Semiconductor laser, semiconductor laser device, and semiconductor laser manufacturing process

Abstract

A semiconductor laser (100) has a ridge (5) formed on an n-type semiconductor substrate (1) and a buried layer (25) buried such that it covers both sides in an x-direction perpendicular to a y-direction, which is the direction in which the ridge extends. On a positive side of a z-direction, which is the direction in which the ridge projects, and on the positive side of the buried layer in the z-direction, a p-type second cladding layer (9), a p-type contact layer (10), a surface electrode (12) connected to the p-type contact layer, and a semi-insulating layer (11) are provided, which is formed at an outer edge separated from the ridge in the x-direction. The semi-insulating layer or front electrode is formed on sides in the direction of x-direction ends (29a, 29b) of the semiconductor laser (100) on the positive side in the z-direction.

Description

Technical area

[0001] The present application relates to a semiconductor laser, a semiconductor laser device, and a semiconductor laser production method. State of the art

[0002] A semiconductor laser is widely used as a light source for optical communications, and it is essential that it has a small size, high-speed operation, high efficiency, and low power loss. Patent Document 1 discloses a semiconductor laser having a buried heterostructure.The semiconductor laser of Patent Document 1 is provided with a ridge comprising an n-type semiconductor substrate, an n-type cladding layer, an active layer, and a p-type cladding layer, a buried region in which the ridge is buried, a pair of trench grooves formed in the buried region, the p-type cladding layer and a contact layer stacked on the ridge and the buried region, an anode electrode connected to the contact layer, a cathode electrode formed on a rear surface of the n-type substrate, and an insulating layer covering the contact layer and the trench grooves except for a region directly above the ridge. The insulating layer formed of silicon dioxide (SiO2) or the like allows a current to be efficiently injected from the anode electrode to the active layer.

[0003] Furthermore, to improve the characteristics of a semiconductor laser, it is important to reduce the resistance of a current injection path. The resistance of the current injection path is appropriately referred to as the injection resistance. Especially in a semiconductor laser used for high output power, the operating current is high, heat generation is high due to the injection resistance, and the deterioration of characteristics is significant. Therefore, it is very important to efficiently dissipate the heat generated during operation.

[0004] To efficiently dissipate the heat generated during operation of the semiconductor laser, a so-called "junction-down" mounting can be used, in which the semiconductor laser is mounted such that a pn junction of the semiconductor laser faces a heat sink. Patent Document 2 discloses a semiconductor laser device in which a semiconductor laser is mounted on a heat sink by the "junction-down" mounting.

[0005] In the semiconductor laser device of Patent Document 2, in order to efficiently dissipate heat generated during operation of the semiconductor laser to the heat sink, a cladding layer, a contact layer, and an electrode metal are sequentially stacked on a waveguide layer including an active layer. A groove (trench) penetrating the contact layer and reaching the vicinity of the active layer is formed in the cladding layer, and a heat transfer material is filled between the groove (trench) and the heat sink. In the semiconductor laser device of Patent Document 2, the heat transfer material having high thermal conductivity is disposed near the active layer, which is a heat generation source, to increase the thermal conductivity of a heat dissipation path to the heat sink, thereby improving heat dissipation performance. Citation listPatent document Patent Document 1: Japanese Patent Application Laid-Open No. 2011-216680 ( Fig. 1) Patent Document 2: Japanese Patent Application Laid-Open No. 2001-94210 ( Fig. 1, Fig. 8) Summary of the inventionProblem to be solved by the invention

[0006] In the semiconductor laser of Patent Document 2, a thick cladding layer is formed above the waveguide layer including the active layer, and the resistance of the injection current path is larger than that of the semiconductor laser of Patent Document 1. To reduce the resistance of the injection current path and suppress leakage current that does not contribute to laser oscillation, a semiconductor laser with a buried structure, such as the semiconductor laser of Patent Document 1, is typically used. When the semiconductor laser of Patent Document 1 is mounted on the heat sink by junction-down mounting, the thermal resistance of the heat dissipation path to the heat sink increases due to the insulating layer with low thermal conductivity, since an insulating layer exists covering the contact layer and the trench grooves, except for the region directly above the ridge including the active layer.

[0007] In the case where the semiconductor laser of Patent Document 1 is mounted on the heat sink by the junction-down mounting, the thermal resistance of the heat dissipation path increases, and a problem occurs that the heat dissipation of the semiconductor laser is insufficient.

[0008] The technology disclosed in the specification of the present application aims to achieve excellent heat dissipation while suppressing the leakage current that does not contribute to the laser oscillation when the junction-down mounting is applied with respect to the heat sink. Means to solve the problem

[0009] A semiconductor laser as an example disclosed in the present specification includes a ridge formed on an n-type semiconductor substrate and a buried layer buried to cover both sides opposite each other in a direction perpendicular to an extension direction of the ridge. The semiconductor laser is mounted on a side where the ridge protrudes from a surface. A z-direction is a direction in which the ridge protrudes from one side of a front surface of the n-type semiconductor substrate, a y-direction is an extension direction in which the ridge extends, and an x-direction is a direction perpendicular to the z-direction and the y-direction. The ridge includes an n-type cladding layer, an active layer, and a p-type first cladding layer, which are sequentially formed from one side of the n-type semiconductor substrate.The buried layer includes a p-type first buried layer in contact with a side surface of the ridge on a negative side in the x-direction and a side surface of the ridge on a positive side in the x-direction, a second buried layer, and an n-type third buried layer.The semiconductor laser includes a p-type second cladding layer and a p-type contact layer sequentially formed from the n-type semiconductor substrate side on the positive side of the ridge in the z-direction and on the positive side of the n-type third buried layer in the z-direction, a front electrode connected to the p-type contact layer, and a semi-insulating layer formed in the outer edges in the x-direction separately from a ridge part having the ridge and the p-type first buried layer in contact with the both side surfaces of the ridge, and the semi-insulating layer or the front electrode is formed on the positive side in the z-direction on sides toward x-direction ends in the semiconductor laser. Effects of the invention

[0010] An example of the semiconductor laser disclosed in the specification of the present application has the semi-insulating layer at the outer edge, which is separated in the x-direction from the ridge portion containing the active layer, and is located on the side opposite the n-type semiconductor substrate. Therefore, when the semiconductor laser is mounted from the front electrode side, it is possible to achieve excellent heat dissipation while suppressing leakage current that does not contribute to laser oscillation. Short description of the characters Fig. 1 is a diagram showing a cross-sectional structure of a first semiconductor laser according to Embodiment 1. Fig. 2 is a diagram showing a cross-sectional structure of a semiconductor laser according to Embodiment 1. Fig. 3 is a diagram showing a cross-sectional structure of a second semiconductor laser according to Embodiment 1. Fig. 4 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 1 shows. Fig. 5 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 1 shows. Fig. Fig. 6 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 1 shows. Fig. Fig. 7 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 1 shows. Fig. Fig. 8 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 1 shows. Fig. Fig. 9 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 1 shows. Fig. 10 is a diagram showing a cross-sectional structure of a semiconductor laser of a comparative example. Fig. 11 is a diagram showing a cross-sectional structure of a semiconductor laser device of the comparative example. Fig. 12 is a diagram showing a cross-sectional structure of a semiconductor laser according to Embodiment 2. Fig. 13 is a diagram showing a cross-sectional structure of a semiconductor laser according to Embodiment 2. Fig. 14 is a diagram showing a width of a prominent part of the semiconductor laser of Fig. 12 shows. Fig. 15 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 12 shows. Fig. 16 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 12 shows. Fig. 17 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 12 shows. Fig. 18 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 12 shows. Fig. 19 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 12 shows. Fig. 20 is a diagram showing a cross-sectional structure of a semiconductor laser according to Embodiment 3. Fig. 21 is a diagram showing a cross-sectional structure of a semiconductor laser according to Embodiment 3. Fig. 22 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 20 shows. Fig. 23 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 20 shows. Fig. 24 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 20 shows. Fig. 25 is a diagram showing a cross-sectional structure of a first semiconductor laser according to Embodiment 4. Fig. 26 is a diagram showing a cross-sectional structure of a first semiconductor laser device according to Embodiment 4. Fig. 27 is a diagram showing a cross-sectional structure of a second semiconductor laser according to Embodiment 4. Fig. 28 is a diagram showing a cross-sectional structure of a second semiconductor laser device according to Embodiment 4. Fig. 29 is a diagram showing a cross-sectional structure of a third semiconductor laser according to Embodiment 4. Fig. 30 is a diagram showing a width of a protruding part in the semiconductor laser according to Embodiment 4. Fig. 31 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 25 shows. Fig. 32 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 25 shows. Fig. 33 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 25 shows. Fig. 34 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 25 shows. Fig. 35 is a diagram showing a cross-sectional structure of a first semiconductor laser according to Embodiment 5. Fig. 36 is a diagram showing a cross-sectional structure of a first semiconductor laser device according to Embodiment 5. Fig. 37 is a diagram showing a cross-sectional structure of a second semiconductor laser according to Embodiment 5. Fig. 38 is a diagram showing a cross-sectional structure of a second semiconductor laser device according to Embodiment 5. Fig. 39 is a diagram showing a cross-sectional structure of a third semiconductor laser according to Embodiment 5. Fig. 40 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 35 shows. Modes for carrying out the inventionEmbodiment 1

[0011] Fig. 1 is a diagram showing a cross-sectional structure of a first semiconductor laser according to Embodiment 1, and Fig. 2 is a diagram showing a cross-sectional structure of a semiconductor laser device according to Embodiment 1. Fig. 3 is a diagram showing a cross-sectional structure of a second semiconductor laser according to Embodiment 1. Fig. 4 to Fig. 9 are diagrams showing a method of manufacturing the semiconductor laser of Fig. Show 1. Fig. 10 is a diagram showing a cross-sectional structure of a semiconductor laser of a comparative example, and Fig. 11 is a diagram showing a cross-sectional structure of a semiconductor laser device of the comparative example. A semiconductor laser 100 of Embodiment 1 includes a ridge 5 formed on an n-type semiconductor substrate 1, which is an n-type InP layer, and a buried layer 25 buried so as to cover both sides of the ridge 5 that are opposite to each other in a direction perpendicular to an extension direction of the ridge 5. A direction in which the ridge 5 protrudes from the front surface side of the n-type semiconductor substrate 1 is defined as a z-direction, the extension direction in which the ridge 5 extends is defined as a y-direction, and a direction perpendicular to the z-direction and the y-direction is defined as an x-direction. In the semiconductor laser 100 shown in Fig. As shown in Fig. 1, the ridge 5 protrudes from the front side of the n-type semiconductor substrate 1 to the positive side in the z-direction, the end on the positive side in the x-direction indicated by a dashed line 51a is an x-direction end 29b, and the end on the negative side in the x-direction indicated by a dashed line 51d is an x-direction end 29a. The ridge 5 is formed between a dashed line 41a and a dashed line 41b, and a ridge part 50 is formed between a dashed line 43a and a dashed line 43b. Note that the positive side in the z-direction is referred to as a front surface side, and the negative side in the z-direction is referred to as a rear surface side, where appropriate.

[0012] The semiconductor laser 100 is provided with the ridge 5 having an n-type cladding layer 2, an active layer 3, and a p-type first cladding layer 4, which are sequentially formed from one side of the n-type semiconductor substrate, and the buried layer 25 having a p-type first buried layer 6 in contact with the positive side surface in the x-direction and the negative side surface in the x-direction in the ridge 5, a second buried layer 7, and an n-type third buried layer 8, and it is provided with a p-type second cladding layer 9, a p-type contact layer 10, which are formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction sequentially from the side of the n-type semiconductor substrate 1, an anode electrode 12 having a front side electrode is,which is connected to the p-type contact layer 10, and a semi-insulating layer 11 formed in outer edges separated in the x-direction from the ridge part 50, which has the ridge 5 and the p-type first buried layer 6 in contact with two side surfaces of the ridge 5, and which is further provided with a cathode electrode 13 which is a backside electrode,formed on a rear surface of the n-type semiconductor substrate 1. The semi-insulating layer 11 and the anode 12 are formed on the positive side in the z-direction on sides toward x-direction ends 29a and 29b of the semiconductor laser 100. On the x-direction end 29a side of the semiconductor laser 100, the semi-insulating layer 11 is formed in an end region 24 extending from the dashed line 51a to a dashed line 51b. Similarly, on the x-direction end 29b side of the semiconductor laser 100, the semi-insulating layer 11 is formed in the end region 24 extending from a dashed line 51c to a dashed line 51d.

[0013] The semiconductor laser device 200 of Embodiment 1 includes the semiconductor laser 100 and a heat sink 17, and the positive side in the z-direction on which the anode electrode 12 of the semiconductor laser 100 is formed is connected to the heat sink 17 by a connecting member 14 such as a gold-tin solder. Fig. 2 shows a cross-section of the semiconductor laser device 200 mounted on the heat sink 17 by a junction-down mounting. The semiconductor laser 100 is mounted on the heat sink 17 by the junction-down mounting from the side of the surface from which the ridge 5 protrudes, that is, from the positive side in the z-direction.

[0014] The n-type semiconductor substrate 1 is the n-type InP substrate, which is an InP substrate doped with, for example, sulfur (S). The n-type cladding layer 2 is, for example, an n-type InP layer doped with sulfur. The active layer 3 includes a multiple quantum well made of an AlGaInAS-based or InGaASP-based material. The p-type first cladding layer 4 is, for example, a p-type InP cladding layer doped with zinc (Zn). The ridge 5 has a stripe shape extending in the y-direction.

[0015] The ridge 5 is formed by etching the semiconductor layers of the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4, which are successively formed on the n-type substrate 1, to a position lower than the active layer 3, that is, to a position lower than the negative side of the active layer 3 in the z-direction. The first semiconductor laser 100, which is Fig. 1 is an example in which a ridge etching position 52 reaches the n-type semiconductor substrate 1, and a second semiconductor laser 100 arranged in Fig. 3 is an example in which the fin etching position 52 is arranged in the n-type cladding layer 2. The fin 5 is buried to a position higher than the active layer 3, that is, a position higher than a surface position 44 of the active layer (see Fig. 6) is located on the positive side of the active layer 3 in the z-direction, by the p-type first buried layer 6 in contact with the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction, the second buried layer 7, and the n-type third buried layer 8. The p-type first buried layer 6 is, for example, a p-type InP buried layer doped with zinc, the second buried layer 7 is a semi-insulating InP buried layer doped with iron (Fe), which is a semi-insulating material, and the n-type third buried layer 8 is, for example, an n-type InP buried layer doped with sulfur.

[0016] The first semiconductor laser 100, which was Fig. 1 is an example in which the second buried layer 7 is formed up to a position on the positive side of the ridge 5 in the z-direction, and the second semiconductor laser 100 formed in Fig. 3 is an example in which the second buried layer 7 is formed up to the surface position 44 of the active layer. The second buried layer 7 may be a semi-insulating InP buried layer doped with a material such as titanium (Ti), cobalt (Co), or rubidium (Ru). Further, the p-type first buried layer 6 and the second buried layer 7 may be formed by combining with other semiconductor layers each having different impurity concentrations or conductivity types. The n-type third buried layer 8 is formed on the surface of the second buried layer 7, and the p-type second cladding layer 9 is formed on the n-type third buried layer 8 and the ridge 5 on the positive side in the z-direction.The p-type contact layer 10 is formed on the p-type second cladding layer 9 on the positive side in the z-direction, and the semi-insulating layer 11 is formed on the p-type contact layer 10 in the end regions 24 on the positive side in the z-direction. The anode electrode 12 is formed so as to cover the surface of the semi-insulating layer 11 and the surface of the p-type contact layer 10 from which the semi-insulating layer 11 is removed, and the cathode electrode 13 is formed on the rear surface side of the n-type semiconductor substrate 1. An opening of the semi-insulating layer 11 is arranged on the positive side in the z-direction in a region of the p-type contact layer 10 on which the ridge part 50 is enclosed.The region in which the opening of the semi-insulating layer 11 is located is a region through which a current flows from the anode 12 to the ridge 5 via the p-type contact layer 10 and the p-type second cladding layer 9. The first semiconductor laser 100 shown in FIG. Fig. 1 is an example in which the n-type third buried layer 8 is formed at a position farther from the n-type semiconductor substrate 1 than the positive side of the ridge 5 in the z-direction, and the second semiconductor laser 100 formed in Fig. 3 is an example in which the n-type third buried layer 8 is formed closer to the semiconductor substrate 1 than the positive side of the ridge 5 in the z-direction. Fig. 1 and Fig. 3 show an example in which the anode electrode 12 covers the entire positive side of the semiconductor laser 100 in the z-direction.

[0017] The p-type second cladding layer 9 is, for example, the p-type InP cladding layer doped with zinc, and the p-type contact layer 10 is, for example, a p-type InGaAs contact layer doped with zinc. The semiconductor layer 11 is, for example, an InP semi-insulating layer doped with iron. The semi-insulating layer 11 may be a semi-insulating InP layer doped with a material such as titanium, cobalt, rubidium, etc. The material of the anode electrode 12 and the cathode electrode 13 is a metal such as gold (Au), germanium (Ge), zinc, platinum (Pt), or titanium.In the case where the connecting element 14 is a gold-tin solder, when the semiconductor laser 100 is mounted by the junction-down mounting, a barrier metal such as platinum may be inserted between the p-type contact layer 10 and the anode electrode 12 to prevent gold from diffusing into the p-type contact layer 10 and a semiconductor layer closer to the n-type semiconductor substrate 1 than the p-type contact layer 10.

[0018] Next, a method for manufacturing the semiconductor laser 100 of Embodiment 1 will be described using an example shown in Fig. 4 to Fig. 9. Although Fig. 4 to Fig. 9 shows a method of manufacturing the first semiconductor laser 100, the description will further be given to include a method of manufacturing the second semiconductor laser 100. Fig. 4 shows a ridge formation step for forming the ridge 5. In the ridge formation step, the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 are sequentially formed on the n-type semiconductor substrate 1, and a first mask 31 made of SiO2, SiN, or the like is formed with a width of the ridge 5 in the x-direction. Next, using the first mask 31, by etching down to a position lower than the negative side of the active layer 3 in the z-direction, which is on the n-type semiconductor substrate 1 side, the ridge 5 including the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4, and in which the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction are exposed, is formed.The ridge etching position 52 for forming the ridge 5 is a position lower than the negative side of the active layer 3 in the z-direction.

[0019] Fig. 5 and Fig. 6 shows a burying step for burying the ridge 5 by means of the buried layer 25. In the burying step, the p-type first buried layer 6 is formed on the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction, that is, both side surfaces of the ridge 5, using the first mask 31, and the ridge 5 is buried to a position higher than the position 44 of the active layer, which is a position of the active layer 3 on a positive side in the z-direction, by the second buried layer 7 and the n-type third buried layer 8, which are formed successively. The first semiconductor laser 100 shown in Fig. 1 and the second semiconductor laser 100 shown in Fig. 3 are examples in which the second buried layer 7 is formed up to the position higher than the surface position 44 of the active layer.

[0020] Fig. 7 and Fig. 8 show a stacking step of semiconductor layers on the surfaces of the ridge 5 and the buried layer 25. As in Fig. As shown in Figure 7, the first mask 31 is removed using buffered hydrofluoric acid or hydrofluoric acid as a preprocessing step for the stacking step. Subsequently, in the stacking step, the p-type second cladding layer 9, the p-type contact layer 10, and the semi-insulating layer 11 are sequentially formed on the positive side of the ridge 5 in the z direction and on the positive side of the n-type third buried layer 8 in the z direction.

[0021] Fig. 9 shows a contact layer exposure step for exposing the p-type contact layer 10. In the contact layer exposure step, a resist mask 32 is formed in which a region in an x-direction including the fin part 50 having the fin 5 and the p-type first buried layer 6 in contact with the two side surfaces of the fin 5 is opened. Then, the semi-insulating layer 11 is selectively etched with hydrochloric acid using the resist mask 32 to expose the p-type contact layer 10. Subsequently, the resist mask 32 is removed.

[0022] Next, as in Fig. 1 to Fig. 3, a front electrode formation step of forming the anode electrode 12 as the front electrode is performed on the exposed p-type contact layer 10, on the positive side of the semi-insulating layer 11 in the z direction, and the side surfaces in the semi-insulating layer 11 on the ridge part 50 side, and a back electrode formation step of forming the cathode electrode 13 as the back electrode is performed on the back surface side of the n-type semiconductor substrate 1, that is, on the negative side in the z direction. The semiconductor laser 100 of Embodiment 1 is manufactured through the steps described above.

[0023] Fig. 10 and Fig. 11 shows a semiconductor laser 110 and a semiconductor laser device 210 as the comparative example. The semiconductor laser 110 of the comparative example differs from the first semiconductor laser 100 of Embodiment 1 in that an insulating layer 28 made of SiO2 is formed on the p-type contact layer 10 instead of the semi-insulating layer 11.

[0024] An operation of the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 1 will be described. During operation, a forward bias voltage is applied between the anode electrode 12 and the cathode electrode 13 of the semiconductor laser 100. In the semiconductor laser device 200 of Embodiment 1, the forward bias voltage is applied between the anode electrode 12 and the cathode electrode 13 of the semiconductor laser 100 via the heat sink 17. When the forward bias voltage is applied between the anode electrode 12 and the cathode electrode 13, a current is injected from the anode electrode 12 into the p-type contact layer 10 of an opening region of the semi-insulating layer, which has the ridge part 50 and in which the semi-insulating layer 11 is removed. The opening region of the semi-insulating layer is a current injection region.The injected current is confined to the region of the ridge 5, which has the stripe shape, by the second buried layer 7 and the n-type third buried layer 8, and is injected into the ridge 5. A laser light with a wavelength corresponding to the band gap energy of the semiconductor layer constituting the active layer 3 is generated by the current injected into the active layer 3, and the laser light is emitted to the outside of the semiconductor laser 100. The laser light is emitted in the y-direction in which the ridge 5 extends.

[0025] The main heat source of the semiconductor laser 100 is the active layer 3. The heat generated in the active layer 3 is conducted to the surrounding semiconductor layers and spreads to the outside of the active layer 3. In the semiconductor laser 110 and the semiconductor laser device 210 of the comparative example, the heat generated in the active layer 3 is conducted from the active layer 3 to the surrounding semiconductor layers, that is, the p-type first buried layer 6, the second buried layer 7, the n-type third buried layer 8, the p-type second cladding layer 9, and the p-type contact layer 10. In the semiconductor laser 110 and the semiconductor laser device 210 of the comparative example, the current injection region is an opening region of the insulating layer in which the insulating layer 28 is removed. In the current injection region, heat is conducted from the p-type contact layer 10 to the anode electrode 12.However, in the outer regions outside the current injection region where the insulating layer 28 exists, heat is conducted from the p-type contact layer 10 to the anode electrode 12 through the insulating layer 28. Then, the heat is dissipated from the anode electrode 12 to the heat sink 17 through the connecting member 14. In the semiconductor laser 110 of the comparative example, the p-type contact layer 10, except for the current injection region, is covered with the insulating layer 28, which covers the ridge 5 containing the active layer 3, to suppress leakage current to regions other than the active layer 3. The thermal conductivity of SiO2 used as the insulating layer 28 is 1.38 W / (m·K). Compared with InP, which has a thermal conductivity of 70 W / (m·K), SiO2 has a poor thermal conductivity.Therefore, in the semiconductor laser device in which the semiconductor laser 110 of the comparative example is mounted by junction-down mounting, that is, the semiconductor laser device 210 of the comparative example, heat dissipation from the surface regions of the insulating layer 28, i.e., from the outer regions described above, is insufficient, and the high-temperature characteristics thereof deteriorate. In the semiconductor laser device 210 of the comparative example in which the semiconductor laser 110 of the comparative example is mounted by junction-down mounting, heat dissipation is insufficient because the thermal resistance of the heat dissipation path is high.

[0026] In contrast, in the semiconductor laser 100 of Embodiment 1, the semi-insulating layer 11 made of InP, instead of the insulating layer 28, is interposed between the p-type contact layer 10 and the anode electrode 12 outside the current injection region, that is, in the end regions 24 on the positive side and the negative side of the current injection region in the x-direction. Therefore, the thermal resistance of the heat dissipation path in the end regions 24 is lower than that in the comparative example, thereby improving heat dissipation compared with the comparative example. Since the semi-insulating layer 11 is doped with, for example, iron and has the semi-insulating property, it is possible to suppress leakage current to other parts except the active layer 3 at the time of current injection.Since the semiconductor laser 100 of Embodiment 1 has the semi-insulating layer 11 in the end regions 24 on the positive side of the p-type contact layer 10 in the z-direction, it is possible to achieve excellent heat dissipation and improve high-temperature characteristics while suppressing the leakage current to those deviating from the active layer 3, which does not contribute to the laser oscillation.

[0027] Note that the material of the semi-insulating layer 11 is not limited to InP, but may be formed of a material whose thermal conductivity is 10 times greater than that of SiO2. Even in this case, the semiconductor laser 100 of Embodiment 1 can reduce the thermal resistance of the heat dissipation path compared to the comparative example, and can achieve excellent heat dissipation while suppressing the leakage current that does not contribute to laser oscillation.

[0028] As described above, the semiconductor laser 100 of Embodiment 1 includes the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried so as to cover both sides of the ridge facing each other in the direction perpendicular to the extending direction of the ridge 5, and is a semiconductor laser mounted on the side from which the ridge 5 protrudes from the surface. A direction in which the ridge 5 protrudes from the front surface side of the n-type semiconductor substrate 1 is defined as the z-direction, an extending direction in which the ridge 5 extends is defined as the y-direction, and a direction perpendicular to the z-direction and the y-direction is defined as the x-direction.The ridge 5 includes the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4, which are sequentially formed from the n-type semiconductor substrate 1 side. The buried layer 25 includes the p-type first buried layer 6, which is in contact with the positive side surface of the ridge 5 in the x-direction and the negative side surface of the ridge 5 in the x-direction, the second buried layer 7, and the n-type third buried layer 8.The semiconductor laser 100 includes the p-type second cladding layer 9, the p-type contact layer 10 sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction in this order from the n-type semiconductor substrate 1 side, the front electrode (anode electrode 12) connected to the p-type contact layer 10, and the semi-insulating layer 11, the semi-insulating layer 11 being formed at the outer edges separated in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5. The semi-insulating layer 11 or the front side electrode (anode electrode 12) is formed on the positive side in the z-direction on sides toward the x-direction ends (x-direction ends 29a and 29b) in the semiconductor laser 100.With this configuration, the semiconductor laser 100 of Embodiment 1 includes the semi-insulating layer 11 separated in the x-direction from the ridge portion 50 having the active layer 3, and is located at the outer edges on the side opposite to the n-type semiconductor substrate 1. Therefore, when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side, excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to laser oscillation.

[0029] The semiconductor laser device 200 of Embodiment 1 includes the semiconductor laser 100 of Embodiment 1 and the heat sink 17, and the positive side in the z-direction, on which the front electrode (anode electrode 12) of the semiconductor laser 100 is formed, is connected to the heat sink 17 by means of the connecting member 14. With this configuration, the semiconductor laser device 200 of Embodiment 1 includes the semi-insulating layer 11 at the outer edges separated in the x-direction from the ridge part 50 having the active layer 3 and located on the side opposite to the n-type semiconductor substrate 1, and the positive side in the z-direction, on which the front electrode (anode electrode 12) is formed, is connected to the heat sink 17 by means of the connecting member.Therefore, in the case of mounting from the front electrode (anode electrode 12), excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to the laser oscillation.

[0030] The semiconductor laser production method of Embodiment 1 is a semiconductor laser production method for manufacturing the semiconductor laser 100 including the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried to cover both sides of the ridge that are opposite to each other in the direction perpendicular to the extending direction of the ridge 5. The semiconductor laser production method of Embodiment 1 includes the ridge formation step, the burying step, the stacking step, the contact layer exposure step, and the front-side electrode formation step, which are described below.In the ridge formation step, the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 are sequentially formed on the n-type semiconductor substrate 1. Then, by etching down to a position lower than the negative side of the active layer 3 in the z direction, which is on the n-type semiconductor substrate 1 side, the ridge 5, which includes the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 and in which the positive side surface in the x direction and the negative side surface in the x direction are exposed, is formed. In the burying step, the p-type first buried layer 6 is formed on the positive side surface in the x direction and the negative side surface in the x direction in the ridge 5., and the fin 5 is buried by the second buried layer 7 and the n-type third buried layer 8, which are sequentially formed up to a position higher than the active layer surface position 44, which is a position on the positive side of the active layer 3 in the z-direction. In the stacking step, the p-type cladding layer 9, the p-type contact layer 10, and the semi-insulating layer 11 are sequentially formed on the positive side of the fin 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction. In the contact layer exposing step, the p-type contact layer 10 is exposed by etching the semi-insulating layer 11 in a region in the x-direction having the fin part 50 including the fin 5 and the p-type first buried layer 6 in contact with the second side surfaces of the fin 5.In the front electrode formation step, the front electrode (anode electrode 12) is formed on the exposed p-type contact layer 10, on the positive side of the semi-insulating layer 11 in the z-direction, and on the side surfaces of the semi-insulating layer 11 on the ridge part 50 side. With this configuration, the semiconductor laser production method of Embodiment 1 can manufacture the semiconductor laser 100 including the semi-insulating layer 11, which is separated in the x-direction from the ridge part 50 having the active layer 3 and which is located at the outer edges on the positive side of the n-type semiconductor substrate 1, so that excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to the laser oscillation when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side. Embodiment 2

[0031] Fig. 12 is a diagram showing a cross-sectional structure of a semiconductor laser device according to Embodiment 2, and Fig. 13 is a diagram showing a cross-sectional structure of a semiconductor laser device according to Embodiment 2. Fig. 14 is a diagram showing a width of a prominent part of the semiconductor laser of Fig. 12 shows. Fig. 15 to Fig. 19 are diagrams showing a method of manufacturing the semiconductor laser of Fig. 12. The semiconductor laser 100 of Embodiment 2 differs from the semiconductor laser 100 of Embodiment 1 in that the semiconductor laser 100 of Embodiment 2 has two grooves 19 formed to extend in the y-direction between outer sides of the ridge part 50 in the x-direction and the x-direction ends 29a and 29b. Differences between the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 1 will be mainly described.

[0032] Similar to the semiconductor laser 100 of Embodiment 1, the semiconductor laser 100 of Embodiment 2 includes the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 formed to cover both sides of the ridge facing each other in the direction perpendicular to the extending direction of the ridge 5, the p-type second cladding layer 9 formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction, the p-type contact layer 10, the semi-insulating layer 11 formed at the outer edges separated from the ridge part 50 in the x-direction, the anode electrode 12, and the cathode electrode 13.The semiconductor laser 100 of Embodiment 2 further includes two trenches 19 formed to extend in the y-direction between the outer sides of the ridge portion 50 in the x-direction and the x-direction ends 29a and 29b, and an insulating layer 15 formed on the inner surfaces of the trenches 19. The material of the insulating layer 15 is SiO2, SiN, or another material having an insulating property. Fig. 12 and Fig. 13 shows an example in which the x-direction end 29a side of the semi-insulating layer 11 on the negative side in the x-direction and the x-direction end 29b side of the semi-insulating layer 11 on the positive side in the x-direction are exposed. However, the surface of the semi-insulating layer 11 may be covered with the anode electrode 12 or a metal that is not connected to the anode electrode 12.

[0033] The trenches 19 penetrate the p-type contact layer 10, the p-type second cladding layer 9, and the n-type third buried layer 8, and the bottom portions 22 of the trenches 19 are located at the same position as the active layer surface position 44, which is a positive side of the active layer 3 in the z-direction in the second buried layer 7, or the position of the bottom portions 22 of the trenches 19 is farther from the n-type semiconductor substrate 1 than the active layer surface position 44 in the second buried layer 7. That is, the bottom portions 22 of the trenches 19 should be located between the active layer surface position 44 and the positive side of the second buried layer 7 in the z-direction. The anode electrode 12 is connected to the p-type contact layer 10 in the protruding portion 18 formed between the two trenches 19.The protruding portion 18 is formed such that it extends in the y-direction in a region extending from a dashed line 42a to a dashed line 42b in the x-direction. Since the grooves 19 correspond to mesa grooves, the protruding portion 18 can also be referred to as a mesa stripe.

[0034] Side surfaces of the trenches 19 in the x-direction on the side separated from the protruding part 18 are first trench side surfaces 46, and side surfaces of the trenches 19 in the x-direction on the sides closer to the protruding part 18 than the first trench side surfaces 46 are second trench side surfaces 47. On the side of the x-direction end 29b, the trench 19 is formed between the dashed line 42b and a dashed line 51c, and the end region 24 is formed between the dashed line 51c and the dashed line 51d. On the x-direction end 29a side, the trench 19 is formed between the dashed line 42a and the dashed line 51b, and the end region 24 is formed between the dashed line 51b and the dashed line 51a.The semi-insulating layer 11 is formed on the positive side of the p-type contact layer 10 in the z-direction from the first trench side surfaces 46 of the trenches 19 to the x-direction ends (x-direction ends 29a and 29b) opposite the protruding part 18 of the semiconductor laser 100, and is not covered with the anode electrode on the sides toward the x-direction ends of the semiconductor laser 100. That is, the semi-insulating layer 11 is formed on the positive side of the p-type contact layer 10 in the z-direction in the end region 24 on the z-direction end 29b side, and it is formed on the positive side of the p-type contact layer 10 in the z-direction in the end region 24 on the x-direction end 29b side.

[0035] Fig. 13 shows an example of the semiconductor laser device 200 in which the semiconductor laser 100 of Embodiment 2 is mounted on the heat sink 17 by junction-down mounting, while the interconnection member 14 is filled into the trenches 19, and the interconnection member 14, in a negative-side position in the z-direction, covers a part of the second buried layer 7 at the x-direction ends 29a and 29b. A protruding portion width W2, which is the x-direction width of the protruding portion 18, is larger than a ridge width W1, which is the x-direction width of the ridge portion 50.

[0036] Next, a method for manufacturing the semiconductor laser 100 of Embodiment 2 will be described with reference to the above Fig. 4 to Fig. 8 and one in Fig. 15 to Fig. 19. The ridge forming step, the burying step, and the stacking step described in the Fig. 4 to Fig. 8 are the same as those of Embodiment 1. After the stacking step shown in Fig. 8, a trench formation step is carried out, which in Fig. 15. In the semiconductor layers formed up to the semi-insulating layer 11, two trenches 19 are formed on both sides of the ridge portion 50 in the x-direction using a resist mask 32 so that the bottom portions 22 are located at a position lower than the n-type third buried layer 8 and higher than the active layer 3.More specifically, in the trench forming step, the trenches 19 are formed to penetrate the semi-insulating layer 11, the p-type contact layer 10, the p-type second cladding layer 9, and the n-type third buried layer 8 at two outer edges separated by the ridge part 50 on the positive side and the negative side in the x-direction, and the trenches 19 are formed such that the position of the bottom parts 22 in the z-direction is the same as the active layer surface position 44 of the active layer 3 in the second buried layer 7, or the bottom parts 22 are positioned on the positive side of the active layer surface position 44.

[0037] Next, the contact layer exposure step for exposing the p-type contact layer 10 by etching the semi-insulating layer 11 of the protruding part 18 formed between the two trenches 19 and an insulating layer formation step for forming the insulating layer 15 on both side surfaces in the x-direction and the bottom part 22 of each trench 19 are performed. As shown in Fig. 16, a resist mask 32 is formed such that an opening is formed in the center of the protruding part 18 in the x-direction, and the semi-insulating layer 11 of the protruding part 18 is selectively etched by hydrochloric acid. Fig. 16 shows an example in which the width of the opening of the resist mask 32 in the x-direction is smaller than that of the projecting part 18.

[0038] Next, the insulating layer 15 which has a final shape, that is, the insulating layer 15 which has the Fig. 19. After the resist mask 32 has been applied as shown in Fig. 17, the insulating layer 15 is formed on the exposed surface of the semiconductor layers and the inner surfaces of the trenches 19. Next, a resist mask 32 is formed such that it covers the trenches 19 as shown in Fig. 18 shown, and the shape of the insulating layer 15 is as shown in Fig. 19 shown by etching. Subsequently, the resist mask 32 is removed. In Fig. 18 shows an example in which the width of the resist mask 32 in the x-direction is greater than the width of the trench 19 in the x-direction. In the Fig. 19, the insulating layer forming step for forming the insulating layer 15 in the final shape by etching the insulating layer 15 and the contact layer exposing step for exposing the p-type contact layer 10 by etching the insulating layer 15 on the protruding part 18 are carried out simultaneously. In the contact layer exposing step for exposing the p-type contact layer 10, a Fig. 16 shown step and one in Fig. 19 is carried out. As the insulating layer forming step for forming the insulating layer 15 on both side surfaces of the trenches 19 in the x-direction and the bottom parts 22, the Fig. 17 to Fig. 19 steps shown.

[0039] Then, as in Fig. As shown in FIG. 12, the front electrode formation step of forming the anode electrode 12 such that the p-type contact layer 10 is covered where the insulating layer 15 of the protruding part 18 is not formed in the insulating layer formation step, and the back electrode formation step of forming the cathode electrode 13 are performed on the rear surface side of the n-type semiconductor substrate 1, that is, on the negative side in the z direction. The anode electrode 12 is patterned using a resist mask. The semiconductor laser 100 of Embodiment 2 is manufactured through the steps described above.

[0040] In the semiconductor laser device 200 of Embodiment 2, in which the semiconductor laser 100 of Embodiment 2 is mounted by junction-down mounting, heat generated in the active layer 3 is conducted from the active layer 3 to the surrounding semiconductor layers, that is, the p-type first buried layer 6, the second buried layer 7, the n-type third buried layer 8, the p-type second cladding layer 9, and the p-type contact layer 10. In the protruding part 18, the heat from the active layer 3 is dissipated from the anode electrode 12 to the heat sink 17 through the connecting member 14. In the end regions 24, the heat is conducted from the active layer 3 to the semi-insulating layer 11, and it is conducted from the semi-insulating layer 11 to the heat sink 17 via the connecting member 14.

[0041] In the semiconductor laser 100 of Embodiment 2, as in the semiconductor laser 100 of Embodiment 1, the semi-insulating layer 11 of InP covers the p-type contact layer 10 in the end regions 24 on the positive and negative sides in the x-direction on both sides of the x-direction ends 29b, 29a, and the insulating layer 15 formed on the inner surfaces of the trenches 19 is thinner than the insulating layer 28 of the semiconductor laser 110 of the comparative example shown in Fig. 10, so the thermal resistance of the heat dissipation path in the end regions 24 is lower than that of the comparative example, and the heat dissipation property can be improved in the same way as that of the semiconductor laser 100 of Embodiment 1 compared to the comparative example. Since the semi-insulating layer 11 has a semi-insulating property, it is possible to suppress leakage current to those other than the active layer 3 at the time of current injection.Since the semiconductor laser 100 of Embodiment 2 has the semi-insulating layer 11 in the end regions 24 on the positive side of the p-type contact layer 10 in the z-direction as in the semiconductor laser 100 of Embodiment 1, excellent heat dissipation can be achieved and high-temperature characteristics can be improved while suppressing the leakage current with respect to that deviating from the active layer 3, which does not contribute to the laser oscillation.

[0042] In the semiconductor laser 100 of Embodiment 2, as in the semiconductor laser 100 of Embodiment 1, the buried layer 25, which functions as a current blocking layer, is provided on both sides of the active layer 3 to improve the efficiency of current injection into the active layer 3. The buried layer 25 has a structure in which the semi-insulating second buried layer 7, doped with iron or the like, is inserted between the p-type first buried layer 6 and the n-type third buried layer 8. Since the buried layer 25 has a structure similar to that of a capacitor in which a dielectric is inserted on both sides of the x-direction ends 29a and 29b, the buried layer 25 has a parasitic capacitance. In order to achieve high-speed operation of the semiconductor laser 100, it is effective to reduce the parasitic capacitance of the buried layer 25.In the semiconductor laser device 100 of Embodiment 2, the protruding part 18 is formed to encompass both sides of the ridge part 50 in the x-direction, and the n-type third buried layer 8 of the buried layer 25 is divided by the trenches 19, whereby the area of ​​the n-type third buried layer 8 on the second buried layer 7 side can be made smaller than in the semiconductor laser 100 of Embodiment 1, and thus the area of ​​the n-type third buried layer 8 on the second buried layer 7 side can also be made smaller in the vicinity of the active layer 3. In the vicinity of the active layer 3, where the distance between the p-type first buried layer 6 and the n-type third buried layer 8 in the buried layer 25 is small, the parasitic capacitance is larger than that on the sides of the x-direction ends 29a and 29b.In the semiconductor laser 100 of Embodiment 2, since the area of ​​the n-type third buried layer 8 near the active layer 3 is smaller than that of the semiconductor laser 100 of Embodiment 1, the parasitic capacitance can be reduced more than that of the semiconductor laser 100 of Embodiment 1. That is, the semiconductor laser 100 of Embodiment 2 can achieve higher speed operation than the semiconductor laser 100 of Embodiment 1.

[0043] As described above, the semiconductor laser 100 of Embodiment 2 includes the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried so as to cover both sides of the ridge opposite to each other in the direction perpendicular to the extending direction of the ridge 5, and is a semiconductor laser mounted from the surface on the side from which the ridge 5 protrudes. The z-direction, the y-direction, and the x-direction are as described above. The ridge 5 includes the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4, which are sequentially formed from the n-type semiconductor substrate 1 side.The buried layer 25 includes the p-type first buried layer 6 which is in contact with the side surface of the ridge 5 on the positive side in the x-direction and the side surface of the ridge 5 on the negative side in the x-direction, the second buried layer 7, and the n-type third buried layer 8.The semiconductor laser 100 includes the p-type second cladding layer 9, the p-type contact layer 10 sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction in this order from the n-type semiconductor substrate 1 side, the front electrode (anode electrode 12) connected to the p-type contact layer 10, and the semi-insulating layer 11, the semi-insulating layer 11 being formed at the outer edges separated in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5. The semi-insulating layer 11 is formed on the positive side in the z-direction on sides toward the x-direction ends (x-direction ends 29a and 29b) in the semiconductor laser 100.Between the side surface of the ridge part 50 on the positive side in the x-direction and the end on the positive side in the x-direction in the semiconductor laser 100 (x-direction end 29b), and between the side surface of the ridge part 50 on the negative side in the x-direction and the end of the negative side in the x-direction in the semiconductor laser 100 (x-direction end 29a), the trenches 19 are formed to extend in the y-direction.Each of the trenches 19 penetrates the p-type contact layer 10, the p-type second cladding layer 9, and the n-type third buried layer 8, and the bottom parts 22 of the trenches 19 are located at the same position as the surface position 44 of the active layer, which is a position on the positive side of the active layer 3 in the z-direction in the second buried layer 7, or the bottom parts 22 of the trenches 19 are located farther away from the n-type semiconductor substrate 1 than the surface position 44 of the active layer in the second buried layer 7. The front side electrode (anode electrode 12) is connected to the p-type contact layer 10 in the projecting part 18 formed between the two trenches 19.The side surfaces of the trenches 19 in the x-direction on the side separated from the protruding part 18 are referred to as the first trench side surfaces 46, and the side surfaces of the trenches 19 in the x-direction on the side closer to the protruding part 18 than the first trench side surfaces 46 are referred to as the second trench side surfaces 47. The semi-insulating layer 11 is formed on the positive side of the p-type contact layer 10 in the z-direction from the first trench side surfaces 46 of the trenches 19 to the x-direction ends (x-direction ends 29a, 29b) opposite the protruding part 18 of the semiconductor laser 100. The insulating layer 15 is provided on the inner surfaces of the trenches 19.With this configuration, the semiconductor laser 100 of Embodiment 2 includes the semi-insulating layer 11 separated in the x-direction from the ridge portion 50 having the active layer 3, and is located at the outer edges on the side opposite to the n-type semiconductor substrate 1. Therefore, when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side, excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to laser oscillation.

[0044] Furthermore, the semiconductor laser production method of Embodiment 2 is a semiconductor laser production method for manufacturing the semiconductor laser 100 including the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried to cover both sides of the ridge that are opposite to each other in the direction perpendicular to the extending direction of the ridge 5. The semiconductor laser production method of Embodiment 2 includes the ridge formation step, the burying step, the stacking step, the trench formation step, the contact layer exposure step, the insulating layer formation step, and the front electrode formation step, which will be described below.In the ridge forming step, the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 are sequentially formed on the n-type semiconductor substrate 1, and then, by etching down to a position lower than the negative side of the active layer 3 in the z-direction, which is on the n-type semiconductor substrate 1 side, the ridge 5 comprising the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 and in which the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction are exposed is formed.In the burying step, the p-type first buried layer 6 is formed on the positive side surface in the x-direction and the negative side surface in the x-direction in the ridge 5, and the ridge 5 is buried by the second buried layer 7 and the n-type third buried layer 8, which are sequentially formed up to the position higher than the active layer surface position 44, which is a positive side position of the active layer 3 in the z-direction. In the stacking step, the p-type cladding layer 9, the p-type contact layer 10, and the semi-insulating layer 11 are sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction.In the trench formation step, the trenches 19 are formed so as to penetrate the semi-insulating layer 11, the p-type contact layer 10, the p-type second cladding layer 9, and the n-type third buried layer 8 at the two outer edges separated on the positive side and the negative side in the x-direction from the ridge part 50 including the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5, and the trenches 19 are formed such that the position of the bottom parts 22 in the z-direction is the same as the active layer surface position 44 of the active layer 3 in the second buried layer 7, or the bottom parts 22 are positioned on the positive side of the active layer surface position 44.In the contact layer exposure step, the semi-insulating layer 11 formed on the protruding portion 18 between the two trenches 19 is etched to expose the p-type contact layer 10. In the insulating layer formation step, the insulating layer 15 is formed on both side surfaces (the first trench side surface 46 and the second trench side surface 47) in the x-direction and the bottom part 22 of each of the trenches 19. In the front electrode formation step, the front electrode (the anode electrode 12) is formed to cover the p-type contact layer 10 where the insulating layer 15 is not formed on the protruding portion 18 in the insulating layer formation step.With this configuration, the semiconductor laser production method of Embodiment 2 can manufacture the semiconductor laser 100 including the semi-insulating layer 11 separated in the x-direction from the ridge part 50 having the active layer 3 and located at the outer edges on the positive side of the n-type semiconductor substrate 1, so that excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to the laser oscillation when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side. Embodiment 3

[0045] Fig. 20 is a diagram showing a cross-sectional structure of a semiconductor laser according to Embodiment 3, and Fig. 21 is a diagram showing a cross-sectional structure of a semiconductor laser device according to Embodiment 3. Fig. 22 to Fig. 24 are diagrams showing a method of manufacturing the semiconductor laser of Fig. 20. The semiconductor laser 100 of Embodiment 3 differs from the semiconductor laser 100 of Embodiment 2 in that the bottom portions 22 of the trenches 19 are not covered with the insulating layer 15. Differences between the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 2 will be mainly described. Fig. 20 shows an example in which the anode electrode 12 covers the insulating layer 15 on the first trench side surfaces 46 and the second trench side surfaces 47 of the trenches 19 and the bottom parts 22 of the trenches 19.

[0046] A method for manufacturing the semiconductor laser 100 of Embodiment 3 will be described with reference to the above-described Fig. 4 to Fig. 8 and Fig. 15 to Fig. 19, and one in Fig. 22 to Fig. 24. The ridge formation step, the burying step, and the stacking step in Fig. 4 to Fig. 8 are the same as those of Embodiment 1, and the steps shown in Fig. 15 to Fig. 19 are the same as those of Embodiment 2. In the semiconductor laser 100 of Embodiment 3, a trench bottom part exposure step is added, which is a step for further processing the Fig. 19. The formation step of the insulating layer of Embodiment 3 is carried out in the steps of Fig. 17 to Fig. 19 and Fig. 22 to Fig. 24. The trench bottom part exposure step is a part of the insulating layer formation step. In the contact layer exposure step of Embodiment 3, the Fig. 16 and the step shown in Fig. 19 as in Embodiment 2.

[0047] The trench bottom partial exposure step is described. As in Fig. 22, a resist mask 32 is formed on the positive side of the end regions 24 in the z-direction, on the positive side of the insulating layer 15 at the protruding part 18 in the z-direction, on end parts of the insulating layer arranged in the end regions 24 on the positive side in the z-direction, and on the positive side of the protruding part 18 in the z-direction, in the semiconductor laser 100 in the middle of the manufacturing, which in Fig. 19, that is, the intermediate manufacturing stage. Fig. 22 to 24 show an example in which four end portions of the insulating layer exist. As in Fig. 23, using the resist mask 32, the insulating layer 15 is etched at the bottom portions 22 of the trenches 19 to expose the bottom portions 22 of the trenches 19. Subsequently, as shown in Fig. 24, the resist mask 32 is removed.

[0048] Next, as in Fig. 20, the front electrode formation step of forming the anode electrode 12 such that it covers the p-type contact layer 10 where the insulating layer 15 of the protruding part 18 is not formed in the insulating layer formation step, and the back electrode formation step of forming the cathode electrode 13 are performed on the rear surface side of the n-type semiconductor substrate 1, that is, on the negative side in the z-direction. The anode electrode 12 is patterned using a resist mask, and the anode electrode 12 may extend to a region other than the p-type contact layer 10 of the protruding part 18. As described above, Fig. 20 shows an example in which the anode electrode 12 covers the insulating layer 15 on the first trench side surfaces 46 and the second trench side surfaces 47 of the trenches 19 and the bottom portions 22 of the trenches 19. The semiconductor laser 100 of Embodiment 3 is manufactured through the steps described above.

[0049] The semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 3 have the same effects as the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 2. In the Fig. In the semiconductor laser 100 shown in Figure 20, the insulating layer 15 is not present on the bottom portions 22 of the trenches 19, and the anode electrode 12, which has a high thermal conductivity, is arranged on the second buried layer 7. In the case where the anode 12 is formed of gold, for example, the thermal conductivity corresponds to 300 W / (m·K). In the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 3, heat generated from the active layer 3 is more easily dissipated from the bottom parts 22 of the trenches 19 due to the metal disposed at the bottom parts 22 of the trenches 19 as well as from the positive side of the protruding part 18 in the z-direction and the positive side of the end regions 24 in the z-direction than in the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 2, thereby improving the high-temperature characteristics.It should be noted that the bottom portions 22 of the trenches 19 do not need to be connected to the anode electrode 12, and it is possible that the metal is not disposed on the bottom portions 22 of the trenches 19. Even if the metal is not disposed on the bottom portions 22 of the trenches 19, the heat is dissipated to the heat sink 17 via the connecting element 14 filled in the trenches 19.

[0050] As described above, the semiconductor laser 100 of Embodiment 3 includes the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried so as to cover both sides of the ridge opposite to each other in the direction perpendicular to the extending direction of the ridge 5, and is a semiconductor laser mounted from the surface on the side from which the ridge 5 protrudes. The z-direction, the y-direction, and the x-direction are as described above. The ridge 5 includes the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4, which are sequentially formed from the n-type semiconductor substrate 1 side.The buried layer 25 includes the p-type first buried layer 6 which is in contact with the side surface of the ridge 5 on the positive side in the x-direction and the side surface of the ridge 5 on the negative side in the x-direction, the second buried layer 7, and the n-type third buried layer 8.The semiconductor laser 100 includes the p-type second cladding layer 9, the p-type contact layer 10 sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction in this order from the n-type semiconductor substrate 1 side, the front electrode (anode electrode 12) connected to the p-type contact layer 10, and the semi-insulating layer 11, the semi-insulating layer 11 being formed at the outer edges separated in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5. The semi-insulating layer 11 is formed on the positive side in the z-direction on sides toward the x-direction ends (x-direction ends 29a and 29b) in the semiconductor laser 100.Between the side surface of the ridge part 50 on the positive side in the x-direction and the end on the positive side in the x-direction in the semiconductor laser 100 (x-direction end 29b), and between the side surface of the ridge part 50 on the negative side in the x-direction and the end of the negative side in the x-direction in the semiconductor laser 100 (x-direction end 29a), the trenches 19 are formed to extend in the y-direction.Each of the trenches 19 penetrates the p-type contact layer 10, the p-type second cladding layer 9, and the n-type third buried layer 8, and the bottom parts 22 of the trenches 19 are located at the same positions as the active layer surface position 44, which is a position of the positive side of the active layer 3 in the z-direction in the second buried layer 7, or the position of the bottom parts 22 of the trenches 19 is farther from the n-type semiconductor substrate 1 than the active layer surface position 44 in the second buried layer 7. The front side electrode (anode electrode 12) is connected to the p-type contact layer 10 in the protruding part 18 formed between the two trenches 19.The semi-insulating layer 11 is formed on the positive side of the p-type contact layer 10 in the z-direction from the first trench side surfaces 46 of the trenches 19 to the x-direction ends (x-direction ends 29a, 29b) which are opposite to the projecting part 18 of the semiconductor laser 100. The insulating layer 15 is provided on the first trench side surfaces 46 and the second trench side surfaces 47 of the trenches 19, and the front-side electrode (the anode electrode 12) covers the insulating layer 15 on the first trench side surfaces 46 and the second trench side surfaces 47 and the bottom parts 22 of the trenches 19. With this configuration, the semiconductor laser 100 of Embodiment 3 includes the semi-insulating layer 11 separated in the x-direction from the ridge part 50 having the active layer 3, and is located at the outer edges on the side opposite to the n-type semiconductor substrate 1.Therefore, when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side, excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to the laser oscillation.

[0051] The semiconductor laser production method of Embodiment 3 is a semiconductor laser production method for manufacturing the semiconductor laser 100 including the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried to cover both sides of the ridge that are opposite to each other in the direction perpendicular to the extending direction of the ridge 5. The semiconductor laser production method of Embodiment 3 includes the ridge formation step, the burying step, the stacking step, the trench formation step, the contact layer exposure step, the insulating layer formation step, and the front electrode formation step, which will be described below.In the ridge forming step, the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 are sequentially formed on the n-type semiconductor substrate 1, and then, by etching down to a position lower than the negative side of the active layer 3 in the z-direction, which is on the n-type semiconductor substrate 1 side, the ridge 5 comprising the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 and in which the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction are exposed is formed.In the burying step, the p-type first buried layer 6 is formed on the positive side surface in the x-direction and the negative side surface in the x-direction in the ridge 5, and the ridge 5 is buried by the second buried layer 7 and the n-type third buried layer 8, which are sequentially formed up to the position higher than the active layer surface position 44, which is a positive side position of the active layer 3 in the z-direction. In the stacking step, the p-type cladding layer 9, the p-type contact layer 10, and the semi-insulating layer 11 are sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction.In the fin forming step, the trenches 19 are formed such that the semi-insulating layer 11, the p-type contact layer 10, the p-type second cladding layer 9, and the n-type third buried layer 8 penetrate at the two outer edges separated on the positive side and the negative side in the x-direction from the fin part 50 comprising the fin 5 and the p-type first buried layer 6 in contact with the two side surfaces of the fin 5, and the trenches 19 are formed such that the bottom parts 22 in the z-direction are the same as the active layer surface position 44 of the active layer 3 in the second buried layer 7, or the bottom parts 22 are positioned on the positive side of the active layer surface position 44.In the contact layer exposure step, the semi-insulating layer 11 formed on the protruding portion 18 between the two trenches 19 is etched to expose the p-type contact layer 10. In the insulating layer formation step, the insulating layer 15 is formed on both side surfaces (the first trench side surface 46 and the second trench side surface 47) in the x-direction of each of the trenches 19. In the front electrode forming step, the front electrode (the anode electrode 12) is formed so as to cover the p-type contact layer 10 on which the insulating layer 15 of the protruding part 18 is not formed in the insulating layer forming step, and to cover the insulating layer 15 on both sides (the first trench side surface 46 and the second trench side surface 47) of the trenches 19, and the bottom parts 22 of the trenches 19.With this configuration, the semiconductor laser production method of Embodiment 3 can manufacture the semiconductor laser 100 including the semi-insulating layer 11 separated in the x-direction from the ridge part 50 having the active layer 3 and located at the outer edges on the positive side of the n-type semiconductor substrate 1, so that excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to the laser oscillation when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side. Embodiment 4

[0052] Fig. 25 is a diagram showing a cross-sectional structure of a first semiconductor laser according to Embodiment 4, and Fig. 26 is a diagram showing a cross-sectional structure of a first semiconductor laser device according to Embodiment 4. Fig. 27 is a diagram showing a cross-sectional structure of a second semiconductor laser according to Embodiment 4, and Fig. 28 is a diagram showing a cross-sectional structure of a second semiconductor laser device according to Embodiment 4. Fig. 29 is a diagram showing a cross-sectional structure of a third semiconductor laser according to Embodiment 4. Fig. 30 is a diagram showing a width of the protruding part in the semiconductor laser of Embodiment 4. Fig. 31 to Fig. 34 are diagrams showing a method of manufacturing the semiconductor laser of Fig. 25. The first and third semiconductor lasers 100 of Embodiment 4 differ from the semiconductor laser 100 of Embodiment 2 in that the inner surfaces of the trenches 19 are covered not with the insulating layer 15 but with the semi-insulating layer 11. Further, the second semiconductor laser 100 of Embodiment 4 differs from the semiconductor laser 100 of Embodiment 2 in that the trenches 19 are changed to the recessed portions 21 having bottom portions 23 extending to the x-direction ends 29a and 29b, and the bottom portions 23 and the side surfaces 48 of the recessed portions in the recessed portions 21 are covered with the semi-insulating layer 11. Since the bottom parts 23 of the recessed parts 21 extend to the x-direction ends 29a and 29b in the x-direction, the bottom parts 23 of the recessed parts 21 can also be referred to as the end regions 24.Differences between the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 2 will be mainly described.

[0053] The first semiconductor laser 100 of Embodiment 4 shown in Fig. 25 and the third semiconductor laser 100 of Embodiment 4 shown in Fig. 29 are examples in which the trenches 19 are provided, and the inner surfaces of the trenches 19 and the surface of the p-type contact layer 10 in the end regions 24 are covered with the semi-insulating layer 11. The bottom parts 22 of the trenches 19 should be arranged at an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1. The third semiconductor laser 100 of Embodiment 4 shown in Fig. 29 is an example in which the bottom parts 22 of the trenches 19 are arranged at a position of the n-type semiconductor substrate 1 in the z-direction. Fig. Fig. 29 shows an example in which the bottom parts 22 of the trenches 19 are arranged closer to the rear surface side of the n-type semiconductor substrate 1 than the area in the n-type semiconductor substrate 1 formed in the ridge 5. In the first semiconductor laser 100 of Embodiment 4 shown in Fig. 25 and the semiconductor laser 100 of Embodiment 4 shown in Fig. 29, the semi-insulating layer 11 is formed directly on the inner surfaces of the trenches 19, and on the positive side of the p-type contact layer 10 in the z-direction from the first trench side surfaces 46 of the trenches 19 to the x-direction ends (x-direction ends 29a and 29b) which are opposite to the projecting part 18 of the semiconductor laser 100.

[0054] The second semiconductor laser 100 of Embodiment 4 includes the recessed portions 21 formed to extend in the y-direction between the side surface of the ridge portion 50 on the positive side in the x-direction and the positive side end in the x-direction in the semiconductor laser 100 (x-direction end 29b), and between the side surface of the ridge portion 50 on the negative side in the x-direction and the negative side end in the x-direction in the semiconductor laser 100 (x-direction end 29a). In each of the recessed portions 21, the p-type contact layer 10 is removed, and the bottom portions 23 of the recessed portions 21 are located at an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1.The semi-insulating layer 11 is formed directly on the side surface (the side surface 48 of the recessed part) and the bottom part 23 of the recessed part 21 on the positive side in the x-direction and on the side surface (the side surface 48 of the recessed part) and the bottom part 23 of the recessed part 21 on the negative side in the x-direction.

[0055] Fig. 26 shows an example of the semiconductor laser device 200 in which the first semiconductor laser 100 of Embodiment 4 is mounted on the heat sink 17 by the junction-down mounting, while the interconnection member 14 is filled in the trenches 19, and the interconnection member 14, in a position on the negative side in the z-direction, covers a part of the second buried layer 7 at the x-direction ends 29a and 29b. Fig. 28 shows an example of the semiconductor laser device 200 in which the second semiconductor laser 100 of Embodiment 4 is mounted on the heat sink 17 by the junction-down mounting, while the interconnection member 14 is filled in the recessed portions 21, and the interconnection member 14, in a position on the negative side in the z-direction, covers a part of the second buried layer 7 at the x-direction ends 29a and 29b. The protruding portion 18 formed between the two recessed portions 21 is the same as the protruding portion 18 formed between the two trenches 19. The width W2 of the protruding portion, which is the width of the protruding portions 18 in the x-direction, is larger than the ridge width W1, which is the width of the ridge portion 50 in the x-direction.

[0056] Fig. 25 and Fig. 29 shows an example in which the semi-insulating layer 11 is exposed on the inner surface of the trenches 19 and on the positive side of the end regions 24 in the z-direction. However, this is not a limitation, and the surface of the semi-insulating layer 11 need not be covered with the anode electrode 12 or a metal that is not connected to the anode electrode 12. Fig. 27 shows an example in which the semi-insulating layer 11 is exposed on the side surfaces 48 of the recessed portion and the positive side of the bottom portions 23 in the z-direction in the recessed portions 21. However, this is not a limitation, and the surface of the semi-insulating layer 11 does not need to be covered with the anode electrode 12 or a metal that is not connected to the anode electrode 12.

[0057] Next, a method for manufacturing the first or third semiconductor laser 100 of Embodiment 4 will be described with reference to the above-described Fig. 4 to Fig. 7 and one in Fig. 31 to Fig. 34 shown example. The ridge formation step and the burying step in Fig. 4 to Fig. 7 are the same as those of Embodiment 1. It should be noted that Fig. 7 shows a state before the start of the stacking step and further shows the state at the end of the burying step. After the burying step, which is shown in Fig. 7, the stacking step is carried out, which is shown in Fig. 31, in which the p-type second cladding layer 9 and the p-type contact layer 10 are successively formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type buried layer 8 in the z-direction. Subsequently, the Fig. 32 is performed. In the ridge forming step, two trenches 19 are formed on both sides of the ridge part 50 in the x-direction using a resist mask 32 in the semiconductor layer formed up to the p-type contact layer 10 so that the bottom parts 22 are located at any position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1. More specifically, in the trench forming step, the p-type contact layer 10 is etched at two outer edges separated from the ridge part 50, on the positive side and the negative side in the x-direction, and the trenches 19 are formed by the etching such that the position of the bottom parts 22 in the z-direction is any position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1.

[0058] Next, a semi-insulating layer forming step is carried out to form the semi-insulating layer 11. In the semi-insulating layer forming step, as shown in Fig. 33, a second mask 33 formed of SiO2, SiN, or the like is formed on the positive side of the protruding part 18 in the z-direction. As shown in Fig. 34, the semi-insulating layer 11 is formed in a region except for the positive side of the protruding part 18 in the z-direction using the second mask 33. The semi-insulating layer 11 is formed by selective growth. More specifically, the semi-insulating layer 11 is formed directly on the positive side of the p-type contact layer 10 in the z-direction, on the sides separated in the x-direction from the protruding part 18 formed between the two trenches 19 and located outside the trenches 19, and on the inner surfaces of the two trenches 19. Subsequently, the second mask 33 is removed using a buffered hydrofluoric acid or a hydrofluoric acid.

[0059] Subsequently, the front electrode forming step of forming the anode electrode 12 such that the p-type contact layer 10, on which the semi-insulating layer 11 of the protruding portion 18 is not formed in the insulating layer forming step, is covered, and the back electrode forming step of forming the cathode electrode 13 are performed on the rear surface side of the n-type semiconductor substrate 1, that is, on the negative side in the z direction. The anode electrode 12 is patterned using a resist mask. Through the above steps, the first or third semiconductor laser 100 of Embodiment 4 is manufactured.

[0060] Next, a method for manufacturing the second semiconductor laser 100 of Embodiment 4 will be described with reference to an example. The steps up to Fig. 31 are the same as those in the method for manufacturing the first or third semiconductor laser 100 of Embodiment 4. Next, similar to the trench formation step, a recessed portion formation step is performed. In the recessed portion formation step, in the semiconductor layers formed up to the p-type contact layer 10, the two recessed portions 21 are formed on both sides of the ridge portion 50 in the x-direction using the resist mask 32 formed on the positive side of the protruding portion 18 in the z-direction such that the bottom portions 23 are located at an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1.More specifically, in the recessed part formation step, the p-type contact layer 10 is etched at two outer edges separated from the ridge part 50 on the positive side and the negative side in the x-direction, and the recessed parts 21 are etched by etching down to the position of the bottom parts 23 in the z-direction, which is an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1.

[0061] Next, the semi-insulating layer forming step is carried out to form the semi-insulating layer 11. In the semi-insulating layer forming step, the second mask 33 is formed on the positive side of the protruding part 18 in the z-direction as shown in Fig. 33. Using the mask 33, the semi-insulating layer 11 is formed in a region deviating from the positive side of the projecting part 18 in the z-direction as shown in Fig. 34. Specifically, the semi-insulating layer 11 is formed directly on the side surface (the recessed portion side surface 48) and the bottom portion 23 of the recessed portion 21 on the positive side in the x-direction, and on the side surface (the recessed portion side surface 48) and the bottom portion 23 of the recessed portion 21 on the negative side in the x-direction. Subsequently, the second mask 33 is removed using a buffered hydrofluoric acid or hydrofluoric acid.

[0062] Next, the front electrode formation step of forming the anode electrode 12 so that it covers the p-type contact layer 10, on which the semi-insulating layer 11 of the protruding portion 18 is not formed in the insulating layer formation step, and the back electrode formation step of forming the cathode electrode 13 on the rear surface side of the n-type semiconductor substrate 1, that is, on the negative side in the z direction, are performed. The anode electrode 12 is patterned using a resist mask. The second semiconductor laser 100 of Embodiment 4 is manufactured through the steps described above.

[0063] In the semiconductor laser 100 of Embodiment 4, the area of ​​the n-type third buried layer 8 on the second buried layer 7 side can be reduced by the trenches 19 or the recessed portions 21, and the area of ​​the n-type third buried layer 8 on the second buried layer 7 side can also be reduced near the active layer 3. Therefore, the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 4 have the same effects as the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 2.In the semiconductor laser 100 of Embodiment 4, since the semi-insulating layer 11 having high thermal conductivity is used instead of the insulating layer 15, heat can be dissipated also from the inner surfaces (the first trench side surfaces 46, the second trench side surfaces 47, and the bottom parts 22) of the trenches 19 or the side surfaces of the recessed part and the bottom parts 23 of the recessed parts 21, so that the high-temperature characteristics can be improved compared with the semiconductor laser 100 of Embodiment 2.

[0064] As described above, the first or third semiconductor laser 100 of Embodiment 4 includes the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried so as to cover both sides of the ridge that are opposite to each other in the direction perpendicular to the extending direction of the ridge 5, and is a semiconductor laser mounted from the surface on the side from which the ridge 5 protrudes. The z-direction, the y-direction, and the x-direction are as described above. The ridge 5 includes the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4, which are sequentially formed from the n-type semiconductor substrate 1 side.The buried layer 25 includes the p-type first buried layer 6 which is in contact with the side surface of the ridge 5 on the positive side in the x-direction and the side surface of the ridge 5 on the negative side in the x-direction, the second buried layer 7, and the n-type third buried layer 8.The semiconductor laser 100 includes the p-type second cladding layer 9, the p-type contact layer 10 sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction in this order from the n-type semiconductor substrate 1 side, the front electrode (anode electrode 12) connected to the p-type contact layer 10, and the semi-insulating layer 11, the semi-insulating layer 11 being formed at the outer edges separated in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5. The semi-insulating layer 11 is formed on the positive side in the z-direction on the sides of the x-direction ends (x-direction ends 29a and 29b) in the semiconductor laser 100.Between the positive side surface of the ridge portion 50 in the x-direction and the positive side end in the x-direction in the semiconductor laser 100 (x-direction end 29b), and between the negative side surface of the ridge portion 50 in the x-direction and the negative side end in the x-direction in the semiconductor laser 100 (x-direction end 29a), the trenches 19 are formed to extend in the y-direction. Each of the trenches 19 penetrates the p-type contact layer 10, and the bottom portions 22 of the trenches 19 are arranged at an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1. The front side electrode (anode electrode 12) is connected to the p-type contact layer 10 in the protruding part 18 which is formed between the two trenches 19.The semi-insulating layer 11 is formed directly on the inner surfaces of the trenches 19 and on the positive side of the p-type contact layer 10 in the z-direction from the first trench side surfaces 46 of the trenches 19 to the x-direction ends (x-direction ends 29a, 29b) opposite the protruding part 18 of the semiconductor laser 100. With this configuration, the first or third semiconductor laser 100 of Embodiment 4 includes the semi-insulating layer 11 separated in the x-direction from the ridge part 50 having the active layer 3 and located at the outer edges on the side opposite the n-type semiconductor substrate 1. Therefore, when the semiconductor laser 100 is mounted starting from the front electrode (anode electrode 12) side, excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to laser oscillation.

[0065] The third semiconductor laser 100 of Embodiment 4 includes the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried to cover both sides of the ridge that are opposite to each other in the direction perpendicular to the extending direction of the ridge 5, and is a semiconductor laser mounted from the surface from which the ridge 5 protrudes. The ridge 5 includes the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4, which are sequentially formed from the n-type semiconductor substrate 1 side. The buried layer 25 includes the p-type first buried layer 6 which is in contact with the side surface of the ridge 5 on the positive side in the x-direction and the side surface of the ridge 5 on the negative side in the x-direction, the second buried layer 7, and the n-type third buried layer 8.The semiconductor laser 100 includes the p-type second cladding layer 9, the p-type contact layer 10 sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction in this order from the n-type semiconductor substrate 1 side, the front electrode (anode electrode 12) connected to the p-type contact layer 10, and the semi-insulating layer 11, the semi-insulating layer 11 being formed at the outer edges separated in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5. The semi-insulating layer 11 is formed on the positive side in the z-direction on the sides of the x-direction ends (x-direction ends 29a and 29b) in the semiconductor laser 100.The recessed parts 21 formed to extend in the y-direction are provided between the side surface of the ridge part 50 on the positive side in the x-direction and the end on the positive side in the x-direction in the semiconductor laser 100 (x-direction end 29b) and between the side surface of the ridge part 50 on the negative side in the x-direction and the end on the negative side in the x-direction in the semiconductor laser 100 (x-direction end 29a). In each of the recessed parts 21, the p-type contact layer 10 is removed, and the bottom parts 23 of the recessed parts 21 are located at an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1. The front side electrode (anode electrode 12) is formed with the p-type contact layer 10 in the projecting part 18 between two recessed parts 21.The semi-insulating layer 11 is formed directly on the side surface (side surface 48 of the recessed portion) and the bottom portion 23 in the recessed portion 21 on the positive side in the x-direction, and on the side surface (side surface 48 of the recessed portion) and the bottom portion 23 in the recessed portion on the negative side in the x-direction. With this configuration, the third semiconductor laser 100 of Embodiment 4 has the semi-insulating layer 11 separated in the x-direction from the ridge portion 50 containing the active layer 3, and is located at the outer edges of the side opposite the n-type semiconductor substrate 1. Therefore, when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side, excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to laser oscillation.

[0066] The semiconductor laser production method of Embodiment 4 is a semiconductor laser production method for manufacturing the semiconductor laser 100 including the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried to cover both sides of the ridge that are opposite to each other in the direction perpendicular to the extending direction of the ridge 5. The semiconductor laser production method of Embodiment 4 includes the ridge formation step, the burying step, the stacking step, the trench formation step, the semi-insulating layer formation step, and the front-side electrode formation step, which are described below.In the ridge forming step, the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 are sequentially formed on the n-type semiconductor substrate 1, and then, by etching down to a position lower than the negative side of the active layer 3 in the z-direction, which is on the n-type semiconductor substrate 1 side, the ridge 5 comprising the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 and in which the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction are exposed is formed.In the burying step, the p-type first buried layer 6 is formed on the positive side surface in the x-direction and the negative side surface in the x-direction in the ridge 5, and the ridge 5 is buried by the second buried layer 7 and the n-type third buried layer 8, which are sequentially formed up to the position higher than the active layer surface position 44, which is a positive side position of the active layer 3 in the z-direction. In the stacking step, the p-type second cladding layer 9 and the p-type contact layer 10 are sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction.In the ridge forming step, the p-type contact layer 10 is etched at two outer edges separated on the positive side and the negative side in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5, and the trenches 19 are formed by the etching such that the position of the bottom parts 22 in the z-direction is an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1. In the semi-insulating layer forming step, the semi-insulating layer 11 is formed directly on the positive side of the p-type contact layer 10 in the z-direction on the sides separated in the x-direction from the protruding part 18 formed between two trenches 19 and located outside the trenches 19, and on the inner surfaces of the two trenches 19.In the front electrode formation step, the front electrode (anode electrode 12) is formed so as to cover the p-type contact layer 10, on which the semi-insulating layer 11 of the protruding part 18 is not formed in the semi-insulating layer formation step. With this configuration, the semiconductor laser production method of Embodiment 4 can manufacture the semiconductor laser 100 including the semi-insulating layer 11 separated in the x-direction from the ridge part 50 having the active layer 3 and located at the outer edges on the positive side of the n-type semiconductor substrate 1, so that excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to laser oscillation when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side.

[0067] The other semiconductor laser production method of Embodiment 4 is a semiconductor laser production method for manufacturing the semiconductor laser 100 having the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried to cover both sides of the ridge opposite each other in the direction perpendicular to the extending direction of the ridge 5. The other semiconductor laser production method of Embodiment 4 includes the ridge formation step, the burying step, the stacking step, the recessed part formation step, the semi-insulating layer formation step, and the front electrode formation step, which will be described below.In the ridge forming step, the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 are sequentially formed on the n-type semiconductor substrate 1, and then, by etching down to a position lower than the negative side of the active layer 3 in the z-direction, which is on the n-type semiconductor substrate 1 side, the ridge 5 comprising the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 and in which the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction are exposed is formed.In the burying step, the p-type first buried layer 6 is formed on the positive side surface in the x-direction and the negative side surface in the x-direction in the ridge 5, and the ridge 5 is buried by the second buried layer 7 and the n-type third buried layer 8, which are sequentially formed up to the position higher than the active layer surface position 44, which is a positive side position of the active layer 3 in the z-direction. In the stacking step, the p-type second cladding layer 9 and the p-type contact layer 10 are sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction.In the recessed part formation step, the p-type contact layer 10 is etched at two outer edges separated on the positive side and the negative side in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5, and the recessed parts 21 are formed by etching down to the position of the bottom parts 23 in the z-direction, which may be any position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1.In the semi-insulating layer formation step, the semi-insulating layer 11 is directly formed on the side surface (the recessed portion side surface 48) and the bottom portion 23 of the recessed portion 21 on the positive side in the x-direction, and on the side surface (the recessed portion side surface 48) and the bottom portion 23 of the recessed portion 21 on the negative side in the x-direction. In the front-side electrode formation step, the front-side electrode (anode electrode 12) is formed so as to cover the p-type contact layer 10 on which the semi-insulating layer 11 of the protruding portion 18 is not formed in the semi-insulating layer formation step in the protruding portion 18 formed between the two recessed portions 21.With this configuration, the other semiconductor laser production method of Embodiment 4 can manufacture the semiconductor laser 100 having the semi-insulating layer 11 separated in the x-direction from the ridge part 50 having the active layer 3 and located at the outer edges on the side opposite to the n-type semiconductor substrate 1, so that excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to the laser oscillation when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side. Embodiment 5

[0068] Fig. 35 is a diagram showing a cross-sectional structure of a first semiconductor laser according to Embodiment 5, and Fig. 36 is a diagram showing a cross-sectional structure of a first semiconductor laser device according to Embodiment 5. Fig. 37 is a diagram showing a cross-sectional structure of a second semiconductor laser device according to Embodiment 5, and Fig. 38 is a diagram showing a cross-sectional structure of a second semiconductor laser device according to Embodiment 5. Fig. 39 is a diagram showing a cross-sectional structure of a third semiconductor laser according to Embodiment 5. Fig. 40 is a diagram showing a method of manufacturing the semiconductor laser of Fig. 35 shows. The semiconductor laser 100 of Embodiment 5 differs from the semiconductor laser 100 of Embodiment 4 in that the semi-insulating layer 11 is formed on both side surfaces of the protruding part 18 in the x-direction and from both of the side surfaces to the x-direction ends 29a and 29b via an n-type diffusion blocking layer 16. Differences between the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 4 will be mainly described.

[0069] The first semiconductor laser 100 of Embodiment 5, which is shown in Fig. 35 and the third semiconductor laser 100 of Embodiment 5 shown in Fig. 39 are examples in which the trenches 19 are provided, and the inner surfaces of the trenches 19 and the surfaces of the p-type contact layer 10 in the end regions 24 are covered with the semi-insulating layer 11 via the n-type diffusion blocking layer 16. The bottom parts 22 of the trenches 19 should be arranged at an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1. The third semiconductor laser 100 of Embodiment 5 shown in Fig. 39 is an example in which the bottom parts 22 of the trenches 19 are arranged at a position of the n-type semiconductor substrate 1 in the z-direction. Fig. Fig. 39 shows an example in which the bottom parts 22 of the trenches 19 are arranged closer to the rear surface side of the n-type semiconductor substrate 1 than the area in the n-type semiconductor substrate 1 formed in the ridge 5. In the first semiconductor laser 100 of Embodiment 5, which is shown in Fig. 35, and the semiconductor laser 100 of Embodiment 5, which is shown in Fig. 39, the semi-insulating layer 11 is formed via the n-type diffusion blocking layer 16 on the positive side of the p-type contact layer 10 in the z-direction on the inner surfaces of the trenches 19 and from the first trench side surfaces 46 of the trenches 19 to the x-direction ends (x-direction ends 29a and 29b) opposite the projecting part 18 of the semiconductor laser 100.

[0070] The second semiconductor laser 100 of Embodiment 5 shown in Fig. 37 has two recessed portions 21, and in each of the recessed portions 21, the p-type contact layer 10 is removed, and the bottom portions 23 of the recessed portions 21 are arranged at an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1. The semi-insulating layer 11 is formed on the side surface (the recessed portion side surface 48) and the bottom portion 23 of the recessed portion 21 on the positive side in the x-direction and on the side surface (the recessed portion side surface 48) and the bottom portion 23 of the recessed portion 21 on the negative side in the x-direction via the n-type diffusion blocking layer 16.

[0071] Next, a method for manufacturing the first or third semiconductor laser 100 of Embodiment 5 will be described using the above-described Fig. 4 to Fig. 7 and Fig. 31 to Fig. 33, and an example which is in Fig. 40. The method for manufacturing the first or third semiconductor laser 100 of Embodiment 5 differs from the method for manufacturing the first or third semiconductor laser 100 of Embodiment 4 with respect to the formation step of the semi-insulating layer. The ridge formation step and the burying step in Fig. 4 to Fig. 7 are the same as those of Embodiment 1. It should be noted that Fig. 7 shows a state before the start of the stacking step and further shows the state at the end of the burying step. The stacking step, the trench formation step, and the formation step of the second mask of the semi-insulating layer formation step, which is shown in Fig. 31 to Fig. 33 are the same as those of Embodiment 4.

[0072] The formation step for the semi-insulating layer is described. As in Fig. 40, the n-type diffusion blocking layer 16 and the semi-insulating layer 11 are sequentially formed in a region deviating from the positive side of the protruding part 18 in the z-direction using the second mask 33. The n-type diffusion blocking layer 16 and the semi-insulating layer 11 are formed by selective growth. More specifically, the semi-insulating layer 11 is formed on the positive side of the p-type contact layer 10 in the z-direction, on the sides separated in the x-direction from the protruding part 18 formed between the two trenches 19 and located outside the trenches 19, and on the inner surfaces of the two trenches 19 via the n-type diffusion blocking layer 16. Subsequently, the second mask 33 is removed using a buffered hydrofluoric acid or a hydrofluoric acid.

[0073] Next, the front electrode formation step of forming the anode electrode 12 so that it covers the p-type contact layer 10, on which the semi-insulating layer 11 of the protruding portion 18 is not formed in the insulating layer formation step, and the back electrode formation step of forming the cathode electrode 13 on the rear surface side of the n-type semiconductor substrate 1, that is, on the negative side in the z direction, are performed. The anode electrode 12 is patterned using a resist mask. The first or third semiconductor laser 100 of Embodiment 5 is manufactured through the steps described above.

[0074] Next, a method for manufacturing the second semiconductor laser 100 of Embodiment 5 will be described using an example. The steps up to Fig. 31 are the same as those in the method for manufacturing the second semiconductor laser 100 of Embodiment 4. Subsequently, as in the case of the second semiconductor laser 100 of Embodiment 4, the recessed part forming step is carried out to form the recessed parts 21. Next, the semi-insulating layer forming step is carried out to form the semi-insulating layer 11. In the semi-insulating layer forming step, the second mask 33 is formed on the positive side of the protruding part 18 in the z-direction as shown in Fig. 33. Using the second mask 33, the n-type diffusion blocking layer 16 and the semi-insulating layer 11 are successively formed in the region deviating from the positive side of the protruding part 18 in the z-direction as shown in Fig.40 is formed. The n-type diffusion blocking layer 16 and the semi-insulating layer 11 are formed by selective growth. More specifically, the semi-insulating layer 11 is formed on the side surface (the recessed portion side surface 48) and the bottom portion 23 of the recessed portion 21 on the positive side in the x-direction, and on the side surface (the recessed portion side surface 48) and the bottom portion 23 of the recessed portion 21 on the negative side in the x-direction over the n-type diffusion blocking layer 16. Subsequently, the second mask 33 is removed using a buffered hydrofluoric acid or a hydrofluoric acid. Next, the insulating layer formation step is performed as in the first or third semiconductor laser 100 of Embodiment 5 to form the anode electrode 12 and the cathode electrode 13.

[0075] In the semiconductor laser 100 of Embodiment 5, the area of ​​the n-type third buried layer 8 on the second buried layer 7 side can be reduced by the trenches 19 or the recessed portions 21, and the area of ​​the n-type third buried layer 8 on the second buried layer 7 side can also be reduced near the active layer 3. Therefore, the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 5 have the same effects as the semiconductor laser 100 and the semiconductor laser device 200 of Embodiment 4.

[0076] In the semiconductor laser 100 of Embodiment 4, the semi-insulating layer 11 covers all but the positive side of the protruding part 18 in the z-direction. However, if zinc or the like doped in the p-type second cladding layer 9 and the p-type contact layer 10 diffuses into the semi-insulating layer 11 doped with iron or the like, the semi-insulating property of the semi-insulating layer 11 is weakened, and the effect of blocking the leakage current by the semi-insulating layer 11 may be reduced.Therefore, in the semiconductor laser 100 of Embodiment 5, the n-type diffusion blocking layer 16 is formed, and the semi-insulating layer 11 is formed on the surface of the n-type diffusion blocking layer 16, so that zinc or the like doped in the p-type second cladding layer 9 and the p-type contact layer 10 can be prevented from diffusing into the buried layer 25. As a result, the semiconductor laser 100 of Embodiment 5 can reduce the parasitic capacitance of the buried layer 25 while preventing the diffusion of zinc or the like, which causes the weakening of the semi-insulating property of the semi-insulating layer 11, thereby effectively injecting current into the active layer 3 and improving heat dissipation of the heat generated in the active layer 3 compared to the semiconductor laser 100 of Embodiment 4.

[0077] As described above, the first or third semiconductor laser 100 of Embodiment 5 includes the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried so as to cover both sides of the ridge that are opposite to each other in the direction perpendicular to the extending direction of the ridge 5, and is a semiconductor laser mounted from the surface on the side from which the ridge 5 protrudes. The z-direction, the y-direction, and the x-direction are as described above. The ridge 5 includes the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4, which are sequentially formed from the n-type semiconductor substrate 1 side.The buried layer 25 includes the p-type first buried layer 6 which is in contact with the side surface of the ridge 5 on the positive side in the x-direction and the side surface of the ridge 5 on the negative side in the x-direction, the second buried layer 7, and the n-type third buried layer 8.The semiconductor laser 100 includes the p-type second cladding layer 9, the p-type contact layer 10 sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction in this order from the n-type semiconductor substrate 1 side, the front electrode (anode electrode 12) connected to the p-type contact layer 10, and the semi-insulating layer 11, the semi-insulating layer 11 being formed at the outer edges separated in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5. The semi-insulating layer 11 is formed on the positive side in the z-direction on the sides of the x-direction ends (x-direction ends 29a and 29b) in the semiconductor laser 100.Between the positive side surface of the ridge portion 50 in the x-direction and the positive side end in the x-direction in the semiconductor laser 100 (x-direction end 29b), and between the negative side surface of the ridge portion 50 in the x-direction and the negative side end in the x-direction in the semiconductor laser 100 (x-direction end 29a), the trenches 19 are formed to extend in the y-direction. Each of the trenches 19 penetrates the p-type contact layer 10, and the bottom portions 22 of the trenches 19 are arranged at an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1. The front side electrode (anode electrode 12) is connected to the p-type contact layer 10 in the protruding part 18 which is formed between the two trenches 19.The semi-insulating layer 11 is formed on the inner surfaces of the trenches 19 and on the positive side of the p-type contact layer 10 in the z-direction from the first trench side surfaces 46 of the trenches 19 to the x-direction ends (x-direction ends 29a, 29b) opposite the protruding part 18 of the semiconductor laser 100 via the n-type diffusion blocking layer. With this configuration, the first or third semiconductor laser 100 of Embodiment 5 includes the semi-insulating layer 11 separated in the x-direction from the ridge part 50 having the active layer 3 and located at the outer edges on the side opposite the n-type semiconductor substrate 1. Therefore, when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side, excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to the laser oscillation.

[0078] The third semiconductor laser 100 of Embodiment 5 includes the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried so as to cover both sides of the ridge facing each other in the direction perpendicular to the extending direction of the ridge 5, and is a semiconductor laser mounted from the surface where the ridge 5 protrudes. The ridge 5 includes the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4, which are sequentially formed from the n-type semiconductor substrate 1 side. The buried layer 25 includes the p-type first buried layer 6 which is in contact with the side surface of the ridge 5 on the positive side in the x-direction and the side surface of the ridge 5 on the negative side in the x-direction, the second buried layer 7, and the n-type third buried layer 8.The semiconductor laser 100 includes the p-type second cladding layer 9, the p-type contact layer 10 sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction in this order from the n-type semiconductor substrate 1 side, the front electrode (anode electrode 12) connected to the p-type contact layer 10, and the semi-insulating layer 11, the semi-insulating layer 11 being formed at the outer edges separated in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5. The semi-insulating layer 11 is formed on the positive side in the z-direction on the sides of the x-direction ends (x-direction ends 29a and 29b) in the semiconductor laser 100.The recessed parts 21 formed to extend in the y-direction are provided between the side surface of the ridge part 50 on the positive side in the x-direction and the end on the positive side in the x-direction in the semiconductor laser 100 (x-direction end 29b) and between the side surface of the ridge part 50 on the negative side in the x-direction and the end on the negative side in the x-direction in the semiconductor laser 100 (x-direction end 29a). In each of the recessed parts 21, the p-type contact layer 10 is removed, and the bottom parts 23 of the recessed parts 21 are located at an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1. The front electrode (anode electrode 12) is formed with the p-type contact layer 10 in the projecting part 18 between two recessed parts 21.The semi-insulating layer 11 is formed on the side surface (recessed portion side surface 48) and the bottom portion 23 in the recessed portion 21 on the positive side in the x-direction, and on the side surface (recessed portion side surface 48) and the bottom portion 23 in the recessed portion on the negative side in the x-direction, via the n-type diffusion blocking layer 16. With this configuration, the third semiconductor laser 100 of Embodiment 5 has the semi-insulating layer 11 separated in the x-direction from the ridge portion 50 having the active layer 3, and is located at the outer edges of the side opposite to the n-type semiconductor substrate 1. Therefore, when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side, excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to the laser oscillation.

[0079] The semiconductor laser production method of Embodiment 5 is a semiconductor laser production method for manufacturing the semiconductor laser 100, which includes the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried so as to cover both sides of the ridge that are opposite to each other in the direction perpendicular to the extending direction of the ridge 5. The semiconductor laser production method of Embodiment 5 includes the ridge formation step, the burying step, the stacking step, the trench formation step, the semi-insulating layer formation step, and the front-side electrode formation step, which are described below.In the ridge forming step, the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 are sequentially formed on the n-type semiconductor substrate 1, and then, by etching down to a position lower than the negative side of the active layer 3 in the z-direction, which is on the n-type semiconductor substrate 1 side, the ridge 5 comprising the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 and in which the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction are exposed is formed.In the burying step, the p-type first buried layer 6 is formed on the positive side surface in the x-direction and the negative side surface in the x-direction in the ridge 5, and the ridge 5 is buried by the second buried layer 7 and the n-type third buried layer 8, which are sequentially formed up to the position higher than the surface position 44 of the active layer, that is, a position on a positive side of the active layer in the z-direction. In the stacking step, the p-type second cladding layer 9 and the p-type contact layer 10 are sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction.In the ridge forming step, the p-type contact layer 10 is etched at two outer edges separated on the positive side and the negative side in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with the two side surfaces of the ridge 5, and the trenches 19 are formed by the etching such that the position of the bottom parts 22 in the z-direction is an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1.In the semi-insulating layer forming step, the semi-insulating layer 11 is formed on the positive side of the p-type contact layer 10 in the z-direction on the sides separated in the x-direction from the protruding part 18 formed between the two trenches 19 and located outside the trenches 19, and on inner surfaces of the two trenches 19 via the n-type diffusion blocking layer 16. In the front-side electrode forming step, the front-side electrode (anode electrode 12) is formed so as to cover the p-type contact layer 10 on which the semi-insulating layer 11 of the protruding part 18 is not formed in the semi-insulating layer forming step.With this configuration, the semiconductor laser production method of Embodiment 5 can manufacture the semiconductor laser 100 including the semi-insulating layer 11 separated in the x-direction from the ridge part 50 having the active layer 3 and located at the outer edges on the positive side of the n-type semiconductor substrate 1, so that excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to the laser oscillation when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side.

[0080] The other semiconductor laser production method of Embodiment 5 is a semiconductor laser production method for manufacturing the semiconductor laser 100 having the ridge 5 formed on the n-type semiconductor substrate 1 and the buried layer 25 buried to cover both sides of the ridge opposite each other in the direction perpendicular to the extending direction of the ridge 5. The other semiconductor laser production method of Embodiment 5 includes the ridge formation step, the burying step, the stacking step, the recessed part formation step, the semi-insulating layer formation step, and the front electrode formation step, which will be described below.In the ridge forming step, the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 are sequentially formed on the n-type semiconductor substrate 1, and then, by etching down to a position lower than the negative side of the active layer 3 in the z-direction, which is on the n-type semiconductor substrate 1 side, the ridge 5 comprising the n-type cladding layer 2, the active layer 3, and the p-type first cladding layer 4 and in which the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction are exposed is formed.In the burying step, the p-type first buried layer 6 is formed on the positive side surface in the x-direction and the negative side surface in the x-direction in the ridge 5, and the ridge 5 is buried by the second buried layer 7 and the n-type third buried layer 8, which are sequentially formed up to the position higher than the surface position 44 of the active layer, that is, a position on a positive side of the active layer in the z-direction. In the stacking step, the p-type second cladding layer 9 and the p-type contact layer 10 are sequentially formed on the positive side of the ridge 5 in the z-direction and on the positive side of the n-type third buried layer 8 in the z-direction.In the recessed part formation step, the p-type contact layer 10 is etched at two outer edges separated on the positive side and the negative side in the x-direction from the ridge part 50 having the ridge 5 and the p-type first buried layer 6 in contact with two side surfaces of the ridge 5, and the recessed parts 21 are formed by etching down to the position of the bottom parts 23 in the z-direction, which is an arbitrary position in the z-direction between the p-type second cladding layer 9 and the inside of the n-type semiconductor substrate 1.In the protruding layer forming step, the semi-insulating layer is formed on the side surface (the recessed part side surface 48) and the bottom part 23 of the recessed part 21 on the positive side in the x-direction, and on the side surface (the recessed part side surface 48) and the bottom part 23 of the recessed part 21 on the negative side in the x-direction via the n-type diffusion blocking layer 16. In the front electrode forming step, the front electrode (anode electrode 12) is formed so as to cover the p-type contact layer 10 on which the semi-insulating layer 11 of the protruding part 18 is not formed in the semi-insulating layer forming step in the protruding part 18 formed between the two recessed parts 21.With this configuration, the other semiconductor laser production method of Embodiment 5 can manufacture the semiconductor laser 100 having the semi-insulating layer 11 separated in the x-direction from the ridge part 50 having the active layer 3 and located at the outer edges on the side opposite to the n-type semiconductor substrate 1, so that excellent heat dissipation can be achieved while suppressing the leakage current that does not contribute to the laser oscillation when the semiconductor laser 100 is mounted from the front electrode (anode electrode 12) side.

[0081] It should be noted that although numerous exemplary embodiments and examples are described in the present application, various features, aspects, and functions described in one or more embodiments do not belong to a particular embodiment, and they may be applied to any embodiment alone or in their various combinations. Accordingly, countless variations are contemplated within the scope of the technique disclosed herein, which are not illustrated. For example, the case where at least one component is modified, added, or omitted, and a case where at least one component is extracted and combined with another component in another embodiment are included. List of reference symbols

[0082] 1: n-type semiconductor substrate, 2: n-type cladding layer; 3: active layer, 4: p-type first cladding layer, 5: fin, 6: p-type first buried layer, 7: second buried layer, 8: n-type third buried layer, 9: p-type second cladding layer, 10: p-type contact layer, 11: semi-insulating layer, 12: anode electrode (front side electrode), 14: connecting element, 15: insulating layer, 16: n-type diffusion blocking layer, 17: heat sink, 18: protruding part, 19: trench, 21: recessed part, 22: bottom part, 23: bottom part, 25: buried layer, 29a, 29b: x-direction end, 44: surface position of the active layer, 46: first trench side surface, 47: second trench side surface, 48: side surface of the recessed part, 50: ridge part, 100: semiconductor laser, 200: semiconductor laser device

Claims

[1] Semiconductor laser comprising: • a fin formed on an n-type semiconductor substrate; and • a buried layer which is buried so as to cover both sides which are opposite to each other in a direction perpendicular to an extension direction of the ridge, wherein • the semiconductor laser is mounted on a surface on one side from which the ridge protrudes, • a z-direction is a direction in which the ridge protrudes from a side of a front surface of the n-type semiconductor substrate, • a y-direction is an extension direction in which the ridge extends, • an x-direction is a direction perpendicular to the z-direction and the y-direction, • the ridge has an n-type cladding layer, an active layer, and a p-type first cladding layer, which are formed sequentially from one side of the n-type semiconductor substrate, • the buried layer comprises a p-type first buried layer in contact with a side surface of the ridge on a negative side in the x-direction and a side surface of the ridge on a positive side in the x-direction, a second buried layer, and an n-type third buried layer, • a p-type second cladding layer and a p-type contact layer formed sequentially from the n-type semiconductor substrate side on the positive side of the ridge in the z-direction and on the positive side of the n-type third buried layer in the z-direction, a front electrode connected to the p-type contact layer, and a semi-insulating layer formed in outer edges separated in the x-direction from a ridge part having the ridge and the p-type first buried layer in contact with the two side surfaces of the ridge, and • the semi-insulating layer or the front electrode on the positive side in the z-direction is formed on sides toward x-direction ends in the semiconductor laser. [2] A semiconductor laser according to claim 1, wherein • between the side surface of the ridge part on the positive side in the x-direction and one end on the positive side in the x-direction in the semiconductor laser and between the side surface of the ridge part on the negative side in the x-direction and one end on the negative side in the x-direction in the semiconductor laser, respective trenches are provided so as to extend in the y-direction, • each of the trenches penetrates the p-type contact layer, the p-type second cladding layer, and the n-type third buried layer, and wherein bottom parts of the trenches are located at the same position as a surface position of an active layer, which is a position of a positive side of the active layer in the z-direction in the second buried layer, or wherein the bottom parts of the trenches are located farther away from the n-type semiconductor substrate than the surface position of the active layer in the second buried layer, • the front side electrode with the p-type contact layer is formed in a protruding part between the two trenches, • first trench side surfaces are side surfaces in the x-direction in the trenches on sides which are separated from the protruding part and second trench side surfaces are side surfaces in the x-direction in the trenches on sides which are closer to the protruding part than the first trench side surfaces in the trenches, and • the semi-insulating layer is formed on the positive side of the p-type contact layer in the z-direction from the first trench side surfaces of the trenches to ends in the x-direction opposite the projecting part of the semiconductor laser. [3] A semiconductor laser according to claim 2, wherein an insulating layer is provided in inner surfaces of the trenches. [4] A semiconductor laser according to claim 2, wherein • an insulating layer is provided on the first trench side surfaces and the second trench side surfaces in the trenches, and • the front side electrode covers the insulating layer on the first trench side surfaces, the second trench side surfaces, and the bottom parts of the trenches. [5] A semiconductor laser according to claim 1, wherein • between the side surface of the ridge part on the positive side in the x-direction and one end on the positive side in the x-direction in the semiconductor laser and between the side surface of the ridge part on the negative side in the x-direction and one end on the negative side in the x-direction in the semiconductor laser, respective trenches are provided so as to extend in the y-direction, • each of the trenches penetrates the p-type contact layer, and bottom parts of the trenches are arranged at an arbitrary position in the z-direction between the p-type second cladding layer and an inner side of the n-type semiconductor substrate, • the front side electrode with the p-type contact layer is formed in a protruding part between the two trenches, • first trench side surfaces are side surfaces in the x-direction in the trenches on sides which are separated from the protruding part and second trench side surfaces are side surfaces in the x-direction in the trenches on sides which are closer to the protruding part than the first trench side surfaces in the trenches, and • the semi-insulating layer is formed directly or via an n-type diffusion blocking layer on inner surfaces of the trenches and on the positive side of the p-type contact layer in the z-direction from the first trench side surfaces of the trenches to ends in the x-direction opposite the projecting part of the semiconductor laser. [6] A semiconductor laser according to claim 1, wherein • between the side surface of the ridge part on the positive side in the x-direction and one end on the positive side in the x-direction in the semiconductor laser and between the side surface of the ridge part on the negative side in the x-direction and one end on the negative side in the x-direction in the semiconductor laser, respective recessed parts are provided so as to extend in the y-direction, • in each of the recessed parts, the p-type contact layer is removed, and bottom parts of the recessed parts are arranged at an arbitrary position in the z-direction between the p-type second cladding layer and an inner side of the n-type semiconductor substrate, • the front electrode is formed with the p-type contact layer in a projecting part between the two recessed parts, and • the semi-insulating layer is formed directly or via an n-type diffusion blocking layer on a side surface and the bottom part of the recessed part on the positive side in the x-direction and on a side surface and the bottom part of the recessed part on the negative side in the x-direction. [7] A semiconductor laser according to claim 1, wherein, on the positive side in the z-direction on the sides toward the x-direction ends in the semiconductor laser, the front side electrode covers the positive side of the semi-insulating layer in the z-direction. [8] A semiconductor laser according to any one of claims 2 to 6, wherein the semi-insulating layer is not covered with the front electrode on the sides toward the x-direction ends in the semiconductor laser. [9] Semiconductor laser device comprising: • the semiconductor laser according to one of claims 1 to 8; and • a heat sink, where • a positive side in the z-direction, on which the front electrode of the semiconductor laser is formed, is connected to the heat sink by means of a connecting element. [10] A semiconductor laser production method for producing a semiconductor laser having a ridge formed on an n-type semiconductor substrate and a buried layer buried to cover both sides opposite to each other in a direction perpendicular to an extending direction of the ridge, the method comprising: • a ridge forming step in which an n-type cladding layer, an active layer, and a p-type first cladding layer are sequentially formed on the n-type semiconductor substrate, and the ridge including the n-type cladding layer, the active layer, and the p-type first cladding layer and having a side surface on a positive side in an x-direction and a side surface on a negative side in the x-direction exposed is formed by etching down to a position lower than the negative side of the active layer in a z-direction, which is one side of the n-type semiconductor substrate; • a burying step in which a p-type first buried layer is formed on the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction in the ridge, and the ridge is replaced by a second buried layer and an n-type third buried layer which are successively formed up to a position higher than a surface position of the active layer, which is a position on the positive side of the active layer in the z-direction; • a stacking step in which a p-type second cladding layer, a p-type contact layer and a semi-insulating layer are sequentially formed on the positive side of the ridge in the z-direction and on the positive side of the n-type buried layer in the z-direction; • a contact layer exposure step in which the p-type contact layer is exposed by etching the semi-insulating layer in a region in the x-direction having a ridge part including the ridge and the p-type first buried layer in contact with the two side surfaces of the ridge; and • a front electrode forming step in which a front electrode is formed on the exposed p-type contact layer and the semi-insulating layer on the positive side in the z-direction and the side surfaces thereof on one side of the ridge part, wherein • the z-direction is a direction in which the ridge protrudes from one side of the front surface of the n-type semiconductor substrate, • the y-direction is an extension direction in which the ridge extends, and • the x-direction is a direction perpendicular to the z-direction and the y-direction. [11] A semiconductor laser production method for producing a semiconductor laser having a ridge formed on an n-type semiconductor substrate and a buried layer buried to cover both sides opposite to each other in a direction perpendicular to an extending direction of the ridge, the method comprising: • a ridge forming step in which an n-type cladding layer, an active layer, and a p-type first cladding layer are sequentially formed on the n-type semiconductor substrate, and the ridge including the n-type cladding layer, the active layer, and the p-type first cladding layer and having a side surface on a positive side in an x-direction and a side surface on a negative side in the x-direction exposed is formed by etching down to a position lower than the negative side of the active layer in a z-direction, which is one side of the n-type semiconductor substrate; • a burying step in which a p-type first buried layer is formed on the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction in the ridge, and the ridge is replaced by a second buried layer and an n-type third buried layer which are successively formed up to a position higher than a surface position of the active layer, which is a position on the positive side of the active layer in the z-direction; • a stacking step in which a p-type second cladding layer, a p-type contact layer and a semi-insulating layer are sequentially formed on the positive side of the ridge in the z-direction and on the positive side of the n-type third buried layer in the z-direction; • a trench forming step in which trenches are formed so as to penetrate the semi-insulating layer, the p-type contact layer, the p-type second cladding layer, and the n-type third buried layer at two outer edges separated on the positive side and the negative side in the x-direction by a ridge part having the ridge and the p-type first buried layer in contact with the two side surfaces of the ridge, and the trenches are formed such that a position of bottom parts thereof in the z-direction is the same as the surface position of the active layer of the active layer in the second buried layer or the bottom parts are positioned on the positive side of the surface position of the active layer; • a contact layer exposing step in which the semi-insulating layer formed on a projecting part between the two trenches is etched to expose the p-type contact layer; • an insulating layer forming step in which an insulating layer is formed on both side surfaces in the x-direction in each of the trenches; and • a front electrode forming step in which a front electrode is formed so as to cover the p-type contact layer where the insulating layer is not formed on the projecting part in the insulating layer forming step, wherein • the z-direction is a direction in which the ridge protrudes from one side of the front surface of the n-type semiconductor substrate, • the y-direction is an extension direction in which the ridge extends, and • the x-direction is a direction perpendicular to the z-direction and the y-direction. [12] The semiconductor laser production method according to claim 11, wherein the insulating layer is formed on the bottom part of each of the trenches. [13] The semiconductor laser production method according to claim 11, wherein the front electrode covers the insulating layer on both of the side surfaces of the trenches and the bottom parts of the trenches. [14] A semiconductor laser production method for producing a semiconductor laser having a ridge formed on an n-type semiconductor substrate and a buried layer buried to cover both sides opposite to each other in a direction perpendicular to an extending direction of the ridge, the method comprising: • a ridge forming step in which an n-type cladding layer, an active layer, and a p-type first cladding layer are sequentially formed on the n-type semiconductor substrate, and the ridge including the n-type cladding layer, the active layer, and the p-type first cladding layer and having a side surface on a positive side in an x-direction and a side surface on a negative side in the x-direction exposed is formed by etching down to a position lower than the negative side of the active layer in a z-direction, which is one side of the n-type semiconductor substrate; • a burying step in which a p-type first buried layer is formed on the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction in the ridge, and the ridge is replaced by a second buried layer and an n-type third buried layer which are successively formed up to a position higher than a surface position of the active layer, which is a position on the positive side of the active layer in the z-direction; • a stacking step in which a p-type second cladding layer and a p-type contact layer are sequentially formed on the positive side of the ridge in the z-direction and on the positive side of the n-type third buried layer in the z-direction; • a trench forming step in which the p-type contact layer is etched at two outer edges separated on the positive side and the negative side in the x-direction by a ridge part having the ridge and the p-type first buried layer in contact with both side surfaces of the ridge, and trenches are formed by etching such that a position of bottom parts thereof in the z-direction has an arbitrary position in the z-direction between the p-type second cladding layer and an inside of the n-type semiconductor substrate; • a semi-insulating layer forming step in which a semi-insulating layer is formed directly or via an n-type diffusion blocking layer on the positive side of the p-type contact layer in the z-direction on sides separated in the x-direction from a projecting part formed between the two trenches and located outside the trenches, and on inner surfaces of the two trenches; • a front electrode forming step in which a front electrode is formed so as to cover the p-type contact layer on which the semi-insulating layer of the projecting part is not formed in the semi-insulating layer forming step, wherein • the z-direction is a direction in which the ridge protrudes from one side of the front surface of the n-type semiconductor substrate, • the y-direction is an extension direction in which the ridge extends, and • the x-direction is a direction perpendicular to the z-direction and the y-direction. [15] A semiconductor laser production method for producing a semiconductor laser having a ridge formed on an n-type semiconductor substrate and a buried layer buried to cover both sides opposite to each other in a direction perpendicular to an extending direction of the ridge, the method comprising: • a ridge forming step in which an n-type cladding layer, an active layer, and a p-type first cladding layer are sequentially formed on the n-type semiconductor substrate, and the ridge including the n-type cladding layer, the active layer, and the p-type first cladding layer and having a side surface on a positive side in an x-direction and a side surface on a negative side in the x-direction exposed is formed by etching down to a position lower than the negative side of the active layer in a z-direction, which is one side of the n-type semiconductor substrate; • a burying step in which a p-type first buried layer is formed on the side surface on the positive side in the x-direction and the side surface on the negative side in the x-direction in the ridge, and the ridge is replaced by a second buried layer and an n-type third buried layer which are successively formed up to a position higher than a surface position of the active layer, which is a position on the positive side of the active layer in the z-direction; • a stacking step in which a p-type second cladding layer and a p-type contact layer are sequentially formed on the positive side of the ridge in the z-direction and on the positive side of the n-type third buried layer in the z-direction; • a recessed part forming step in which the p-type contact layer is etched at two outer edges separated on the positive side and the negative side in the x-direction by a ridge part having the ridge and the p-type first buried layer in contact with the two side surfaces of the ridge, and buried parts are formed by etching such that a position of bottom parts thereof in the z-direction is located at an arbitrary position in the z-direction between the p-type second cladding layer and an inside of the n-type semiconductor substrate; • a semi-insulating layer forming step in which a semi-insulating layer is formed directly or via an n-type diffusion blocking layer on a side surface and the bottom part of the recessed part on the positive side in the x-direction and on a side surface and the bottom part of the recessed part on the negative side in the x-direction; and • a front electrode forming step in which a front electrode is formed so as to cover the p-type contact layer on which the semi-insulating layer of a projecting part is not formed in the forming step of the semi-insulating layer in the projecting part formed between the two recessed parts, wherein • the z-direction is a direction in which the ridge protrudes from a side of a front surface of the n-type semiconductor substrate; • the y-direction is an extension direction in which the ridge extends; • the x-direction is a direction perpendicular to the z-direction and the y-direction.

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