first light-emitting layer 22a and the second light-emitting layer 22b have the same composition and film thickness, the first P-side semiconductor layer 23a and the second P-side semiconductor layer 23b have the same composition and film thickness, and the first P-side contact layer 24a and the second P-side contact layer 24b have the same composition and film thickness.

[0024] The N-side semiconductor layer 21 is located above the substrate 10. The N-side semiconductor layer 21 includes at least an n-type cladding layer. The n-type cladding layer is an n-type semiconductor layer intentionally doped with impurities. In this embodiment, the n-type cladding layer in the N-side semiconductor layer 21 is, for example, an n-type AlInP layer. The impurity doped into the n-type cladding layer is, for example, silicon (Si).

[0025] The N-side semiconductor layer 21 may include an n-type semiconductor layer other than the n-type cladding layer, or may include an undoped semiconductor layer that is not intentionally doped with impurities.

[0026] The light-emitting layer 22 is located above the N-side semiconductor layer 21. The light-emitting layer 22 is formed, for example, directly on the n-type cladding layer of the N-side semiconductor layer 21. The light-emitting layer 22 is an active layer and a PN junction in the semiconductor stacked structure 20. The light-emitting layer 22 has a layered structure in which well layers and barrier layers are alternately stacked. The light-emitting layer 22 may have either a single quantum well structure (SQW) or a multiple quantum well structure (MQW). In this embodiment, the light-emitting layer 22 further includes an n-side guide layer and a p-side guide layer. As an example, the light-emitting layer 22 has a five-layer structure in which an n-side guide layer, a barrier layer, a well layer, a barrier layer, and a p-side guide layer are stacked in this order. In this case, the light emitting layer 22 can be composed of an n-type guide layer made of AlGaInP, a barrier layer made of AlGaInP, a well layer made of GaInP, a barrier layer made of AlGaInP, and a p-type guide layer made of AlGaInP.

[0027] The P-side semiconductor layer 23 is located above the light-emitting layer 22. The P-side semiconductor layer 23 includes at least a p-type cladding layer. The p-type cladding layer is a p-type semiconductor layer intentionally doped with impurities. In this embodiment, the p-type cladding layer in the P-side semiconductor layer 23 is, for example, a p-type AlInP layer. The impurities doped into the p-type cladding layer are, for example, zinc (Zn) or magnesium (Mg).

[0028] The P-side semiconductor layer 23 may include a p-type semiconductor layer other than the p-type cladding layer, or may include an undoped semiconductor layer that is not intentionally doped with impurities.

[0029] The P-side contact layer 24 is located above the P-side semiconductor layer 23. For example, the P-side contact layer 24 is formed directly on the p-type cladding layer of the P-side semiconductor layer 23. The P-side contact layer 24 includes at least a p-type contact layer. The p-type contact layer is a p-type semiconductor layer intentionally doped with impurities. The p-type contact layer in the P-side contact layer 24 is, for example, a p-type GaAs layer. The impurities doped into the p-type contact layer are, for example, zinc (Zn) or carbon (C).

[0030] The p-side contact layer 24 may include a p-type semiconductor layer other than the p-type contact layer. In this embodiment, the p-side contact layer 24 includes three p-type semiconductor layers, namely, a first intermediate layer, a second intermediate layer, and a third intermediate layer, in addition to the p-type contact layer. Specifically, the p-side contact layer 24 has a structure in which a first intermediate layer made of AlGaInP, a second intermediate layer made of AlGaInP, a third intermediate layer made of AlGaInP, and a p-type contact layer are stacked in this order on the p-side semiconductor layer 23. The first intermediate layer, the second intermediate layer, and the third intermediate layer are AlGaInP layers having different Al and Ga composition ratios.

[0031] The P-side contact layer 24 is provided for each of the plurality of light-emitting regions 1a. That is, the semiconductor laser device 1 has a plurality of P-side contact layers 24. In the present embodiment, the semiconductor laser device 1 has two light-emitting regions 1a, and therefore the plurality of P-side contact layers 24 has two P-side contact layers 24. One of the two P-side contact layers 24 is a first P-side contact layer 24a, and the other of the two P-side contact layers 24 is a second P-side contact layer 24b.

[0032] The semiconductor laminated structure 20 configured in this manner has a ridge portion 31 and a flat portion 32 that spreads laterally from the base of the ridge portion 31. That is, the semiconductor laser element 1 is a semiconductor laser with a ridge stripe structure having the ridge portion 31, and the ridge portion 31 forms a waveguide of the semiconductor laser element 1. In this embodiment, the semiconductor laser element 1 has a plurality of ridge portions 31. The ridge portion 31 is provided for each of the plurality of light-emitting regions 1a. Specifically, the semiconductor laser element 1 has two ridge portions 31. One of the two ridge portions 31 is a first ridge portion 31a, and the other of the two ridge portions 31 is a second ridge portion 31b. In each semiconductor laminated structure 20, the ridge portion 31 and the flat portion 32 extend along the cavity length direction of the semiconductor laser element 1.

[0033] The ridge portion 31 and the flat portion 32 can be formed by etching and engraving the semiconductor laminated structure 20. In this embodiment, the ridge portion 31 and the flat portion 32 are formed by engraving the P-side semiconductor layer 23 and the P-side contact layer 24.

[0034] In this case, the P-side semiconductor layer 23 has a lower layer 23m, which is a portion of the P-side semiconductor layer 23 that is not recessed, and an upper layer 23n, which is a portion of the P-side semiconductor layer 23 that is recessed. In this embodiment, the P-side semiconductor layer 23 is a p-type cladding layer, so the lower layer 23m is a first p-type cladding layer and the upper layer 23n is a second p-type cladding layer. The upper layer 23n is located on the lower layer 23m. Specifically, the upper layer 23n is a convex portion that protrudes from the lower layer 23m. The flat surface of the flat portion 32 is the surface of the lower layer 23m.

[0035] The P-side contact layer 24 is formed on the upper layer 23n (convex portion) of the P-side semiconductor layer 23. The ridge portion 31 includes the upper layer 23n (convex portion) of the P-side semiconductor layer 23 and the P-side contact layer 24 located on the upper layer 23n (convex portion). In the ridge portion 31, the P-side contact layer 24 is the uppermost layer of the ridge portion 31.

[0036] The width and height of the ridge portion 31 are not particularly limited, but as an example, the ridge width (stripe width) of the ridge portion 31 is 1 μm or more and 100 μm or less, and the height of the ridge portion 31 is 0.1 μm or more and 1 μm or less. The ridge width of the ridge portion 31 is preferably 2 μm or more in the case of a single mode, and 5 μm or more in the case of a multimode. The width of the P-side contact layer 24 is the same as the ridge width of the ridge portion 31, but is not limited to this.

[0037] Furthermore, in this embodiment, by digging into the semiconductor laminated structure 20, convex wing portions 33 are further formed in the semiconductor laminated structure 20. That is, the semiconductor laminated structure 20 has a ridge portion 31 and wing portions 33 as a convex structure. Like the ridge portion 31, the wing portions 33 are composed of the P-side semiconductor layer 23 and the P-side contact layer 24. Furthermore, the height of the wing portions 33 is the same as the height of the ridge portion 31, but is not limited to this. The top surfaces of the ridge portion 31 and the wing portions 33 are both flat.

[0038] The wing portions 33 are formed on both sides of the ridge portion 31. That is, each of the plurality of semiconductor stacked structures 20 has a pair of wing portions 33. The ridge portion 31 is sandwiched between the pair of wing portions 33 via the flat portion 32. The pair of wing portions 33, like the ridge portion 31, extend along the cavity length direction of the semiconductor laser device 1. By providing the wing portions 33 on both sides of the ridge portion 31 in this way, it is possible to alleviate the stress applied to the ridge portion 31 when the semiconductor laser device 1 is mounted junction-down.

[0039] The semiconductor laser element 1 also has a separation trench 34. The separation trench 34 separates the semiconductor laser element 1 into a plurality of semiconductor laminate structures 20. In this embodiment, the semiconductor laser element 1 has one separation trench 34, and the separation trench 34 separates the semiconductor laser element 1 into two semiconductor laminate structures 20, a first semiconductor laminate structure 20a and a second semiconductor laminate structure 20b. The separation trench 34 can be formed by digging the semiconductor laminate structure 20. In this embodiment, the separation trench 34 is formed by digging the semiconductor laminate structure 20 down to the substrate 10. In other words, the bottom surface of the separation trench 34 is the upper surface of the substrate 10.

[0040] The width of the separation groove 34 is preferably 5 μm or more. This separates the two adjacent semiconductor laminate structures 20, thereby isolating the heat between the two adjacent light-emitting regions 1 a. In other words, it is possible to prevent one of the two semiconductor laminate structures 20 from being affected by the heat of the other. Furthermore, the distance (emitter distance) between the two adjacent light-emitting regions 1 a is preferably 40 μm or more, and even more preferably 60 μm or more. This prevents the two light-emitting regions 1 a from being affected by heat.

[0041] The semiconductor laser device 1 further includes, as a p-side electrode, a first p-electrode 41 located on the P-side contact layer 24. The first p-electrode 41 is formed directly on the P-side contact layer 24. The first p-electrode 41 is provided for each of the plurality of P-side contact layers 24 so as to be in contact with each of the plurality of P-side contact layers 24.

[0042] The first p-electrode 41 is provided for each of the plurality of light-emitting regions 1a. That is, the first p-electrode 41 is provided for each of the plurality of ridge portions 31. Therefore, the semiconductor laser device 1 includes a plurality of first p-electrodes 41. Each of the plurality of first p-electrodes 41 is provided on the ridge portion 31. The semiconductor laser device 1 of this embodiment has two light-emitting regions 1a and therefore includes two first p-electrodes 41. One of the two first p-electrodes 41 is a first first p-electrode 41a, and the other of the two first p-electrodes 41 is a second first p-electrode 41b. The first first p-electrode 41a is formed on the first P-side contact layer 24a so as to be in contact with the first P-side contact layer 24a. The second first p-electrode 41b is formed on the second P-side contact layer 24b so as to be in contact with the second P-side contact layer 24b.

[0043] The width of the first first p-electrode 41a is equal to or smaller than the width of the first P-side contact layer 24a. On the other hand, the width of the second first p-electrode 41b is greater than the width of the second P-side contact layer 24b. That is, the width of the second first p-electrode 41b is greater than the width of the first first p-electrode 41a. Specifically, the first first p-electrode 41a is formed only on the ridge portion 31, but the second first p-electrode 41b is formed not only on the ridge portion 31 but also on the flat portion 32 and the wing portion 33. That is, the second first p-electrode 41b is formed across the ridge portion 31, the flat portion 32, and the wing portion 33.

[0044] At least two of the plurality of first p electrodes 41 include a first electrode material and a second electrode material having a refractive index different from that of the first electrode material. In the present embodiment, there are two first p electrodes 41, and the first electrode material constituting the first first p electrode 41a, which is one of the two first p electrodes 41, and the second electrode material constituting the second first p electrode 41b, which is the other of the two first p electrodes 41, have different refractive indices. Specifically, the first first p electrode 41a and the second first p electrode 41b are made of different electrode materials.

[0045] The first p-electrode 41 is an ohmic electrode that makes ohmic contact with the p-side contact layer 24. Therefore, the electrode material constituting the first p-electrode 41 can be a metal material such as silver (Ag), aluminum (Al), palladium (Pd), nickel (Ni), rhodium (Rh), titanium (Ti), platinum (Pt), chromium (Cr), tungsten (W), or molybdenum (Mo), or a transparent conductive material such as indium tin oxide (ITO). Therefore, by selecting different materials from among these electrode materials for the first p-electrode 41a and the second p-electrode 41b, the refractive indices of the first p-electrode 41a and the second p-electrode 41b can be made different. In addition, in this embodiment, as described above, the widths of the first p-electrode 41a and the second p-electrode 41b are different. In this way, by making the widths of the first first p electrode 41a and the second first p electrode 41b, which have different refractive indices, different from each other, it is possible to adjust the influence of the refractive index for each light-emitting region 1a. In this embodiment, the first electrode material constituting the first first p electrode 41a is silver (Ag), and the second electrode material constituting the second first p electrode 41b is titanium (Ti). In other words, the first first p electrode 41a is a single layer of silver (Ag layer), and the second first p electrode 41b is a single layer of titanium (Ti layer).

[0046] The thickness of each of the plurality of first p-electrodes 41 is, for example, 0.015 μm to 0.300 μm (15 nm to 300 nm). If the thickness of the first p-electrode 41 is less than 0.015 μm, it will be easily affected by the refractive index of the second p-electrode 42 formed on the first p-electrode 41. On the other hand, if the thickness of the first p-electrode 41 exceeds 0.300 μm, the cleavability when cleaving and dividing the wafer will decrease, and cracks will be more likely to occur on the cleavage planes.

[0047] The semiconductor laser device 1 further includes, as p-side electrodes, second p-electrodes 42 located above each of the plurality of first p-electrodes 41. That is, a second p-electrode 42 is provided for each of the plurality of first p-electrodes 41, and the semiconductor laser device 1 includes a plurality of second p-electrodes 42. The semiconductor laser device 1 of this embodiment includes two first p-electrodes 41 and therefore two second p-electrodes 42. One of the two second p-electrodes 42 is a first second p-electrode 42a, and the other is a second second p-electrode 42b. The first second p-electrode 42a is located above the first first p-electrode 41a, and the second second p-electrode 42b is located above the second first p-electrode 41b. The first second p-electrode 42a and the second second p-electrode 42b are formed across the ridge portion 31, the flat portion 32, and the wing portion 33.

[0048] In this embodiment, an adhesion layer 43 is provided between the first first p-electrode 41a and the first second p-electrode 42a. Therefore, the first second p-electrode 42a is provided on the adhesion layer 43. The adhesion layer 43 is an example of an electrode layer formed across the ridge portion 31, the flat portion 32, and the wing portion 33. The adhesion layer 43 is made of the same material as the second electrode material constituting the second first p-electrode 41b. Specifically, the adhesion layer 43 is made of Ti. This allows the adhesion layer 43 to be formed simultaneously with the formation of the second first p-electrode 42b, thereby improving the adhesion of the first first p-electrode 41a and further reducing the number of electrode formation steps, thereby reducing manufacturing costs. Meanwhile, the second second p-electrode 42b is formed directly on the second first p-electrode 41b. In other words, the second second p-electrode 42b is in contact with the second first p-electrode 41b. The adhesion layer 43 may be a part of the first p-electrode 41a.

[0049] The first second p-electrode 42a and the second second p-electrode 42b are made of the same electrode material. As an example, the first second p-electrode 42a and the second second p-electrode 42b each have a two-layer structure. Specifically, the first second p-electrode 42a and the second second p-electrode 42b each have a first electrode layer made of platinum (Pt) and a second electrode layer made of gold (Au) formed on the first electrode layer. Note that the second p-electrode 42 may have a single-layer structure instead of a two-layer structure, or may have three or more layers.

[0050] A pad electrode 50 is formed on the second p-electrode 42. A pad electrode 50 is provided for each of the plurality of second p-electrodes 42, and the semiconductor laser device 1 includes a plurality of pad electrodes 50. Since the semiconductor laser device 1 of this embodiment has two second p-electrodes 42, the semiconductor laser device 1 has two pad electrodes 50. One of the two pad electrodes 50 is a first pad electrode 50a, and the other is a second pad electrode 50b. The first pad electrode 50a is formed so as to contact the first second p-electrode 42a, and the second pad electrode 50b is formed so as to contact the second second p-electrode 42b. The first pad electrode 50a and the second pad electrode 50b are formed across the ridge portion 31, the flat portion 32, and the wing portion 33. The pad electrodes 50 are made of a metal material such as Au.

[0051] An n-electrode 60 (n-side electrode) is formed on the other surface, that is, the lower surface (rear surface), of the substrate 10. The n-electrode 60 is an ohmic electrode that makes ohmic contact with the substrate 10, which is a semiconductor substrate. The n-electrode 60 is formed using at least one metal material, such as Cr, Ti, Ni, Pd, Pt, Au, and Ge. The n-electrode 60 may be either a single-layer film or a multilayer film. In this embodiment, the n-electrode 60 is configured as a multilayer film. As an example, the n-electrode 60 is a multilayer film with a three-layer structure in which a first electrode layer 61 (Ti layer) made of Ti, a second electrode layer 62 (Pt layer) made of Pt, and a third electrode layer 63 (Au layer) made of Au are stacked.

[0052] The semiconductor laminated structure 20 is made of SiO 3 except for the portion on the ridge portion 31 where the first p-electrode 41 is formed. ２ The p-side semiconductor layer 23 and the p-side contact layer 24 are covered with an insulating film 70 made of a dielectric film such as SiN or the like. Specifically, the insulating film 70 is formed so as to cover the p-side semiconductor layer 23 and the p-side contact layer 24 except for the portion on the ridge portion 31 where the first p-electrode 41 is formed (i.e., so as to have an opening above the ridge portion 31). The insulating film 70 functions as a current blocking film. Therefore, the opening in the insulating film 70 above the ridge portion 31 serves as a current injection window through which current passes. The insulating film 70 may be formed up to the side surfaces of the semiconductor stacked structure 20.

[0053] The semiconductor laser element 1 configured as above is mounted on a submount 2 as shown in FIG. 2 . For example, as shown in FIG. 2 , the semiconductor laser element 1 is mounted on the submount 2 in a junction-down manner. FIG. 2 is a cross-sectional view of a semiconductor laser device according to an embodiment, showing the semiconductor laser element 1 mounted on the submount 2. The body of the submount 2 can be made of an insulating material such as AlN, SiC, or diamond. A conductive layer 2 a is formed on the surface of the body of the submount 2. The semiconductor laser element 1 and the submount 2 are bonded with a conductive bonding material 3 such as AuSn solder. In this case, multiple pad electrodes 50 of the semiconductor laser element 1 are bonded to the conductive layer 2 a of the submount 2 with the conductive bonding material 3. Gold wires 4 a for connection to a positive electrode terminal are wire-bonded to the conductive layer 2 a of the submount 2. Furthermore, gold wires 4 b for connection to a negative electrode terminal are wire-bonded to the n-electrode 60 of the semiconductor laser element 1.

[0054] As described above, in the semiconductor laser element 1 according to this embodiment, a plurality of P-side contact layers 24 are provided corresponding to a plurality of light-emitting regions 1 a, and at least two of the plurality of first p-electrodes 41 provided for each of the plurality of P-side contact layers 24 are made of electrode materials having different refractive indices.

[0055] With this configuration, the degree of light absorbed by the multiple first p electrodes 41 located above the P-side contact layer 24 varies, so that the waveguide loss (light loss) due to the first p electrodes 41 can be made different for each of the multiple first p electrodes 41.

[0056] Specifically, in this embodiment, the plurality of first p-electrodes 41 are each composed of a first first p-electrode 41 a and a second first p-electrode 41 b, and the first first p-electrode 41 a and the second first p-electrode 41 b are made of different electrode materials, so that the waveguide loss due to the first first p-electrode 41 a can be made different from the waveguide loss due to the second first p-electrode 41 b.

[0057] As a result, when a constant current is applied to the semiconductor laser element 1, the operating point differs for each light-emitting region 1a, and therefore the wavelength of the laser light oscillated in each light-emitting region 1a can be made different, thereby reducing speckle noise.

[0058] The inventors conducted a simulation to confirm this effect, which will be described below. In this simulation, the oscillation wavelength of the laser light was set to the 635 nm band, and calculations were performed using a semiconductor laser device 1 having the cross-sectional structure shown in FIG. 1 and the model structure shown in FIG. 3. The chip size of the semiconductor laser device 1 was set to a chip width of 400 μm, a cavity length of 1500 μm, and a chip thickness of 100 μm. The reflectivity of the front facet of the semiconductor laser device 1 was set to 7%.

[0059] 4 and 5 show the results of the simulation. Fig. 4 shows the IL and IV characteristics for each light-emitting region 1a when the electrode material of the first first p-electrode 41a is Ag and the electrode material of the second first p-electrode 41b is Ti. In Fig. 4, αi represents the waveguide loss.

[0060] 4, the waveguide loss of the first semiconductor laminated structure 20a provided with the first first p-electrode 41a (Ag) is different from the waveguide loss of the second semiconductor laminated structure 20b provided with the second first p-electrode 41b (Ti). Specifically, the waveguide loss of the first semiconductor laminated structure 20a provided with the first first p-electrode 41a (Ag) is 3 cm －１ The waveguide loss of the second semiconductor laminated structure 20b provided with the second first p-electrode 41b (Ti) is 6 cm －１ is.

[0061] 5 shows the waveguide loss dependence at the operating point 2.2A of FIG. 4 . As shown in FIG. 5 , the wavelength of the laser light emitted from the light-emitting region 1a of the first semiconductor laminated structure 20a provided with the first first p-electrode 41a (Ag) is different from the wavelength of the laser light emitted from the light-emitting region 1a of the second semiconductor laminated structure 20b provided with the second first p-electrode 41b (Ti). Specifically, the wavelength difference between the laser light emitted from the light-emitting region 1a of the first semiconductor laminated structure 20a provided with the first first p-electrode 41a (Ag) and the laser light emitted from the light-emitting region 1a of the second semiconductor laminated structure 20b provided with the second first p-electrode 41b (Ti) is 1.5 nm or more. In this way, by making the wavelength difference between the two laser lights emitted from the semiconductor laser element 1 1.5 nm or more, speckle noise can be effectively reduced.

[0062] As described above, according to the semiconductor laser device 1 according to the present embodiment, the plurality of first p-electrodes 41 (the first first p-electrode 41 a and the second first p-electrode 41 b) are made of electrode materials having different refractive indices, and therefore speckle noise can be reduced.

[0063] Here, a combination of electrode materials for the plurality of first p-electrodes 41 in the semiconductor laser device 1 will be described with reference to Fig. 6. Fig. 6 shows a diagram in which materials that can be used as the electrode materials for forming the first p-electrodes 41 are grouped.

[0064] 6 , when materials that can be used as the electrode material for the first p-electrode 41 are divided into three groups, group A, group B, and group C, the electrode materials for the first first p-electrode 41 a and the second first p-electrode 41 b may be selected from different groups. For example, when the first electrode material for the first first p-electrode 41 a is selected from group A, the second electrode material for the second first p-electrode 41 b may be selected from group B or group C.

[0065] When the electrode material is a metal material, the materials are divided into groups A, B, and C based on their refractive index. Specifically, group A is a group of metal materials whose refractive index n is 1 or less (n≦1), group B is a group of metal materials whose refractive index n is greater than 1 and less than 3 (1<n<3), and group C is a group of metal materials whose refractive index n is 3 or more (n≧3). When the electrode material is a conductive material other than a metal, conductive materials whose extinction coefficient is 1 or less belong to group A. An example of a conductive material used as the electrode material for the first p-electrode 41 is ITO (indium tin oxide).

[0066] Furthermore, the refractive index of the electrode material varies depending on the wavelength band of the laser light. Therefore, as shown in (a) to (c) of Figure 6, the metal materials included in the three groups also vary depending on the wavelength band of the laser light. (a) of Figure 6 shows groups A, B, and C for the 635 nm wavelength band (red light), (b) of Figure 6 shows groups A, B, and C for the 530 nm wavelength band (green light), and (c) of Figure 6 shows groups A, B, and C for the 450 nm wavelength band (blue light). For example, as can be seen by comparing (a) and (b) of Figure 6, Al belongs to group B because its refractive index is greater than 1 in the 635 nm wavelength band, but it belongs to group A because its refractive index is less than 1 in the 530 nm and 450 nm wavelength bands. Cr belongs to group C because its refractive index is greater than 3 in the 635 nm and 530 nm wavelength bands, but it belongs to group B because its refractive index is less than 3 in the 450 nm wavelength band.

[0067] In this way, by selecting the electrode materials constituting the plurality of first p-electrodes 41 (the first first p-electrode 41 a and the second first p-electrode 41 b) from different groups out of the three groups, it is possible to maximize the difference in optical loss for each light-emitting region 1 a. This makes it easier to create a difference in wavelength between the two laser beams, thereby effectively reducing speckle noise.

[0068] In the present embodiment, when selecting the first electrode material of the first first p-electrode 41 a and the second electrode material of the second first p-electrode 41 b, the electrode materials are selected from different groups among the three groups, but this is not limiting. As long as the wavelength difference between the two laser beams can be made 1.5 nm or more, the first electrode material of the first first p-electrode 41 a and the second electrode material of the second first p-electrode 41 b may be selected from electrode materials belonging to the same group among the three groups.

[0069] In the semiconductor laser device 1 according to this embodiment, the refractive index difference between the first electrode material constituting the first first p-electrode 41a and the second electrode material constituting the second first p-electrode 41b may be 0.7 or more, preferably 1.0 or more, and even more preferably 1.5 or more. For example, the refractive index difference can be 0.7 or more in the 635 nm wavelength band by combining Cr and Pt from different electrode material groups for the first first p-electrode 41a and the second first p-electrode 41b, or by combining Al and Pt from the same electrode material group. Furthermore, the refractive index difference can be 1.0 or more in the 635 nm wavelength band by combining Ag and Al from different electrode material groups for the first first p-electrode 41a and the second first p-electrode 41b.

[0070] In this way, by increasing the refractive index difference between the first first p electrode 41 a and the second first p electrode 41 b, the optical absorption difference (optical loss difference) between the first first p electrode 41 a and the second first p electrode 41 b can be increased. This increases the difference in waveguide loss between the first first p electrode 41 a and the second first p electrode 41 b, thereby increasing the wavelength difference between the two laser beams and reducing speckle noise. In particular, by making the refractive index difference between the first first p electrode 41 a and the second first p electrode 41 b 1.5 or more, speckle noise can be effectively reduced.

[0071] 7A to 7C , by reducing the thickness of the convex portion (upper layer 23n) of the P-side semiconductor layer 23 (i.e., the thickness from the ridge bottom surface of the ridge portion 31 to the top surface of the convex portion), the optical absorption difference (optical loss difference) between the first first p-electrode 41a and the second first p-electrode 41b can be increased, and the wavelength difference between the two laser beams can be further increased. FIGS. 7A to 7C show the relationship between the refractive index difference between the first first p-electrode 41a and the second first p-electrode 41b and the wavelength difference between the two laser beams. FIG. 7A shows the case where the thickness of the convex portion (upper layer 23n) of the P-side semiconductor layer 23 is 0.3 μm, FIG. 7B shows the case where the thickness of the convex portion (upper layer 23n) of the P-side semiconductor layer 23 is 0.43 μm, and FIG. 7C shows the case where the thickness of the convex portion (upper layer 23n) of the P-side semiconductor layer 23 is 0.6 μm. 7A to 7C show simulation results calculated using the model structure shown in FIG.

[0072] 8 shows the relationship between the thickness of the convex portion (upper layer 23n) of the P-side semiconductor layer 23, which is a P clad layer, and the waveguide loss for 10 types of electrode materials that can be used for the first p electrode 41. Fig. 9 shows the relationship between the thickness of the convex portion (upper layer 23n) of the P-side semiconductor layer 23, which is a P clad layer, and the wavelength difference between the two laser beams for 10 types of electrode materials that can be used for the first p electrode 41. Figs. 8 and 9 show the results of a simulation calculated using the model structure shown in Fig. 3, with the thickness of the convex portion (upper layer 23n) of the P-side semiconductor layer 23 varied from 0.25 μm to 0.6 μm.

[0073] 8 and 9 , it can be seen that there are many combinations of electrode materials that can ensure a wavelength difference of 1.5 nm or more between the two laser beams by setting the thickness of the convex portion of the P-side semiconductor layer 23 (i.e., the thickness from the ridge bottom surface of the ridge portion 31 to the top surface of the convex portion) to 0.43 μm or less. As an example, when the thickness of the convex portion of the P-side semiconductor layer 23 is 0.30 μm, the wavelength difference can be 1.5 nm or more in the 635 nm wavelength band by combining Ag and Al selected from different electrode material groups for the first and second p-electrodes 41 a and 41 b. Furthermore, the wavelength difference can be 3.0 nm or more in the 635 nm wavelength band by combining Ag and Mo selected from different electrode material groups for the first and second p-electrodes 41 a and 41 b.

[0074] 6 has been exemplified as an electrode material for the first p-electrode 41 in the present embodiment, but the present invention is not limited to this. In other words, an electrode material for the first p-electrode 41 may be a material other than that shown in FIG.

[0075] [Method for Manufacturing Semiconductor Laser Device] Next, a method for manufacturing the semiconductor laser device 1 according to the embodiment will be described with reference to Figures 10A to 10U. Figures 10A to 10U are diagrams for explaining each step in the method for manufacturing the semiconductor laser device 1 according to the embodiment.

[0076] 10A , a semiconductor laminated structure 20 is formed by laminating a plurality of semiconductor layers on a substrate 10. Specifically, an n-type GaAs substrate wafer is prepared as the substrate 10, and an N-side semiconductor layer 21, a light-emitting layer 22, a P-side semiconductor layer 23, and a P-side contact layer 24 are sequentially crystal-grown on the substrate 10 to form a semiconductor laminated structure 200 having an epitaxial structure. The N-side semiconductor layer 21, the light-emitting layer 22, the P-side semiconductor layer 23, and the P-side contact layer 24 can be formed by epitaxially growing semiconductor materials using, for example, a metal organic chemical vapor deposition (MOCVD) method.

[0077] 10B to 10E , the P-side contact layer 24 is patterned to form a plurality of P-side contact layers 24 for each of the plurality of light-emitting regions 1 a. In this embodiment, a plurality of ridge portions 31 are formed in the semiconductor stacked structure 200, thereby forming a plurality of P-side contact layers 24 separated for each of the plurality of ridge portions 31.

[0078] 10B , a resist 81 serving as a mask is first formed on the semiconductor stacked structure 200. More specifically, the resist 81 is applied onto the P-side contact layer 24. A photosensitive resin material can be used as the resist 81.

[0079] 10C, the resist 81 is exposed and developed to form an opening 81a in the resist 81. The opening 81a is formed at a position corresponding to the flat portion 32 of the semiconductor stacked structure 20.

[0080] 10D , etching is performed using the resist 81 with the opening 81 a formed therein as a mask, thereby engraving the semiconductor stacked structure 200 in the portion corresponding to the opening 81 a. This forms a ridge portion 31, a flat portion 32, and a wing portion 33 in the semiconductor stacked structure 200. Specifically, a first ridge portion 31 a and a second ridge portion 31 b are formed as the ridge portion 31.

[0081] 10E , the resist 81 is removed to expose the semiconductor stack 200. Specifically, the P-side contact layer 24 is exposed. This allows the semiconductor stack 200 having a plurality of ridge portions 31 to be formed.

[0082] 10F to 10I, separation grooves 34 are formed in the semiconductor stack 200 to form a plurality of semiconductor stacks 20 for each of the plurality of ridge portions 31. In the present embodiment, by forming the separation grooves 34 in the semiconductor stack 200, a first semiconductor stack 20a having a first ridge portion 31a and a second semiconductor stack 20b having a second ridge portion 31b are formed as a plurality of semiconductor stacks 20.

[0083] 10F , a resist 82 serving as a mask is first formed on the semiconductor stacked structure 200 in which the multiple ridge portions 31 are formed. More specifically, the resist 82 is applied onto the P-side contact layer 24. A photosensitive resin material can be used as the resist 82.

[0084] 10G, the resist 82 is exposed and developed to form openings 82a in the resist 82. The openings 82a are formed at positions corresponding to the separation grooves 34.

[0085] 10H , the resist 82 with the openings 82 a formed therein is used as a mask to perform etching, thereby engraving the semiconductor stack 200 in the portions corresponding to the openings 82 a. Specifically, the semiconductor stack 200 is engraved until the top surface of the substrate 10 is exposed. This allows the semiconductor stack 200, which has multiple ridges 31, to be separated by the separation trenches 34 into a first semiconductor stack 20 a having a first ridge 31 a and a second semiconductor stack 20 b having a second ridge 31 b. Furthermore, the N-side semiconductor layer 21, the light-emitting layer 22, the P-side semiconductor layer 23, and the P-side contact layer 24 are each separated by the separation groove 34 into a first N-side semiconductor layer 21 a and a second N-side semiconductor layer 21 b, a first light-emitting layer 22 a and a second light-emitting layer 22 b, a first P-side semiconductor layer 23 a and a second P-side semiconductor layer 23 b, and a first P-side contact layer 24 a and a second P-side contact layer 24 b.

[0086] 10I, the resist 82 is removed to expose each of the semiconductor stacked structures 20. Specifically, the P-side contact layer 24 of each of the first semiconductor stacked structure 20a and the second semiconductor stacked structure 20b is exposed. This makes it possible to form the first semiconductor stacked structure 20a having the first ridge portion 31a and the second semiconductor stacked structure 20b having the second ridge portion 31b.

[0087] 10J to 10N, an insulating film 70 having openings 70a is formed so as to cover the separated semiconductor stacked structures 20. In this embodiment, the insulating film 70 having openings 70a is formed on the first semiconductor stacked structure 20a and the second semiconductor stacked structure 20b.

[0088] 10J, an insulating film 70 is first formed to cover the semiconductor stack 20 in which the separation grooves 34 are formed. More specifically, the insulating film 70 is formed to cover the first semiconductor stack 20a and the second semiconductor stack 20b. As a result, the ridge portion 31, the flat portion 32, and the wing portion 33 are covered with the insulating film 70.

[0089] 10K, a resist 83 serving as a mask is formed on the insulating film 70. Specifically, the resist 83 made of a photosensitive resin material is applied onto the insulating film 70.

[0090] 10L, the resist 83 is exposed and developed to form openings 83a in the resist 83. The openings 83a are formed at positions corresponding to the ridge portions 31. Specifically, the openings 83a are formed above the first ridge portion 31a and the second ridge portion 31b.

[0091] 10M, etching is performed using the resist 83 with the openings 83a formed therein as a mask, thereby forming openings 70a in the insulating film 70 in the portions corresponding to the openings 83a. As a result, openings 70a are formed in the insulating film 70 above the ridge portion 31, exposing the upper surface of the ridge portion 31. Specifically, the upper surfaces of the first ridge portion 31a and the second ridge portion 31b are exposed.

[0092] 10N, the resist 83 is removed, thereby exposing the entire insulating film 70 having the opening 70 a. This allows the insulating film 70 having the opening 70 a to be formed on the first semiconductor stacked structure 20 a and the second semiconductor stacked structure 20 b.

[0093] 10O to 10R, a first p-electrode 41 is formed on each of the separated semiconductor laminated structures 20. Specifically, a first p-electrode 41 is formed for each of the plurality of P-side contact layers 24 so as to be in contact with each of the plurality of P-side contact layers 24. In this embodiment, a first first p-electrode 41a is formed on the first semiconductor laminated structure 20a, and a second first p-electrode 41b is formed on the second semiconductor laminated structure 20b.

[0094] 10O, a resist 84 made of a photosensitive resin material having openings 84a is formed by photolithography and etching so as to cover the plurality of semiconductor stacked structures 20 covered with the insulating film 70 having openings 70a. The opening 84a in the resist 84 is formed on at least one of the plurality of ridge portions 31. In this embodiment, the opening 84a in the resist 84 is formed on the first ridge portion 31a of the first ridge portion 31a and the second ridge portion 31b.

[0095] 10P, an electrode film 41M made of a first electrode material that will form the first first p-electrode 41a to be formed on the first ridge portion 31a is formed by vapor deposition or sputtering so as to cover the resist 84 with the opening 84a formed therein. At this time, since the opening 84a in the resist 84 exists above the first ridge portion 31a, the first first p-electrode 41a is formed on the upper surface of the first ridge portion 31a as part of the electrode film 41M. Note that the first electrode material that will form the first first p-electrode 41a (i.e., the material of the electrode film 41M) can be, for example, Ag.

[0096] 10Q, the resist 84 is removed. As a result, the resist 84 is removed and the electrode film 41M formed on the resist 84 is also removed by lift-off, leaving only the first first p-electrode 41a (part of the electrode film 41M) formed on the upper surface of the first ridge portion 31a. In other words, the first first p-electrode 41a made of the first electrode material is formed only on the first P-side contact layer 24a.

[0097] 10R, an adhesion layer 43 is formed on the first semiconductor laminated structure 20a, and a second first p-electrode 41b is formed on the second semiconductor laminated structure 20b. Specifically, the adhesion layer 43 is formed on the first semiconductor laminated structure 20a so as to be in contact with the first first p-electrode 41a. The second first p-electrode 41b is formed on the second semiconductor laminated structure 20b so as to be in contact with the upper surface of the second ridge portion 31b. That is, the second first p-electrode 41b is formed on the second P-side contact layer 24b so as to be in contact with the second P-side contact layer 24b.

[0098] In this case, although not shown, an electrode film made of a second electrode material constituting the second first p electrode 41b formed on the second ridge portion 31b is formed by vapor deposition or sputtering so as to cover the first semiconductor laminated structure 20a and the second semiconductor laminated structure 20b, and the electrode film is patterned and separated by photolithography and etching, thereby forming an adhesion layer 43 on the first semiconductor laminated structure 20a and simultaneously forming the second first p electrode 41b on the second semiconductor laminated structure 20b. In other words, the adhesion layer 43 and the second first p electrode 41b are formed simultaneously by the same process. Therefore, the adhesion layer 43 and the second first p electrode 41b are made of the same material and have the same film thickness. The second electrode material constituting the second first p electrode 41b and the adhesion layer 43 can be made of, for example, Ti.

[0099] In this manner, in this process, the adhesion layer 43 is formed on the first first p-electrode 41 a as an electrode layer made of a second electrode material having a refractive index different from that of the first electrode material, and at the same time, the second first p-electrode 41 b made of the second electrode material can be formed on the second P-side contact layer 24 b.

[0100] 10S, a second p electrode 42 is formed on each of the plurality of first p electrodes 41. Specifically, a first second p electrode 42a is formed on the first first p electrode 41a formed on the first ridge portion 31a via an adhesion layer 43, and a second second p electrode 42b is formed on the second first p electrode 41b formed on the second ridge portion 31b. At this time, since the adhesion layer 43 is formed on the first first p electrode 41a, the adhesion layer 43 can improve the adhesion between the first first p electrode 41a and the first second p electrode 42a.

[0101] In this case, although not shown, an electrode film made of the electrode material constituting the second p electrode 42 is formed by vapor deposition or sputtering so as to cover the first semiconductor laminated structure 20a and the second semiconductor laminated structure 20b, and the electrode film is patterned by photolithography and etching to separate the electrode film, thereby forming the first second p electrode 42a directly on the adhesion layer 43 on the first p electrode 41a and simultaneously forming the second second p electrode 42b directly on the second first p electrode 41b. In other words, the first second p electrode 42a and the second second p electrode 42b are formed simultaneously by the same process. Therefore, the first second p electrode 42a and the second second p electrode 42b are made of the same material and have the same film thickness.

[0102] 10T, a pad electrode 50 is formed on each of the plurality of second p electrodes 42. Specifically, a first pad electrode 50a is formed on the first second p electrode 42a on the first ridge portion 31a, and a second pad electrode 50b is formed on the second second p electrode 42b on the second ridge portion 31b.

[0103] In this case, although not shown, an electrode film made of the electrode material constituting the pad electrode 50 is formed by electroplating, vapor deposition, or sputtering so as to cover the first semiconductor laminated structure 20a and the second semiconductor laminated structure 20b, and the electrode film is patterned by photolithography and etching and separated by lift-off, thereby forming the first pad electrode 50a on the first second p-electrode 42a and the second pad electrode 50b on the second second p-electrode 42b at the same time. In other words, the first pad electrode 50a and the second pad electrode 50b are formed simultaneously by the same process.

[0104] 10U, an n-electrode 60 is formed on the rear surface of the substrate 10. Specifically, electrode films made of materials constituting a first electrode layer 61, a second electrode layer 62, and a third electrode layer 63 are sequentially formed on the rear surface of the substrate 10 by vapor deposition or sputtering, and the three electrode films are simultaneously patterned by photolithography and etching, followed by lift-off to form the n-electrode 60 made of the first electrode layer 61, the second electrode layer 62, and the third electrode layer 63.

[0105] Thereafter, although not shown, the wafer thus produced is divided into a plurality of bar-shaped substrates (primary dividing step), and then an end face coating film is formed on both end faces of each bar-shaped substrate, after which each bar-shaped substrate is divided into individual pieces for each of the plurality of ridge portions 31 (secondary dividing step).This allows the production of a plurality of semiconductor laser elements 1 that have been separated into chips.

[0106] In the present embodiment, photolithography and etching are performed in each of the steps of forming the adhesion layer 43 and the second first p electrode 41 b ( FIG. 10R ), the step of forming the plurality of second p electrodes 42 (first second p electrode 42 a, second second p electrode 42 b) ( FIG. 10S ), and the step of forming the plurality of pad electrodes 50 (first pad electrode 50 a, second pad electrode 50 b) ( FIG. 10T ). However, this is not limiting. That is, these steps may be performed by a single photolithography and etching. Specifically, after the electrode film constituting the adhesion layer 43 and the second first p electrode 41 b, the electrode film constituting the plurality of second p electrodes 42, and the electrode film constituting the pad electrode 50 are successively formed, the three electrode films may be simultaneously patterned by photolithography and etching.

[0107] (Modification 1) FIG. 11 shows a cross section of a semiconductor laser device 1A of modification 1.

[0108] In the semiconductor laser device 1 according to the above embodiment, the second first p-electrode 41 b in contact with the second P-side contact layer 24 b is provided in common (in the same layer) with the adhesion layer 43 on the first first p-electrode 41 a, and the second first p-electrode 41 b is formed across the ridge portion 31 (second ridge portion 31 b) and the wing portion 33; however, the present invention is not limited to this.

[0109] 11, the second first p-electrode 41bA may be formed only on the second ridge portion 31b. In this case, the second first p-electrode 41bA is formed to have the same width as the first first p-electrode 41a. In this modification, the second first p-electrode 41bA and the first first p-electrode 41a also have the same shape in plan view.

[0110] However, since the second electrode material constituting the second first p electrode 41bA is different from the first electrode material constituting the first first p electrode 41a, the second first p electrode 41bA and the first first p electrode 41a are formed in different processes, not in the same process. Therefore, in this modification, it is necessary to add a separate process for fabricating the second first p electrode 41bA to the above embodiment.

[0111] 11 , in this modification, the adhesion layer 43 is formed not only on the first first p electrode 41a but also on the second first p electrode 41bA. That is, the adhesion layer 43 is formed between the second first p electrode 41bA and the second pad electrode 50b. This improves the adhesion between the second first p electrode 41bA and the second second p electrode 42b. In this case, the adhesion layer 43 on the first first p electrode 41a and the adhesion layer 43 on the second first p electrode 41bA can be formed simultaneously in the same process.

[0112] As described above, in the semiconductor laser device 1A according to this modification, as in the above embodiment, the first electrode material constituting the first p-electrode 41a and the second electrode material constituting the second p-electrode 41bA are electrode materials with different refractive indices. This configuration allows the waveguide loss of the first p-electrode 41a and the waveguide loss of the second p-electrode 41bA to be different, thereby allowing the wavelength of the laser light oscillated in each light-emitting region 1a to be different. As a result, speckle noise can be reduced.

[0113] Furthermore, in this modification, the second first p electrode 41bA is fabricated in a different process from the adhesion layer 43 on the first first p electrode 41a. Therefore, when selecting a second electrode material for the second first p electrode 41bA, a material different from the material for the adhesion layer 43 on the first first p electrode 41a can be selected. In other words, for the semiconductor laser device 1A in this modification, the electrode material for the second first p electrode 41bA can be selected regardless of the material for the adhesion layer 43. Therefore, in this modification, the degree of freedom in selecting the material for the second first p electrode 41bA can be improved compared to the semiconductor laser device 1 in the above embodiment. Therefore, the number of combination patterns of the first electrode material for the first first p electrode 41a and the second electrode material for the second first p electrode 41bA can be increased.

[0114] In this case, the first electrode material constituting the first first p-electrode 41a and the second electrode material constituting the second first p-electrode 41bA can be selected from three groups (Group A, Group B, and Group C) shown in FIG. 6. As an example, as shown in FIG. 12, the first electrode material constituting the first first p-electrode 41a can be selected from Group A (e.g., Ag), and the second electrode material constituting the second first p-electrode 41bA can be selected from Group B (e.g., Ti). Alternatively, the first electrode material constituting the first first p-electrode 41a can be selected from Group B (e.g., Ti), and the second electrode material constituting the second first p-electrode 41bA can be selected from Group C (e.g., Mo). By using these combinations, the wavelength difference between the two laser beams emitted from the two light-emitting regions 1a can be made 1.5 nm or more.

[0115] (Modification 2) FIG. 13 shows a cross section of a semiconductor laser device 1B according to Modification 2. As shown in FIG.

[0116] Although the semiconductor laser device 1A in the first modification has two light-emitting regions 1a, this is not limiting. Specifically, as shown in FIG. 13 , a semiconductor laser device 1B according to this modification has three light-emitting regions 1a, 1b, and 1c. In this case, three ridge portions 31 are formed corresponding to the three light-emitting regions 1a to 1c, and a first p electrode 41 is formed for each of the three ridge portions 31. Specifically, the semiconductor laser device 1 is provided with the three ridge portions 31, namely, a first ridge portion 31a, a second ridge portion 31b, and a third ridge portion 31c. A first first p electrode 41a is formed on the first ridge portion 31a, a second first p electrode 41bA is formed on the second ridge portion 31b, and a third first p electrode 41c is formed on the third ridge portion 31c. Specifically, the first p-electrode 41a, the second p-electrode 41bA, and the third p-electrode 41c are formed to have the same width.

[0117] In this modification, the first electrode material constituting the first first p electrode 41a, the second electrode material constituting the second first p electrode 41bA, and the third electrode material constituting the third first p electrode 41c are different materials. In this case, the first first p electrode 41a, the second first p electrode 41bA, and the third first p electrode 41c cannot be formed in the same process, so a process for fabricating the third first p electrode 41c needs to be added to the above modification 1. Note that an adhesion layer may also be formed on the third first p electrode 41c.

[0118] As described above, in the semiconductor laser device 1A according to this modification, the first electrode material constituting the first p-electrode 41a, the second electrode material constituting the second p-electrode 41bA, and the third electrode material constituting the third p-electrode 41c are electrode materials with mutually different refractive indices. This configuration allows the waveguide losses of the first p-electrode 41a, the second p-electrode 41bA, and the third p-electrode 41c to be different from one another, thereby enabling the wavelengths of the laser beams oscillated in the light-emitting regions 1a to 1c to be different from one another. As a result, speckle noise can be reduced.

[0119] For example, the first electrode material constituting the first first p-electrode 41a, the second electrode material constituting the second first p-electrode 41bA, and the third electrode material constituting the third first p-electrode 41c can be selected from three groups (Group A, Group B, and Group C) shown in FIG. 6 . As an example, as shown in FIG. 14 , the first electrode material constituting the first first p-electrode 41a can be selected from Group A (e.g., Ag), the second electrode material constituting the second first p-electrode 41bA can be selected from Group B (e.g., Ti), and the third electrode material constituting the third first p-electrode 41c can be selected from Group C (e.g., Mo). In this case, it is preferable to select a metal material with a refractive index of 3 or more as the third electrode material constituting the third first p-electrode 41c. This allows the wavelength differences between the three laser beams emitted from the three light-emitting regions 1a to be 1.5 nm or more.

[0120] In addition, when there are three light-emitting regions 1 a as in this modified example, as shown in Figures 8 and 9 above, it can be seen that there is a combination of electrode materials that can ensure a wavelength difference of 1.5 nm or more among the three laser lights by setting the thickness of the convex portion of the P-side semiconductor layer 23 (that is, the thickness from the ridge bottom surface of the ridge portion 31 to the top surface of the convex portion) to 0.3 μm or less.

[0121] In this modification, the electrode materials constituting the three first p-electrodes 41 are selected from different groups among the three groups shown in Fig. 6, but this is not limiting. For example, two of the three first p-electrodes 41 may be made of electrode materials selected from the same group. In this case, even if selected from the same group, the electrode materials constituting the two first p-electrodes 41 may have different refractive indices.

[0122] In addition, in this modification, the electrode materials constituting the three first p electrodes 41 are different from one another, but this is not limiting. Specifically, two of the three first p electrodes 41 may be made of the same electrode material. In other words, it is sufficient that at least two of the three first p electrodes 41 are made of electrode materials with different refractive indices.

[0123] The number of light-emitting regions 1a is not limited to three, and may be four, five, or six or more. Even when the number of light-emitting regions 1a is four or more, the electrode material constituting the plurality of first p-electrodes can be selected from the three groups (group A, group B, and group C) shown in FIG.

[0124] 15 , in the case of a semiconductor laser device 1C having four light-emitting regions, an example of a combination of electrode materials for the four first p-electrodes is a combination example (combination example 1) in which the electrode material for the first first p-electrode from the left is selected from group A, the electrode material for the second first p-electrode from the left is selected from group B, the electrode material for the third first p-electrode from the left is selected from group B, and the electrode material for the fourth first p-electrode from the left is selected from group A. Alternatively, there is a combination example (combination example 2) in which the electrode material for the first first p-electrode from the left is selected from group B, the electrode material for the second first p-electrode from the left is selected from group C, the electrode material for the third first p-electrode from the left is selected from group C, and the electrode material for the fourth first p-electrode from the left is selected from group B.

[0125] 16 , in the case of a semiconductor laser device 1D having five light-emitting regions, an example of a combination of electrode materials constituting the five first p-electrodes is a combination example (combination example 1) in which the electrode material constituting the first first p-electrode from the left is selected from group A, the electrode material constituting the second first p-electrode from the left is selected from group B, the electrode material constituting the third first p-electrode from the left is selected from group C, the electrode material constituting the fourth first p-electrode from the left is selected from group B, and the electrode material constituting the fifth first p-electrode from the left is selected from group A. Other examples include combination example 2, combination example 3, combination example 4, and combination example 5 shown in FIG.

[0126] Even when the number of light-emitting regions 1a is four or five, two or three of the four or five first p electrodes 41 may be made of electrode materials selected from the same group. In this case, even if selected from the same group, the electrode materials making up the two or three first p electrodes 41 may be materials with different refractive indices, but the two or three first p electrodes 41 may be made of the same electrode material. In other words, it is sufficient that at least two of the four or five first p electrodes 41 are made of electrode materials with different refractive indices.

[0127] Furthermore, when the number of light emitting regions 1a is three or more, the refractive index of the electrode material constituting one or more central electrodes located in the center of the semiconductor laser element among the plurality of first p electrodes 41 may be different from the refractive index of the electrode material constituting one or more peripheral electrodes located in the periphery of the semiconductor laser element among the plurality of first p electrodes 41. Specifically, the refractive index of the electrode material constituting one or more central electrodes located in the center of the semiconductor laser element among the plurality of first p electrodes 41 is greater than the refractive index of the electrode material constituting one or more peripheral electrodes located in the periphery of the semiconductor laser element among the plurality of first p electrodes 41.

[0128] For example, as shown in Fig. 13, when there are three light-emitting regions 1a, the peripheral electrodes of the three first p electrodes 41 are the first and third first p electrodes 41 from the left, and the central electrode of the three first p electrodes 41 is the second first p electrode 41 from the left. Also, as shown in Fig. 15, when there are four light-emitting regions 1a, the peripheral electrodes of the four first p electrodes 41 are the first and fourth first p electrodes 41 from the left, and the central electrodes of the four first p electrodes 41 are the second and third first p electrodes 41 from the left. Also, as shown in Fig. 16, when there are five light-emitting regions 1a, the peripheral electrodes of the five first p electrodes 41 are the first and fifth first p electrodes 41 from the left, and the central electrodes of the five first p electrodes 41 are the second, third, and fourth first p electrodes 41 from the left. Alternatively, the peripheral electrodes of the five first p electrodes 41 may be the first, second, fourth, and fifth first p electrodes 41 from the left, and the central electrode of the five first p electrodes 41 may be the third first p electrode 41 from the left.

[0129] Thus, when the number of light-emitting regions 1a is three or more, by differentiating the refractive index of the electrode material constituting one or more central electrodes 41 located in the center of the semiconductor laser element from the refractive index of the electrode material constituting one or more peripheral electrodes 41 located in the periphery of the semiconductor laser element, this refractive index difference not only produces a wavelength difference in the laser light between the central and peripheral (outer) portions of the semiconductor laser element, but also produces a wavelength difference in the laser light between the central and peripheral portions due to a temperature difference between the central and peripheral portions. In other words, because the central portion of the semiconductor laser element dissipates heat more slowly than the peripheral portion, the central light-emitting region of the semiconductor laser element generates more heat than the peripheral light-emitting region of the semiconductor laser element, resulting in a temperature difference between the central and peripheral portions of the semiconductor laser element. This temperature difference also produces a wavelength difference in the laser light between the central and peripheral portions of the semiconductor laser element. In this way, the wavelength difference can be increased by the synergistic effect of the wavelength difference due to the refractive index difference and the wavelength difference due to the temperature difference. Therefore, speckle noise can be effectively reduced.

[0130] (Modification 3) FIG. 17 shows a cross section of a semiconductor laser device 1E according to Modification 3.

[0131] In the semiconductor laser device 1 according to the above embodiment, each of the plurality of first p-electrodes 41 is a single layer, but this is not limiting. Specifically, at least one of the plurality of first p-electrodes 41 may be configured as a multi-layer structure of two or more layers.

[0132] 17 , in the semiconductor laser device 1E of this modification, the second of the two first p electrodes 41, a first p electrode 41bA, is a single-layer film, while the first of the two first p electrodes 41, a first p electrode 41aE, is a laminated film made up of multiple layers. Specifically, the first p electrode 41aE has a first electrode layer 411 and a second electrode layer 412 laminated on the first electrode layer 411. The first electrode layer 411 is in contact with the first p-side contact layer 24a. The second electrode layer 412 is in contact with the first electrode layer 411 and the first second p electrode 42a.

[0133] The electrode material for the first electrode layer 411 may be selected from group B of the three groups shown in Fig. 6. The electrode material for the second electrode layer 412 may be selected from group A of the three groups shown in Fig. 6.

[0134] As an example, the electrode material constituting the second electrode layer 412 is Ag. By using a low-refractive index material such as Ag from Group A for the second electrode layer 412, the first electrode layer 411, which is in contact with the first P-side contact layer 24a, may be used as an adhesion layer (underlayer) having a thickness that does not significantly increase light absorption (a waveguide loss increase of 10% or less). In this case, Ti, Ni, Pd, or Cr from Group B may be used as the electrode material constituting the first electrode layer 411. As shown in FIG. 18 , when the first electrode layer 411 is used as an adhesion layer, the thickness of the first electrode layer 411 is preferably 1.5 nm or less to ensure a thickness that does not significantly increase light absorption (a waveguide loss increase of 10% or less). This allows the wavelength difference between the light-emitting regions 1a to be maintained while improving adhesion between the first P-electrode 41aE and the first P-side contact layer 24a without changing the light absorption of the first P-electrode 41aE.

[0135] In the semiconductor laser device 1E according to this modification, similarly to the first modification, the refractive index of the first p-electrode 41aE is different from that of the second p-electrode 41bA. The second p-electrode 41bA can be made of a material from Group B or Group C, and may be made of the same electrode material as the first electrode layer 411, such as Ti, Ni, Pd, or Cr. This configuration allows the waveguide loss of the first p-electrode 41aE to be different from that of the second p-electrode 41bA, thereby enabling the wavelength of the laser light oscillated in each light-emitting region 1a to be different. As a result, speckle noise can be reduced.

[0136] (Modification 4) FIG. 19 shows a cross section of a semiconductor laser device 1F of modification 4.

[0137] In the semiconductor laser device 1 according to the above embodiment, the multiple P-side contact layers 24 have the same thickness, but this is not limited to this. Specifically, as in the semiconductor laser device 1F of this modified example shown in FIG. 19 , the film thicknesses of the multiple P-side contact layers 24 may be different for each of the multiple light-emitting regions 1a. In this modified example, the film thickness of the first P-side contact layer 24aF of the two P-side contact layers 24 is greater than the film thickness of the second P-side contact layer 24b. In other words, the film thickness of the second P-side contact layer 24b is smaller than the film thickness of the first P-side contact layer 24aF. This results in a step d between the upper surface of the first semiconductor laminated structure 20a (the upper surface of the first P-side contact layer 24aF) and the upper surface of the second semiconductor laminated structure 20b (the upper surface of the second P-side contact layer 24b).

[0138] To differentiate the thickness of the first P-side contact layer 24aF from the thickness of the second P-side contact layer 24b, for example, the thickness of the P-type contact layer in the first P-side contact layer 24aF may be differentiated from the thickness of the P-type contact layer in the second P-side contact layer 24b. In this case, the P-type contact layers of the first P-side contact layer 24aF and the second P-side contact layer 24b are first grown by common crystal growth, and then pre-processing (sulfuric acid-based wet etching) is performed before the formation of the first p-electrode 41, thereby differentiating the thickness of the P-type contact layer between the first P-side contact layer 24aF and the second P-side contact layer 24b. In other words, the thickness of the P-type contact layer can be adjusted by the pre-processing before the formation of the first p-electrode 41.

[0139] As described above, in the semiconductor laser device 1F according to this modification, similarly to the above embodiment, the refractive indexes of the plurality of first p electrodes 41 are different from one another. With this configuration, the degree of light absorbed by the plurality of first p electrodes 41 differs, and therefore the waveguide loss due to the plurality of first p electrodes 41 can be made different for each of the plurality of first p electrodes 41. This allows the wavelength of the laser light oscillated to differ for each of the light-emitting regions 1a, thereby reducing speckle noise.

[0140] In this modification, the thicknesses of the p-side contact layers 24 in contact with the first p-electrode 41 are different for each of the light-emitting regions 1a.

[0141] With this configuration, the distance from the light-emitting layer 22 to the first p electrode 41 differs for each light-emitting region 1a, so that the degree of light absorbed by the plurality of first p electrodes 41 can be made to differ greatly. In other words, it is possible to increase the difference in light loss absorbed by the plurality of first p electrodes 41. This allows the waveguide loss due to the first p electrode 41 to differ greatly for each of the plurality of first p electrodes 41, so that it is possible to easily increase the difference in wavelength of laser light oscillated for each light-emitting region 1a.

[0142] Furthermore, by reducing the thickness of the P-side contact layer 24 that contacts the first p electrode 41 made of an electrode material with a higher refractive index among the multiple first p electrodes 41, the difference in waveguide loss among the multiple first p electrodes 41 can be further increased.

[0143] (Other Modifications) The semiconductor laser element and the method for manufacturing the semiconductor laser element according to the present disclosure have been described above based on the embodiment and modifications 1 to 4, but the present disclosure is not limited to the above embodiment and modifications 1 to 4.

[0144] In the above-described embodiment and each modification, the semiconductor laser device 1 is mounted on the submount in a junction-down position, but this is not limiting. Specifically, the semiconductor laser device 1 may be mounted on the submount in a junction-up position.

[0145] In the above-described embodiment and each modification, the waveguide in the semiconductor laser element is the ridge portion 31, but this is not limiting. For example, the waveguide in the semiconductor laser element may have an electrode stripe structure composed of only divided electrodes instead of the ridge stripe structure composed of the ridge portion 31, or may have a buried current confinement structure in which a current blocking layer is buried in the semiconductor laminated structure 20.

[0146] In the above-described embodiment and each modification, the semiconductor stacked structure 20 of the semiconductor laser element has the same layer configuration, but this is not limited to this. For example, by changing the thickness of the convex portion of the P-side semiconductor layer 23 for each of the plurality of light-emitting regions 1 a, the waveguide loss of the first p-electrode can be made different, and therefore the wavelength of the laser light oscillated for each of the light-emitting regions 1 a can be made different.

[0147] In the above-described embodiment and each modification, the semiconductor layer structure of the semiconductor laser element is made of a III-V group compound semiconductor made of an AlGaInAs-based semiconductor material, but is not limited to this. The semiconductor layer structure of the semiconductor laser element may be made of a nitride-based semiconductor material or the like.

[0148] In addition, the present disclosure also includes forms obtained by applying various modifications to the above-described embodiments that would occur to those skilled in the art, and forms realized by arbitrarily combining the components and functions of the embodiments within the scope of the present disclosure. Furthermore, the present disclosure also includes any combination of two or more claims from among the multiple claims set forth in the claims at the time of filing, within the scope of technical compatibility. For example, when a dependent claim set forth in the claims at the time of filing is made into a multiple claim or multiple multiple claims that cite all of the superordinate claims within the scope of technical compatibility, the present disclosure also includes all combinations of claims included in that multiple claim or multiple multiple multiple claims.

[0149] The semiconductor laser device according to the present disclosure is useful as a light source for various products, including projectors, optical discs, vehicle headlamps, lighting devices, laser processing devices, and the like.

[0150] REFERENCE SIGNS LIST 1, 1A, 1B, 1C, 1D, 1E, 1F Semiconductor laser element 1a Light emitting region 2 Submount 2a Conductive layer 3 Conductive bonding member 4a, 4b Gold wire 10 Substrate 20, 200 Semiconductor laminated structure 20a First semiconductor laminated structure 20b Second semiconductor laminated structure 21 N-side semiconductor layer 21a First N-side semiconductor layer 21b Second N-side semiconductor layer 22 Light emitting layer 22a First light emitting layer 22b Second light emitting layer 23 P-side semiconductor layer 23a First P-side semiconductor layer 23b Second P-side semiconductor layer 23m Lower layer 23n Upper layer 24 P-side contact layer 24a, 24aF First P-side contact layer 24b Second P-side contact layer 31 Ridge portion 31a First ridge portion 31b Second ridge portion 31c Third ridge portion 32 Flat portion 33 Wing portion 34 Separation groove 41 First p-electrode 41M Electrode film 41a, 41aE First first p-electrode 41b, 41bA Second first p-electrode 41c Third first p-electrode 411 First electrode layer 412 Second electrode layer 42 Second p-electrode 42a First second p-electrode 42b Second second p-electrode 43 Adhesion layer 50 Pad electrode 50a First pad electrode 50b Second pad electrode 60 N-electrode 61 First electrode layer 62 Second electrode layer 63 Third electrode layer 70 Insulating film 70a Opening 81, 82, 83, 84 Resist 81a, 82a, 83a, 84a Opening

Claims

1. A semiconductor laser device having a plurality of light-emitting regions, comprising: a substrate; an N-side semiconductor layer located above the substrate; a light-emitting layer located above the N-side semiconductor layer; a P-side semiconductor layer located above the light-emitting layer; a plurality of P-side contact layers located above the P-side semiconductor layer and provided for each of the plurality of light-emitting regions; and a first p-electrode provided for each of the plurality of P-side contact layers so as to be in contact with each of the plurality of P-side contact layers, wherein at least two of the plurality of first p-electrodes include a first electrode material in one and a second electrode material having a refractive index different from that of the first electrode material in the other.

2. The semiconductor laser device according to claim 1, wherein the N-side semiconductor layer is provided for each of the plurality of light-emitting regions, the light-emitting layer is provided for each of the plurality of N-side semiconductor layers, and the P-side semiconductor layer is provided for each of the plurality of light-emitting layers.

3. The semiconductor laser device according to claim 1, wherein the refractive index difference between the first electrode material and the second electrode material is 1.5 or more.

4. The semiconductor laser device according to any one of claims 1 to 3, wherein the semiconductor laser device has a plurality of ridge portions provided for each of the plurality of first p-electrodes, each of the plurality of ridge portions includes a convex portion in the P-side semiconductor layer and one of the plurality of P-side contact layers formed on the convex portion, and in each of the plurality of ridge portions, the thickness from the bottom surface of the ridge to the upper surface of the convex portion is 0.43 μm or less.

5. The semiconductor laser device according to claim 1, wherein the plurality of first p-electrodes include a first first p-electrode, the first first p-electrode is composed of a metal material having a refractive index of 1 or less, and the metal material is one of the first electrode material and the second electrode material.

6. The semiconductor laser device according to claim 1, wherein the plurality of first p-electrodes include a first first p-electrode, the first first p-electrode is composed of a conductive material having an attenuation coefficient of 0.01 or less, and the conductive material is one of the first electrode material and the second electrode material.

7. The plurality of first p-electrodes further have a second first p-electrode, the second first p-electrode is composed of a metal material having a refractive index greater than 1 and less than 3, and the metal material is the other of the first electrode material and the second electrode material. The semiconductor laser element according to claim 5 or 6.

8. The plurality of first p-electrodes further have a second first p-electrode, the second first p-electrode is composed of a metal material having a refractive index of 3 or more. The semiconductor laser element according to claim 5 or 6.

9. The plurality of first p-electrodes further have a third first p-electrode, the third first p-electrode is composed of a metal material having a refractive index of 3 or more. The semiconductor laser element according to claim 7.

10. The plurality of light-emitting regions are three or more light-emitting regions, and the refractive index of the electrode material constituting one or more central electrodes located at the central portion of the semiconductor laser element among the plurality of first p-electrodes is different from the refractive index of the electrode material constituting one or more peripheral electrodes located at the peripheral portion of the semiconductor laser element among the plurality of first p-electrodes. The semiconductor laser element according to any one of claims 1 to 3.

11. The plurality of light-emitting regions are three or more light-emitting regions, and the refractive index of the electrode material constituting one or more central electrodes located at the central portion of the semiconductor laser element among the plurality of first p-electrodes is greater than the refractive index of the electrode material constituting one or more peripheral electrodes located at the peripheral portion of the semiconductor laser element among the plurality of first p-electrodes. The semiconductor laser element according to any one of claims 1 to 3.

12. At least one of the plurality of first p-electrodes is composed of two or more layers, and the film thickness of the layer in contact with the P-side contact layer in the first p-electrode composed of the plurality of layers is 1.5 nm or less. The semiconductor laser element according to any one of claims 1 to 3.

13. The plurality of P-side contact layers include a first P-side contact layer and a second P-side contact layer. One of the at least two first p electrodes is a first first p electrode that is in contact with the first P-side contact layer and is made of the first electrode material. The other of the at least two first p electrodes is a second first p electrode that is in contact with the second P-side contact layer and is made of the second electrode material. The width of the first first p electrode is equal to or less than the width of the first P-side contact layer. The width of the second first p electrode is greater than the width of the second P-side contact layer. The semiconductor laser element according to any one of claims 1 to 3.

14. The plurality of P-side contact layers include a first P-side contact layer and a second P-side contact layer. One of the at least two first p electrodes is a first first p electrode that is in contact with the first P-side contact layer and is made of the first electrode material. The other of the at least two first p electrodes is a second first p electrode that is in contact with the second P-side contact layer and is made of the second electrode material. An electrode layer made of the second electrode material is formed on the first first p electrode. The semiconductor laser element according to any one of claims 1 to 3.

15. The film thicknesses of the plurality of P-side contact layers are different for each of the plurality of light-emitting regions. The semiconductor laser element according to any one of claims 1 to 3.

16. Further, a plurality of second p electrodes are provided, each of which is located above each of the plurality of first p electrodes and is provided for each of the plurality of first p electrodes. The semiconductor laser element according to any one of claims 1 to 3.

17. A method for manufacturing a semiconductor laser device having a plurality of light-emitting regions, the method including: forming an N-side semiconductor layer, a light-emitting layer, a P-side semiconductor layer, and a P-side contact layer above a substrate; forming a plurality of P-side contact layers for each of the plurality of light-emitting regions by patterning the P-side contact layer; and forming a first p electrode for each of the plurality of P-side contact layers so as to be in contact with each of the plurality of P-side contact layers. The plurality of P-side contact layers include a first P-side contact layer and a second P-side contact layer, and the plurality of first p electrodes include a first first p electrode located above the first P-side contact layer and a second first p electrode located above the second P-side contact layer. The step of forming the first p electrode includes: forming a first first p electrode made of a first electrode material above the first P-side contact layer; and then forming an electrode layer made of a second electrode material having a refractive index different from that of the first electrode material above the first first p electrode and forming a second first p electrode made of the second electrode material above the second P-side contact layer. A method for manufacturing a semiconductor laser device.

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