Semiconductor laser element

Abstract

This semiconductor laser element comprises a substrate and at least one light-emitting layer. The at least one light-emitting layer includes a first n-type cladding layer, a second n-type cladding layer, an active layer, a first p-type cladding layer, and a second p-type cladding layer. The aluminum composition of the first n-type cladding layer is smaller than the aluminum composition of the second n-type cladding layer. The aluminum composition of the first p-type cladding layer is smaller than the aluminum composition of the second p-type cladding layer.

Description

semiconductor laser element

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

[0002] Japanese Patent Laid-Open Publication No. 2022-60630 (Patent Document 1) discloses a semiconductor laser element including a semiconductor substrate, a light emitting portion, a first electrode, and a second electrode.

[0003] JP 2022-60630 A

[0004] [Summary] An object of the present disclosure is to provide a semiconductor laser device with reduced warpage and improved optical output.

[0005] The semiconductor laser device of the present disclosure includes a substrate and at least one light-emitting layer disposed on the substrate. The at least one light-emitting layer includes a first n-type cladding layer, a second n-type cladding layer, an active layer, a first p-type cladding layer, and a second p-type cladding layer. The active layer is disposed between the first n-type cladding layer and the first p-type cladding layer. The first n-type cladding layer is disposed between the active layer and the second n-type cladding layer. The first p-type cladding layer is disposed between the active layer and the second p-type cladding layer. The aluminum composition of the first n-type cladding layer is smaller than the aluminum composition of the second n-type cladding layer. The aluminum composition of the first p-type cladding layer is smaller than the aluminum composition of the second p-type cladding layer.

[0006] Fig. 1 is a schematic cross-sectional view of a semiconductor laser device according to an embodiment. Fig. 2 is a schematic, partially enlarged cross-sectional view of a light-emitting layer of the semiconductor laser device according to an embodiment. Fig. 3 is a schematic, partially enlarged cross-sectional view of an active layer of the semiconductor laser device according to an embodiment. Fig. 4 is a schematic, partially enlarged cross-sectional view of a tunnel layer of the semiconductor laser device according to an embodiment. Fig. 5 is a flowchart illustrating an example of a method for manufacturing a semiconductor laser device according to an embodiment.

[0007] [Detailed Description] The details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated. At least some of the configurations of the embodiments described below may be combined in any manner.

[0008] 1 to 4, a semiconductor laser device 1 according to an embodiment will be described. The semiconductor laser device 1 includes a substrate 10, at least one light-emitting layer 15, a tunnel layer 16, a p-type contact layer 17, a first electrode 13, a second electrode 19, and an insulating layer 18.

[0009] 1 , substrate 10 is a semiconductor substrate such as a GaAs substrate. In this embodiment, substrate 10 is an n-type GaAs substrate. Substrate 10 contains at least one of silicon (Si), tellurium (Te), and selenium (Se) as an n-type dopant. Substrate 10 has a first major surface 11 and a second major surface 12 opposite to first major surface 11.

[0010] 1 to 4 , at least one light-emitting layer 15 is disposed on the first main surface 11 of the substrate 10. The at least one light-emitting layer 15 may be a plurality of light-emitting layers 15, and the plurality of light-emitting layers 15 may be stacked on the first main surface 11 of the substrate 10. The at least one light-emitting layer 15 may be four or more light-emitting layers 15. The plurality of light-emitting layers 15 stacked on the substrate 10 may have a mesa structure.

[0011] Referring to FIG. 2 , at least one light-emitting layer 15 includes an n-type cladding layer 21, an active layer 20, and a p-type cladding layer 25. The n-type cladding layer 21 is formed of, for example, n-type AlGaAs. The n-type cladding layer 21 contains, for example, at least one of silicon (Si), tellurium (Te), and selenium (Se) as an n-type dopant. The p-type cladding layer 25 is formed of, for example, n-type AlGaAs. The p-type cladding layer 25 contains, for example, carbon (C) as a p-type dopant. The n-type cladding layer 21 includes a first n-type cladding layer 22 and a second n-type cladding layer 23. The p-type cladding layer 25 includes a first p-type cladding layer 26 and a second p-type cladding layer 27.

[0012] 2 , the first n-type cladding layer 22 is a portion of the n-type cladding layer 21 that is closer to the active layer 20. The second n-type cladding layer 23 is a portion of the n-type cladding layer 21 that is farther from the active layer 20. The first n-type cladding layer 22 is disposed between the active layer 20 and the second n-type cladding layer 23.

[0013] The aluminum composition (Al composition) of the first n-type cladding layer 22 is smaller than the Al composition of the second n-type cladding layer 23. The first n-type cladding layer 22 is made of AlGaAs having an Al composition of, for example, 0.25 or more and 0.32 or less. The second n-type cladding layer 23 is made of AlGaAs having an Al composition of, for example, 0.40 or more and 0.50 or less. In this specification, AlGaAs having an Al composition x is defined as Al ｘ Ga １－ｘ As.

[0014] The thickness of the second n-type cladding layer 23 is smaller than the thickness of the first n-type cladding layer 22. The thickness of the first n-type cladding layer 22 is, for example, not less than 930 nm and not more than 1340 nm. The thickness of the second n-type cladding layer 23 is, for example, not less than 640 nm and not more than 860 nm.

[0015] 2 , the first p-type cladding layer 26 is a portion of the p-type cladding layer 25 that is closer to the active layer 20. The second p-type cladding layer 27 is a portion of the p-type cladding layer 25 that is farther from the active layer 20. The first p-type cladding layer 26 is disposed between the active layer 20 and the second p-type cladding layer 27.

[0016] The Al composition of the first p-type cladding layer 26 is smaller than the Al composition of the second p-type cladding layer 27. The first p-type cladding layer 26 is made of AlGaAs having an Al composition of 0.25 or more and 0.32 or less, for example. The second p-type cladding layer 27 is made of AlGaAs having an Al composition of 0.40 or more and 0.50 or less, for example.

[0017] The thickness of the second p-type cladding layer 27 is smaller than the thickness of the first p-type cladding layer 26. The thickness of the first p-type cladding layer 26 is, for example, not less than 700 nm and not more than 1000 nm. The thickness of the second p-type cladding layer 27 is, for example, not less than 480 nm and not more than 640 nm.

[0018] 2 and 3 , the active layer 20 is disposed between the n-type cladding layer 21 and the p-type cladding layer 25 and is in contact with the n-type cladding layer 21 and the p-type cladding layer 25. More specifically, the active layer 20 is disposed between the first n-type cladding layer 22 and the first p-type cladding layer 26 and is in contact with the first n-type cladding layer 22 and the first p-type cladding layer 26. The wavelength of the light emitted from the active layer 20 is, for example, not less than 800 nm and not more than 990 nm. The wavelength of the light emitted from the active layer 20 may be, for example, not less than 850 nm and not more than 950 nm. The active layer 20 includes a well layer 30 and barrier layers 31 and 32. The active layer 20 may further include a first guide layer 33 and a second guide layer 34.

[0019] The well layer 30 is disposed between the barrier layer 31 and the barrier layer 32. The band gap energy of the well layer 30 is smaller than the band gap energy of the barrier layers 31 and 32. The well layer 30 is, for example, InGaAs having an indium composition of 0 or more and 0.15 or less. In this specification, InGaAs having an indium composition y is defined as In ｙ Ga １－ｙ The barrier layers 31 and 32 are made of, for example, AlGaAs having an Al composition of 0.05 to 0.15.

[0020] The first guide layer 33 is a portion of the active layer 20 that is close to the n-type cladding layer 21 (more specifically, the first n-type cladding layer 22) and is in contact with the n-type cladding layer 21 (more specifically, the first n-type cladding layer 22). The barrier layer 31 is disposed between the well layer 30 and the first guide layer 33. At the wavelength of light emitted from the active layer 20, the refractive index of the first guide layer 33 is greater than the refractive index of the n-type cladding layer 21. The first guide layer 33 is formed of, for example, AlGaAs having an Al composition of 0.05 or more and 0.15 or less.

[0021] The second guide layer 34 is a portion of the active layer 20 that is close to the p-type cladding layer 25 (more specifically, the first p-type cladding layer 26) and is in contact with the p-type cladding layer 25 (more specifically, the first p-type cladding layer 26). The barrier layer 32 is disposed between the well layer 30 and the second guide layer 34. At the wavelength of light emitted from the active layer 20, the refractive index of the second guide layer 34 is greater than the refractive index of the p-type cladding layer 25. The second guide layer 34 is formed of, for example, AlGaAs having an Al composition of 0.05 or more and 0.15 or less.

[0022] 1 and 4 , the tunnel layer 16 is disposed between adjacent first and second light-emitting layers among the plurality of light-emitting layers 15. The tunnel layer 16 includes a p-type tunnel layer 35 and an n-type tunnel layer 36.

[0023] The p-type tunnel layer 35 is disposed on the second p-type cladding layer 27 of the first light-emitting layer. The p-type tunnel layer 35 is in contact with the second p-type cladding layer 27 of the first light-emitting layer. The p-type tunnel layer 35 contains, for example, carbon (C) as a p-type dopant. The p-type tunnel layer 35 has a higher p-type dopant concentration than the second p-type cladding layer 27 of the first light-emitting layer.

[0024] The n-type tunnel layer 36 is disposed on the p-type tunnel layer 35. The n-type tunnel layer 36 is in contact with the second n-type cladding layer 23 of the second light-emitting layer. The n-type tunnel layer 36 contains at least one of silicon (Si), tellurium (Te), and selenium (Se) as an n-type dopant. The n-type tunnel layer 36 has a higher n-type dopant concentration than the second n-type cladding layer 23 of the second light-emitting layer.

[0025] 1 , the p-type contact layer 17 is disposed on the second p-type cladding layer 27. When the at least one light-emitting layer 15 is a plurality of light-emitting layers 15, the p-type contact layer 17 is disposed on the second p-type cladding layer 27 of the light-emitting layer 15 that is closest to the second electrode 19 among the plurality of light-emitting layers 15. The p-type contact layer 17 is, for example, a p-type GaAs layer. The p-type contact layer 17 contains, for example, carbon (C) as a p-type dopant. The p-type contact layer 17 has a p-type dopant concentration that is greater than the p-type dopant concentration of the first p-type cladding layer 26 and greater than the p-type dopant concentration of the second p-type cladding layer 27.

[0026] 1 , the insulating layer 18 covers the side surfaces of the mesa structure of the light emitting layer 15. The insulating layer 18 may further cover a portion of the first main surface 11 of the substrate 10. The insulating layer 18 is formed of, for example, silicon nitride.

[0027] 1 , the first electrode 13 is formed on the second main surface 12 of the substrate 10. The first electrode 13 is, for example, a Ti (titanium) / Au (gold) laminate. The second electrode 19 is formed on the p-type contact layer 17. The second electrode 19 is, for example, an AuGeNi / Au laminate.

[0028] The optical output of the semiconductor laser element 1 is, for example, 10 W or more. The laser light output of the semiconductor laser element 1 may be 20 W or more, 50 W or more, 100 W or more, 150 W or more, or 200 W or more. The semiconductor laser element 1 is used, for example, as a light source for LiDAR (Light Detection and Ranging, or Laser Imaging Detection and Ranging), which is an example of a distance measurement device. Because the optical output of the semiconductor laser element 1 is high, the distance measurement accuracy of the LiDAR is improved.

[0029] An example of a manufacturing method for the semiconductor laser device 1 of this embodiment will be described with reference to FIG. 5 . The light-emitting layer 15, tunnel layer 16, and p-type contact layer 17 are formed on the first main surface 11 of the substrate 10 (Step S1). The light-emitting layer 15 and tunnel layer 16 are formed, for example, by metalorganic chemical vapor deposition (MOCVD). Then, the semiconductor stack including the light-emitting layer 15, tunnel layer 16, and p-type contact layer 17 is etched to form a mesa structure (Step S2). An insulating layer 18 is formed on the side surface of the mesa structure (Step S3). The insulating layer 18 is formed, for example, by plasma CVD. A first electrode 13 is formed on the second main surface 12 of the substrate 10, and a second electrode 19 is formed on the p-type contact layer 17 (Step S4). The first electrode 13 and second electrode 19 are formed, for example, by vapor deposition. In this manner, the semiconductor laser device 1 is obtained.

[0030] The operation of the semiconductor laser device 1 of this embodiment will be described. A voltage higher than that applied to the first electrode 13 is applied to the second electrode 19, thereby applying a forward voltage to the semiconductor laser device 1. A forward current flows through the semiconductor laser device 1. Holes are injected from the second electrode 19 into the light-emitting layer 15. Electrons are injected from the first electrode 13 into the light-emitting layer 15. Electrons and holes combine in the active layer 20 (more specifically, the well layer 30), causing the light-emitting layer 15 to emit light. In this way, the semiconductor laser device 1 emits laser light.

[0031] The operation of the semiconductor laser device 1 of this embodiment will be described below in comparison with the semiconductor laser device of a first comparative example and the semiconductor laser device of a second comparative example. The semiconductor laser device of the first comparative example has the same configuration as the semiconductor laser device 1 of this embodiment, but differs from the semiconductor laser device 1 of this embodiment in that the n-type cladding layer 21 is composed only of the second n-type cladding layer 23, and the p-type cladding layer 25 is composed only of the second p-type cladding layer 27. The semiconductor laser device of the second comparative example has the same configuration as the semiconductor laser device 1 of this embodiment, but differs from the semiconductor laser device 1 of this embodiment in that the n-type cladding layer 21 is composed only of the first n-type cladding layer 22, and the p-type cladding layer 25 is composed only of the first p-type cladding layer 26.

[0032] As the Al composition of an AlGaAs-based semiconductor material increases, the difference between the thermal expansion coefficient of the semiconductor material and that of the substrate 10 (e.g., a GaAs substrate) increases. In the first comparative example, the n-type cladding layer 21 is formed only with the second n-type cladding layer 23, which has a higher Al composition, so there is a large difference between the thermal expansion coefficient of the light-emitting layer 15 and that of the substrate 10. Heat applied to the substrate 10 and the light-emitting layer 15 during the manufacturing process of the semiconductor laser device 1 causes the substrate 10 to warp significantly. Stress caused by the warping of the substrate 10 is applied to the light-emitting layer 15.

[0033] Therefore, the semiconductor laser element of the first comparative example is prone to cracking and failure. The reliability of the semiconductor laser element of the first comparative example is low. Furthermore, due to the warping of the substrate 10, it becomes difficult to hold the laminate of the light-emitting layer 15 and the substrate 10 with a suction device, making it difficult to transport the substrate 10 on which the light-emitting layer 15 has been formed to a film-forming device for forming the insulating layer 18 and the first electrode 13 and the second electrode 19. The productivity of the semiconductor laser element of the first comparative example is reduced.

[0034] In contrast, in the semiconductor laser device 1 of this embodiment, the n-type cladding layer 21 includes, in addition to the second n-type cladding layer 23, a first n-type cladding layer 22 having an Al composition lower than that of the second n-type cladding layer 23. The p-type cladding layer 25 includes, in addition to the second p-type cladding layer 27, a first p-type cladding layer 26 having an Al composition lower than that of the second p-type cladding layer 27. Therefore, in this embodiment, the difference between the thermal expansion coefficient of the light-emitting layer 15 and the thermal expansion coefficient of the substrate 10 (e.g., a GaAs substrate) is reduced. Warping of the substrate 10 caused by heat applied to the substrate 10 and the light-emitting layer 15 during the manufacturing process of the semiconductor laser device 1 is reduced. Stress applied to the light-emitting layer 15 due to warping of the substrate 10 is reduced.

[0035] Therefore, the semiconductor laser device 1 of this embodiment is less likely to crack and malfunction, improving the reliability of the semiconductor laser device 1 of this embodiment. In addition, the stack of the light-emitting layer 15 and the substrate 10 can be easily transported, improving the productivity of the semiconductor laser device 1.

[0036] As the Al composition of an AlGaAs-based semiconductor material decreases, the bandgap energy of the semiconductor material decreases and the refractive index of the semiconductor material increases. Therefore, in the second comparative example, the difference between the bandgap energy of the active layer 20 and the bandgap energy of the n-type cladding layer 21 and the difference between the bandgap energy of the active layer 20 and the bandgap energy of the p-type cladding layer 25 decrease. The difference between the refractive index of the active layer 20 and the n-type cladding layer 21 and the difference between the refractive index of the active layer 20 and the p-type cladding layer 25 decrease. Confinement of carriers (electrons and holes) in the active layer 20 and confinement of light in the active layer 20 decrease. The optical output of the semiconductor laser device of the second comparative example decreases.

[0037] In contrast, in the semiconductor laser device 1 of this embodiment, the n-type cladding layer 21 includes, in addition to the first n-type cladding layer 22, a second n-type cladding layer 23 having a higher Al composition than the first n-type cladding layer 22. The p-type cladding layer 25 includes, in addition to the first p-type cladding layer 26, a second p-type cladding layer 27 having a higher Al composition than the first p-type cladding layer 26. Therefore, in the semiconductor laser device 1 of this embodiment, the difference between the bandgap energy of the active layer 20 and the bandgap energy of the n-type cladding layer 21 and the difference between the bandgap energy of the active layer 20 and the bandgap energy of the p-type cladding layer 25 are increased. The difference between the refractive index of the active layer 20 and the n-type cladding layer 21 and the difference between the refractive index of the active layer 20 and the p-type cladding layer 25 are also increased. Confinement of carriers (electrons and holes) in the active layer 20 and confinement of light in the active layer 20 are improved. The optical output of the semiconductor laser device 1 of this embodiment increases.

[0038] (Example) Semiconductor laser devices 1 of Samples 1 to 9 were fabricated. In the semiconductor laser devices 1 of Samples 1 to 9, the substrate 10 was a GaAs substrate. At least one light-emitting layer 15 was a five-layer light-emitting layer. The first n-type cladding layer 22 and the first p-type cladding layer 26 were made of AlGaAs. The first n-type cladding layer 22 had a thickness of 1350 nm, and the first p-type cladding layer 26 had a thickness of 1000 nm. The Al compositions of the first n-type cladding layer 22 and the first p-type cladding layer 26 were as shown in Table 1. The second n-type cladding layer 23 and the second p-type cladding layer 27 were made of AlGaAs. The second n-type cladding layer 23 had a thickness of 860 nm, and the second p-type cladding layer 27 had a thickness of 640 nm. The Al compositions of the second n-type cladding layer 23 and the second p-type cladding layer 27 are as shown in Table 1. The curvatures of the substrates 10 of the semiconductor laser devices 1 of Samples 1 to 9 are as shown in Table 1. The semiconductor laser devices 1 of Samples 1 to 9 were provided with a current of 247 A / cm ２ The light emission efficiencies of the semiconductor laser devices 1 of Samples 1 to 9 when a forward current having a current density of 1000 .mu.m / s are passed through them are as shown in Table 1.

[0039]

[0040] In Samples 1 to 9, the curvature of the substrate 10 is 0.245 rad / m or less. Therefore, the warpage of the semiconductor laser elements 1 of Samples 1 to 9 is small. Furthermore, the light emission efficiency of the semiconductor laser elements 1 of Samples 1 to 9 is 5.4 W / A or more. Therefore, the light emission efficiency of the semiconductor laser elements 1 of Samples 1 to 9 is high, and the light output of the semiconductor laser elements 1 of Samples 1 to 9 is improved.

[0041] The effects of the semiconductor laser device 1 of this embodiment will be described.

[0042] The semiconductor laser device 1 of this embodiment includes a substrate 10 and at least one light-emitting layer 15 disposed on the substrate 10. The at least one light-emitting layer 15 includes a first n-type cladding layer 22, a second n-type cladding layer 23, an active layer 20, a first p-type cladding layer 26, and a second p-type cladding layer 27. The active layer 20 is disposed between the first n-type cladding layer 22 and the first p-type cladding layer 26. The first n-type cladding layer 22 is disposed between the active layer 20 and the second n-type cladding layer 23. The first p-type cladding layer 26 is disposed between the active layer 20 and the second p-type cladding layer 27. The aluminum composition of the first n-type cladding layer 22 is smaller than the aluminum composition of the second n-type cladding layer 23. The aluminum composition of the first p-type cladding layer 26 is smaller than the aluminum composition of the second p-type cladding layer 27.

[0043] At least one light-emitting layer 15 includes a first n-type cladding layer 22 and a first p-type cladding layer 26 having a smaller aluminum composition. This reduces the difference between the thermal expansion coefficient of the at least one light-emitting layer 15 and the thermal expansion coefficient of the substrate 10. This reduces warpage of the semiconductor laser device 1 caused by heat during the manufacturing of the semiconductor laser device 1. Furthermore, at least one light-emitting layer 15 includes a second n-type cladding layer 23 and a second p-type cladding layer 27 having a larger aluminum composition. This improves carrier confinement in the active layer 20 and light confinement in the active layer 20. This improves the optical output of the semiconductor laser device 1.

[0044] In the semiconductor laser device 1 of this embodiment, the substrate 10 is a GaAs substrate. The first n-type cladding layer 22 is made of AlGaAs having an aluminum composition of 0.25 or more and 0.32 or less. The second n-type cladding layer 23 is made of AlGaAs having an aluminum composition of 0.40 or more and 0.50 or less. The first p-type cladding layer 26 is made of AlGaAs having an aluminum composition of 0.25 or more and 0.32 or less. The second p-type cladding layer 27 is made of AlGaAs having an aluminum composition of 0.40 or more and 0.50 or less.

[0045] Therefore, the difference between the thermal expansion coefficient of at least one light-emitting layer 15 and the thermal expansion coefficient of the substrate 10 is reduced. Warping of the semiconductor laser device 1 caused by heat during the manufacturing of the semiconductor laser device 1 is reduced. Furthermore, the confinement of carriers in the active layer 20 and the confinement of light in the active layer 20 are improved. The optical output of the semiconductor laser device 1 is improved.

[0046] In the semiconductor laser device 1 of this embodiment, the thickness of the second p-type cladding layer 27 is smaller than the thickness of the first p-type cladding layer 26. The thickness of the second n-type cladding layer 23 is smaller than the thickness of the first n-type cladding layer 22.

[0047] Therefore, warping of the semiconductor laser element 1 caused by heat during the manufacturing of the semiconductor laser element 1 is reduced.

[0048] In the semiconductor laser device 1 of this embodiment, the thickness of the first p-type cladding layer 26 is not less than 700 nm and not more than 1000 nm. The thickness of the first n-type cladding layer 22 is not less than 930 nm and not more than 1340 nm. The thickness of the second p-type cladding layer 27 is not less than 480 nm and not more than 640 nm. The thickness of the second n-type cladding layer 23 is not less than 640 nm and not more than 860 nm.

[0049] This reduces warpage of the semiconductor laser device 1 due to heat generated during the manufacture of the semiconductor laser device 1. Furthermore, the thickness of the second p-type cladding layer 27 is 480 nm or more, and the thickness of the second n-type cladding layer 23 is 640 nm or more, which improves the confinement of carriers in the active layer 20 and the confinement of light in the active layer 20. The optical output of the semiconductor laser device 1 is improved.

[0050] The semiconductor laser device 1 of this embodiment further includes a tunnel layer 16. At least one light-emitting layer 15 is a plurality of light-emitting layers 15. The tunnel layer 16 is disposed between a first light-emitting layer and a second light-emitting layer adjacent to each other among the plurality of light-emitting layers 15. The tunnel layer 16 includes a p-type tunnel layer 35 and an n-type tunnel layer 36. The p-type tunnel layer 35 is disposed on the second p-type cladding layer 27 of the first light-emitting layer. The p-type tunnel layer 35 has a higher p-type dopant concentration than the second p-type cladding layer 27 of the first light-emitting layer. The n-type tunnel layer 36 is disposed on the second n-type cladding layer 23 of the second light-emitting layer. The n-type tunnel layer 36 has a higher n-type dopant concentration than the second n-type cladding layer 23 of the second light-emitting layer.

[0051] The tunnel layer 16 promotes the movement of carriers (electrons and holes) between the plurality of light-emitting layers 15. This allows the number of light-emitting layers 15 included in the semiconductor laser device 1 to be increased, thereby improving the optical output of the semiconductor laser device 1.

[0052] In the semiconductor laser device 1 of this embodiment, at least one light emitting layer 15 is four or more light emitting layers 15 .

[0053] This allows the number of light-emitting layers 15 included in the semiconductor laser device 1 to be increased, thereby improving the optical output of the semiconductor laser device 1.

[0054] In the semiconductor laser device 1 of this embodiment, the wavelength of the light emitted from the active layer 20 is not less than 800 nm and not more than 990 nm.

[0055] Therefore, a semiconductor material that reduces the difference between the thermal expansion coefficient of the well layer 30 and that of the substrate 10 can be used for the well layer 30. The difference between the thermal expansion coefficient of the at least one light-emitting layer 15 and that of the substrate 10 is reduced. Warpage of the semiconductor laser device 1 caused by heat during the manufacturing of the semiconductor laser device 1 is reduced.

[0056] In the semiconductor laser device 1 of this embodiment, the active layer 20 includes barrier layers 31 and 32 and a well layer 30. The well layer 30 is made of InGaAs having an indium composition of 0 to 0.15.

[0057] This reduces the difference between the thermal expansion coefficient of the well layer 30 and the thermal expansion coefficient of the substrate 10, thereby reducing the difference between the thermal expansion coefficient of the at least one light-emitting layer 15 and the thermal expansion coefficient of the substrate 10. Warpage of the semiconductor laser device 1 caused by heat during the manufacturing of the semiconductor laser device 1 is reduced.

[0058] In the semiconductor laser device 1 of this embodiment, the output of the laser light from the semiconductor laser device 1 is 10 W or more.

[0059] As a result, the optical output of the semiconductor laser device 1 is improved.

[0060] Aspects of the present disclosure are summarized below as appendices. (Appendix 1) A semiconductor laser device comprising: a substrate; and at least one light-emitting layer disposed on the substrate, wherein the at least one light-emitting layer includes a first n-type cladding layer, a second n-type cladding layer, an active layer, a first p-type cladding layer, and a second p-type cladding layer, wherein the active layer is disposed between the first n-type cladding layer and the first p-type cladding layer, the first n-type cladding layer is disposed between the active layer and the second n-type cladding layer, and the first p-type cladding layer is disposed between the active layer and the second p-type cladding layer, wherein an aluminum composition of the first n-type cladding layer is smaller than an aluminum composition of the second n-type cladding layer, and wherein an aluminum composition of the first p-type cladding layer is smaller than an aluminum composition of the second p-type cladding layer. (Supplementary Note 2) The semiconductor laser device according to Supplementary Note 1, wherein the substrate is a GaAs substrate, The first n-type cladding layer is formed of AlGaAs having the aluminum composition of 0.25 or more and 0.32 or less, The second n-type cladding layer is formed of AlGaAs having the aluminum composition of 0.40 or more and 0.50 or less, The first p-type cladding layer is formed of AlGaAs having the aluminum composition of 0.25 or more and 0.32 or less, The second p-type cladding layer is formed of AlGaAs having the aluminum composition of 0.40 or more and 0.50 or less. (Supplementary Note 3) The semiconductor laser device according to Supplementary Note 1 or Supplementary Note 2, wherein the thickness of the second p-type cladding layer is smaller than the thickness of the first p-type cladding layer, The thickness of the second n-type cladding layer is smaller than the thickness of the first n-type cladding layer. (Supplementary Note 4) The semiconductor laser element according to Supplementary Note 3, wherein the thickness of the first p-type cladding layer is 700 nm or more and 1000 nm or less, the thickness of the first n-type cladding layer is 930 nm or more and 1340 nm or less, the thickness of the second p-type cladding layer is 480 nm or more and 640 nm or less, and the thickness of the second n-type cladding layer is 640 nm or more and 860 nm or less.(Supplementary Note 5) The semiconductor laser device according to any one of Supplementary Note 1 to Supplementary Note 4, further comprising a tunnel layer, wherein the at least one light emitting layer is a plurality of light emitting layers, the tunnel layer is disposed between a first light emitting layer and a second light emitting layer adjacent to each other among the plurality of light emitting layers, the tunnel layer includes a p-type tunnel layer and an n-type tunnel layer, the p-type tunnel layer is disposed on the second p-type clad layer of the first light emitting layer, a p-type dopant concentration of the p-type tunnel layer is higher than a p-type dopant concentration of the second p-type clad layer of the first light emitting layer, the n-type tunnel layer is disposed on the second n-type clad layer of the second light emitting layer, and a n-type dopant concentration of the n-type tunnel layer is higher than an n-type dopant concentration of the second n-type clad layer of the second light emitting layer. (Supplementary Note 6) The semiconductor laser device according to any one of Supplementary Note 1 to Supplementary Note 5, wherein the at least one light emitting layer is four or more light emitting layers. (Supplementary Note 7) The semiconductor laser element according to any one of Supplementary Notes 1 to 6, wherein the wavelength of light emitted from the active layer is 800 nm or more and 990 nm or less. (Supplementary Note 8) The semiconductor laser element according to any one of Supplementary Notes 1 to 7, wherein the active layer includes a barrier layer and a well layer, and the well layer is formed of InGaAs having an indium composition of 0 or more and 0.15 or less. (Supplementary Note 9) The semiconductor laser element according to any one of Supplementary Notes 1 to 8, wherein an output of laser light is 10 W or more.

[0061] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0062] REFERENCE SIGNS LIST 1 semiconductor laser element, 10 substrate, 11 first main surface, 12 second main surface, 13 first electrode, 15 light emitting layer, 16 tunnel layer, 17 p-type contact layer, 18 insulating layer, 19 second electrode, 20 active layer, 21 n-type cladding layer, 22 first n-type cladding layer, 23 second n-type cladding layer, 25 p-type cladding layer, 26 first p-type cladding layer, 27 second p-type cladding layer, 30 well layer, 31, 32 barrier layers, 33 first guide layer, 34 second guide layer, 35 p-type tunnel layer, 36 n-type tunnel layer.

Claims

1. A semiconductor laser device comprising: a substrate; and at least one light-emitting layer disposed on the substrate, the at least one light-emitting layer including a first n-type cladding layer, a second n-type cladding layer, an active layer, a first p-type cladding layer, and a second p-type cladding layer, the active layer being disposed between the first n-type cladding layer and the first p-type cladding layer, the first n-type cladding layer being disposed between the active layer and the second n-type cladding layer, and the first p-type cladding layer being disposed between the active layer and the second p-type cladding layer, the aluminum composition of the first n-type cladding layer being smaller than the aluminum composition of the second n-type cladding layer, and the aluminum composition of the first p-type cladding layer being smaller than the aluminum composition of the second p-type cladding layer.

2. The semiconductor laser device according to claim 1, wherein the substrate is a GaAs substrate, the first n-type cladding layer is formed of AlGaAs having the aluminum composition of 0.25 or more and 0.32 or less, the second n-type cladding layer is formed of AlGaAs having the aluminum composition of 0.40 or more and 0.50 or less, the first p-type cladding layer is formed of AlGaAs having the aluminum composition of 0.25 or more and 0.32 or less, and the second p-type cladding layer is formed of AlGaAs having the aluminum composition of 0.40 or more and 0.50 or less.

3. A semiconductor laser device according to claim 1 or 2, wherein the thickness of the second p-type cladding layer is smaller than the thickness of the first p-type cladding layer, and the thickness of the second n-type cladding layer is smaller than the thickness of the first n-type cladding layer.

4. The semiconductor laser device according to claim 3, wherein the thickness of the first p-type cladding layer is 700 nm or more and 1000 nm or less, the thickness of the first n-type cladding layer is 930 nm or more and 1340 nm or less, the thickness of the second p-type cladding layer is 480 nm or more and 640 nm or less, and the thickness of the second n-type cladding layer is 640 nm or more and 860 nm or less.

5. The semiconductor laser device according to any one of claims 1 to 4, further comprising a tunnel layer, wherein the at least one light-emitting layer is a plurality of light-emitting layers, and the tunnel layer is disposed between a first light-emitting layer and a second light-emitting layer adjacent to each other among the plurality of light-emitting layers, and the tunnel layer includes a p-type tunnel layer and an n-type tunnel layer, and the p-type tunnel layer is disposed on the second p-type clad layer of the first light-emitting layer, and a p-type dopant concentration of the p-type tunnel layer is higher than a p-type dopant concentration of the second p-type clad layer of the first light-emitting layer, and the n-type tunnel layer is disposed on the second n-type clad layer of the second light-emitting layer, and a n-type dopant concentration of the n-type tunnel layer is higher than a n-type dopant concentration of the second n-type clad layer of the second light-emitting layer.

6. A semiconductor laser device according to any one of claims 1 to 5, wherein the at least one light-emitting layer is four or more light-emitting layers.

7. A semiconductor laser device according to any one of claims 1 to 6, wherein the wavelength of light emitted from the active layer is not less than 800 nm and not more than 990 nm.

8. A semiconductor laser device according to any one of claims 1 to 7, wherein the active layer includes a barrier layer and a well layer, and the well layer is formed of InGaAs having an indium composition of 0 to 0.

15.

9. The semiconductor laser device according to any one of claims 1 to 8, wherein the laser light output of the semiconductor laser device is 10 W or more.

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