Semiconductor laser element, semiconductor laser device, and method for manufacturing semiconductor laser element

Abstract

To provide a semiconductor laser element capable of securing satisfactory heat dissipation characteristics on at least a first end face while suppressing reduction in quality of at least the first end face, a semiconductor laser device, and a manufacturing method of the semiconductor laser element.SOLUTION: A semiconductor laser element 1 comprises: a semiconductor wafer 2; a semiconductor laminate 3; and a first electrode 5 and a second electrode which are formed on the semiconductor laminate 3 in a state where a ridge part 30 of the semiconductor laminate 3 is embedded. A first region 53a of a side face 53 of the first electrode 5 is separated from a first end face 3a in such a manner that the first region is away from the first end face 3a in a Y-axis direction farther as it is away from the ridge part 30 to both sides in an X-axis direction. A shortest distance between a first side face 21 and the first region 53a is smaller than a shortest distance between a third side face 23 and a third region 53c and a shortest distance between a fourth side face 24 and a fourth region 53d. The first region 53a does not include a corner in a range satisfying D1≤S1 and D1≤S2.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a semiconductor laser element, a semiconductor laser device, and a method for manufacturing a semiconductor laser element. [Background technology]

[0002] A conventional semiconductor laser element is known that includes a semiconductor substrate having a first and second main surface opposed to each other, a semiconductor laminate having a ridge portion constituting a first end facet and a second end facet opposed to each other and including an active layer and formed on the first main surface of the semiconductor substrate, a first electrode formed on the semiconductor laminate with the ridge portion buried in it, and a second electrode formed on the second main surface of the semiconductor substrate (see, for example, Patent Document 1). In such a semiconductor laser element, the ridge portion is buried in the first electrode, so that sufficient heat dissipation characteristics can be ensured. Moreover, the manufacturing process of the semiconductor laser element can be simplified compared to the case where buried growth layers are formed on both sides of the ridge portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 083896 Summary of the Invention [Problem to be solved by the invention]

[0004] In the semiconductor laser element described above, in order to ensure good heat dissipation characteristics at the first and second end faces which are most likely to generate heat, it is preferable that the first electrode extends to the vicinity of each of the first and second end faces. However, if the first electrode is so thick that it buries the ridge portion, and extends to the vicinity of each of the first and second end faces, cleavage defects may occur during the manufacture of the semiconductor laser element, degrading the quality of each of the first and second end faces.

[0005] An object of the present invention is to provide a semiconductor laser element, a semiconductor laser device, and a method for manufacturing a semiconductor laser element that can ensure good heat dissipation characteristics at least at the first facet while suppressing deterioration in quality of at least the first facet. [Means for solving the problem]

[0006] A semiconductor laser element of the present invention comprises: a semiconductor substrate having a first main surface and a second main surface opposing each other in a first direction, a first side surface and a second side surface opposing each other in a second direction perpendicular to the first direction, and a third side surface and a fourth side surface opposing each other in a third direction perpendicular to both the first and second directions; a semiconductor laminate having a ridge portion including an active layer and constituting first and second end faces opposing each other in the second direction, the first electrode formed on the semiconductor laminate with the ridge portion embedded; and a second electrode formed on the second main surface, the side surfaces of the first electrode including a first region on the first side surface, a second region on the second side surface, a third region on the third side surface, and a fourth region on the fourth side surface, the first region being located inside the first side surface when viewed from the first direction, and the second region being located inside the second side surface when viewed from the first direction. the third region is located on the inside of the third side surface when viewed from the first direction, the fourth region is located on the inside of the fourth side surface when viewed from the first direction, the first region is away from the first end surface such that the further away from the ridge portion in the third direction the first region is, the further away from the first end surface in the second direction the first region is, and the shortest distance between the first side surface and the first region in the second direction is smaller than the shortest distance between the third side surface and the third region in the third direction and the shortest distance between the fourth side surface and the fourth region in the third direction, respectively, and when the distance between the first side surface and the first region in the second direction is D1, the shortest distance between the third side surface and the third region in the third direction is S1, and the shortest distance between the fourth side surface and the fourth region in the third direction is S2, the first region does not have corners in a range that satisfies D1≦S1 and D1≦S2 when viewed from the first direction.

[0007] In this semiconductor laser element, the shortest distance between the first side surface of the semiconductor substrate and the first region of the first electrode is smaller than the shortest distance between the third side surface of the semiconductor substrate and the third region of the first electrode, and the shortest distance between the fourth side surface of the semiconductor substrate and the fourth region of the first electrode. This brings the first region of the first electrode closer to the first end face, so that good heat dissipation characteristics can be ensured at the first end face. Furthermore, when viewed from the thickness direction (first direction) of the semiconductor substrate, the first region is distant from the first end face so that the farther it is from the ridge portion on both sides in the width direction (third direction) of the ridge portion, the farther it is from the first end face in the length direction (second direction) of the ridge portion, and the first region does not have corners in a range that satisfies D1≦S1 and D1≦S2 (D1: distance between the first end face and the first region in the length direction of the ridge portion, S1: shortest distance between the third side surface and the third region in the width direction of the ridge portion, S2: shortest distance between the fourth side surface and the fourth region in the width direction of the ridge portion). This makes it possible to suppress deterioration in quality of the first end facet due to poor cleavage during manufacture of the semiconductor laser device, even if the shortest distance between the first side surface and the first region is reduced so that good heat dissipation characteristics can be ensured at the first end facet. Therefore, with this semiconductor laser device, good heat dissipation characteristics can be ensured at least at the first end facet while suppressing deterioration in quality of at least the first end facet.

[0008] In the semiconductor laser device of the present invention, when the width of the ridge in the third direction is w and the width of the first region in the third direction is W1, the first region does not have to have corners as long as W1≦10w is satisfied when viewed from the first direction. This makes it possible to reliably suppress deterioration in the quality of the first end facet in the ridge and its vicinity.

[0009] In the semiconductor laser device of the present invention, the shortest distance in the second direction between the first side surface and the first region may be equal to or less than 50 μm, which can reliably ensure good heat dissipation characteristics at the first end facet.

[0010] In the semiconductor laser element of the present invention, when viewed from the first direction, the second region is away from the second end face such that the further away from the ridge portion in the third direction the more away from the second end face in the second direction, and the shortest distance between the second side face and the second region in the second direction is smaller than the shortest distance between the third side face and the third region in the third direction and the shortest distance between the fourth side face and the fourth region in the third direction, and when the distance between the second side face and the second region in the second direction is D2, the shortest distance between the third side face and the third region in the third direction is S1, and the shortest distance between the fourth side face and the fourth region in the third direction is S2, the second region may not have corners when viewed from the first direction within a range that satisfies D2≦S1 and D2≦S2. In this semiconductor laser element, the shortest distance between the second side surface of the semiconductor substrate and the second region of the first electrode is smaller than the shortest distance between the third side surface of the semiconductor substrate and the third region of the first electrode, and the shortest distance between the fourth side surface of the semiconductor substrate and the fourth region of the first electrode. This brings the second region of the first electrode closer to the second end face, so that good heat dissipation characteristics can be ensured at the second end face. Furthermore, when viewed in the thickness direction of the semiconductor substrate, the second region is distant from the second end face so that the farther it is from the ridge portion in the width direction of the ridge portion, the farther it is from the second end face in the length direction of the ridge portion, and the second region does not have corners in a range that satisfies D2≦S1 and D2≦S2 (D1: distance between the first end face and the first region in the length direction of the ridge portion, S1: shortest distance between the third side surface and the third region in the width direction of the ridge portion, S2: shortest distance between the fourth side surface and the fourth region in the width direction of the ridge portion). This makes it possible to suppress deterioration in quality of the second end facet due to cleavage defects during manufacture of the semiconductor laser element, even if the shortest distance between the second end facet and the second region in the length direction of the ridge portion is reduced so that good heat dissipation characteristics can be ensured at the second end facet. Therefore, with this semiconductor laser element, good heat dissipation characteristics can be ensured at least at the second end facet while suppressing deterioration in quality of at least the second end facet.

[0011] In the semiconductor laser device of the present invention, when the width of the ridge in the third direction is w and the width of the second region in the third direction is W2, the second region does not have to have corners as long as W2≦10w is satisfied when viewed from the first direction. This makes it possible to reliably suppress deterioration in the quality of the second end facet in the ridge and its vicinity.

[0012] In the semiconductor laser device of the present invention, the shortest distance in the second direction between the second side surface and the second region may be equal to or less than 50 μm, which can reliably ensure good heat dissipation characteristics at the second end facet.

[0013] In the semiconductor laser device of the present invention, the height of the ridge in the first direction may be 5 μm or more. This makes the thickness of the first electrode 5 μm or more, which can ensure good heat dissipation characteristics, but increases the risk of cleavage defects occurring during the manufacture of the semiconductor laser device. However, with the above configuration, it is possible to ensure good heat dissipation characteristics at least at the first facet while suppressing deterioration in the quality of at least the first facet.

[0014] In the semiconductor laser element of the present invention, the first electrode may have a metal underlayer formed on the semiconductor laminate and a metal plating layer formed on the metal underlayer, and the side surface may be composed of at least the metal plating layer. This makes it possible to easily and reliably obtain the first electrode having a thickness that ensures good heat dissipation characteristics. On the other hand, although there is an increased risk of cleavage defects occurring during the manufacture of the semiconductor laser element, the above configuration makes it possible to ensure good heat dissipation characteristics at least at the first end face while suppressing deterioration in the quality of at least the first end face.

[0015] In the semiconductor laser device of the present invention, the active layer may have a quantum cascade structure, which makes it possible to obtain a high-quality quantum cascade laser device.

[0016] A semiconductor laser device of the present invention includes the above-described semiconductor laser element and a drive section that drives the semiconductor laser element.

[0017] According to this semiconductor laser device, it is possible to ensure good heat dissipation characteristics at least at the first end facet while suppressing deterioration in the quality of at least the first end facet in the semiconductor laser element.

[0018] A method for manufacturing a semiconductor laser element of the present invention is a method for manufacturing the semiconductor laser element, comprising: a first step of preparing a semiconductor wafer including a plurality of substrate portions each of which becomes a semiconductor substrate, and forming a semiconductor layer including a plurality of stacked body portions each of which becomes a semiconductor stacked body on one main surface of the semiconductor wafer; a second step of forming a first electrode layer on the semiconductor layer including a plurality of first electrode portions each of which becomes a first electrode; a third step of forming a second electrode layer on the other main surface of the semiconductor wafer including a plurality of second electrode portions each of which becomes a second electrode; and a fourth step of cleaving the semiconductor wafer and the semiconductor layer along each of a plurality of lines separating the plurality of element portions each of which becomes a semiconductor laser element. In a first step, a semiconductor layer is formed on one main surface of a semiconductor wafer so that a plurality of laminate portions are arranged in a matrix pattern; in a second step, a first electrode layer is formed on the semiconductor layer so that a plurality of first electrode portions correspond to the plurality of laminate portions; in a third step, a second electrode layer is formed on the other main surface of the semiconductor wafer so that a plurality of second electrode portions correspond to the plurality of laminate portions; and in a fourth step, the semiconductor wafer and the semiconductor layer are cleaved along each of a plurality of first lines among the plurality of lines extending in a third direction, and then the semiconductor wafer and the semiconductor layer are cleaved along each of a plurality of second lines among the plurality of lines extending in a second direction.

[0019] According to this method for manufacturing a semiconductor laser device, in the manufactured semiconductor laser device, deterioration in quality of at least the first facet can be suppressed, while good heat dissipation characteristics can be ensured at least at the first facet. Effect of the Invention

[0020] According to the present invention, it is possible to provide a semiconductor laser element, a semiconductor laser device, and a method for manufacturing a semiconductor laser element that can ensure good heat dissipation characteristics at least at the first facet while suppressing deterioration in quality of at least the first facet. [Brief description of the drawings]

[0021] [Figure 1] 1 is a perspective view of a semiconductor laser element according to an embodiment; [Diagram 2] FIG. 2 is a cross-sectional view of the semiconductor laser device shown in FIG. [Diagram 3] FIG. 2 is a cross-sectional view of the semiconductor laser device shown in FIG. [Figure 4] FIG. 2 is a plan view of a portion of the semiconductor laser device shown in FIG. [Diagram 5] FIG. 2 is a plan view of a portion of the semiconductor laser device shown in FIG. [Figure 6] 2A to 2C are diagrams illustrating a manufacturing method of the semiconductor laser device shown in FIG. [Figure 7] 2A to 2C are diagrams illustrating a manufacturing method of the semiconductor laser device shown in FIG. [Figure 8] FIG. 2 is a plan view of a plurality of element portions integrated in a matrix arrangement. [Figure 9] FIG. 13 is a photograph showing a cleavage plane of a plurality of element portions integrated in a one-dimensionally aligned state. [Figure 10] 2 is a cross-sectional view of a semiconductor laser device including the semiconductor laser element shown in FIG. [Figure 11] FIG. 13 is a plan view of a portion of a semiconductor laser element according to a modified example. [Figure 12] FIG. 13 is a plan view of a portion of a semiconductor laser element according to a modified example. [Figure 13] FIG. 13 is a perspective view of a semiconductor laser element according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted. [Configuration of semiconductor laser element]

[0023] As shown in FIG. 1, FIG. 2, and FIG. 3, the semiconductor laser element 1 includes a semiconductor substrate 2, a semiconductor laminate 3, an insulating film 4, a first electrode 5, and a second electrode 6. The semiconductor substrate 2 has a first main surface 2a and a second main surface 2b, and a first side surface 21, a second side surface 22, a third side surface 23, and a fourth side surface 24. The first main surface 2a and the second main surface 2b face each other in the Z-axis direction (first direction). The first side surface 21 and the second side surface 22 face each other in the Y-axis direction (second direction perpendicular to the first direction). The third side surface 23 and the fourth side surface 24 face each other in the X-axis direction (third direction perpendicular to both the first and second directions). The semiconductor substrate 2 is plate-shaped with the Z-axis direction as the thickness direction, the X-axis direction as the width direction, and the Y-axis direction as the length direction. The semiconductor substrate 2 is, for example, a rectangular plate-shaped N-type InP single crystal substrate. As an example, the length of the semiconductor substrate 2 is about 4 mm, the width of the semiconductor substrate 2 is about 500 μm, and the thickness of the semiconductor substrate 2 is about 150 μm.

[0024] The semiconductor laminate 3 is formed on the first main surface 2a of the semiconductor substrate 2. The semiconductor laminate 3 includes an active layer 31 having a quantum cascade structure. The semiconductor laminate 3 is configured to oscillate laser light having a predetermined central wavelength (for example, a wavelength in the mid-infrared region, and a central wavelength having any value between 4 and 11 μm). In this embodiment, the semiconductor laminate 3 is configured by laminating a lower cladding layer 32, a lower guide layer (not shown), an active layer 31, an upper guide layer (not shown), an upper cladding layer 33, and a contact layer (not shown) in this order from the semiconductor substrate 2 side. The upper guide layer may have a diffraction grating structure that functions as a distributed feedback (DFB) structure.

[0025] The active layer 31 is, for example, a layer having an InGaAs / InAlAs multiple quantum well structure. The lower cladding layer 32 and the upper cladding layer 33 are, for example, Si-doped InP layers. The lower guide layer and the upper guide layer are, for example, Si-doped InGaAs layers. The contact layer is, for example, a Si-doped InGaAs layer.

[0026] The semiconductor laminate 3 has a ridge portion 30 extending in the Y-axis direction. The ridge portion 30 is composed of a portion of the lower cladding layer 32 on the opposite side to the semiconductor substrate 2, the lower guide layer, the active layer 31, the upper guide layer, the upper cladding layer 33, and the contact layer. That is, the ridge portion 30 includes the active layer 31. The width of the ridge portion 30 in the X-axis direction is smaller than the width of the semiconductor substrate 2 in the X-axis direction. The length of the ridge portion 30 in the Y-axis direction is equal to the length of the semiconductor substrate 2 in the Y-axis direction. As an example, the length of the ridge portion 30 is about 4 mm, the width of the ridge portion 30 is about 10 μm to 50 μm, and the height of the ridge portion 30 is about 5 μm to 20 μm. The ridge portion 30 is located at the center of the semiconductor substrate 2 in the X-axis direction. On both sides of the ridge portion 30 in the X-axis direction, the layers constituting the semiconductor laminate 3 are not present.

[0027] The semiconductor laminate 3 has a first end face 3a and a second end face 3b that face each other in the Y-axis direction. That is, the ridge portion 30 has a first end face 3a and a second end face 3b that face each other in the Y-axis direction. The Y-axis direction is the extension direction of the ridge portion 30 and the optical waveguide direction of the ridge portion 30. The first end face 3a and the second end face 3b function as light emitting end faces. The first end face 3a is located on the same plane as the first side face 21 of the semiconductor substrate 2. The second end face 3b is located on the same plane as the second side face 22 of the semiconductor substrate 2. Both side faces of the semiconductor laminate 3 that face each other in the X-axis direction are located on the same plane as the third side face 23 and the fourth side face 24 of the semiconductor substrate 2, respectively.

[0028] The insulating film 4 is formed on the side surfaces 30b of the ridge portion 30 and the surface 32a of the lower cladding layer 32 so that the surface 30a of the ridge portion 30 opposite the semiconductor substrate 2 is exposed. The side surfaces 30b of the ridge portion 30 are both side surfaces of the ridge portion 30 that face each other in the X-axis direction. The surface 32a of the lower cladding layer 32 is the surface of the portion of the lower cladding layer 32 that does not constitute the ridge portion 30 opposite the semiconductor substrate 2. The insulating film 4 is, for example, a SiN film or a SiO2 film.

[0029] The first electrode 5 is formed on a surface 3c of the semiconductor laminate 3 opposite to the semiconductor substrate 2. The surface 3c of the semiconductor laminate 3 is a surface constituted by a surface 30a of the ridge portion 30, a side surface 30b of the ridge portion 30, and a surface 32a of the lower cladding layer 32. When viewed from the Z-axis direction, the outer edge of the first electrode 5 is located inside the outer edges of the semiconductor substrate 2 and the semiconductor laminate 3. The first electrode 5 is in contact with the surface 30a of the ridge portion 30 on the surface 30a of the ridge portion 30, and is in contact with the insulating film 4 on the side surface 30b of the ridge portion 30 and the surface 32a of the lower cladding layer 32. As a result, the first electrode 5 is electrically connected to the upper cladding layer 33 via the contact layer.

[0030] The first electrode 5 has a metal underlayer 51 and a metal plating layer 52. The metal underlayer 51 is formed so as to extend along the surface 3c of the semiconductor laminate 3. That is, the metal underlayer 51 is formed on the semiconductor laminate 3. The metal underlayer 51 is, for example, a Ti / Au layer. The metal plating layer 52 is formed on the metal underlayer 51 so that the ridge portion 30 is embedded in the metal plating layer 52. That is, the first electrode 5 is formed on the semiconductor laminate 3 with the ridge portion 30 embedded. The metal plating layer 52 is, for example, an Au plating layer. A surface 52a of the metal plating layer 52 on the side opposite to the semiconductor substrate 2 is a flat surface perpendicular to the Z-axis direction. As an example, the surface 52a of the metal plating layer 52 is a polished surface that has been flattened by chemical mechanical polishing, and polishing marks are formed on the surface 52a of the metal plating layer 52. The state in which the ridge portion 30 is embedded in the first electrode 5 refers to a state in which the thickness of the portions of the first electrode 5 located on both sides of the ridge portion 30 in the X-axis direction (the thickness of those portions in the Z-axis direction) is greater than the height of the ridge portion 30 (the thickness of the ridge portion 30 in the Z-axis direction), and the ridge portion 30 is covered by the first electrode 5.

[0031] The second electrode 6 is formed on the second main surface 2b of the semiconductor substrate 2. The second electrode 6 is, for example, an AuGe / Au film, an AuGe / Ni / Au film, or an Au film. The second electrode 6 is electrically connected to the lower cladding layer 32 via the semiconductor substrate 2.

[0032] In the semiconductor laser device 1 configured as above, when a bias voltage is applied to the active layer 31 via the first electrode 5 and the second electrode 6, light is emitted from the active layer 31, and light having a predetermined central wavelength among the light is resonated in the distributed feedback structure. As a result, laser light having a predetermined central wavelength is emitted from each of the first end face 3a and the second end face 3b. When a low-reflection film is formed on one of the first end face 3a and the second end face 3b, laser light having a predetermined central wavelength is also emitted from the other of the first end face 3a and the second end face 3b, but the laser light having the predetermined central wavelength is emitted with high power from the one end face on which the low-reflection film is formed. In addition, a high-reflection film may be formed on one of the first end face 3a and the second end face. In that case, laser light having a predetermined central wavelength is emitted from the other end face of the first end face 3a and the second end face. [Configuration of the first electrode]

[0033] 1, the first electrode 5 has a side surface 53. The side surface 53 intersects with each of the first main surface 2a of the semiconductor substrate 2 and the surface 52a of the metal plating layer 52. In this embodiment, the side surface 53 is composed of a metal base layer 51 and a metal plating layer 52. The width of the side surface 53 in the Z-axis direction is 50% or more of the height of the ridge portion 30 in the Z-axis direction. The thickness of the metal base layer 51 is about several hundred nm, the thickness of the metal plating layer 52 is 5 μm or more, and the height of the ridge portion 30 is 5 μm or more.

[0034] As shown in FIG. 4 and FIG. 5, the side surface 53 of the first electrode 5 includes a first region 53a on the first side surface 21 side, a second region 53b on the second side surface 22 side, a third region 53c on the third side surface 23 side, and a fourth region 53d on the fourth side surface 24 side. The first region 53a is located inside the first side surface 21 when viewed from the Z-axis direction. The second region 53b is located inside the second side surface 22 when viewed from the Z-axis direction. The third region 53c is located inside the third side surface 23 when viewed from the Z-axis direction. The fourth region 53d is located inside the fourth side surface 24 when viewed from the Z-axis direction. In this embodiment, each of the third region 53c and the fourth region 53d extends linearly along the Y-axis direction when viewed from the Z-axis direction.

[0035] 4, when viewed from the Z-axis direction, the first region 53a is distant from the first end face 3a such that the further away from the ridge portion 30 in the X-axis direction the more distant the first region 53a is from the first end face 3a in the Y-axis direction. The shortest distance between the first end face 3a and the first region 53a in the Y-axis direction is 50 μm or less. Since the first end face 3a is located on the same plane as the first side face 21 of the semiconductor substrate 2, the shortest distance between the first side face 21 and the first region 53a in the Y-axis direction is also 50 μm or less.

[0036] The shortest distance between the first side surface 21 and the first region 53a in the Y-axis direction is smaller than the shortest distance between the third side surface 23 and the third region 53c in the X-axis direction and the shortest distance between the fourth side surface 24 and the fourth region 53d in the X-axis direction. In this embodiment, the shortest distance between the third side surface 23 and the third region 53c in the X-axis direction and the shortest distance between the fourth side surface 24 and the fourth region 53d in the X-axis direction are equal to each other.

[0037] If the distance between the first side surface 21 and the first region 53a in the Y-axis direction is D1, the shortest distance between the third side surface 23 and the third region 53c in the X-axis direction is S1, and the shortest distance between the fourth side surface 24 and the fourth region 53d in the X-axis direction is S2, the first region 53a does not have corners in the range that satisfies D1≦S1 and D1≦S2 when viewed from the Z-axis direction. If the width of the ridge portion 30 in the X-axis direction is w and the width of the first region 53a in the X-axis direction is W1, the first region 53a does not have corners in the range that satisfies W1≦10w when viewed from the Z-axis direction. The fact that the first region 53a does not have corners in a predetermined range when viewed from the Z-axis direction means that, for the "intersection line between a plane perpendicular to the Z-axis direction and the first region 53a" in the predetermined range, if the intersection line is a curve, the inclination of the tangent to the curve changes continuously, and if the intersection line is a straight line and a curve, the inclination of the straight line and the inclination of the tangent to the curve change continuously. In other words, even in the range satisfying D1≦S1 and D1≦S2, and also in the range satisfying W1≦10w, the intersection line between the plane perpendicular to the Z-axis direction and the first region 53a extends smoothly. As an example, when viewed from the Z-axis direction, the first region 53a extends in the shape of a convex arc (semicircle with a radius of about 200 μm) toward the first end face 3a, and is smoothly connected to each of the third region 53c and the fourth region 53d. In this case, the distance between the third region 53c and the fourth region 53d is about 400 μm.

[0038] In this embodiment, when the shortest distance between the first side surface 21 and the first region 53a in the Y-axis direction is d1, the semiconductor laser element 1 satisfies D1-d1≦500 / d1. The semiconductor laser element 1 satisfies d1≦w. The semiconductor laser element 1 satisfies d1≦"thickness of the metal plating layer 52". When viewed from the Z-axis direction, the first region 53a and the third region 53c are smoothly connected without having any corners. When viewed from the Z-axis direction, the first region 53a and the fourth region 53d are smoothly connected without having any corners. For a region that includes the first region 53a and connects the third region 53c and the fourth region 53d, half the width of the region in the X-axis direction is larger than the width of the region in the Y-axis direction.

[0039] 5, when viewed from the Z-axis direction, the second region 53b is separated from the second end face 3b such that the further away from the ridge portion 30 in the X-axis direction the further away from the second end face 3b in the Y-axis direction. The shortest distance between the second end face 3b and the second region 53b in the Y-axis direction is 50 μm or less. Since the second end face 3b is located on the same plane as the second side face 22 of the semiconductor substrate 2, the shortest distance between the second side face 22 and the second region 53b in the Y-axis direction is also 50 μm or less.

[0040] The shortest distance between the second side surface 22 and the second region 53b in the Y-axis direction is smaller than the shortest distance between the third side surface 23 and the third region 53c in the X-axis direction and the shortest distance between the fourth side surface 24 and the fourth region 53d in the X-axis direction. In this embodiment, the shortest distance between the third side surface 23 and the third region 53c in the X-axis direction and the shortest distance between the fourth side surface 24 and the fourth region 53d in the X-axis direction are equal to each other.

[0041] If the distance between the second side surface 22 and the second region 53b in the Y-axis direction is D2, the shortest distance between the third side surface 23 and the third region 53c in the X-axis direction is S1, and the shortest distance between the fourth side surface 24 and the fourth region 53d in the X-axis direction is S2, the second region 53b does not have corners in the range that satisfies D2≦S1 and D2≦S2 when viewed from the Z-axis direction. If the width of the ridge portion 30 in the X-axis direction is w and the width of the second region 53b in the X-axis direction is W2, the second region 53b does not have corners in the range that satisfies W2≦10w when viewed from the Z-axis direction. The fact that the second region 53b does not have corners in a predetermined range when viewed from the Z-axis direction means that, for the "intersection line between a plane perpendicular to the Z-axis direction and the second region 53b" in the predetermined range, if the intersection line is a curve, the slope of the tangent to the curve changes continuously, and if the intersection line is a straight line and a curve, the slope of the straight line and the slope of the tangent to the curve change continuously. In other words, even in the range satisfying D2≦S1 and D2≦S2, and also in the range satisfying W2≦10w, the intersection line between the plane perpendicular to the Z-axis direction and the second region 53b extends smoothly. As an example, when viewed from the Z-axis direction, the second region 53b extends in the shape of a convex arc (semicircle with a radius of about 200 μm) toward the second end face 3b side, and is smoothly connected to each of the third region 53c and the fourth region 53d.

[0042] In this embodiment, when the shortest distance between the second side surface 22 and the second region 53b in the Y-axis direction is d2, the semiconductor laser element 1 satisfies D2-d2≦500 / d2. The semiconductor laser element 1 satisfies d2≦w. The semiconductor laser element 1 satisfies d2≦"thickness of the metal plating layer 52". When viewed from the Z-axis direction, the second region 53b and the third region 53c are smoothly connected without having any corners. When viewed from the Z-axis direction, the second region 53b and the fourth region 53d are smoothly connected without having any corners. For a region that includes the second region 53b and connects the third region 53c and the fourth region 53d, half the width of the region in the X-axis direction is larger than the width of the region in the Y-axis direction. [Method of manufacturing semiconductor laser element]

[0043] As shown in FIG. 6, a semiconductor wafer 200 including a plurality of substrate portions 210 is prepared, and a semiconductor layer 300 including a plurality of stacked body portions 310 is formed on one main surface 200a of the semiconductor wafer 200 (first step). Each of the plurality of substrate portions 210 is a portion that will become a semiconductor substrate 2. Each of the plurality of stacked body portions 310 is a portion that will become a semiconductor stacked body 3. In the first step, the semiconductor layer 300 is formed on one main surface 200a of the semiconductor wafer 200 such that the plurality of stacked body portions 310 are arranged in a matrix. In the first step, for example, epitaxial growth for forming the plurality of stacked body portions 310, dry etching for forming the plurality of ridge portions 30, and the like are performed.

[0044] Next, an insulating layer 400 including a plurality of film portions 410 is formed on the semiconductor layer 300 so that the surface 30a (see FIG. 2) of each ridge portion 30 is exposed. Each of the plurality of film portions 410 is a portion that will become the insulating film 4. Next, a first electrode layer 500 including a plurality of first electrode portions 510 is formed on the semiconductor layer 300 (second step). Each of the plurality of first electrode portions 510 is a portion that will become the first electrode 5. In the second step, the first electrode layer 500 is formed on the semiconductor layer 300 so that the plurality of first electrode portions 510 correspond to the plurality of stacked body portions 310. In the second step, for example, sputtering of Ti and Au to form a plurality of metal underlayers 51, plating of Au to form a plurality of metal plating layers 52, chemical mechanical polishing to collectively form a plurality of surfaces 52a of the plurality of metal plating layers 52, and the like are performed.

[0045] Next, a second electrode layer 600 including a plurality of second electrode portions 610 is formed on the other main surface 200b of the semiconductor wafer 200 (third step). Each of the plurality of second electrode portions 610 is a portion that will become the second electrode 6. In the third step, the second electrode layer 600 is formed on the other main surface 200b of the semiconductor wafer 200 so that the plurality of second electrode portions 610 correspond to the plurality of stacked body portions 310. In the third step, for example, polishing of the other main surface 200b to thin the semiconductor wafer 200, alloy heat treatment of the second electrode layer 600, etc. are performed. As a result, a plurality of element portions 100 that are integrated in a matrix arrangement are obtained. Each of the plurality of element portions 100 is a portion that will become the semiconductor laser element 1. Note that the third step is not limited to being performed after the second step, and may be performed at another timing (for example, between the formation of the insulating layer 400 and the second step, or during the second step).

[0046] Next, the semiconductor wafer 200 and the semiconductor layer 300 are cleaved along each of the lines that separate the device portions 100 from one another (fourth step). Specifically, as shown in FIG. 7A, the semiconductor wafer 200 and the semiconductor layer 300 are cleaved along each of the first lines L1 that extend in the X-axis direction among the lines (primary cleavage). As a result, as shown in FIG. 7B, a plurality of device portions 100 are obtained that are integrated in a state that they are one-dimensionally arranged in the X-axis direction. After the primary cleavage, the semiconductor wafer 200 and the semiconductor layer 300 are cleaved along each of the second lines L2 that extend in the Y-axis direction among the lines (secondary cleavage). As a result, a plurality of semiconductor laser devices 1 are obtained.

[0047] Here, cleavage defects occurring during the manufacture of the semiconductor laser element 1 will be described. In the comparative example shown in FIG. 8(a), in each of the multiple element portions 100 integrated in a matrix arrangement, the first electrode portion 510 has a rectangular shape when viewed from the Z-axis direction. In this case, when focusing on a pair of element portions 100 adjacent to each other via the first line L1, one of the element portions 100 has a pair of corners 54 in a range that satisfies D1≦S1D1≦S2, and the other element portion 100 has a pair of corners 54 in a range that satisfies D2≦S1D2≦S2. Therefore, the pair of corners 54 of one element portion 100 and the pair of corners 54 of the other element portion 100 face each other in a close proximity.

[0048] In this state, when the semiconductor wafer 200 and the semiconductor layer 300 are cleaved along each of the first lines L1 (primary cleavage), as shown in FIG. 9(a), a plurality of streaks are likely to appear on the cleavage surface of the plurality of element portions 100 integrated in a one-dimensionally arranged state. The photograph shown in FIG. 9(a) was obtained for a semiconductor laser element 1 having a side surface 53 with a width (see FIG. 1) of about 9 μm in the Z-axis direction and a street width (i.e., d1+d2) of about 10 μm. The reason why such a plurality of streaks appear is considered to be that stress is concentrated in the portions corresponding to each of the pair of corners 54 during the primary cleavage. When the semiconductor wafer 200 and the semiconductor layer 300 are cleaved along each of the second lines L2 in the state where such a plurality of streaks appear (secondary cleavage), a pair of streaks remains on each of the first end face 3a and the second end face 3b of the semiconductor laser element 1 obtained, and the quality of each of the first end face 3a and the second end face 3b is degraded.

[0049] 8(b), in each of the multiple element portions 100 integrated in a matrix arrangement, the first electrode portion 510 has an oval shape (in other words, a track shape) when viewed from the Z-axis direction. In this case, when focusing on a pair of element portions 100 adjacent to each other via a first line L1, one element portion 100 has no corners in a range that satisfies D1≦S1D1≦S2, and the other element portion 100 has no corners in a range that satisfies D2≦S1D2≦S2.

[0050] In this state, when the semiconductor wafer 200 and the semiconductor layer 300 are cleaved along each of the first lines L1 (primary cleavage), the above-mentioned streaks are unlikely to appear on the cleavage plane of the multiple element portions 100 integrated in a one-dimensional arrangement, as shown in FIG. 9B. The photograph shown in FIG. 9B is a photograph obtained when the width of the side surface 53 in the Z-axis direction (see FIG. 1) is about 9 μm and the minimum value of the street width (i.e., d1+d2) is about 10 μm. When the semiconductor wafer 200 and the semiconductor layer 300 are cleaved along each of the second lines L2 in a state in which the above-mentioned streaks do not appear (secondary cleavage), deterioration in the quality of each of the first end face 3a and the second end face 3b is suppressed in the obtained semiconductor laser element 1. If d1 and d2 are each less than 5 μm (i.e., d1+d2 is less than 10 μm), adjacent first electrode portions 510 across the first line L1 may be connected due to manufacturing errors, which may result in poor cleavage. Therefore, it is preferable that d1 and d2 are each 5 μm or more. [Configuration of semiconductor laser device]

[0051] 10, a semiconductor laser device 10 includes the above-mentioned semiconductor laser element 1, a support 11, a bonding member 12, and a drive unit 13. The support 11 has a body 111 and an electrode pad 112. The support 11 is, for example, a submount in which the body 111 is made of AlN. The support 11 supports the semiconductor laser element 1 in a state in which the semiconductor laminate 3 is located on the support 11 side with respect to the semiconductor substrate 2 (i.e., in an epi-side down state).

[0052] The bonding member 12 bonds the electrode pad 112 of the support 11 and the first electrode 5 of the semiconductor laser device 1 in an epi-side down state. The bonding member 12 is, for example, a solder member such as an AuSn member. The thickness of the portion of the bonding member 12 disposed between the electrode pad 112 and the first electrode 5 is, for example, about several μm.

[0053] The driving unit 13 drives the semiconductor laser element 1 so that the semiconductor laser element 1 continuously oscillates a laser beam. The driving unit 13 is electrically connected to each of the electrode pad 112 of the support part 11 and the second electrode 6 of the semiconductor laser element 1. In order to electrically connect the driving unit 13 to each of the electrode pad 112 and the second electrode 6, wire bonding is performed to each of the electrode pad 112 and the second electrode 6.

[0054] In the semiconductor laser device 10 configured as above, a heat sink (not shown) is provided on the support 11 side. Therefore, the configuration in which the semiconductor laser element 1 is mounted on the support 11 in an epi-side down state makes it easy to ensure the heat dissipation characteristics of the semiconductor laminate 3. Therefore, the epi-side down configuration is effective when the semiconductor laser element 1 is driven to continuously oscillate laser light. In particular, when the semiconductor laminate 3 is configured to oscillate laser light having a relatively short central wavelength in the mid-infrared region (for example, a central wavelength of any value between 4 and 6 μm among 4 to 11 μm) and the semiconductor laser element 1 is driven to continuously oscillate laser light, the epi-side down configuration is effective. Note that in the epi-side down configuration, the surface 52a of the metal plating layer 52 of the first electrode 5 is flattened, so that the support state of the semiconductor laser element 1 on the support 11 is stable. [Action and Effects]

[0055] In the semiconductor laser device 1, the shortest distance between the first side surface 21 of the semiconductor substrate 2 and the first region 53a of the first electrode 5 is smaller than the shortest distance between the third side surface 23 of the semiconductor substrate 2 and the third region 53c of the first electrode 5, and the shortest distance between the fourth side surface 24 of the semiconductor substrate 2 and the fourth region 53d of the first electrode 5. This brings the first region 53a of the first electrode 5 closer to the first end face 3a, ensuring good heat dissipation characteristics at the first end face 3a. Furthermore, when viewed from the Z-axis direction (thickness direction of the semiconductor substrate 2), the first region 53a is distant from the first end face 3a such that the further it is from the ridge 30 on both sides in the X-axis direction (width direction of the ridge 30), the further it is from the first end face 3a in the Y-axis direction (length direction of the ridge 30), and the first region 53a does not have corners in a range that satisfies D1≦S1 and D1≦S2 (D1: distance between the first end face 3a and the first region 53a in the Y-axis direction, S1: shortest distance between the third side face 23 and the third region 53c in the width direction of the ridge 30, S2: shortest distance between the fourth side face 24 and the fourth region 53d in the width direction of the ridge 30) when viewed from the Z-axis direction. This makes it possible to suppress deterioration in quality of the first end face 3a due to poor cleavage during the manufacture of the semiconductor laser device 1, even if the shortest distance between the first side face 21 and the first region 53a is made small so as to ensure good heat dissipation characteristics at the first end face 3a. Similarly, the shortest distance between the second side surface 22 of the semiconductor substrate 2 and the second region 53b of the first electrode 5 is smaller than the shortest distance between the third side surface 23 of the semiconductor substrate 2 and the third region 53c of the first electrode 5, and the shortest distance between the fourth side surface 24 of the semiconductor substrate 2 and the fourth region 53d of the first electrode 5. This brings the second region 53b of the first electrode 5 closer to the second end face 3b, ensuring good heat dissipation characteristics at the second end face 3b.Furthermore, when viewed from the Z-axis direction, the second region 53b is distant from the second end face 3b such that the further it is from the ridge 30 on both sides in the X-axis direction, the further it is from the second end face 3b in the Y-axis direction, and the second region 53b does not have corners in a range that satisfies D2≦S1 and D2≦S2 (D2: distance between the second end face 3b and the second region 53b in the Y-axis direction, S1: shortest distance between the third side face 23 and the third region 53c in the width direction of the ridge 30, S2: shortest distance between the fourth side face 24 and the fourth region 53d in the width direction of the ridge 30) when viewed from the Z-axis direction. This makes it possible to suppress deterioration in quality of the second end face 3b caused by poor cleavage during the manufacture of the semiconductor laser device 1, even if the shortest distance between the second side face 22 and the second region 53b is made small so as to ensure good heat dissipation characteristics at the second end face 3b. As described above, according to the semiconductor laser device 1, it is possible to ensure good heat dissipation characteristics at each of the first end facet 3a and the second end facet 3b while suppressing deterioration in the quality of each of the first end facet 3a and the second end facet 3b.

[0056] In the semiconductor laser element 1, if the width of the ridge portion 30 in the X-axis direction is w and the width of the first region 53a in the X-axis direction is W1, the first region 53a does not have corners in a range that satisfies W1≦10w when viewed from the Z-axis direction. This makes it possible to reliably suppress deterioration of the quality of the first end facet 3a in the ridge portion 30 and its vicinity. Similarly, in the semiconductor laser element 1, if the width of the ridge portion 30 in the X-axis direction is w and the width of the second region 53b in the X-axis direction is W2, the second region 53b does not have corners in a range that satisfies W2≦10w when viewed from the Z-axis direction. This makes it possible to reliably suppress deterioration of the quality of the second end facet 3b in the ridge portion 30 and its vicinity.

[0057] In the semiconductor laser element 1, the shortest distance between the first side surface 21 and the first region 53a in the Y-axis direction is 50 μm or less. This ensures good heat dissipation characteristics at the first end facet 3a. Similarly, in the semiconductor laser element 1, the shortest distance between the second side surface 22 and the second region 53b in the Y-axis direction is 50 μm or less. This ensures good heat dissipation characteristics at the second end facet 3b.

[0058] In the semiconductor laser device 1, the height of the ridge portion 30 in the Z-axis direction is 5 μm or more. This makes the thickness of the first electrode 5 5 μm or more, which can ensure good heat dissipation characteristics, but increases the risk of cleavage defects occurring during the manufacture of the semiconductor laser device 1. However, with the above configuration, it is possible to ensure good heat dissipation characteristics at each of the first end facet 3a and the second end facet 3b while suppressing deterioration in the quality of each of the first end facet 3a and the second end facet 3b.

[0059] In the semiconductor laser device 1, the side surface 53 of the first electrode 5 is composed of a metal underlayer 51 and a metal plating layer 52. This makes it possible to easily and reliably obtain the first electrode 5 having a thickness that can ensure good heat dissipation characteristics. On the other hand, although there is an increased risk of cleavage defects occurring during the manufacture of the semiconductor laser device 1, the above configuration makes it possible to ensure good heat dissipation characteristics at each of the first end facet 3a and the second end facet 3b while suppressing deterioration in the quality of each of the first end facet 3a and the second end facet 3b.

[0060] In the semiconductor laser device 1, the active layer 31 has a quantum cascade structure, which makes it possible to obtain a high-quality quantum cascade laser device.

[0061] According to the semiconductor laser device 10, it is possible to ensure good heat dissipation characteristics at each of the first end facet 3a and the second end facet 3b in the semiconductor laser element 1 while suppressing deterioration in the quality of each of the first end facet 3a and the second end facet 3b.

[0062] According to the manufacturing method of the semiconductor laser device 1, it is possible to ensure good heat dissipation characteristics at each of the first end facet 3 a and the second end facet 3 b while suppressing deterioration in the quality of each of the first end facet 3 a and the second end facet 3 b in the manufactured semiconductor laser device 1. [Variations]

[0063] The present invention is not limited to the above-mentioned embodiment. For example, a known quantum cascade structure can be applied to the active layer 31. A known laminated structure can be applied to the semiconductor laminate 3. As an example, in the semiconductor laminate 3, the upper guide layer does not need to have a diffraction grating structure that functions as a distributed feedback structure. In addition, the semiconductor laminate 3 may be configured as, for example, a laser diode. The present invention can also be applied to semiconductor laser elements other than quantum cascade laser elements.

[0064] The first region 53a may have no corners in a range that satisfies W1 ≦ 5w when viewed from the Z-axis direction, and may further have no corners in a range that satisfies W1 ≦ w. Similarly, the second region 53b may have no corners in a range that satisfies W2 ≦ 5w when viewed from the Z-axis direction, and may further have no corners in a range that satisfies W2 ≦ w.

[0065] The first region 53a is distant from the first end face 3a in the Y-axis direction as it moves away from the ridge portion 30 on both sides in the X-axis direction, and does not have any corners in the range that satisfies at least D1≦S1 and D1≦S2 when viewed from the Z-axis direction. Similarly, the second region 53b is distant from the second end face 3b in the Y-axis direction as it moves away from the ridge portion 30 on both sides in the X-axis direction, and does not have any corners in the range that satisfies at least D2≦S1 and D2≦S2 when viewed from the Z-axis direction. In the above-mentioned embodiment, S1 (the shortest distance between the third side face 23 and the third region 53c in the X-axis direction) and S2 (the shortest distance between the fourth side face 24 and the fourth region 53d in the X-axis direction) are equal to each other, but S1 and S2 may be different from each other.

[0066] As long as the semiconductor laser element 1 has a configuration in which the first region 53a "is distant from the first end face 3a in the Y-axis direction as it moves away from the ridge portion 30 on both sides in the X-axis direction, and does not have any corners in the range that satisfies at least D1≦S1 and D1≦S2 when viewed from the Z-axis direction," the second region 53b does not have to have a configuration in which "it is distant from the second end face 3b in the Y-axis direction as it moves away from the ridge portion 30 on both sides in the X-axis direction, and does not have any corners in the range that satisfies at least D2≦S1 and D2≦S2 when viewed from the Z-axis direction." When at least the first region 53a of the semiconductor laser element 1 has the above-mentioned configuration, even if the second region 53b has corners, the corners do not face each other in close proximity before the primary cleavage during the manufacture of the semiconductor laser element 1, and therefore cleavage defects can be suppressed.

[0067] As shown in Fig. 11, the first region 53a may extend linearly on both sides of the ridge portion 30 in the X-axis direction when viewed from the Z-axis direction. In this case, the first region 53a does not have corners in the ranges that satisfy D1 ≦ S1 and D1 ≦ S2 when viewed from the Z-axis direction. In the modification shown in Fig. 11, the first region 53a does not have corners in the range that satisfies W1 ≦ 10w when viewed from the Z-axis direction. The above points also apply to the second region 53b.

[0068] The first region 53a may have a corner 54 outside the range that satisfies D1≦S1 and D1≦S2 when viewed from the Z-axis direction, as shown in Fig. 12. In the modification shown in Fig. 12, the corner 54 is located outside the range that satisfies W1≦10w when viewed from the Z-axis direction. The above items also apply to the second region 53b.

[0069] The side surface 53 of the first electrode 5 may be formed of at least the metal plating layer 52. When the side surface 53 is formed of only the metal plating layer 52, the outer edge of the metal underlayer 51 may coincide with the outer edges of the semiconductor substrate 2 and the semiconductor laminate 3 when viewed from the Z-axis direction, as shown in FIG. 13. That is, in the manufacturing method of the semiconductor laser device 1, the part of the metal underlayer 51 along the first line L1 does not need to be removed by etching. Even in this case, the semiconductor wafer 200 and the semiconductor layer 300 can be cleaved with high accuracy. Note that, if the outer edge of the metal underlayer 51 coincides with at least the first end face 3a and the second end face 3b when viewed from the Z-axis direction, the heat dissipation characteristics at the first end face 3a and the second end face 3b can be ensured.

[0070] The first electrode 5 is not limited to having the metal underlayer 51 and the metal plating layer 52. The first electrode 5 may be composed of a plurality of laminated metal layers, or may be composed of a single metal layer.

[0071] The driving unit 13 is not limited to a unit that drives the semiconductor laser element 1 so that the semiconductor laser element 1 continuously oscillates a laser beam, and may be a unit that drives the semiconductor laser element 1 so that the semiconductor laser element 1 oscillates a laser beam in a pulsed manner. In other words, the driving unit 13 may be a unit that drives the semiconductor laser element 1.

[0072] The supporting portion 11 is not limited to supporting the semiconductor laser element 1 in an epi-side-down state, and may support the semiconductor laser element 1 in a state in which the semiconductor substrate 2 is located on the supporting portion 11 side with respect to the semiconductor laminate 3 (i.e., in an epi-side-up state). In other words, the supporting portion 11 may be any supporting portion that supports the semiconductor laser element 1. In the epi-side-up configuration, the surface 52a of the metal plating layer 52 of the first electrode 5 is flattened, so that there is a large degree of freedom in the position at which wire bonding is performed on the first electrode 5.

[0073] It is sufficient that the insulating film 4 is formed so that at least a part of the surface 30a of the ridge portion 30 is exposed. In other words, in the manufacturing method of the semiconductor laser device 1, it is sufficient that the insulating layer 400 is formed so that at least a part of the surface 30a of the ridge portion 30 is exposed. However, in the semiconductor laser device 1, if the insulating film 4 is formed so that the entire surface 30a of the ridge portion 30 is exposed, the contact area between the first electrode 5 and the ridge portion 30 increases, so that a wide current injection region can be secured in the ridge portion 30, and highly efficient optical output characteristics can be obtained. [Explanation of symbols]

[0074] 1...semiconductor laser element, 2...semiconductor substrate, 2a...first main surface, 2b...second main surface, 3...semiconductor laminate, 3a...first end surface, 3b...second end surface, 5...first electrode, 6...second electrode, 10...semiconductor laser device, 13...driver, 21...first side surface, 22...second side surface, 23...third side surface, 24...fourth side surface, 30...ridge portion, 31...active layer, 51...metal underlayer, 52...metal plating layer, 53...side surface, 53a...first region, 53b...second region, 53c...third region, 53d...fourth region, 100...element portion, 200...semiconductor wafer, 200a...one main surface, 200b...other main surface, 210...substrate portion, 300...semiconductor layer, 310...laminated body portion, 500...first electrode layer, 510...first electrode portion, 600...second electrode layer, 610...second electrode portion, L1...first line, L2...second line.

Claims

1. a semiconductor substrate having a first main surface and a second main surface opposed to each other in a first direction, a first side surface and a second side surface opposed to each other in a second direction perpendicular to the first direction, and a third side surface and a fourth side surface opposed to each other in a third direction perpendicular to both the first direction and the second direction; a semiconductor laminate formed on the first main surface, the semiconductor laminate having a ridge portion including an active layer and constituting a first end surface and a second end surface opposed to each other in the second direction; a first electrode formed on the semiconductor laminate in a state in which the ridge portion is buried; a second electrode formed on the second main surface, a side surface of the first electrode includes a first region on the first side surface, a second region on the second side surface, a third region on the third side surface, and a fourth region on the fourth side surface, the first region is located inside the first side surface when viewed from the first direction, the second region is located inside the second side surface when viewed from the first direction, the third region is located inside the third side surface when viewed from the first direction, the fourth region is located inside the fourth side surface when viewed from the first direction, the first region is spaced apart from the first end face such that, when viewed from the first direction, the first region becomes farther from the first end face in the second direction as it moves away from the ridge portion on both sides in the third direction, and a shortest distance between the first side surface and the first region in the second direction is smaller than a shortest distance between the third side surface and the third region in the third direction and a shortest distance between the fourth side surface and the fourth region in the third direction, The distance between the first side surface and the first region in the second direction is D １ and the shortest distance between the third side surface and the third region in the third direction is S １ and the shortest distance between the fourth side surface and the fourth region in the third direction is S ２ Then, the first region has a width D １ ≦S １ and D. １ ≦S ２ A semiconductor laser element that does not have corners to the extent that the above requirement is satisfied.

2. The width of the ridge portion in the third direction is w, and the width of the first region in the third direction is W １ Then, the first region has a width W １ 2. The semiconductor laser device according to claim 1, which has no corners in a range that satisfies ≦10w.

3. 3. The semiconductor laser device according to claim 1, wherein the shortest distance between the first side surface and the first region in the second direction is 50 μm or less.

4. the second region is spaced apart from the second end face such that, when viewed from the first direction, the second region becomes farther from the second end face in the second direction as the second region becomes farther from the ridge portion on both sides in the third direction, a shortest distance between the second side surface and the second region in the second direction is smaller than a shortest distance between the third side surface and the third region in the third direction and a shortest distance between the fourth side surface and the fourth region in the third direction, The distance between the second side surface and the second region in the second direction is D ２ and the shortest distance between the third side surface and the third region in the third direction is S １ and the shortest distance between the fourth side surface and the fourth region in the third direction is S ２ Then, the second region has a width D ２ ≦S １ and D. ２ ≦S ２ 4. The semiconductor laser device according to claim 1, wherein said semiconductor laser device has no corners within a range satisfying the above.

5. The width of the ridge portion in the third direction is w, and the width of the second region in the third direction is W ２ Then, the second region has a width W ２ The semiconductor laser device according to claim 4 , which has no corners in a range that satisfies ≦10w.

6. 6. The semiconductor laser device according to claim 4, wherein the shortest distance between the second side surface and the second region in the second direction is 50 μm or less.

7. 7. The semiconductor laser device according to claim 1, wherein the height of the ridge in the first direction is 5 μm or more.

8. The first electrode is a metal underlayer formed on the semiconductor laminate; a metal plating layer formed on the metal underlayer, 8. The semiconductor laser element according to claim 1, wherein the side surface is formed of at least the metal plating layer.

9. 9. The semiconductor laser device according to claim 1, wherein the active layer has a quantum cascade structure.

10. A semiconductor laser element according to any one of claims 1 to 9, a driver for driving the semiconductor laser element.

11. A method for manufacturing a semiconductor laser device according to any one of claims 1 to 9, comprising the steps of: A first step of preparing a semiconductor wafer including a plurality of substrate portions each of which becomes the semiconductor substrate, and forming a semiconductor layer including a plurality of stacked body portions each of which becomes the semiconductor stacked body on one main surface of the semiconductor wafer; a second step of forming a first electrode layer on the semiconductor layer, the first electrode layer including a plurality of first electrode portions each of which becomes the first electrode; a third step of forming a second electrode layer on the other main surface of the semiconductor wafer, the second electrode layer including a plurality of second electrode portions each of which becomes the second electrode; a fourth step of cleaving the semiconductor wafer and the semiconductor layer along a plurality of lines separating a plurality of element portions each of which becomes the semiconductor laser element, In the first step, the semiconductor layer is formed on the one main surface of the semiconductor wafer so that the plurality of laminated body portions are arranged in a matrix, In the second step, the first electrode layer is formed on the semiconductor layer such that the first electrode portions correspond to the stacked body portions; In the third step, the second electrode layer is formed on the other main surface of the semiconductor wafer such that the second electrode portions correspond to the stacked body portions; a semiconductor laser element manufacturing method, in which in the fourth step, the semiconductor wafer and the semiconductor layer are cleaved along each of a plurality of first lines among the plurality of lines extending in the third direction, and thereafter, the semiconductor wafer and the semiconductor layer are cleaved along each of a plurality of second lines among the plurality of lines extending in the second direction.

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