semiconductor laser device

Abstract

To provide a semiconductor laser device capable of suppressing reduction in long-term reliability.SOLUTION: A semiconductor laser device 100 comprises: a heat sink 2; and a semiconductor laser element 1 that is joined to the heat sink 2 via a joining member 3 and provided with a pad electrode 70. The semiconductor laser element 1 is arranged so that the pad electrode 70 is located on the heat sink 2 side. The semiconductor laser element 1 has an exposed surface 61a that is exposed from the pad electrode 70 due to a front-end surface of the pad electrode 70 being present at a position recessed from a front-end surface of the semiconductor laser element 1. The joining member 3 is connected to the exposed surface 61a of the semiconductor laser element 1. In a vertical cross-section parallel to a longitudinal direction of a resonator of the semiconductor laser element 1; the front-end surface of the pad electrode 70 is formed so as to be at least partially recessed; and a gap 4 is formed between the joining member 3 and the front-end surface of the pad electrode 70.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a semiconductor laser device including a semiconductor laser element and a method for manufacturing a semiconductor laser element used in a semiconductor laser device. [Background technology]

[0002] Semiconductor laser elements are used as light sources for products in a variety of fields, both consumer and industrial. For example, semiconductor lasers are used as light sources for image display devices such as displays and projectors, for automobile headlamps, and for industrial equipment such as laser processing devices.

[0003] In particular, semiconductor laser elements used as light sources for projectors or laser processing devices are required to have high optical output powers that far exceed 1 W. For example, semiconductor laser elements that emit infrared laser light (for example, wavelengths in the 915 nm band) are used as light sources for laser processing devices that perform laser processing such as welding, joining, or cutting, and in this case, optical output powers of about 10 W to several tens of W are required.

[0004] Such high-power semiconductor laser elements have a very large operating current and generate a large amount of heat at the front end (light-emitting end) from which the laser light is emitted, which can lead to catastrophic optical damage (COD) at the front end. Therefore, to achieve stable operation of the semiconductor laser element over a long period of time while maintaining high output, it is important to quickly dissipate the heat generated at the front end to the outside and prevent the operating temperature at the front end from rising.

[0005] Therefore, conventionally, a semiconductor laser device has been proposed in which a semiconductor laser element is bonded to a heat sink (submount) by junction-down mounting using a bonding material such as solder. Patent Documents 1 and 2 disclose techniques that further improve this type of semiconductor laser device.

[0006] Specifically, in the semiconductor laser device disclosed in Patent Document 1, the adhesive that bonds the semiconductor laser element and the heat dissipation member together extends from between the semiconductor laser element and the heat dissipation member to the front end face of the heat dissipation member directly below the front end face of the semiconductor laser element. Also, in the semiconductor laser device disclosed in Patent Document 2, the materials of the bonding layer that bonds the semiconductor laser element and the heat sink are different between the bonding layer that is connected to the front end of the semiconductor laser element and the bonding layer that is connected to the other parts, and the melting point of the bonding layer that is connected to the front end is increased. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2013 / 150715 [Patent Document 2] Japanese Patent Application Publication No. 2017-191899 Summary of the Invention [Problem to be solved by the invention]

[0008] In a semiconductor laser device in which a semiconductor laser element and a heat sink are bonded together with a bonding material, a part of the bonding material interposed between the semiconductor laser element and the heat sink may be extended to the front end of the semiconductor laser element to form a fillet of the bonding material in order to dissipate heat generated at the front end of the semiconductor laser element to the heat sink. This stabilizes the COD level and prevents a decrease in the optical output of the semiconductor laser element due to self-heating.

[0009] However, when a fillet is formed on the bonding member connected to the front end of the semiconductor laser element, the fillet applies stress to the front end of the semiconductor laser element. This may result in a decrease in the long-term reliability of the semiconductor laser element. In particular, in the structure of the semiconductor laser device disclosed in Patent Document 1, the stress applied to the semiconductor laser element from the end of the fillet of the bonding member increases. Furthermore, in the structure of the semiconductor laser device disclosed in Patent Document 2, the composition ratio of the bonding layer is changed between the front end and the other portions of the semiconductor laser element, resulting in a difference in the amount of residual strain between the front end and the other portions. This may result in uneven stress being applied to the semiconductor laser element, which may result in a decrease in the long-term reliability of the semiconductor laser element.

[0010] The present disclosure is intended to solve such problems, and aims to provide a semiconductor laser device and a method for manufacturing a semiconductor laser element that can prevent a decrease in long-term reliability even when a bonding member is connected to the front end of the semiconductor laser element. [Means for solving the problem]

[0011] In order to solve the above problems, one aspect of the semiconductor laser device according to the present disclosure includes a heat sink and a semiconductor laser element bonded to the heat sink via a bonding member and provided with a pad electrode, wherein the semiconductor laser element is arranged so that the pad electrode faces the heat sink, the semiconductor laser element has an exposed surface exposed from the pad electrode as a result of the front end face of the pad electrode being located at a position set back from the front end face of the semiconductor laser element, the bonding member is connected to the exposed surface of the semiconductor laser element, and in a vertical cross section parallel to the resonator length direction of the semiconductor laser element, the front end face of the pad electrode is formed so that at least a portion of it is recessed, and a gap is formed between the bonding member and the front end face of the pad electrode.

[0012] Furthermore, 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 that is bonded to a heat sink via a bonding member by junction-down mounting, and includes the steps of forming a semiconductor laminate structure including an active layer, forming an electrode layer above the semiconductor laminate structure, and forming a pad electrode above the electrode layer, wherein in the step of forming the pad electrode, the pad electrode is formed so that at least a portion of a front end surface of the pad electrode is recessed. [Effects of the Invention]

[0013] According to the present disclosure, even if a bonding member is connected to the front end portion of a semiconductor laser element, the stress acting on the semiconductor laser element can be alleviated, thereby preventing a decrease in the long-term reliability of the semiconductor laser element. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a plan view of a semiconductor laser device according to a first embodiment. [Figure 2A] FIG. 2A is a cross-sectional view of the semiconductor laser device according to the first embodiment taken along line IIA-IIA in FIG. [Figure 2B] FIG. 2B is a cross-sectional view of the semiconductor laser device according to the first embodiment taken along line IIB-IIB in FIG. [Figure 2C] FIG. 2C is a cross-sectional view of the semiconductor laser device according to the first embodiment taken along line IIC-IIC in FIG. [Figure 3] FIG. 3 is a plan view of the semiconductor laser device according to the first embodiment. [Figure 4A] FIG. 4A is a cross-sectional view of the semiconductor laser device according to the first embodiment taken along line IVA-IVA in FIG. [Figure 4B] 4B is a cross-sectional view of the semiconductor laser device according to the first embodiment taken along line IVB-IVB in FIG. [Figure 4C] 4C is a cross-sectional view of the semiconductor laser device according to the first embodiment taken along the line IVC-IVC in FIG. [Figure 5]FIG. 5 is an enlarged cross-sectional view of the semiconductor laser device according to the first embodiment. [Figure 6A] FIG. 6A is a cross-sectional view showing a step of forming a semiconductor stack on a substrate in a method for manufacturing a semiconductor laser device according to the first embodiment. [Figure 6B] FIG. 6B is a cross-sectional view showing a step of forming a window region in the semiconductor stack in the method for manufacturing the semiconductor laser device according to the first embodiment. [Figure 6C] FIG. 6C is a cross-sectional view showing a step of forming an opening in the semiconductor stack in the method for manufacturing the semiconductor laser device according to the first embodiment. [Figure 6D] FIG. 6D is a cross-sectional view showing a step of forming separation grooves in the semiconductor stack in the method for manufacturing the semiconductor laser device according to the first embodiment. [Figure 6E] FIG. 6E is a cross-sectional view showing a step of forming an insulating film on the semiconductor stack in the method for manufacturing the semiconductor laser device according to the first embodiment. [Figure 6F] FIG. 6F is a cross-sectional view showing a step of forming a p-side electrode layer and a pad electrode in the method for manufacturing the semiconductor laser device according to the first embodiment. [Figure 6G] FIG. 6G is a cross-sectional view showing a step of forming an n-side electrode layer in the method for manufacturing the semiconductor laser device according to the first embodiment. [Figure 7] FIG. 7 is a diagram for explaining a step of forming a pad electrode in the method for manufacturing the semiconductor laser device according to the first embodiment. [Figure 8] FIG. 8 is an SEM image of the semiconductor laser device according to the first embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing the configuration of a semiconductor laser device of a comparative example. [Figure 10] FIG. 10 is a cross-sectional view showing the configuration of the semiconductor laser device according to the first embodiment. [Figure 11] FIG. 11 is a diagram showing the relationship between the distance from the light emitting end face to the end of the pad electrode and the COD breakdown current. [Figure 12]FIG. 12 is a cross-sectional view showing a configuration of a semiconductor laser device according to a first modification of the first embodiment. [Figure 13] FIG. 13 is a cross-sectional view showing a configuration of a semiconductor laser device according to Modification 2 of Embodiment 1. In FIG. [Figure 14] FIG. 14 is a diagram for explaining a warped state of the semiconductor laser element in the semiconductor laser device according to the first embodiment. [Figure 15] FIG. 15 is a diagram showing the relationship between the position in the cavity length direction of the semiconductor laser element and the amount of warpage. [Figure 16] FIG. 16 is a plan view of a semiconductor laser device according to the second embodiment. [Figure 17A] 17A is a cross-sectional view of the semiconductor laser device according to the second embodiment taken along line XVIIA-XVIIA in FIG. [Figure 17B] 17B is a cross-sectional view of the semiconductor laser device according to the second embodiment taken along line XVIIB-XVIIB in FIG. [Figure 17C] 17C is a cross-sectional view of the semiconductor laser device according to the second embodiment taken along line XVIIC-XVIIC in FIG. [Figure 18] FIG. 18 is an enlarged cross-sectional view of a semiconductor laser device according to the second embodiment. [Figure 19] FIG. 19 is an enlarged cross-sectional view of a semiconductor laser device according to a modification of the second embodiment. [Figure 20A] FIG. 20A is a cross-sectional view showing a step of forming a second p-side electrode layer in a method for manufacturing a semiconductor laser device according to the second embodiment. [Figure 20B] FIG. 20B is a cross-sectional view showing a step of forming an n-side electrode layer in the method for manufacturing the semiconductor laser device according to the second embodiment. [Figure 21] FIG. 21 is a plan view of a semiconductor laser device according to the third embodiment. [Figure 22A] FIG. 22A is a diagram showing a part of a cross section of the semiconductor laser device according to the third embodiment taken along the line XXIIA-XXIIA in FIG. [Figure 22B]FIG. 22B is a diagram showing a part of a cross section of the semiconductor laser device according to the third embodiment taken along the line XXIIB-XXIIB in FIG. [Figure 22C] FIG. 22C is a diagram showing a part of a cross section of the semiconductor laser device according to the third embodiment taken along the line XXIIC-XXIIC in FIG. [Figure 23A] FIG. 23A is a cross-sectional view showing a step of forming a pad electrode, a second pad electrode, and a second p-side electrode layer in a manufacturing method of a semiconductor laser device according to the third embodiment. [Figure 23B] FIG. 23B is a cross-sectional view showing a step of forming an n-side electrode layer in the method for manufacturing the semiconductor laser device according to the third embodiment. [Figure 24] FIG. 24 is a plan view of a semiconductor laser device according to a first modification of the third embodiment. [Figure 25] FIG. 25 is a plan view of a semiconductor laser device according to Modification 2 of Embodiment 3. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] 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.

[0017] In this specification, the terms "above" and "below" do not refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. Furthermore, the terms "above" and "below" are applied not only to cases where two components are arranged with a gap between them and another component exists between the two components, but also to cases where two components are arranged in contact with each other.

[0018] (Embodiment 1) [Semiconductor laser element] First, the configuration of a semiconductor laser device 1 according to the first embodiment will be described with reference to FIGS. 1, 2A, 2B, and 2C. FIG. 1 is a plan view of the semiconductor laser device 1 according to the first embodiment. FIGS. 2A to 2C are cross-sectional views of the semiconductor laser device 1 according to the first embodiment. FIGS. 2A, 2B, and 2C show cross sections taken along lines IIA-IIA, IIB-IIB, and IIC-IIC in FIG. 1, respectively. FIG. 2A shows a cross section of a portion corresponding to a current injection region, which is a region into which current is injected, and FIG. 2B shows a cross section of a portion corresponding to a non-current injection region, which is a region at the front end of the semiconductor laser device 1 into which current is not injected.

[0019] 1, the semiconductor laser device 1 has a front end facet 1a and a rear end facet 1b opposite to the front end facet 1a. The front end facet 1a is a front end facet (light-emitting end facet) from which laser light is emitted, and the rear end facet 1b is a rear end facet from which laser light is not emitted.

[0020] The semiconductor laser device 1 has an optical waveguide with the front end facet 1a and the rear end facet 1b as cavity reflecting mirrors. Therefore, the front end facet 1a and the rear end facet 1b serve as cavity end faces. That is, in the semiconductor laser device 1, the front end facet 1a and the rear end facet 1b form a cavity. Therefore, the rear end facet 1b has a higher reflectivity than the front end facet 1a. As an example, the reflectivity of the front end facet 1a is 5%, and the reflectivity of the rear end facet 1b is 95%. The cavity length of the semiconductor laser device 1 is the distance between the front end facet 1a and the rear end facet 1b. In this embodiment, the cavity length of the semiconductor laser device 1 is 2 mm or more, and may be 4 mm or more. The cavity length of the semiconductor laser device 1 may be less than 2 mm. The semiconductor laser device 1 has a shape that is elongated in the cavity length direction.

[0021] The semiconductor laser element 1 emits laser light from the front end facet 1a with an optical output of about 10 W to several tens of W. As an example, the semiconductor laser element 1 emits infrared light with an optical output of 25 W and a peak wavelength in the 976 nm band. However, the peak wavelength of the laser light from the semiconductor laser element 1 is not limited to this.

[0022] 2A to 2C, the semiconductor laser device 1 has a substrate 10 and a semiconductor stack 20 formed above the substrate 10. The semiconductor laser device 1 in this embodiment is a compound semiconductor laser made of an AlGaInAs-based III-V semiconductor material. Therefore, the semiconductor stack 20 has a structure in which a plurality of semiconductor layers, each made of a III-V semiconductor material, are stacked.

[0023] As shown in FIGS. 1 and 2C, a first facet coating film 20a is formed on the front facet of the semiconductor laminated structure 20. A second facet coating film 20b is formed on the rear facet of the semiconductor laminated structure 20. The first facet coating film 20a and the second facet coating film 20b are reflective films made of dielectric multilayer films. For example, the first facet coating film 20a is a multilayer film of Al2O3 and SiO2, and the second facet coating film 20b is a multilayer film of Al2O3, SiO2, and Ta2O5. As an example, the reflectivity of the first facet coating film 20a is 5%, and the reflectivity of the second facet coating film 20b is 95%. The front facet of the first facet coating film 20a becomes the front facet 1a of the semiconductor laser device 1, and the rear facet of the second facet coating film 20b becomes the rear facet 1b of the semiconductor laser device 1.

[0024] 2A and 2B, a separation groove 20c is formed on the side of the semiconductor laminated structure 20. The separation groove 20c is a groove used when separating the semiconductor laser device 1, and extends in the cavity length direction when viewed from above. In this embodiment, the separation groove 20c is formed so as to be constricted.

[0025] The substrate 10 is a planar substrate whose main surface is uniformly flat. The substrate 10 is a semiconductor substrate such as a GaAs substrate or an insulating substrate such as a sapphire substrate. In this embodiment, the substrate 10 is an n-type GaAs substrate.

[0026] 2A to 2C, the semiconductor stacked structure 20 has an n-type semiconductor layer 21, an active layer 22, a p-type semiconductor layer 23, and a p-type contact layer 24, in that order, on one surface of the substrate 10. That is, the n-type semiconductor layer 21 is formed on the substrate 10, the active layer 22 is formed on the n-type semiconductor layer 21, the p-type semiconductor layer 23 is formed on the active layer 22, and the p-type contact layer 24 is formed on the p-type semiconductor layer 23.

[0027] The n-type semiconductor layer 21 is an example of a first conductivity type first semiconductor layer. In this embodiment, the n-type semiconductor layer 21 has an n-type buffer layer, an n-type first compositionally graded layer, an n-type cladding layer, and an n-type second compositionally graded layer, which are stacked in this order on the substrate 10.

[0028] The n-type buffer layer, the n-type first compositionally graded layer, the n-type cladding layer, and the n-type second compositionally graded layer are n-type semiconductor layers intentionally doped with impurities such as silicon (Si), and are composed of, for example, an n-type GaAs layer or an n-type AlGaAs layer. Note that the n-type semiconductor layer 21 may include an undoped semiconductor layer that is not intentionally doped with impurities.

[0029] For example, the n-type buffer layer is an n-type GaAS layer made of n-GaAs with a thickness of 0.50 μm, and the n-type first composition gradient layer is an n-Al layer made of n-GaAs with a thickness of 0.05 μm. x Ga 1-x The n-type AlGaAs layer is made of As (x=0.15-0.32), and the n-type cladding layer is made of n-AlGaAs with a thickness of 3.0 μm. 0.32 Ga 0.715 The n-type AlGaAs layer is made of As, and the n-type second composition gradient layer is made of n-AlGaAs with a thickness of 0.03 μm. x Ga 1-x It is an n-type AlGaAs layer with As (x=0.32~0.285).

[0030] The active layer 22 is formed on the n-type semiconductor layer 21. In this embodiment, the active layer 22 has an n-type guide layer, an n-side second barrier layer, an n-side first barrier layer, a well layer, a p-side first barrier layer, a p-side second barrier layer, and a p-type guide layer, which are stacked in this order on the n-type semiconductor layer 21.

[0031] The n-type guide layer, the n-side second barrier layer, and the n-side first barrier layer are n-type semiconductor layers intentionally doped with impurities such as silicon, and are composed of, for example, an n-type AlGaAs layer or an n-type AlGaInAs layer.

[0032] As an example, the n-type guide layer is made of n-Al with a thickness of 1.05 μm.0.285 Ga 0.715 The n-type AlGaAs layer is made of As, and the n-side second barrier layer is made of n-AlGaAs with a thickness of 0.0268 μm. 0.15 Ga 0.85 An n-type AlGaAs layer consisting of As and a 0.0083 μm thick Al 0.15 Ga 0.85 The n-side first barrier layer is an undoped AlGaAs layer with a thickness of 0.0018 μm. 0.50 Ga 0.32 In 0.18 It is an AlGaInAs layer made of As.

[0033] The p-side first barrier layer, the p-side second barrier layer, and the p-type guide layer are p-type semiconductor layers intentionally doped with impurities such as carbon (C), and are composed of, for example, a p-type AlGaAs layer or a p-type AlGaInAs layer. The p-side first barrier layer and the p-side first barrier layer may have undoped regions in addition to doped regions.

[0034] As an example, the p-side first barrier layer is made of 0.0018 μm Al 0.50 Ga 0.32 In 0.18 The p-side second barrier layer is an AlGaInAs layer made of As, and the thickness is 0.0083 μm. 0.15 Ga 0.85 An undoped AlGaAs layer consisting of As and a 0.025 μm thick p-Al 0.15 Ga 0.85 The p-type AlGaAs layer is made of As and the p-type AlGaAs layer is made of As. 0.28 Ga 0.72 It is a p-type AlGaAs layer made of As.

[0035] The well layer has a single quantum well structure including a single quantum well layer. The well layer is made of an undoped InGaAs layer. For example, the well layer is made of an InGaAs layer having a thickness of 0.0090 μm. 0.135 Ga 0.865It is an InGaAs layer made of As. The well layer is not limited to a single quantum well structure, but may be a multiple quantum well structure including a plurality of quantum well layers.

[0036] The p-type semiconductor layer 23 is an example of a second semiconductor layer of a second conductivity type different from the first conductivity type. In this embodiment, the p-type semiconductor layer 23 has a p-type first compositional gradient layer, a p-type cladding layer, and a p-type second compositional gradient layer, which are sequentially stacked on the active layer 22. The p-type first compositional gradient layer, the p-type cladding layer, and the p-type second compositional gradient layer are p-type semiconductor layers intentionally doped with impurities such as carbon, and are made of, for example, a p-type AlGaAs layer. The impurity concentrations of the p-type first compositional gradient layer, the p-type cladding layer, and the p-type second compositional gradient layer are, for example, 1.0×10 19 (cm -3 ) is less than

[0037] As an example, the p-type first composition gradient layer is a p-Al layer with a thickness of 0.05 μm. x Ga 1-x The p-type AlGaAs layer is made of As (x=0.28-0.70), and the p-type cladding layer is made of p-AlGaAs with a thickness of 0.75 μm. 0.70 Ga 0.30 The p-type AlGaAs layer is made of As, and the p-type second composition gradient layer is made of p-AlGaAs with a thickness of 0.05 μm. x Ga 1-x It is a p-type AlGaAs layer made of As (x=0.70 to 0.15).

[0038] The p-type contact layer 24 is an example of a third semiconductor layer of the second conductivity type. The p-type contact layer is a p-type semiconductor layer intentionally doped with impurities such as carbon, and is made of, for example, a p-type GaAs layer. The impurity concentration of the p-type contact layer is, for example, 1.0×10 19 (cm -3 ) or more. As an example, the p-type contact layer is a p-type GaAs layer made of p-GaAs with a film thickness of 0.25 μm.

[0039] The semiconductor laser device 1 has a ridge portion 1R formed in a ridge shape as a waveguide extending in the cavity length direction. The ridge portion 1R extends in the cavity length direction. The ridge portion 1R functions as a current injection region in the semiconductor laser device 1. As shown in FIGS. 2A and 2B, the ridge portion 1R is formed in the p-type semiconductor layer 23 and the p-type contact layer 24.

[0040] 2A, the ridge portion 1R is formed by digging an opening 30 into the p-type semiconductor layer 23 and the p-type contact layer 24. In this embodiment, the uppermost layer of the ridge portion 1R is the p-type contact layer 24. A bottom 30a of the opening 30 forms the ridge bottom and is a flat portion located within the p-type semiconductor layer 23.

[0041] In this embodiment, the opening 30 has a pair of lateral grooves 31. As shown in Fig. 2A, the ridge portion 1R is sandwiched between the pair of lateral grooves 31 in the opening 30. As shown in Fig. 1, the pair of lateral grooves 31 in the opening 30 are parallel to each other and extend in the laser cavity length direction.

[0042] 1 and 2B, the opening 30 has not only a pair of lateral grooves 31 but also a front groove 32 and a rear groove 33. The front groove 32 is formed at the front end of the semiconductor laser element 1 on an extension of the ridge portion 1R, and the rear groove 33 is formed at the rear end of the semiconductor laser element 1 on an extension of the ridge portion 1R. By forming the front groove 32 and the rear groove 33 in the p-type semiconductor layer 23 and the p-type contact layer 24, the ridge portion 1R is not present at the front end or rear end of the semiconductor laser element 1. The pair of lateral grooves 31, the front groove 32, and the rear groove 33 are formed continuously. Therefore, the ridge portion 1R is configured to be surrounded by the opening 30. The front groove 32 and the rear groove 33 do not necessarily have to be formed.

[0043] 2A, by forming an opening 30 in the p-type semiconductor layer 23 and the p-type contact layer 24, a pair of wing portions 40 are formed in the semiconductor laser device 1. The pair of wing portions 40 are located on the sides of the ridge portion 1R. In other words, the ridge portion 1R is sandwiched between the pair of wing portions 40 via the opening 30. The pair of wing portions 40 extend along the cavity length direction of the semiconductor laser device 1.

[0044] 2A to 2C, an insulating film 50 made of a dielectric film such as SiO2 or SiN is formed on the p-type contact layer 24, except for a portion above the ridge portion 1R. Specifically, the insulating film 50 is formed to have an opening 50a above the ridge portion 1R of the p-type contact layer 24. The insulating film 50 functions as a current blocking film. Therefore, the opening 50a in the insulating film 50 is a current injection window through which current passes.

[0045] Furthermore, the insulating film 50 covers the bottom 30a of the opening 30 formed in the p-type semiconductor layer 23 and the p-type contact layer 24. Therefore, the bottom 30a of the opening 30 at the front end of the semiconductor laser element 1 (specifically, the bottom of the front groove 32) is covered with the insulating film 50. In other words, when viewed from above, the insulating film 50 covers the front end of the semiconductor laser element 1. This makes it possible to prevent current from spreading to the front end and window region of the semiconductor laser element 1, and to prevent a decrease in optical output and a decrease in reliability.

[0046] 2A and 2B, the insulating film 50 also covers the side surfaces of the semiconductor stack 20. Specifically, the insulating film 50 covers the entire side surfaces of the p-type contact layer 24, the entire side surfaces of the p-type semiconductor layer 23, the entire side surfaces of the active layer 22, and part of the side surfaces of the n-type semiconductor layer 21.

[0047] As shown in FIG. 2C , the semiconductor laminated structure 20 in the semiconductor laser device 1 has a window region 22a (facet window structure) at its front end in the cavity length direction. Specifically, the window region 22a is formed in a region of a predetermined length from the front end facet 1a in a current non-injection region of the active layer 22 near the front end facet of the ridge portion 1R. The window region 22a is formed at the front end of the semiconductor laminated structure 20. The region of the waveguide where the window region 22a is not formed is the gain region. By forming the window region 22a (facet window structure) at the front end of the semiconductor laser device 1 in this way, the front end of the semiconductor laser device 1 can be made transparent, thereby reducing light absorption near the front end facet 1a. This makes it possible to suppress COD at the front end of the semiconductor laser device 1. A similar window region may also be formed at the rear end of the semiconductor laminated structure 20. Window regions may not be formed at the front and rear ends of the semiconductor laser device 1.

[0048] The semiconductor laser device 1 has a p-side electrode layer 61 as a first p-side electrode. The p-side electrode layer 61 is formed on the semiconductor stacked structure 20. Specifically, the p-side electrode layer 61 is formed above the p-type contact layer 24. In this embodiment, the p-side electrode layer 61 is formed above the ridge portion 1R so as to be in contact with the p-type contact layer 24. Specifically, the p-side electrode layer 61 is in ohmic contact with the p-type contact layer 24. In this embodiment, the p-side electrode layer 61 is formed not only on the ridge portion 1R but also in the opening 30 and on the wing portion 40 via the insulating film 50.

[0049] The p-side electrode layer 61 is a metal layer made of a metal material. The p-side electrode layer 61 is, for example, a single-layer film or a multilayer film made of at least one of Pt, Ti, Cr, Ni, Mo, and Au. In this embodiment, the p-side electrode layer 61 is made of a multilayer film. As an example, the p-side electrode layer 61 is a multilayer film with a three-layer structure in which a Ti film, a Pt film, and an Au film are stacked in this order from the p-type contact layer 24 side.

[0050] The semiconductor laser device 1 also has an n-side electrode layer 62 as a second electrode on the n-side. The n-side electrode layer 62 is formed below the other surface (lower surface) of the substrate 10, which is the surface opposite to one surface (the surface on the semiconductor laminated structure 20 side). In this embodiment, the n-side electrode layer 62 is formed directly on the other surface of the substrate 10.

[0051] The n-side electrode layer 62 is a metal layer made of a metal material. The n-side electrode layer 62 is, for example, a single-layer film or a multilayer film made of at least one of Cr, Ti, Ni, Pd, Pt, Au, and Ge. In this embodiment, the n-side electrode layer 62 is made of a multilayer film. As an example, the n-side electrode layer 62 is a multilayer film with a six-layer structure in which, from the substrate 10 side, an AuGe film, a Ni film, an Au film, a Ti film, a Pt film, and an Au film are stacked in this order.

[0052] Furthermore, the semiconductor laser device 1 has a pad electrode 70. The pad electrode 70 is formed above the p-side electrode layer 61. Specifically, the pad electrode 70 is stacked on the p-side electrode layer 61 so as to be in contact with the upper surface of the p-side electrode layer 61. That is, the p-side electrode layer 61 is formed on the lower surface of the pad electrode 70. The pad electrode 70 is a p-side pad electrode that constitutes a p-side electrode together with the p-side electrode layer 61. In this embodiment, the pad electrode 70 is formed above the p-side electrode layer 61. Therefore, the pad electrode 70 is formed not only above the ridge portion 1R but also above the wing portions 40.

[0053] The pad electrode 70 is a metal layer made of a metal material. In this embodiment, the pad electrode 70 is an Au plated film, but is not limited to this.

[0054] 2C , the front end face of the pad electrode 70 is located at a position recessed from the front end face 1a of the semiconductor laser element 1. Since the front end face of the pad electrode 70 is located at a position recessed from the front end face 1a of the semiconductor laser element 1 in this manner, the semiconductor laser element 1 has an exposed surface 61a exposed from the pad electrode 70. In this embodiment, this exposed surface 61a is the surface of the p-side electrode layer 61. The distance L between the front end face of the pad electrode 70 and the front end face 1a of the semiconductor laser element 1 (the recession amount of the front end of the pad electrode 70) is, for example, not less than 5 μm and not more than 15 μm, but is not limited to this.

[0055] Furthermore, in a vertical cross section parallel to the cavity length direction of the semiconductor laser device 1, the front end face of the pad electrode 70 is formed so that at least a portion thereof is recessed. Specifically, an overhang portion 71 is formed at the front end portion of the pad electrode 70. In this manner, in this embodiment, the overhang portion 71 is formed at the front end portion of the pad electrode 70, so that a portion of the front end face of the pad electrode 70 is recessed. As a result, a recess 70a is formed in the front end face of the pad electrode 70, where a portion of the front end face is recessed rearward in the cavity length direction.

[0056] 2A, in this embodiment, the overhanging portion 71 is also formed on the side surface of the pad electrode 70. Although not shown, the overhanging portion 71 is also formed on the rear end surface of the pad electrode 70. In other words, the overhanging portion 71 is formed around the entire periphery of the pad electrode 70.

[0057] [Semiconductor laser device] Next, the configuration of a semiconductor laser device 100 using the semiconductor laser element 1 will be described with reference to FIGS. 3, 4A, 4B, 4C, and 5. FIG. 3 is a plan view of the semiconductor laser device 100 according to the first embodiment. FIGS. 4A to 4C are cross-sectional views of the semiconductor laser device 100 according to the first embodiment. FIGS. 4A, 4B, and 4C show cross sections taken along lines IVA-IVA, IVB-IVB, and IVC-IVC in FIG. 3, respectively. FIG. 5 is an enlarged cross-sectional view of a region V surrounded by a dashed line in FIG. 4C.

[0058] 3 to 5, the semiconductor laser device 100 according to this embodiment includes a semiconductor laser element 1, a heat sink 2, and a joining member 3 that joins the semiconductor laser element 1 to the heat sink 2. That is, the semiconductor laser element 1 is joined to the heat sink 2 via the joining member 3.

[0059] The semiconductor laser element 1 is bonded to the heat sink 2 by junction-down mounting. That is, the semiconductor laser element 1 is disposed so that the pad electrodes 70 face the heat sink 2. Specifically, the semiconductor laser element 1 is disposed above the heat sink 2 so that the pad electrodes 70 face downward, and is bonded to the heat sink 2 by a bonding member 3.

[0060] The heat sink 2 is a heat dissipation member for dissipating heat generated by the semiconductor laser device 1. In this embodiment, the heat sink 2 also functions as a submount (base) for mounting the semiconductor laser device 1. The semiconductor laser device 1 is located on the heat sink 2.

[0061] As shown in FIG. 4C, the heat sink 2 has a heat sink body 2a, a first conductor layer 2b, a second conductor layer 2c, a third conductor layer 2d, and a fourth conductor layer 2e.

[0062] The first conductor layer 2b and the second conductor layer 2c are formed on the semiconductor laser element 1 side of the heatsink body 2a. The first conductor layer 2b is formed on the upper surface of the heatsink body 2a, and the second conductor layer 2c is formed on the upper surface of the first conductor layer 2b. In this embodiment, the second conductor layer 2c also covers the front and rear end faces of the first conductor layer 2b so that the first conductor layer 2b is not exposed.

[0063] The third conductor layer 2d and the fourth conductor layer 2e are formed on the side of the heatsink body 2a opposite to the semiconductor laser element 1 side. The third conductor layer 2d is formed on the lower surface of the heatsink body 2a, and the fourth conductor layer 2e is formed on the lower surface of the third conductor layer 2d. In this embodiment, the fourth conductor layer 2e also covers the front and rear end surfaces of the third conductor layer 2d so that the third conductor layer 2d is not exposed.

[0064] The heat sink body 2a is made of a highly thermally conductive material such as AlN, CuW, diamond, SiC, etc. In this embodiment, the heat sink body 2a is made of AlN. The shape of the heat sink body 2a is, for example, a rectangular parallelepiped.

[0065] The first conductor layer 2b, the second conductor layer 2c, the third conductor layer 2d, and the fourth conductor layer 2e are metal layers made of metal materials, and may be single-layer films or multi-layer films.

[0066] The first conductor layer 2b and the third conductor layer 2d in contact with the heat sink body 2a are high heat dissipation conductor layers made of a metal material with high conductivity, such as Cu. In this embodiment, the first conductor layer 2b and the third conductor layer 2d are Cu films.

[0067] The second conductor layer 2c in contact with the bonding member 3 is preferably made of a metal material that has high adhesion to the bonding member 3. In this embodiment, the second semiconductor layer 2c is a multilayer film with a three-layer structure in which a Ni film, an Au film, and a Pt film are formed in this order from the first semiconductor layer 2b toward the bonding member 3. The fourth conductor layer 2e has the same structure as the second conductor layer 2c.

[0068] 5, the semiconductor laser element 1 mounted on the heat sink 2 is disposed so that its front end face 1a does not protrude from the front end face of the heat sink 2. In other words, the front end face 1a of the semiconductor laser element 1 is located at a position set back from the front end face of the heat sink 2. The front end face 1a of the semiconductor laser element 1 is located between the front end face of the heat sink main body 2a of the heat sink 2 and the front end face of the second conductor layer 2c.

[0069] 4A to 4C and 5, the bonding member 3 bonds the semiconductor laser element 1 and the heat sink 2 together, and is interposed between the semiconductor laser element 1 and the heat sink 2. Specifically, the bonding member 3 bonds the pad electrode 70 of the semiconductor laser element 1 to the second conductor layer 2c of the heat sink 2.

[0070] 5, the bonding member 3 extends to the front end of the semiconductor laser device 1 and is connected to the front end of the semiconductor laser device 1. This allows heat generated at the front end of the semiconductor laser device 1 to be conducted to the heat sink 2 via the bonding member 3, thereby preventing COD from occurring at the front end of the semiconductor laser device 1. In this embodiment, the bonding member 3 is connected to an exposed surface 61a at the front end of the semiconductor laser device 1. That is, the bonding member 3 is connected to the p-side electrode layer 61 of the semiconductor laser device 1.

[0071] Specifically, a fillet 3a is formed on the joining member 3, and the fillet 3a is connected to the front end of the semiconductor laser element 1. The fillet 3a is a portion of the joining member 3 that protrudes from between the semiconductor laser element 1 and the heat sink 2. In this embodiment, the joining member 3 is solder, and therefore the fillet 3a is a solder fillet.

[0072] The bonding member 3 is connected to the exposed surface 61a of the semiconductor laser element 1 up to the position of the front end surface of the semiconductor laminated structure 20 of the semiconductor laser element 1. That is, the fillet 3a is formed up to the position of the front end surface of the semiconductor laminated structure 20. Note that the fillet 3a may also be formed up to the position of the front end surface 1a of the semiconductor laser element 1 on the exposed surface 61a.

[0073] In this embodiment, the bonding member 3 is connected not only to the front end of the semiconductor laser element 1 but also to the front end surface of the heat sink 2. Specifically, a fillet 3a of the bonding member 3 protruding forward from between the pad electrode 70 and the heat sink 2 is connected to the exposed surface 61a at the front end of the semiconductor laser element 1 and also to the front end surface of the second conductor layer 2c of the heat sink 2.

[0074] 4A, in a vertical cross section perpendicular to the cavity length direction of the exposed surface 61a of the semiconductor laser device 1, the bonding member 3 is connected to the exposed surface 61a over at least the entire width (ridge width) of the ridge portion 1R. In this embodiment, the bonding member 3 is formed over the entire exposed surface 61a in a vertical cross section perpendicular to the cavity length direction of the exposed surface 61a of the semiconductor laser device 1. Specifically, as shown in FIG. 4A, the width of the bonding member 3 is larger than the width of the exposed surface 61a.

[0075] The joining member 3 is, for example, a solder material such as AuSn solder containing AuSn as a main component, or a metal brazing material. In this embodiment, the joining member 3 is AuSn solder. The thickness of the joining member 3 between the semiconductor laser element 1 and the heat sink 2 is, for example, 3 μm to 7 μm.

[0076] 5, in the semiconductor laser device 100 of this embodiment, a gap 4 is formed between the bonding member 3 and the front end face of the pad electrode 70 in a vertical cross section parallel to the cavity length direction of the semiconductor laser element 1. Specifically, the gap 4 is a void (cavity) surrounded by the fillet 3a of the bonding member 3, the front end face of the pad electrode 70, and the exposed surface 61a of the semiconductor laser element 1, and is formed intentionally. The gap 4 exists at least between the overhanging portion 71 of the pad electrode 70 and the exposed surface 61a of the semiconductor laser element 1.

[0077] The cross-sectional shape of the gap 4 is, for example, a substantially trapezoidal shape. Therefore, the front end surface of the pad electrode 70 and the inner surface of the bonding member 3 (fillet 3a) on the gap 4 side in the gap 4 are both inclined surfaces. In this case, the angle formed between the exposed surface 61a of the semiconductor laser element 1 and the front end surface of the pad electrode 70 is larger than the angle formed between the exposed surface 61a of the semiconductor laser element 1 and the inner surface of the bonding member 3 (fillet 3a).

[0078] The gap 4 extends in a direction perpendicular to the plane of the paper in Fig. 5. In other words, the gap 4 is columnar and extends along a direction perpendicular to both the stacking direction of the semiconductor stacked structure 20 in the semiconductor laser device 1 and the cavity length direction.

[0079] [Method of manufacturing semiconductor laser element] Next, a method for manufacturing the semiconductor laser device 1 shown in Figures 1 to 2C will be described with reference to Figures 6A to 6G. Figures 6A to 6G are cross-sectional views of each step in the method for manufacturing the semiconductor laser device 1 according to the first embodiment. In each of Figures 6A to 6G, (a) shows a cross section corresponding to Figure 2A (a cross section of the current injection region), and (b) shows a cross section corresponding to Figure 2B (a cross section of the non-current injection region at the front end).

[0080] 6A(a) and 6A(b), a substrate 10 is prepared, and a semiconductor stack 20 including an active layer 22 is formed on the substrate 10. Specifically, an n-type semiconductor layer 21, an active layer 22, a p-type semiconductor layer 23, and a p-type contact layer 24 are sequentially formed on the substrate 10, which is a wafer of an n-GaAS substrate, by crystal growth technology using metalorganic chemical vapor deposition (MOCVD).

[0081] Next, as shown in (a) and (b) of FIG. 6B, a window region 22a is formed only in a portion of the semiconductor laminate structure 20 corresponding to the front end in the cavity length direction. In this embodiment, the window region 22a is formed by diffusing vacancies in the active layer 22. Note that the window region 22a is formed by a vacancy diffusion method, but this is not limitative. Note that window regions do not necessarily have to be formed at the front and rear ends of the semiconductor laser device 1.

[0082] 6C (a) and (b), openings 30 for defining the ridge portion 1R and the wing portions 40 are formed in the p-type contact layer 24. Specifically, a mask made of SiO2 or the like is formed in a predetermined pattern on the p-type contact layer 24 by photolithography, and then the openings 30 are formed by wet etching.

[0083] At this time, as shown in (a) of Fig. 6C, by forming the lateral groove 31 in the current injection region, a convex portion 5a is formed in the p-type contact layer 24 in a portion corresponding to the ridge portion 1R, and a convex portion 5b is formed in the p-type contact layer 24 in a portion corresponding to the wing portion 40. On the other hand, as shown in (b) of Fig. 6C, in the front end portion (non-current injection region) of the semiconductor laser device 1, the convex portion 5a is not formed, and a front groove 32 is formed in the p-type contact layer 24. Note that the front groove 32 and the rear groove 33 do not necessarily have to be formed.

[0084] In the chip end region of the semiconductor laser element 1, recesses may be formed separately in the p-type contact layer 24 in portions corresponding to the separation grooves 20c when singulating. These recesses are formed on both sides of the semiconductor laminated structure 20 and extend in the cavity length direction when viewed from above.

[0085] 6D (a) and (b), a separation groove 20c having an inclined surface is formed on the side surface of the semiconductor stacked structure 20. Specifically, a mask made of SiO or the like is formed in a predetermined pattern on the p-type semiconductor layer 23 using photolithography, and then a wet etching technique is used to etch from the p-type semiconductor layer 23 to partway through the n-type semiconductor layer 21, thereby forming the separation groove 20c with an inclined side surface of the semiconductor stacked structure 20.

[0086] The etching solution used to form the separation grooves 20c may be, for example, a sulfuric acid-based etching solution. In this case, an etching solution with a sulfuric acid:hydrogen peroxide:water ratio of 1:1:10 may be used. The etching solution is not limited to a sulfuric acid-based etching solution, and an organic acid-based etching solution or an ammonia-based etching solution may also be used. In this case, the separation grooves 20c are formed by isotropic wet etching. This allows an inclined surface to be formed on the side surface of the semiconductor stacked structure 20, thereby forming a constricted structure on the side surface of the semiconductor stacked structure 20.

[0087] Next, after removing the mask used to form the separation groove 20c with a hydrofluoric acid-based etching solution, a SiN film is deposited as the insulating film 50 all over the surface of the substrate 10, as shown in (a) and (b) of Figure 6E, and then photolithography and etching techniques are used to remove the insulating film 50 from the portion corresponding to the current injection region, thereby forming the opening 50a. Note that, as shown in (b) of Figure 6E, the portion of the insulating film 50 corresponding to the non-current injection region is not removed, and no opening 50a is formed in the insulating film 50 from the portion corresponding to the non-current injection region.

[0088] Wet etching using a hydrofluoric acid-based etching solution or dry etching by reactive ion etching (RIE) can be used to etch the insulating film 50. Although the insulating film 50 is an SiN film, it is not limited to this and may be an SiO2 film or the like.

[0089] Next, as shown in (a) and (b) of FIG. 6F, a p-side electrode layer 61 is formed above the semiconductor laminated structure 20, and then a pad electrode 70 is formed above the p-side electrode layer 61.

[0090] Specifically, a p-side electrode layer 61 made of a laminated film of a Ti film, a Pt film, and an Au film is formed on the p-type contact layer 24 of the semiconductor laminated structure 20 by electron beam evaporation. Then, using the p-side electrode layer 61 as a base electrode, a pad electrode 70 made of an Au plated film is formed on the p-side electrode layer 61. In this process, in the process of forming the pad electrode 70, patterning is performed using a resist mask to form the pad electrode 70 so that at least a portion of the front end surface of the pad electrode 70 is recessed. Note that while the p-side electrode layer 61 is formed over almost the entire length in the resonator length direction, the pad electrode 70 is not formed over the entire length in the resonator length direction and is not formed at the front end.

[0091] Here, the process of forming the pad electrode 70 will be described in detail with reference to FIG. 7. First, as shown in FIG. 7(a), a resist 80 (resist mask) having a predetermined shape is formed on the p-side electrode layer 61 so as to expose a portion of the p-side electrode layer 61. Next, as shown in FIG. 7(b), the pad electrode 70 is formed across the exposed p-side electrode layer 61 and the resist 80. Specifically, an Au plating film is formed by electroplating using the p-side electrode layer 61 as a base electrode, and then the Au plating film near the front end of the semiconductor stack 20 is selectively removed using photolithography, etching, and lift-off techniques, thereby forming the pad electrode 70 having the shape shown in FIG. 7(b). Next, as shown in FIG. 7(c), the resist 80 is removed. This exposes the surface of the p-side electrode layer 61, forming an exposed surface 61a.

[0092] In the step of forming the pad electrode 70, the thickness of the pad electrode 70 (Au plating film) is preferably set to be thicker than the thickness of the resist 80. As a result, the pad electrode 70 (Au plating film) is formed so as to cover the end of the resist 80, so that an overhang portion 71 can be formed at the front end of the pad electrode 70. In this way, the pad electrode 70 having the overhang portion 71 at the front end can be formed. In this case, as shown in FIG. 7(c), the angle θ of the inclined surface of the recess 70a of the pad electrode 70 is 65±15°, and the length d of the overhang portion 71 of the pad electrode 70 is 0.4 μm to 2.0 μm. The thickness of the resist 80 is, for example, 1.8 μm.

[0093] 6G(a) and (b), an n-side electrode layer 62 is formed on the lower surface of the substrate 10. Specifically, an AuGe film, a Ni film, an Au film, a Ti film, a Pt film, and an Au film are sequentially formed from the substrate 10 side, thereby forming the n-side electrode layer 62 on the lower surface of the substrate 10.

[0094] Thereafter, although not shown, the substrate 10 (wafer) on which the semiconductor stack structure 20 of a predetermined shape has been formed is separated into a plurality of bars by dicing or cleaving using a blade, and then the separated bars are further cut along the separation grooves 20c to separate them into chips. This allows individual semiconductor laser elements 1 to be fabricated.

[0095] Then, the semiconductor laser element 1 is bonded to the heat sink 2 by junction-down mounting using the bonding member 3, whereby the semiconductor laser device 100 shown in FIGS. 3 to 5 can be fabricated.

[0096] At this time, the liquid bonding member 3 is pressed by the semiconductor laser element 1, so that the liquid bonding member 3 protrudes from between the semiconductor laser element 1 and the heat sink 2 and connects to the front end of the semiconductor laser element 1. However, in the semiconductor laser element 1 according to this embodiment, the overhanging portion 71 is formed at the front end of the pad electrode 70, so that the liquid bonding member 3 does not go around to the inside of the protruding overhanging portion 71. As a result, as shown in Fig. 5, the bonding member 3 is no longer in contact with the front end surface of the pad electrode 70, so that a gap 4 is formed.

[0097] Fig. 8 is an SEM image of the semiconductor laser device 100 actually fabricated in this manner. As shown in Fig. 8, in the semiconductor laser device 100, a gap 4 is formed between the bonding member 3 and the front end face of the pad electrode 70 in a vertical cross section parallel to the cavity length direction of the semiconductor laser element 1.

[0098] Next, the effects of the semiconductor laser device 100 according to this embodiment will be described in comparison with a semiconductor laser device 100X of a comparative example with reference to FIGS. 9 and 10. FIG. 9 is a cross-sectional view showing the configuration of the semiconductor laser device 100X of the comparative example. FIG. 10 is a cross-sectional view showing the configuration of the semiconductor laser device 100 according to the first embodiment. Note that FIG. 10 is a cross-sectional view corresponding to FIG. 5.

[0099] 9, in the semiconductor laser device 100X of the comparative example, in order to suppress the occurrence of COD, a joining member 3X that joins the semiconductor laser element 1X to the heat sink 2 is connected to the front end of the semiconductor laser element 1X. AuSn solder is used as the joining member 3X.

[0100] In the semiconductor laser device 100X of the comparative example, the front end surface of the pad electrode 70X of the semiconductor laser element 1X is a vertical surface, and the bonding member 3X (fillet 3a) covers the front end surface of the pad electrode 70X and also covers the entire exposed surface 61a (i.e., the surface of the p-side electrode layer 61) of the semiconductor laser element 1X. In other words, the bonding member 3X connected to the front end portion of the semiconductor laser element 1X fills the peripheral region of the front end surface of the pad electrode 70X and the exposed surface 61a without any gaps.

[0101] In such a structure, the contact portion between the bonding member 3X and the front end surface of the pad electrode 70X is alloyed, and the contact portion between the bonding member 3X and the exposed surface 61 a of the p-side electrode layer 61 is alloyed. As a result, new alloy layers are formed at the interface between the bonding member 3X and the front end surface of the pad electrode 70X and the interface between the bonding member 3X and the exposed surface 61 a of the p-side electrode layer 61.

[0102] In this case, the bonding member 3X, the pad electrode 70X, the p-side electrode layer 61, and the new alloy layer all have different linear expansion coefficients. This means that there is a difference in the linear expansion coefficients between the bonding member 3X, the pad electrode 70X, the p-side electrode layer 61, and the new alloy layer. Therefore, in the semiconductor laser device 100X, when the temperature changes, shear stress occurs between the components due to the difference in the linear expansion coefficients between the components. In particular, as shown at point P in FIG. 9 , if the bonding member 3X is tightly packed at the corner between the front end surface of the pad electrode 70X and the exposed surface 61a of the p-side electrode layer 61, a large shear stress will be generated at point P. As a result, shear stress is applied to the front end of the semiconductor laser element 1X, generating shear strain, which then propagates to the light-emitting region inside the semiconductor laser element 1X. This may result in a decrease in the long-term reliability of the semiconductor laser element 1X.

[0103] 10, in the semiconductor laser device 100 according to this embodiment, the bonding member 3 (fillet 3a) is connected to the exposed surface 61a at the front end of the semiconductor laser element 1, but at least a part of the front end face of the pad electrode 70 is formed to be recessed, so that a gap 4 (air gap) is formed between the bonding member 3 and the front end face of the pad electrode 70. In this embodiment, a canopy portion 71 is formed at the front end of the pad electrode 70, so that a part of the front end face of the pad electrode 70 is recessed.

[0104] Thus, if there is a gap 4 between the bonding member 3 and the front end face of the pad electrode 70, the bonding member 3 and the front end face of the pad electrode 70 are separated from each other, and a new alloy layer is not formed between the bonding member 3 and the front end face of the pad electrode 70. This makes it possible to suppress the application of stress to the front end of the semiconductor laser element 1 due to shear stress caused by the difference in linear expansion coefficient between the members. As a result, it is possible to suppress the progression of shear strain in the light-emitting region inside the semiconductor laser element 1, and therefore it is possible to suppress a decrease in the long-term reliability of the semiconductor laser element 1.

[0105] Furthermore, in the semiconductor laser device 100 according to the present embodiment, the gap 4 separates the joining member 3 from a part of the exposed surface 61 a of the p-side electrode layer 61. This also reduces the amount of alloy layer formed between the joining member 3 and the exposed surface 61 a of the p-side electrode layer 61.

[0106] This further reduces the shear stress caused by the difference in linear expansion coefficient between the members from being applied to the front end of the semiconductor laser device 1. Therefore, it is possible to further reduce the deterioration of the long-term reliability of the semiconductor laser device 1.

[0107] As described above, according to the semiconductor laser device 100 of this embodiment, even if the bonding member 3 is connected to the front end of the semiconductor laser element 1 in order to suppress the occurrence of COD, it is possible to alleviate the stress applied to the semiconductor laser element 1. This makes it possible to suppress a decrease in the long-term reliability of the semiconductor laser element 1.

[0108] Furthermore, in the semiconductor laser device 100 according to this embodiment, the semiconductor laser element 1 has a ridge portion 1R extending in the cavity length direction, and in a vertical cross section perpendicular to the cavity length direction at the exposed surface 61a of the semiconductor laser element 1, the bonding member 3 is connected to the exposed surface 61a over at least the entire width of the ridge portion 1R.

[0109] The heat generated when the semiconductor laser device 1 is emitting light is highest in the ridge portion 1R (ridge width region). Therefore, as shown in Fig. 4A, by forming the bonding member 3 (fillet 3a) on the exposed surface 61a across the entire width of the ridge portion 1R (i.e., the entire light-emitting region) rather than just a part of the width of the ridge portion 1R, the heat generated in the ridge width region at the front end of the semiconductor laser device 1 can be effectively dissipated. In other words, heat dissipation in the ridge portion 1R can be promoted.

[0110] As shown in FIG. 10, in the semiconductor laser device 100 according to this embodiment, the joining member 3 is connected up to the position of the front end face of the semiconductor laminate structure 20 of the semiconductor laser element 1 on the exposed surface 61a.

[0111] This configuration ensures that heat at the front end of the semiconductor laser device 1 is dissipated, while the gap 4 effectively reduces shear strain, thereby improving the long-term reliability of the semiconductor laser device 1.

[0112] Here, as shown in FIG. 10, the distance from the front end face 1a (light-emitting end face) of the semiconductor laser element 1 to the front end face (pad electrode end) of the pad electrode 70 is defined as L, and when the COD breakdown current is measured while varying this distance L, the results shown in FIG. 11 are obtained.

[0113] The shorter the distance L between the front end face 1a of the semiconductor laser element 1 and the front end face of the pad electrode 70, the more easily the fillet 3a connected to the front end of the semiconductor laser element 1 is formed, and therefore the COD breakdown current increases. Conversely, as the distance L increases, the fillet 3a is less likely to be formed, and therefore the COD breakdown current decreases. Therefore, from the perspective of obtaining a high COD breakdown current, based on the results shown in FIG. 11, it is preferable to set the distance L to 15 μm or less.

[0114] On the other hand, when the wafer on which the semiconductor laminated structure 20 is formed is cleaved into bars, if the cleavage is performed from above the pad electrode 70, the cleaved end face may be deformed, which may affect the laser characteristics and reliability. For this reason, it is preferable to separate the front end face of the pad electrode 70 from the front end face of the semiconductor laminated structure 20. For this reason, it is preferable that the distance L be 5 μm or more.

[0115] Therefore, the distance L between the front end face 1a of the semiconductor laser device 1 and the front end face of the pad electrode 70 is preferably 5 μm or more and 15 μm or less.

[0116] 10, in the semiconductor laser device 100 according to the present embodiment, the front end face 1a of the semiconductor laser element 1 does not protrude from the front end face of the heat sink 2, but this is not limiting. For example, as in a semiconductor laser device 100A shown in FIG. 12, the front end face 1a of the semiconductor laser element 1 may protrude from the front end face of the heat sink 2. In other words, the semiconductor laser element 1 may be mounted so that the front end face 1a protrudes from the front end face of the heat sink 2.

[0117] Furthermore, in the semiconductor laser device 100 according to the present embodiment, the overhanging portion 71 is formed on the pad electrode 70, thereby causing a portion of the front end surface of the pad electrode 70 to be recessed. However, this is not limited to this. For example, as in the semiconductor laser device 100B shown in FIG. 13, the front end surface of the pad electrode 70B may be recessed without the overhanging portion 71 being formed on the pad electrode 70B. Specifically, in FIG. 13, the entire front end surface of the pad electrode 70B is an inclined surface. In this case, the cross-sectional shape of the gap 4 between the bonding member 3 and the front end surface of the pad electrode 70B is triangular. In other words, the cross-sectional shape of the gap 4 is not limited to a trapezoidal shape. The cross-sectional shape of the gap 4 may be a shape other than a trapezoidal or triangular shape.

[0118] 14(a), the semiconductor laser device 100 according to this embodiment is not warped, but the semiconductor laser device 1 may be warped in the cavity length direction. In this case, as shown in FIG. 14(b), the semiconductor laser device 1 may be warped in the cavity length direction so that the center portion is recessed with respect to the surface joined to the heat sink 2.

[0119] As shown in (a) of FIG. 14, if the semiconductor laser element 1 is flat and not warped, it is difficult to form a fillet 3a of the joining member 3 at the front end of the semiconductor laser element 1. Moreover, if the front end face 1a of the semiconductor laser element 1 and the front end face of the heat sink 2 are nearly flush with each other, there is a risk that the joining member 3 will creep up onto the front end face 1a (light-emitting end face) of the semiconductor laser element 1.

[0120] On the other hand, as shown in (b) of FIG. 14, when the semiconductor laser element 1 is mounted on the heat sink 2 by the bonding member 3, if the semiconductor laser element 1 is warped in the cavity length direction, a fillet 3a of the bonding member 3 is easily formed at the front end portion of the semiconductor laser element 1, and the bonding member 3 can be prevented from creeping up onto the front end face 1a of the semiconductor laser element 1.

[0121] 14(c), if the semiconductor laser element 1 is warped so that the central portion in the cavity length direction of the semiconductor laser element 1 is convex, when the semiconductor laser element 1 and the heat sink 2 are joined with the joining member 3, the joining member 3 may get into the curved inside of the convex semiconductor laser element 1, and the joining member 3 may not be connected to the exposed surface 61a of the semiconductor laser element 1. Therefore, it is preferable that the semiconductor laser element 1 mounted on the heat sink 2 is concave in the cavity length direction as shown in FIG.

[0122] However, even if the semiconductor laser element 1 is warped to form a concave shape, as the amount of warping increases, the gap between the bonding member 3 and the exposed surface 61 a of the semiconductor laser element 1 increases, as shown in (d) of Figure 14, making it difficult for the bonding member 3 to be connected to the exposed surface 61 a of the semiconductor laser element 1.

[0123] 14(b), it is preferable that the central portion of the semiconductor laser element 1 in the cavity length direction be warped to form a concave shape, and that the amount of warping be small. This causes the bonding member 3 pressed by the semiconductor laser element 1 to swell on both end sides of the semiconductor laser element 1, thereby facilitating bonding between the exposed surface 61a of the semiconductor laser element 1 and the bonding member 3.

[0124] Here, when the amount of warpage of the semiconductor laser element 1 in the cavity length direction was measured in the semiconductor laser devices shown in (b), (c), and (d) of Figure 14, the results shown in Figure 15 were obtained. In Figure 15, (b), (c), and (d) indicate the amount of warpage of each semiconductor laser element 1 of (b), (c), and (d) of Figure 14, respectively. From the results shown in Figure 15, it is preferable that the amount of warpage of the semiconductor laser element 1 be 1 μm or more and 3 μm or less.

[0125] The layer structure of the semiconductor laser device 1 in the above-described embodiment 1 is an example as Example 1, and is not limited thereto. For example, the layer structure of the semiconductor laser device 1 in the above-described embodiment 1 may be configured as follows as Example 2.

[0126] Specifically, the substrate 10 is an n-type GaAs substrate, and the semiconductor layer 21 is an n-type GaAS layer having an n-type buffer layer of 0.50 μm thick made of n-GaAs, and an n-type first composition gradient layer of 0.05 μm thick made of n-Al x Ga 1-x The n-type AlGaAs layer is made of As (x=0.15~0.353), and the n-type cladding layer is n-Al 0.353 Ga 0.647 The n-type AlGaAs layer is made of As, and the n-type second composition gradient layer is made of n-Al x Ga 1-x The active layer 22 is an n-type AlGaAs layer with an n-type guide layer of 0.95 μm thick. 0.323 Ga 0.677 The n-type AlGaAs layer is made of As, and the n-side second barrier layer is made of n-Al 0.18 Ga 0.82 An n-type AlGaAs layer consisting of As and a 0.0065 μm thick Al 0.18 Ga 0.82 The first barrier layer on the n-side is an undoped AlGaAs layer with a thickness of 0.0035 μm. 0.35 Ga 0.55 In 0.10 The AlGaInAs layer is made of As, and the well layer is made of In with a thickness of 0.0060 μm. 0.11 Ga 0.89 The InGaAs layer is made of As, and the p-side first barrier layer is 0.0035 μm thick Al 0.35 Ga 0.55 In 0.10 The AlGaInAs layer is made of As, and the p-side second barrier layer is Al 0.18 Ga 0.82 An undoped AlGaAs layer consisting of As and a 0.025 μm thick p-Al 0.18 Ga 0.82 The p-type AlGaAs layer is made of As and the p-type guide layer is made of p-AlGaAs. 0.32 Ga 0.68 The p-type semiconductor layer 23 is a p-type AlGaAs layer made of As.x Ga 1-x The p-type AlGaAs layer is made of As (x=0.32~0.70), and the p-type cladding layer is p-Al 0.70 Ga 0.30 The p-type AlGaAs layer is made of As, and the p-type second composition gradient layer is p-Al x Ga 1-x The p-type contact layer 24 is a p-type GaAs layer made of p-GaAs with a thickness of 0.25 μm. The semiconductor laser device 1 of Example 2 configured as described above also achieves the same effects as the semiconductor laser device 1 of Example 1.

[0127] Furthermore, the layer structure of the semiconductor laser device 1 in the first embodiment may be configured as follows as Example 3.

[0128] Specifically, the substrate 10 is an n-type GaAs substrate, and the n-type semiconductor layer 21 is an n-type GaAs layer having an n-type buffer layer of 0.50 μm thick made of n-GaAs, and an n-type first composition gradient layer of 0.05 μm thick made of n-Al x Ga 1-x The n-type AlGaAs layer is made of As (x=0.15~0.25), and the n-type cladding layer is 3.10μm thick n-Al 0.25 Ga 0.75 The n-type AlGaAs layer is made of As, and the n-type second composition gradient layer is made of n-Al x Ga 1-x The active layer 22 is an n-type AlGaAs layer with an n-type guide layer of 0.27 μm thick. 0.20 Ga 0.80 The n-type AlGaAs layer is made of As, and the n-side second barrier layer is Al 0.16 Ga 0.84 A single layer of undoped AlGaAs made of As, and a well layer of In with a thickness of 0.0090 μm. 0.135 a 0.865 The InGaAs layer is made of As, and the p-side second barrier layer is made of Al with a thickness of 0.01 μm. 0.16 Ga 0.84A single layer of undoped AlGaAs made of As, and a p-type guide layer of p-Al 0.20 Ga 0.80 p-AlGaAs layer consisting of As and 0.28 μm thick p-Al x Ga 1-x The active layer 22 does not have an n-side first barrier layer or a p-side first barrier layer. The p-type semiconductor layer 23 has a p-type first composition gradient layer of p-AlGaAs with a thickness of 0.1 μm. x Ga 1-x The p-type AlGaAs layer is made of As (x=0.21~0.70), and the p-type cladding layer is p-Al 0.70 Ga 0.30 The p-type AlGaAs layer is made of As, and the p-type second composition gradient layer is p-Al x Ga 1-x The p-type contact layer 24 is a p-type AlGaAs layer made of p-GaAs (x=0.70 to 0.15). The p-type contact layer 24 is a p-type GaAs layer made of p-GaAs with a thickness of 0.25 μm. The semiconductor laser device 1 of Example 3 configured as described above also achieves the same effects as the semiconductor laser device 1 of Example 1. Furthermore, the window region 22, the front groove portion 32, and the rear groove portion 33 are not formed in the semiconductor laser device 1 of Example 3. Furthermore, the n-side first barrier layer and the p-side first barrier layer, which have a higher Al composition than the p-side second barrier layer and the n-side second barrier layer, are not formed in the semiconductor laser device 1 of Example 3. This makes it possible to reduce the operating voltage. Furthermore, in the semiconductor laser device 1 of Example 3, the n-side second barrier layer is a single layer, and no n-type AlGaAs is formed therein. This makes it possible to reduce the waveguide loss, thereby improving the slope efficiency.

[0129] (Embodiment 2) Next, a second embodiment will be described with reference to FIGS. 16 to 18. FIG. 16 is a plan view of a semiconductor laser device 1A according to the second embodiment. FIGS. 17A to 17C are cross-sectional views of the semiconductor laser device 1A according to the second embodiment. FIGS. 17A, 17B, and 17C show cross sections taken along lines XVIIA-XVIIA, XVIIB-XVIIB, and XVIIC-XVIIC in FIG. 16, respectively. FIG. 18 is an enlarged cross-sectional view of a semiconductor laser device 101 according to the second embodiment. FIG. 18 is a cross-sectional view corresponding to FIG. 5.

[0130] 16 to 18, the semiconductor laser element 1A and the semiconductor laser device 101 according to this embodiment have a configuration in which, when the p-side electrode layer 61 in the semiconductor laser element 1 and the semiconductor laser device 100 according to the first embodiment is used as the first p-side electrode layer, the semiconductor laser element 1A and the semiconductor laser device 101 further include a second p-side electrode layer 63. Specifically, the second p-side electrode layer 63 is provided in the semiconductor laser element 1A.

[0131] 17A to 17C, the second p-side electrode layer 63 is formed on the pad electrode 70 and also on the p-side electrode layer 61. Therefore, in the semiconductor laser device 101, the second p-side electrode layer 63 is formed on the surface of the pad electrode 70 facing the heat sink 2 and on the surface of the p-side electrode layer 61 facing the heat sink 2, as shown in FIG.

[0132] 18, a second p-side electrode layer 63 is formed on the p-side electrode layer 61 at the front end of the semiconductor laser device 1A. Therefore, in this embodiment, the exposed surface at the front end of the semiconductor laser device 1A is not the surface of the p-side electrode layer 61 but the surface of the second p-side electrode layer 63. Therefore, the joining member 3 (fillet 3a) connected to the front end of the semiconductor laser device 1A is connected to the second p-side electrode layer 63 rather than the p-side electrode layer 61.

[0133] The second p-side electrode layer 63 is a metal layer made of a metal material. The second p-side electrode layer 63 is, for example, a single-layer film or a multilayer film made of at least one of Pt, Ti, Cr, Ni, Mo, and Au. In this embodiment, the second p-side electrode layer 63 is made of the same multilayer film as the p-side electrode layer 61. Therefore, the second p-side electrode layer 63 is a multilayer film with a three-layer structure in which a Ti film, a Pt film, and an Au film are stacked in this order from the pad electrode 70 side.

[0134] Except for the addition of the second p-side electrode layer 63, the semiconductor laser element 1A and the semiconductor laser device 101 according to this embodiment have the same configuration as the semiconductor laser element 1 and the semiconductor laser device 100 according to the first embodiment.

[0135] Therefore, in the semiconductor laser device 101 according to this embodiment, similarly to the semiconductor laser device 100 according to the first embodiment, the bonding member 3 (fillet 3a) is connected to the exposed surface 61a at the front end of the semiconductor laser element 1A, but at least a part of the front end surface of the pad electrode 70 is formed to be recessed. Then, a gap 4 (air gap) is formed between the bonding member 3 and the front end surface of the pad electrode 70.

[0136] This configuration can suppress alloying between the bonding member 3 and the pad electrode 70, thereby suppressing stress from being applied to the front end portion of the semiconductor laser device 1A. As a result, distortion occurring in the semiconductor laser device 1A can be suppressed, and a decrease in the long-term reliability of the semiconductor laser device 1A can be suppressed.

[0137] Furthermore, in the semiconductor laser device 101 according to this embodiment, a second p-side electrode layer 63 is formed on the pad electrode 70 and on the p-side electrode layer 61, and the joining member 3 (fillet 3a) connected to the front end of the semiconductor laser element 1A is connected to the second p-side electrode layer 63.

[0138] This configuration can further suppress the influence of shear stress caused by the alloy layer formed when the joining member 3 is in contact with the semiconductor laser element 1A, thereby further suppressing distortion occurring in the semiconductor laser element 1A. As a result, the semiconductor laser device 101 according to this embodiment can have improved long-term reliability compared to the semiconductor laser device 100 according to the above embodiment.

[0139] 18, the front end facet 1a of the semiconductor laser element 1A does not protrude from the front end facet of the heat sink 2 in the semiconductor laser device 101 of this embodiment, but this is not limiting. For example, as in a semiconductor laser device 101A shown in FIG. 19, the front end facet 1a of the semiconductor laser element 1A may protrude from the front end facet of the heat sink 2. In other words, the semiconductor laser element 1A may be mounted so that the front end facet 1a protrudes from the front end facet of the heat sink 2.

[0140] Moreover, the semiconductor laser device 1A in this embodiment can be fabricated in accordance with the method for manufacturing the semiconductor laser device 1 according to the above-mentioned embodiment 1. Specifically, the devices shown in FIGS. 6A to 6F can be fabricated in the same manner as in the above-mentioned embodiment 1.

[0141] 20A(a) and 20A(b), after the pad electrode 70 is formed, the second p-side electrode layer 63 is formed on the pad electrode 70 and on the p-side electrode layer 61. Specifically, the second p-side electrode layer 63 made of a stacked film of a Ti film, a Pt film, and an Au film is formed on the pad electrode 70 and on the p-side electrode layer 61 by electron beam evaporation.

[0142] 20B (a) and (b), an n-side electrode layer 62 is formed on the lower surface of the substrate 10. Specifically, an AuGe film, a Ni film, an Au film, a Ti film, a Pt film, and an Au film are sequentially formed from the substrate 10 side, thereby forming the n-side electrode layer 62 on the lower surface of the substrate 10.

[0143] Thereafter, although not shown, as in the above-mentioned first embodiment, the substrate 10 (wafer) on which the semiconductor laminate structure 20 of a predetermined shape is formed is separated into multiple bars, and then separated into chips, thereby producing individual semiconductor laser elements 1A.

[0144] In each of Figures 20A and 20B, (a) shows a cross section corresponding to Figure 17A (cross section of the current injection region), and (b) shows a cross section corresponding to Figure 17B (cross section of the non-current injection region at the front end).

[0145] (Embodiment 3) Next, a third embodiment will be described with reference to FIGS. 21 to 22C. FIG. 21 is a plan view of a semiconductor laser element 1B according to the third embodiment. FIGS. 22A to 22C are cross-sectional views of a semiconductor laser device 102 according to the second embodiment. FIGS. 22A, 22B, and 22C show parts of cross sections of the semiconductor laser device 102 according to the third embodiment taken along lines XXIIA-XXIIA, XXIIB-XXIIB, and XXIIC-XXIIC in FIG. 21, respectively. In FIG. 21, hatching is used for convenience in order to indicate the position of a second pad electrode 90.

[0146] 21 to 22C, the semiconductor laser element 1B and the semiconductor laser device 102 according to this embodiment have a configuration in which, when the pad electrode 70 in the semiconductor laser element 1A and the semiconductor laser device 101 according to the second embodiment is used as a first pad electrode, a second pad electrode 90 is further provided. Specifically, the second pad electrode 90 is provided on the semiconductor laser element 1B.

[0147] The second pad electrodes 90 are formed on both sides of the optical waveguide extending in the cavity length direction of the semiconductor laser device 1B. In this embodiment, since a ridge portion 1R is formed as the optical waveguide, as shown in FIG. 21 , the second pad electrodes 90 are formed on both sides of the ridge portion 1R in top view. Specifically, two second pad electrodes 90 are formed to sandwich the ridge portion 1R. The two second pad electrodes 90 are formed parallel to each other so as to extend in the cavity length direction of the semiconductor laser device 1B. The width of each second pad electrode 90 is constant, and the shape of each second pad electrode 90 in top view is an elongated rectangle.

[0148] 22B and 22C, the second pad electrode 90 is formed on the heat sink 2 side of the pad electrode 70 (first pad electrode). In other words, the second pad electrode 90 is formed on the surface of the pad electrode 70 opposite to the p-side electrode layer 61 side. Therefore, the pad electrode 70 is sandwiched between the p-side electrode layer 61 and the second pad electrode 90.

[0149] Except for the addition of the second pad electrode 90, the semiconductor laser element 1B and the semiconductor laser device 102 according to this embodiment have the same configuration as the semiconductor laser element 1A and the semiconductor laser device 101 according to the second embodiment.

[0150] Therefore, in the semiconductor laser device 102 according to this embodiment, similarly to the semiconductor laser device 101 according to the second embodiment, the bonding member 3 (fillet 3a) is connected to the exposed surface 61a at the front end of the semiconductor laser element 1B, but at least a part of the front end surface of the pad electrode 70 is formed to be recessed. Then, a gap 4 (air gap) is formed between the bonding member 3 and the front end surface of the pad electrode 70.

[0151] This configuration can suppress alloying between the bonding member 3 and the pad electrode 70, thereby suppressing stress from being applied to the front end portion of the semiconductor laser device 1B. Therefore, distortion occurring in the semiconductor laser device 1B can be suppressed, and deterioration in the long-term reliability of the semiconductor laser device 1B can be suppressed.

[0152] Furthermore, in the semiconductor laser device 102 according to this embodiment, as in the second embodiment, a second p-side electrode layer 63 is formed on the pad electrode 70 and on the p-side electrode layer 61, and the joining member 3 (fillet 3a) connected to the front end of the semiconductor laser element 1B is connected to the second p-side electrode layer 63.

[0153] With this configuration, as in the second embodiment, it is possible to suppress distortion occurring in the semiconductor laser device 1B, thereby improving long-term reliability.

[0154] Furthermore, in the semiconductor laser device 102 according to this embodiment, a second pad electrode 90 is formed on the heat sink 2 side of the pad electrode 70, and the second pad electrode 90 is formed on both sides of the optical waveguide extending in the cavity length direction of the semiconductor laser element 1B.

[0155] With this configuration, when mounting the semiconductor laser element 1B on the heat sink 2 with the bonding member 3, the bonding member 3 between the semiconductor laser element 1 and the heat sink 2 can be restricted from spreading laterally and can be made to wet and spread in the cavity length direction. This can promote the formation of a fillet 3a of the bonding member 3 in the ridge width region at the front end of the semiconductor laser element 1B. Therefore, since the heat generated when the semiconductor laser element 1B is emitting light is highest in the ridge portion 1R (ridge width region), forming the fillet 3a of the bonding member 3 in the ridge width region at the front end of the semiconductor laser element 1B can effectively dissipate the heat generated in the ridge width region at the front end of the semiconductor laser element 1B.

[0156] Although not shown, the front end face 1a of the semiconductor laser element 1B may protrude from the front end face of the heat sink 2 in the semiconductor laser device 102 of this embodiment as well.

[0157] Moreover, the semiconductor laser device 1B of this embodiment can be fabricated in accordance with the manufacturing method of the semiconductor laser devices 1 and 1A according to the above-mentioned embodiments 1 and 2. Specifically, the devices shown in FIGS. 6A to 6F can be fabricated in the same manner as in the above-mentioned embodiments 1 and 2.

[0158] In this embodiment, after forming the pad electrode 70, a pair of second pad electrodes 90 are formed on the pad electrode 70, as shown in (a) and (b) of Figure 23A, and then a second p-side electrode layer 63 is formed on the pad electrode 70 so as to cover the second pad electrode 90, and a second p-side electrode layer 63 is formed on the p-side electrode layer 61.

[0159] Next, as shown in (a) and (b) of FIG. 23B, an n-side electrode layer 62 is formed on the lower surface of the substrate 10 in the same manner as in the first and second embodiments.

[0160] Thereafter, although not shown, as in the second embodiment, the substrate 10 (wafer) on which the semiconductor stack structure 20 of a predetermined shape is formed is separated into multiple bars, and then separated into chips, thereby producing individual semiconductor laser elements 1B.

[0161] 23A and 23B, (a) shows a cross section of the current injection region, and (b) shows a cross section of the non-current injection region at the front end of the semiconductor laser device 1B.

[0162] In the semiconductor laser device 1B according to the above embodiment, each second pad electrode 90 is formed continuously along the cavity length direction, but this is not limiting. For example, as in a semiconductor laser device 1D shown in Fig. 24, each second pad electrode 90D may be formed discontinuously along the cavity length direction. In other words, the second pad electrode 90D may be partially divided in the cavity length direction.

[0163] Furthermore, in the semiconductor laser device 1B according to the above embodiment, each second pad electrode 90 has an elongated rectangular shape, but this is not limiting. For example, as in the semiconductor laser device 1E shown in FIG. 25, a protrusion that protrudes inward may be formed at each of both longitudinal ends of the second pad electrode 90E in top view. This allows the bonding member 3, which has spread in the cavity length direction, to advance inward at the front end of the semiconductor laser device when the semiconductor laser device 1B is mounted on the heat sink 2 using the bonding member 3. This allows a fillet 3a of the bonding member 3 to be easily formed in the ridge width region at the front end of the semiconductor laser device 1B.

[0164] (Variation) Although the semiconductor laser device and semiconductor laser element according to the present disclosure have been described above based on the embodiments, the present disclosure is not limited to the above-described embodiments.

[0165] For example, in the first to third embodiments, the semiconductor laser element is configured to emit infrared laser light, but this is not limiting. For example, the semiconductor laser element may be configured to emit visible or ultraviolet laser light.

[0166] In the first to third embodiments, the semiconductor laser element is made of an AlGaInAs-based III-V semiconductor material, but is not limited to this. For example, the semiconductor laser element may be a nitride-based semiconductor laser element made of a nitride-based semiconductor material.

[0167] In addition, this disclosure also includes forms obtained by making various modifications to the above embodiments that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions in each embodiment within the scope of the present disclosure. [Industrial Applicability]

[0168] The semiconductor laser device and semiconductor laser element according to the present disclosure can be applied to light sources of various products, including laser processing devices. [Explanation of symbols]

[0169] 1, 1A, 1B, 1D, 1E Semiconductor laser elements 1a Front end surface 1b Rear end surface 1R Ridge 2 heat sinks 2a Heat sink body 2b First conductor layer 2c Second conductor layer 2d Third conductor layer 2e 4th conductor layer 3 Joint materials 3a Fillet 4. Gap 5a, 5b convex parts 10 Substrate 20 Semiconductor laminated structure 20a First facet coating film 20b Second facet coating film 20c separation groove 21 n-type semiconductor layer 22 Active layer 22a Window area 23 p-type semiconductor layer 24 p-type contact layer 30 Opening 30a bottom 31 Horizontal Groove 32 Front groove 33 Posterior groove 40 Wing 50 insulating film 50a opening 61 p-side electrode layer 61a Exposed surface 62 n-side electrode layer 63 Second p-side electrode layer 70, 70B Pad electrode 70a Recess 71 Eaves 80 Resist 90, 90D, 90E Second pad electrode 100, 100A, 100B, 101, 101A, 102 Semiconductor laser device

Claims

1. A heat sink; a semiconductor laser element bonded to the heat sink via a bonding member and provided with a pad electrode; the semiconductor laser element is disposed so that the pad electrode faces the heat sink, the semiconductor laser element has an exposed surface that is exposed from the pad electrode because the front end face of the pad electrode is located at a position recessed from the front end face of the semiconductor laser element, the joining member is connected to the exposed surface of the semiconductor laser element, In a vertical cross section parallel to the cavity length direction of the semiconductor laser element, The front end surface of the pad electrode is formed so as to be at least partially recessed, a gap is formed between the bonding member and the front end surface of the pad electrode, the semiconductor laser element has an electrode layer formed on a surface of the pad electrode opposite to the heat sink side, the exposed surface is a surface of the electrode layer, the electrode layer is a first electrode layer, a second electrode layer is formed on a surface of the pad electrode facing the heat sink and a surface of the electrode layer facing the heat sink; Semiconductor laser device.

2. a visor portion is formed on the front end portion of the pad electrode, so that a part of the front end surface of the pad electrode is recessed; 2. The semiconductor laser device according to claim 1.

3. the angle θ of the inclined surface of the recess of the pad electrode is 65±15°; The length of the overhang portion of the pad electrode is 0.4 μm to 2.0 μm.

3. The semiconductor laser device according to claim 1.

4. the heat sink has a conductor layer on the semiconductor laser element side, the bonding member bonds the conductor layer and the pad electrode together; 4. The semiconductor laser device according to claim 1.

5. the joining member is connected to the front end surface of the conductor layer; 5. The semiconductor laser device according to claim 4.

6. the heat sink has a first conductor layer and a second conductor layer as the conductor layers, the second conductor layer covers the front end surface of the first conductor layer; 6. The semiconductor laser device according to claim 5.

7. the semiconductor laser element has a ridge portion extending in the cavity length direction, In a vertical cross section perpendicular to the cavity length direction at the exposed surface of the semiconductor laser element, the bonding member is connected to the exposed surface over at least the entire width of the ridge portion.

7. The semiconductor laser device according to claim 1.

8. the joining member is connected to the exposed surface up to a position of a front end face of the semiconductor laminate structure of the semiconductor laser element, 8. The semiconductor laser device according to claim 1.

9. a distance between the front end face of the semiconductor laser element and the front end face of the pad electrode is not less than 5 μm and not more than 15 μm; 9. The semiconductor laser device according to claim 1.

10. the semiconductor laser element is warped in the cavity length direction so that a central portion thereof is recessed with respect to a surface joined to the heat sink; 10. The semiconductor laser device according to claim 1.

11. the amount of warpage of the semiconductor laser element is 1 μm or more and 3 μm or less; 11. The semiconductor laser device according to claim 10.

12. the pad electrode is a first pad electrode, a second pad electrode is formed on the heat sink side of the first pad electrode; When viewed from above, the second pad electrodes are formed on both sides of an optical waveguide extending in the cavity length direction of the semiconductor laser element.

12. The semiconductor laser device according to claim 1.

13. the semiconductor laser element includes an insulating film having an opening on an optical waveguide extending in a cavity length direction; When viewed from above, the insulating film covers a front end portion of the semiconductor laser element.

13. The semiconductor laser device according to claim 1.

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