Semiconductor laser element

Abstract

According to one embodiment, a semiconductor laser element includes a semiconductor substrate and a semiconductor laminate formed on the semiconductor substrate. The semiconductor laminate includes: an active layer; a p-type cladding disposed between the semiconductor substrate and the active layer; a non-doped guide layer disposed between the p-type cladding and the active layer; an n-type guide layer disposed on the opposite side from the side on which the non-doped guide layer is located with respect to the active layer; and an n-type cladding layer disposed on the side opposite to the side on which the active layer is located with respect to the n-type guide layer. Zn is doped in the p-type cladding layer. The non-doped guide layer is formed by InAl < x > Ga < 1-x > As (0 lt; x < = 1). The thickness of the n-type guide layer is greater than the thickness of the non-doped guide layer.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor laser element. Background Art

[0002] Patent Document 1 discloses a semiconductor laser device having a structure comprising an n-type cladding layer, an n-type guide layer, an active layer, a p-type guide layer, a p-type carrier blocking layer, and a p-type cladding layer stacked in this order on an n-type InP substrate. In this semiconductor laser device, Zn is used as a dopant in the p-type layer. Furthermore, the thickness of the n-type guide layer is the same as that of the p-type guide layer.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-229742 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] In semiconductor laser devices with the aforementioned structure, Zn, a dopant in the p-type layer, readily thermally diffuses, making it difficult to position the pn junction interface at the desired location within or near the active layer as designed, resulting in reduced yield. Furthermore, laser absorption loss in the p-type layer is greater than in the n-type layer with the same impurity concentration (doping concentration). Therefore, if the laser waveguide mode seeps more into the p-type layer than into the n-type layer, the laser absorption loss increases. The semiconductor laser device disclosed in Patent Document 1 has room for improvement in this regard.

[0008] Therefore, an object of one aspect of the present disclosure is to provide a semiconductor laser element capable of achieving an improvement in yield and suppressing the loss of laser light.

[0009] Means for solving technical problems

[0010] The present invention includes the following semiconductor laser elements [1] to

[14] . [1]

[0012] A semiconductor laser element includes a semiconductor substrate and a semiconductor stack formed on the semiconductor substrate.

[0013] The semiconductor stack comprises:

[0014] active layer;

[0015] A p-type cladding layer disposed between the semiconductor substrate and the active layer;

[0016] An undoped guiding layer disposed between the p-type cladding layer and the active layer;

[0017] An n-type guiding layer disposed on the opposite side of the undoped guiding layer with respect to the active layer; and

[0018] An n-type cladding layer disposed on the opposite side of the active layer with respect to the n-type guiding layer,

[0019] Zn is doped in the p-type cladding layer,

[0020] The undoped guiding layer is formed of InAl x Ga 1-x As (0 < x ≤ 1),

[0021] The thickness of the n-type guiding layer in the stacking direction of the semiconductor laminate is greater than the thickness of the undoped guiding layer in the stacking direction.

[0022] In the above semiconductor laser element, by the undoped guiding layer formed of InAl x Ga 1-x As, the diffusion of the p-type dopant (Zn) from the p-type cladding layer to the n-type cladding layer side can be appropriately suppressed. Thus, it is easy to set the position of the pn junction interface reproducibly at a desired position inside or near the active layer. Furthermore, by making the n-type guiding layer thicker than the undoped guiding layer, the waveguide mode of the laser generated in the active layer can be displaced toward the n-type layer (n-type guiding layer, n-type cladding layer) where the absorption loss of the laser is smaller than that of the p-type layer (p-type cladding layer). Thus, the absorption loss of the laser in the p-type layer can be appropriately suppressed. Therefore, according to the above semiconductor laser element, the yield can be improved and the loss of the laser can be suppressed. [2]

[0024] The semiconductor laser element according to [1], wherein

[0025] The semiconductor substrate is p-type. [3]

[0027] The semiconductor laser element according to [2], wherein

[0028] The semiconductor laminate further has an n-type contact layer disposed on the opposite side of the n-type guiding layer with respect to the n-type cladding layer,

[0029] The semiconductor laser element further includes:

[0030] A first electrode disposed on the n-type contact layer; and

[0031] The second electrode is provided on a surface of the semiconductor substrate on the side opposite to the semiconductor stack.

[0032] According to the above configuration, by using a p-type semiconductor substrate, it is possible to adopt a structure in which electrodes (first electrode and second electrode) for driving the semiconductor laser element are arranged on both sides sandwiching the semiconductor stack and the semiconductor substrate. [4]

[0034] The semiconductor laser element according to [1], wherein

[0035] The semiconductor substrate is n-type,

[0036] The semiconductor stack includes a p-type contact layer provided in contact with the p-type cladding layer.

[0037] According to the above structure, when the semiconductor laser element is constructed as a surface emitting laser that emits laser light from the surface of the semiconductor substrate on the opposite side to the semiconductor stack side, the absorption loss of the laser light in the semiconductor substrate can be reduced compared to the case of using a p-type semiconductor substrate, thereby increasing the output of the laser light. [5]

[0039] The semiconductor laser element according to [4], wherein

[0040] The p-type contact layer is disposed between the semiconductor substrate and the p-type cladding layer.

[0041] The semiconductor stack is provided with a groove portion, the groove portion extending from a surface of the semiconductor stack on the side opposite to the semiconductor substrate to a first surface of the p-type contact layer on the side opposite to the semiconductor substrate, and separating the semiconductor stack into a first portion and a second portion,

[0042] An n-type contact layer is provided in the first portion, and the n-type contact layer is arranged on the side opposite to the side where the n-type guide layer is located with respect to the n-type cladding layer.

[0043] The semiconductor laser element further comprises:

[0044] A first electrode is provided on the n-type contact layer; and

[0045] The second electrode is provided so as to extend from the surface of the second portion on the side opposite to the semiconductor substrate to the first surface.

[0046] With this structure, when using an n-type semiconductor substrate, the second electrode for driving the semiconductor laser element can be appropriately positioned. More specifically, since the first and second electrodes are positioned on a substantially coplanar surface, spatially separated by the groove, the semiconductor laser element can be easily mounted on a wiring substrate using so-called epitaxial-side-down mounting. [6]

[0048] The semiconductor laser element according to [4], wherein

[0049] The semiconductor stack further includes an n-type contact layer, the n-type contact layer being arranged on the side opposite to the side where the n-type guide layer is located with respect to the n-type cladding layer.

[0050] The semiconductor stack is provided with a groove portion extending from a surface of the semiconductor stack on the side opposite to the semiconductor substrate to a position located inside the p-type cladding layer and away from the semiconductor substrate.

[0051] The p-type contact layer is arranged inside the groove portion,

[0052] The semiconductor laser element further comprises:

[0053] A first electrode is provided on the n-type contact layer; and

[0054] The second electrode is disposed on the p-type contact layer.

[0055] According to the above structure, since it is not necessary to form a p-type contact layer between the semiconductor substrate and the p-type cladding layer as in the structure [5] above, it is possible to avoid the occurrence of laser absorption loss in the p-type contact layer. As a result, the laser output can be further increased. [7]

[0057] The semiconductor laser element according to [5] or [6], wherein

[0058] A third electrode is further provided on a surface of the semiconductor substrate on the side opposite to the semiconductor stack.

[0059] According to the above configuration, the first electrode, the second electrode, and the third electrode function as the emitter electrode, the base electrode, and the collector electrode, respectively, so that the semiconductor laser element can be operated as a transistor laser capable of high-speed operation. [8]

[0061] The semiconductor laser element according to any one of [1] to [7], wherein

[0062] The n-type guide layer and the n-type cladding layer are doped with Si.

[0063] By using Si, which is difficult to thermally diffuse, as the n-type dopant, the shift of the pn junction interface due to diffusion of the n-type dopant toward the p-type layer can be appropriately suppressed. As a result, the position of the pn junction interface can be adjusted to the desired position with even greater reproducibility, further improving the yield. [9]

[0065] The semiconductor laser element according to any one of [1] to [8], wherein

[0066] The thickness of the n-type guide layer in the stacking direction is 2 μm or less.

[0067] As described above, by making the n-type guide layer thicker than the undoped guide layer, the waveguide mode can be shifted toward the n-type layer. However, if the n-type guide layer is too thick, the waveguide mode will significantly deviate from the active layer, potentially preventing the achievement of suitable laser oscillation characteristics (the relationship between the magnitude of the light output and the injected current). In contrast, by keeping the thickness of the n-type guide layer below a certain level (less than 2 μm), as described above, this problem can be mitigated.

[10]

[0069] The semiconductor laser element according to any one of [1] to [9], wherein

[0070] The thickness of the non-doped guide layer in the stacking direction is 30 nm to 150 nm.

[0071] By setting the thickness of the undoped guide layer to 30 nm or greater, Zn diffusion from the p-type cladding layer can be appropriately prevented. Furthermore, by setting the thickness of the undoped guide layer to 150 nm or less, the p-type cladding layer can be prevented from being too far away from the active layer. This can prevent the pn junction surface from significantly deviating from the active layer, which could lead to deterioration in laser oscillation characteristics.

[11]

[0073] The semiconductor laser element according to any one of [1] to

[10] , wherein

[0074] A fine structure portion having a fine concavo-convex structure is provided on the n-type guide layer.

[0075] By providing a microstructure portion on the n-type guide layer located on the opposite side of the semiconductor substrate relative to the active layer and having a thickness greater than that of the other guide layer (non-doped guide layer), the microstructure portion can be processed with high precision and the stability of the microstructure portion can be improved.

[12]

[0077] The semiconductor laser element according to

[11] , wherein

[0078] The n-type guide layer includes a base layer having a first refractive index and a plurality of different refractive index regions having a second refractive index different from the first refractive index.

[0079] The fine structure portion is composed of the plurality of different refractive index regions arranged two-dimensionally when viewed from the stacking direction.

[0080] According to the above configuration, the semiconductor laser element can function as a photonic crystal laser (PCSEL: Photonic Crystal Surface Emitting Laser).

[13]

[0082] The semiconductor laser element according to

[11] , wherein

[0083] The fine structure portion has a diffraction grating distributed along a resonance direction of the active layer that is orthogonal to the stacking direction.

[0084] According to the above configuration, the semiconductor laser element can function as a distributed feedback (DFB) semiconductor laser.

[14]

[0086] The semiconductor laser element according to any one of

[11] to

[13] , wherein

[0087] The thickness of the n-type guide layer in the stacking direction is 1.5 times or more the thickness of the undoped guide layer in the stacking direction.

[0088] When microstructures are provided on the n-type guide layer, the waveguide mode shifts toward the p-type layer compared to when the microstructures are not provided. By making the thickness of the n-type guide layer at least 1.5 times that of the undoped guide layer, the extent of this shift can be reduced, preventing the waveguide mode from significantly deviating from the active layer and maintaining appropriate laser oscillation characteristics.

[0089] Effects of the Invention

[0090] According to one aspect of the present invention, a semiconductor laser element can be provided that can improve the yield and suppress the loss of laser light. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] Figure 1 This is a cross-sectional view showing the stacked structure of the semiconductor laser element according to the first embodiment.

[0092] Figure 2 Yes Figure 1 A diagram showing an example of a manufacturing process of a semiconductor laser element.

[0093] Figure 3 Yes Figure 1 A diagram showing an example of a manufacturing process of a semiconductor laser element.

[0094] Figure 4 Yes Figure 1 A diagram showing an example of a manufacturing process of a semiconductor laser element.

[0095] Figure 5 Yes Figure 1 A diagram showing an example of a manufacturing process of a semiconductor laser element.

[0096] Figure 6 Yes Figure 1 A diagram showing an example of a manufacturing process of a semiconductor laser element.

[0097] Figure 7 Yes Figure 1 A diagram showing an example of a manufacturing process of a semiconductor laser element.

[0098] Figure 8 Yes Figure 1 A diagram showing an example of a manufacturing process of a semiconductor laser element.

[0099] Figure 9 It is a cross-sectional view showing the stacked structure of the semiconductor laser element according to the second embodiment.

[0100] Figure 10 It is a cross-sectional view showing a stacked structure of a semiconductor laser element according to a third embodiment.

[0101] Figure 11 Yes Figure 9 FIG. 5 shows the SIMS measurement results of a semiconductor laser element.

[0102] Figure 12 It is a cross-sectional view showing the stacked structure of a semiconductor laser element according to a comparative example.

[0103] Figure 13 It is a cross-sectional view showing a stacked structure of a semiconductor laser element according to a third embodiment.

[0104] Figure 14 Yes Figure 13 A diagram showing an example of a manufacturing process of a semiconductor laser element.

[0105] Figure 15 Yes Figure 13 A diagram showing an example of a manufacturing process of a semiconductor laser element.

[0106] Figure 16 Yes Figure 13 Figure 1 shows an example of mounting a semiconductor laser element.

[0107] Figure 17 It is a cross-sectional view showing a stacked structure of a semiconductor laser element according to a fourth embodiment.

[0108] Figure 18 It is a cross-sectional view showing a stacked structure of a semiconductor laser element according to a fifth embodiment.

[0109] Figure 19 Yes Figure 18 A cross-sectional view showing an example of mounting a semiconductor laser element.

[0110] Explanation of symbols

[0111] 1A, 1B, 1C, 1D, 1E, 1F...semiconductor laser element, 10, 10D...semiconductor substrate, 11, 11B, 11C, 11D, 11E...semiconductor stack, 12...p-type cladding layer, 13...undoped guide layer, 14...active layer, 15, 15B, 15C...n-type guide layer, 14...active layer, 15a...base layer, 15b...different refractive index region (microstructure portion), 15c...diffraction grating (microstructure portion), 17...n-type contact layer, 18, 18E...electrode (first electrode), 19, 19D, 19E...electrode (second electrode), 22, 22E...p-type contact layer, 22a...surface (first surface), 23...electrode (third electrode), G1, G2...groove portion, P1...light-emitting portion (first portion), P2...non-light-emitting portion (second portion). DETAILED DESCRIPTION

[0112] An embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings. In the following description, identical or equivalent elements will be denoted by the same reference numerals, and duplicate descriptions will be omitted. The accompanying drawings may be simplified or exaggerated for ease of understanding, and dimensional ratios are not limited to those shown in the accompanying drawings.

[0113] [First embodiment]

[0114] Figure 1It is a cross-sectional view showing the stacking structure of the semiconductor laser element 1A of the first embodiment. In this specification, for convenience, an XYZ orthogonal coordinate system is defined in which the stacking direction of the semiconductor laser element 1A is set to the Z-axis direction. In this embodiment, as an example, the semiconductor laser element 1A is configured as a photonic crystal surface emitting laser (PCSEL: Photonic Crystal Surface Emitting Laser). For example, the semiconductor laser element 1A is configured as an S-iPMSEL (Static-integrable Phase Modulating Surface Emitting Laser) that outputs a phase-controlled plane wave (laser) in the Z-axis direction. The semiconductor laser element 1A outputs a light image of any two-dimensional shape in a direction perpendicular to the main surface 10a of the semiconductor substrate 10 (i.e., the Z-axis direction) or in a direction inclined relative to the Z-axis direction, or a direction including both.

[0115] like Figure 1 As shown, semiconductor laser element 1A includes a p-type semiconductor substrate 10 and a semiconductor stack 11 formed on semiconductor substrate 10. Semiconductor laser element 1A has a so-called mesa-type shape. Semiconductor substrate 10 and semiconductor stack 11 can be made of an InP-based semiconductor (compound semiconductor). The thickness direction of each layer of semiconductor substrate 10 and semiconductor stack 11 is aligned with the Z-axis direction.

[0116] The semiconductor substrate 10 is, for example, an InP substrate doped with Zn (zinc). The semiconductor substrate 10 is formed into a roughly rectangular parallelepiped shape, having a main surface 10a on which a semiconductor stack 11 is stacked, and a back surface 10b, the surface opposite the main surface 10a, which serves as the laser output surface. In this embodiment, as an example, the size of the semiconductor substrate 10 as viewed in the Z-axis direction is larger than the semiconductor stack 11. More specifically, when viewed in the Z-axis direction, the semiconductor substrate 10 is formed into a quadrilateral (in this embodiment, a roughly square) larger than the semiconductor stack 11, with the semiconductor stack 11 disposed approximately in the center of the main surface 10a of the semiconductor substrate 10. Furthermore, the thickness of the portion of the semiconductor substrate 10 that overlaps with the semiconductor stack 11 (i.e., the approximately center portion of the semiconductor substrate 10 as viewed in the Z-axis direction) is greater than the thickness of the portion of the semiconductor substrate 10 that does not overlap with the semiconductor stack 11 (i.e., the peripheral edge of the semiconductor substrate 10, which is formed into a quadrilateral ring shape as viewed in the Z-axis direction). In other words, the portion of the main surface 10a not overlapping the semiconductor stack 11 is recessed further toward the back surface 10b than the portion of the main surface 10a overlapping the semiconductor stack 11. The thickness of the semiconductor substrate 10 (the portion overlapping the semiconductor stack 11) is, for example, 100 μm to 300 μm.

[0117] A semiconductor stack 11 is formed on the main surface 10a of a semiconductor substrate 10. The semiconductor stack 11 has a p-type cladding layer 12, an undoped guiding layer 13, an active layer 14, an n-type guiding layer 15, an n-type cladding layer 16, and an n-type contact layer 17. The p-type cladding layer 12, the undoped guiding layer 13, the active layer 14, the n-type guiding layer 15, the n-type cladding layer 16, and the n-type contact layer 17 are sequentially stacked on the main surface 10a of the semiconductor substrate 10. The energy band gap of the p-type cladding layer 12 and the energy band gap of the n-type cladding layer 16 are greater than the energy band gap of the active layer 14.

[0118] When viewed from the Z-axis direction, each layer of the semiconductor stack 11 except the n-type contact layer 17 is formed into a quadrilateral of the same size (substantially square in the present embodiment). On the other hand, when viewed from the Z-axis direction, the n-type contact layer 17 is formed into a quadrilateral smaller than the above-mentioned layers (substantially square in the present embodiment) and is disposed at substantially the center of the upper surface of the n-type cladding layer 16 (the surface opposite to the n-type guiding layer 15 side).

[0119] In addition, the semiconductor stack 11 may include layers other than the above-mentioned layers. For example, other layers (such as layers formed of InGaAs, InGaAsP, etc.) may be provided between the semiconductor substrate 10 and the p-type cladding layer 12.

[0120] The p-type cladding layer 12 is formed on the main surface 10a of the semiconductor substrate 10. That is, the p-type cladding layer 12 is disposed between the semiconductor substrate 10 and the active layer 14. The p-type cladding layer 12 may be formed of an InP layer doped with Zn as a p-type dopant, for example. The impurity concentration of the p-type cladding layer 12 is, for example, 1×10 17 ~1×10 18 cm -3 . The thickness of the p-type cladding layer 12 in the stacking direction (Z-axis direction) is, for example, 1000 nm or more.

[0121] The undoped guiding layer 13 is formed on the p-type cladding layer 12. That is, the undoped guiding layer 13 is disposed between the p-type cladding layer 12 and the active layer 14. The undoped guiding layer 13 is not doped with Zn as a p-type dopant. The undoped guiding layer 13 may be formed of InAl x Ga 1-x As (0 < x ≤ 1), for example. By using an InP substrate as the semiconductor substrate 10, the undoped guiding layer 13 having such a composition can be appropriately fabricated. The thickness of the undoped guiding layer 13 in the stacking direction (Z-axis direction) is 30 nm to 150 nm.

[0122] Active layer 14 is a light-emitting layer. It is located between undoped guide layer 13 and n-type guide layer 15. Active layer 14 has a multi-quantum well structure composed of alternating layers of barrier layers made of, for example, InAlGaAs and well layers made of, for example, InGaAs. The thickness of active layer 14 in the stacking direction (Z-axis) is 5 to 200 nm.

[0123] The n-type guide layer 15 is disposed on the active layer 14. Specifically, the n-type guide layer 15 is disposed on the side of the active layer 14 opposite to the side where the undoped guide layer 13 is located. A microstructure having a fine concave-convex structure is provided on the n-type guide layer 15. In this embodiment, the n-type guide layer 15 includes a base layer 15a (i.e., the main body of the n-type guide layer 15) having a first refractive index and a plurality of differential refractive index regions 15b having a second refractive index different from the first refractive index. In this embodiment, as an example, the microstructure comprises the plurality of differential refractive index regions 15b arranged two-dimensionally when viewed in the stacking direction (Z-axis direction).

[0124] The n-type guide layer 15 (basic layer 15a) is doped with Si as an n-type dopant. The n-type guide layer 15 (basic layer 15a) can be formed of, for example, InAlGaAs, InGaAsP, etc. The impurity concentration of the n-type guide layer 15 (basic layer 15a) is, for example, 1×10 17 ~1×10 18 cm -3 . The thickness of the n-type guide layer 15 in the stacking direction (Z-axis direction) is preferably less than 2 μm, for example, 50 nm to 2000 nm. The different refractive index region 15b can be composed of, for example, a hole. However, the structure of the different refractive index region 15b is not limited to the above. For example, the different refractive index region 15b can be formed by burying a semiconductor having a refractive index different from that of the basic layer 15a in the hole. In addition, an inert gas such as argon, nitrogen, or a gas such as hydrogen or air can be sealed inside the different refractive index region 15b serving as a hole.

[0125] The two-dimensional arrangement of the plurality of different refractive index regions 15b may include a substantially periodic structure. When the equivalent refractive index of the mode is set to n, the wavelength λ0 (=( (a is the lattice spacing) is within the emission wavelength range of active layer 14. N-type guide layer 15 can selectively output light with a band-end wavelength near wavelength λ0 of the emission wavelength of active layer 14 to the outside. Laser light incident on n-type guide layer 15 forms a predetermined pattern within n-type guide layer 15 corresponding to the configuration of different refractive index regions 15b, and is then emitted from back surface 10b of semiconductor substrate 10 to the outside as a laser beam having a desired pattern.

[0126] The n-type cladding layer 16 is disposed on the n-type guide layer 15. That is, the n-type cladding layer 16 is disposed on the side opposite to the active layer 14 relative to the n-type guide layer 15. The n-type cladding layer 16 can be formed, for example, of an InP layer doped with Si (silicon) as an n-type dopant. The impurity concentration of the n-type cladding layer 16 is, for example, 1×10 17 ~1×10 18 cm -3 The thickness of the n-type cladding layer 16 in the stacking direction (Z-axis direction) is, for example, 1000 nm or more.

[0127] The n-type contact layer 17 is disposed on the n-type cladding layer 16. That is, the n-type contact layer 17 is disposed on the side opposite to the side where the n-type guide layer 15 is located with respect to the n-type cladding layer 16. Si is doped as an n-type dopant in the n-type contact layer 17. The n-type contact layer 17 can be formed of, for example, InGaAs, InGaAsP, InP, or the like. The impurity concentration of the n-type contact layer 17 is, for example, 5×10 18 cm -3 The thickness of the n-type contact layer 17 is, for example, 20 nm or more.

[0128] The semiconductor laser element 1A further includes an insulating film 20. The insulating film 20 is provided to cover the portion of the upper surface of the n-type cladding layer 16 where the n-type contact layer 17 is not provided, the side surfaces of the semiconductor stack 11 (surfaces intersecting the X-axis or Y-axis directions), and the portion of the main surface 10a of the semiconductor substrate 10 where the semiconductor stack 11 is not provided. Specifically, the insulating film 20 is provided to cover the portion of the surface of the portion of the semiconductor laser element 1A provided on the main surface 10a of the semiconductor substrate 10, excluding the upper surface of the n-type contact layer 17. As a result, the upper surface of the n-type contact layer 17 is not covered by the insulating film 20 and is exposed to the outside. The insulating film 20 can be formed of, for example, silicon nitride (e.g., SiN), silicon oxide (e.g., SiO2), or the like.

[0129] The semiconductor laser element 1A further includes an electrode 18 (first electrode) provided on the n-type contact layer 17 and an electrode 19 (second electrode) provided on the back surface 10b of the semiconductor substrate 10. Electrode 18 forms ohmic contact with the n-type contact layer 17. Electrode 19 forms ohmic contact with the semiconductor substrate 10. In this embodiment, as an example, electrode 18 is provided on the semiconductor stack 11 so as to cover a portion of the insulating film 20 provided on the n-type contact layer 17 and the peripheral portion of the n-type contact layer 17. Specifically, the shape of electrode 18 as viewed from the Z-axis direction is a quadrilateral (roughly square in this embodiment) slightly larger than the n-type contact layer 17. Electrode 19 is formed into a four-sided ring having a quadrilateral opening 19a (roughly square in this embodiment) that exposes the center portion of the back surface 10b. An anti-reflection film 21 is provided on the back surface 10b of the semiconductor substrate 10 where electrode 19 is not provided (including the area within opening 19a). The anti-reflection film 21 can be formed of a dielectric single layer film or a dielectric multilayer film such as silicon nitride (e.g., SiN) or silicon oxide (e.g., SiO2). Furthermore, since the anti-reflection film 21 is used to prevent reflection of the laser light output from the opening 19a, the portion of the anti-reflection film 21 provided in the area outside the opening 19a (i.e., the portion located outside the electrode 19 when viewed in the Z-axis direction) may be removed.

[0130] When a drive current is supplied between electrodes 18 and 19, electrons and holes recombine within active layer 14, causing it to emit light. The electrons and holes contributing to this light emission, and the resulting light, are effectively confined between p-type cladding layer 12 and n-type cladding layer 16. Light emitted from active layer 14 enters n-type guide layer 15 and forms a predetermined pattern corresponding to the lattice structure (i.e., the microstructure composed of multiple different refractive index regions 15b) within n-type guide layer 15. Laser light emitted from n-type guide layer 15 is either directly emitted from back surface 10b through opening 19a to the exterior of semiconductor laser element 1A, or is reflected by electrode 18 and then emitted from back surface 10b through opening 19a to the exterior of semiconductor laser element 1A.

[0131] Furthermore, by modifying the electrode shape, laser light can be emitted from the surface (upper surface) of n-type contact layer 17. For example, instead of providing opening 19a in electrode 19, an opening in electrode 18 can be provided on the upper surface of n-type contact layer 17. This allows laser light to be emitted from the upper surface of n-type contact layer 17 through the opening in electrode 18. In this case, anti-reflection film 21 can be provided inside and around the opening in electrode 18, rather than on the back surface 10b of semiconductor substrate 10.

[0132] Next, refer to Figures 2 to 8 , an example of a method for manufacturing the semiconductor laser element 1A is described.

[0133] First, if Figure 2 As shown in FIG. 1A , a p-type cladding layer 120, a non-doped guide layer 130, an active layer 140, a base layer 150a, and an n-type cap layer 160a are epitaxially grown on a semiconductor substrate 10A using metal organic vapor deposition (MOCVD) or molecular beam epitaxy (MBE) (primary growth process). Here, the semiconductor substrate 10A, the p-type cladding layer 120, the non-doped guide layer 130, the active layer 140, and the base layer 150a are respectively formed by the device isolation process described later (see FIG. 1B ). Figure 5 ) and become predetermined portions of the semiconductor substrate 10, p-type cladding layer 12, undoped guide layer 13, active layer 14, and fundamental layer 15a of each of the plurality of semiconductor laser elements 1A. Figure 2 The structure shown in (A) is a wafer-like structure containing predetermined portions of the multiple semiconductor laser elements 1A. The n-type cap layer 160a constitutes a portion of the n-type cladding layer 16 (the portion located near the n-type guide layer 150) of each of the multiple semiconductor laser elements 1A. The n-type cap layer 160a is provided to protect underlying layers (i.e., the active layer 140, the base layer 150a, etc.) that may contain aluminum. Furthermore, an insulating film 30 composed of SiN, SiO2, or the like is formed on the n-type cap layer 160a, for example, by PCVD, and a resist 31 (EB resist) is applied to the insulating film 30.

[0134] Then, if Figure 2 As shown in (B), a two-dimensional fine pattern is drawn on the resist 31 using an electron beam drawing device and developed, thereby forming a two-dimensional fine pattern (a portion of the hole H1) on the resist 31. Then, using the resist 31 as a mask, etching (e.g., reactive ion etching) is performed on the insulating film 30, thereby also forming a two-dimensional fine pattern on the insulating film 30. As described above, a two-dimensional fine pattern (a plurality of holes H1) is formed on the resist 31 and the insulating film 30.

[0135] Then, if Figure 3 As shown in (A), the resist 31 is removed (stripped). Figure 3 As shown in FIG. 5B , the n-type cap layer 160 a and the base layer 150 a are etched (eg, dry-etched) using the insulating film 30 as a mask, thereby forming the above-mentioned different refractive index region 15 b on the base layer 150 a .

[0136] Then, if Figure 4 As shown in (A), the insulating film 30 is removed. Figure 4 As shown in (B), the n-type cladding layer 160 and the n-type contact layer 170 are epitaxially grown (secondary growth process). The n-type cladding layer 160 and the n-type contact layer 170 are formed by the element separation process described later (see Figure 5 ) and become predetermined portions of the n-type cladding layer 16 and the n-type contact layer 17 of each of the plurality of semiconductor laser elements 1A. Furthermore, the n-type cap layer 160a formed in the primary growth process is integrated with the n-type cladding layer 160 by the secondary growth process.

[0137] Then, if Figure 5 As shown, execute Figure 4 The device separation (cutting) and mesa formation process of the structure (wafer) shown in (B) are performed. Thus, a structure is obtained in which the n-type contact layer 17 covers the entire upper surface of the n-type cladding layer 16 before the electrodes 18, 19 and the insulating film 20 are provided. Figure 5 (B) indicates Figure 5 The top view of the structure shown in (A) (viewed from the positive Z-axis direction side). Figures 6 to 8 By performing the above processing, a plurality of semiconductor laser elements 1A can be obtained.

[0138] Then, if Figure 6 As shown, a portion of the n-type contact layer 17 provided on the peripheral portion of the upper surface of the n-type cladding layer 16 is removed. Figure 6 (B) indicates Figure 6 A top view of the structure shown in (A) (viewed from the positive Z-axis direction side).

[0139] Then, if Figure 7 As shown, an insulating film 20 is formed to cover the upper surface and side surfaces of the n-type contact layer 17, the portion of the upper surface of the n-type cladding layer 16 where the n-type contact layer 17 is not provided, the side surfaces of the semiconductor stack 11 (the surface intersecting the X-axis direction or the Y-axis direction), and the portion of the main surface 10a of the semiconductor substrate 10 where the semiconductor stack 11 is not provided. In addition, an anti-reflection film 21 is provided on the back surface 10b of the semiconductor substrate 10. For example, after forming the anti-reflection film 21 on the entire back surface 10b, a portion corresponding to the predetermined area (a quadrangular ring area when viewed from the Z-axis direction) where the electrode 19 is to be arranged is removed, thereby forming Figure 7 The status shown.

[0140] Then, if Figure 8 As shown, the electrode 19 is formed on the back surface 10b. In addition, by removing the portion of the insulating film 20 that covers the n-type contact layer 17, a contact opening for contacting the n-type contact layer 17 and the electrode 18 is formed. Next, the electrode 18 is formed on the n-type contact layer 17, and the entirety is heated to adapt the electrode 19 to the semiconductor substrate 10 and the electrode 18 to the n-type contact layer 17. As described above, Figure 1 The semiconductor laser device 1A is shown.

[0141] [Effects of the First Embodiment]

[0142] In the semiconductor laser element 1A described above, the InAl x Ga 1-x The non-doped guide layer 13 formed by As can appropriately suppress the diffusion of the p-type dopant (Zn) from the p-type cladding layer 12 to the n-type cladding layer 16 side. As a result, it is easy to set the position of the pn junction interface at a desired position inside or near the active layer 14 with good reproducibility. Furthermore, by making the n-type guide layer 15 thicker than the non-doped guide layer 13, the waveguide mode of the laser generated in the active layer 14 can be displaced to the n-type layer (n-type guide layer 15, n-type cladding 16) side where the absorption loss of the laser is smaller than that of the p-type layer (p-type cladding layer 12, p-type semiconductor substrate 10). As a result, the absorption loss of the laser in the p-type layer can be appropriately suppressed. Therefore, according to the semiconductor laser element 1A, the yield can be improved and the loss of the laser can be suppressed. In addition, as Figure 1 As shown, in the semiconductor laser element 1A, by using the p-type semiconductor substrate 10 , it is possible to adopt a structure in which the electrodes 18 and 19 for driving the semiconductor laser element 1A are arranged on both sides of the semiconductor stack 11 and the semiconductor substrate 10 .

[0143] Furthermore, n-type guide layer 15 and n-type cladding layer 16 are doped with Si. Using Si, which is difficult to thermally diffuse, as the n-type dopant can appropriately suppress the shift of the pn junction interface caused by diffusion of the n-type dopant toward the p-type layer. As a result, the position of the pn junction interface can be adjusted to the desired position with greater reproducibility, further improving the yield.

[0144] Furthermore, the thickness of the n-type guide layer 15 in the stacking direction (Z-axis direction) is 2 μm or less (50 nm to 2000 nm, as an example, in this embodiment). As described above, by making the thickness of the n-type guide layer 15 greater than the thickness of the undoped guide layer 13, the waveguide mode can be shifted toward the n-type layer. However, if the n-type guide layer 15 is too thick, the waveguide mode will significantly deviate from the active layer 14, and suitable laser oscillation characteristics (the relationship between the light output and the magnitude of the injected current) may not be obtained. In contrast, as described above, by keeping the thickness of the n-type guide layer 15 below a certain value (2 μm or less), the above-mentioned problem can be suppressed. Furthermore, if the high-refractive-index n-type guide layer 15 is too thick, not only the fundamental mode but also higher-order modes of light are generated, resulting in unstable waveguide modes and a potential disturbance in the beam pattern. As described above, by keeping the thickness of the n-type guide layer 15 below a certain value, this problem can also be suppressed.

[0145] In addition, the thickness of the undoped guide layer 13 in the stacking direction (Z-axis direction) is 30 nm to 150 nm. By setting the thickness of the undoped guide layer 13 to 30 nm or more, the diffusion of Zn from the p-type cladding layer 12 can be appropriately prevented. Furthermore, by setting the thickness of the undoped guide layer 13 to 150 nm or less, the p-type cladding layer 12 and the active layer 14 can be prevented from being excessively separated. As a result, it is possible to suppress the pn junction surface from significantly deviating from the active layer 14, further suppressing the deterioration of the laser oscillation characteristics. In addition, by suppressing the thickness of the undoped guide layer 13 to a certain level or less (150 nm or less), the amount of Al (Al contained in the undoped guide layer 13), which is prone to degradation, can be reduced, and a reduction in the device life can also be suppressed.

[0146] In addition, a microstructure portion having a fine concavo-convex structure (in this embodiment, a portion consisting of multiple different refractive index regions 15b) is provided on the n-type guide layer 15. By providing the microstructure portion on the n-type guide layer 15, which is located on the side opposite to the semiconductor substrate 10 relative to the active layer 14 and has a thickness greater than that of the other guide layer (undoped guide layer 13), the microstructure portion can be processed with high precision, thereby improving the stability of the microstructure portion. In addition, as in this embodiment, by providing multiple different refractive index regions 15b as the microstructure portion on the n-type guide layer 15, the semiconductor laser element 1A can function as an S-iPMSEL, a type of photonic crystal surface emitting laser (in this embodiment, a photonic crystal surface emitting laser (PCSEL) as an example).

[0147] Furthermore, the thickness of the n-type guide layer 15 in the stacking direction (Z-axis direction) is preferably set to at least 1.5 times (more preferably at least 2 times) the thickness of the undoped guide layer 13 in the stacking direction. For example, when the thickness of the undoped guide layer 13 is 50 nm, the thickness of the n-type guide layer 15 is preferably set to at least 75 nm (more preferably at least 100 nm). When a microstructure (in this embodiment, a portion consisting of multiple different refractive index regions 15b) is provided on the n-type guide layer 15, the waveguide mode is displaced toward the p-type layer compared to a case where no microstructure is provided (i.e., when the n-type guide layer 15 consists solely of the base layer 15a). By setting the thickness of the n-type guide layer 15 to at least 1.5 times the thickness of the undoped guide layer 13, the extent of this displacement can be reduced, suppressing significant deviation of the waveguide mode from the active layer 14 and maintaining appropriate laser oscillation characteristics. Furthermore, by setting the thickness of the n-type guide layer 15 to be at least twice the thickness of the undoped guide layer 13 , the above-described effects can be more reliably obtained.

[0148] [Second embodiment]

[0149] Reference Figure 9, a semiconductor laser element 1B according to the second embodiment will be described. Figure 9 , the electrodes (the structures corresponding to the electrodes 18 and 19 of the semiconductor laser element 1A) are omitted from the illustration. The semiconductor stack 11B of the semiconductor laser element 1B differs from the semiconductor stack 11 of the semiconductor laser element 1A primarily in that it includes an n-type guide layer 15B consisting solely of a fundamental layer 15a, instead of an n-type guide layer 15. That is, the semiconductor laser element 1B differs from the semiconductor laser element 1A primarily in that it is not configured as a photonic crystal surface emitting laser (PCSEL). More specifically, the semiconductor laser element 1B is configured as an end-emission laser diode, causing laser light to resonate between the end faces of the active layer 14 that are opposite in a resonance direction (e.g., the X-axis direction) orthogonal to the stacking direction (the Z-axis direction), and emitting laser light from these end faces.

[0150] The semiconductor laser element 1B configured as an end-emission type also has the same effects as the surface-emitting semiconductor laser element 1A described above. x Ga 1-x Undoped guide layer 13, formed of As, can appropriately suppress the diffusion of the p-type dopant (Zn) from p-type cladding layer 12 toward n-type cladding layer 16. This makes it easy to reproducibly set the position of the pn junction interface at a desired location within or near active layer 14. Furthermore, by making n-type guide layer 15B thicker than undoped guide layer 13, the waveguide mode of laser light generated in active layer 14 can be shifted toward the n-type layer (n-type guide layer 15B, n-type cladding layer 16), where laser light absorption loss is lower than that of the p-type layer (p-type cladding layer 12, p-type semiconductor substrate 10). This effectively suppresses laser light absorption loss in the p-type layer.

[0151] Furthermore, in the end-emission semiconductor laser device 1B, as described above, by making the n-type guide layer 15B thicker than the undoped guide layer 13 and shifting the waveguide mode toward the n-type layer, the following further effects can be achieved. If, during laser resonance, light is excessively concentrated on the active layer 14 (particularly on the end faces of the active layer 14), the band gap of the active layer 14 decreases due to the generated heat, making it more likely that light will be concentrated on the active layer 14, and thus, the active layer 14 will be more susceptible to degradation. This may result in a shortened product life of the semiconductor laser device. In contrast, by shifting the waveguide mode toward the n-type layer, laser light resonating in the resonance direction (e.g., the X-axis direction) can be suppressed from concentrating on the end faces of the active layer 14, thereby suppressing degradation of the active layer 14 and thereby extending the product life of the semiconductor laser device 1B. The above-mentioned effect is particularly significant in the end-emission type semiconductor laser element 1B. However, the surface-emitting type semiconductor laser element 1A can also generate a laser component that resonates in the resonance direction (e.g., the X-axis direction), so the same effect is achieved in the semiconductor laser element 1A.

[0152] [Third embodiment]

[0153] Reference Figure 10 , a semiconductor laser element 1C according to a third embodiment will be described. Figure 10 In the figure, the electrodes (corresponding to electrodes 18 and 19 of semiconductor laser element 1A) are omitted. Semiconductor stack 11C of semiconductor laser element 1C differs from semiconductor stack 11 of semiconductor laser element 1A primarily in that it includes n-type guide layer 15C in place of n-type guide layer 15. Semiconductor laser element 1C is configured as an end-emission laser diode, similar to semiconductor laser element 1B. N-type guide layer 15C differs from n-type guide layer 15B of semiconductor laser element 1B in that it includes a diffraction grating 15c (microstructure) distributed along the resonance direction (e.g., the X-axis direction) of active layer 14, which is orthogonal to the stacking direction (the Z-axis direction).

[0154] Semiconductor laser element 1C also exhibits the same effects as those of semiconductor laser elements 1A and 1B. Furthermore, n-type guide layer 15C provided with diffraction grating 15c enables semiconductor laser element 1C to function as a distributed feedback (DFB) semiconductor laser.

[0155] Next, refer to Figure 11 , for the embodiments of the present disclosure (as an example, Figure 9 The effect of preventing the diffusion of Zn is supplemented by the structure of the semiconductor laser element 1B shown in FIG. Figure 11Graph showing the results of SIMS analysis of elements contained in each layer of the semiconductor stack 11B of the semiconductor laser element 1B. Figure 11 In the figure, the horizontal axis represents the distance (depth) with the upper surface of the n-type contact layer 17 as the origin (0) and the direction toward the semiconductor substrate 10 (negative direction of the Z axis) as the positive direction. In addition, the vertical axis (left) represents the concentration of Zn and Si (atoms / cm 3 : number of atoms per cubic cm), the vertical axis (right) represents the secondary ion intensity of Al (counts / sec: number of secondary ions detected in 1 second). Figure 11 The regions R1, R2, and R3 shown in the graph correspond to Figure 9 Regions R1, R2, and R3 are shown. Specifically, region R1 includes the n-type contact layer 17 and the n-type cladding layer 16, region R2 includes the n-type guide layer 15B, the active layer 14, and the undoped guide layer 13, and region R3 includes the p-type cladding layer 12.

[0156] like Figure 11 As shown in the graph, in the structure of this embodiment (semiconductor laser device 1B), it was confirmed that the undoped guide layer 13 appropriately suppressed Zn diffusion (i.e., Zn diffusion from region R3 to region R2). Furthermore, it was confirmed that the use of a poorly diffusing n-type dopant (Si) also prevented the diffusion of the n-type dopant from region R1 to region R2. While the above SIMS analysis was performed on the structure of semiconductor laser device 1B, similar results were obtained for semiconductor laser devices 1A and 1C, which also have the same undoped guide layer 13 as semiconductor laser device 1B.

[0157] Then, Figure 12 The semiconductor laser device 100 of the comparative example shown will be described, and in particular, the effects of the embodiments of the present disclosure (for example, the semiconductor laser devices 1A and 1C) when a microstructure portion is provided will be supplemented. Figure 12The semiconductor laser device 100 shown includes an n-type semiconductor substrate 110, an n-type cladding layer 112, an n-type guide layer 113, an active layer 114, an undoped guide layer 115, a p-type cladding layer 116, and a p-type contact layer 117, which are sequentially stacked on the semiconductor substrate 110. Thus, the semiconductor laser device 100 has a structure that inverts the n-type and p-type structures of the semiconductor laser device 1A. Specifically, in the semiconductor laser device 1A, by using a p-type semiconductor substrate 10, a p-type layer is arranged below the active layer 14 (on the side of the semiconductor substrate 10 facing the active layer 14), and an n-type layer is arranged above the active layer 14. In contrast, in the semiconductor laser device 100, by using an n-type semiconductor substrate 110, an n-type layer is arranged below the active layer 114 (on the side of the semiconductor substrate 110 facing the active layer 114), and a p-type layer is arranged above the active layer 114.

[0158] Semiconductor substrate 110 is an InP substrate doped with S (sulfur). The n-type cladding layer 112 has the same structure as the n-type cladding layer 16 of semiconductor laser device 1A. The n-type guide layer 113 has the same structure as the n-type guide layer 15 of semiconductor laser device 1A. Specifically, n-type guide layer 113 includes a base layer 113a similar to base layer 15a and multiple different refractive index regions 113b similar to multiple different refractive index regions 15b. The active layer 114 has the same structure as the active layer 14 of semiconductor laser device 1A. The undoped guide layer 115 has the same structure as the undoped guide layer 13 of semiconductor laser device 1A. The p-type cladding layer 116 has the same structure as the p-type cladding layer 12 of semiconductor laser device 1A. The p-type contact layer 117 is formed of an InGaAs layer doped with Zn as a p-type dopant.

[0159] According to the semiconductor laser device 100 constructed as described above, the diffusion of the p-type dopant (Zn) from the p-type cladding layer 116 to the n-type cladding layer 112 can also be suppressed by the undoped guide layer 115. However, in the structure of the semiconductor laser device 100, an n-type guide layer 113 having a sufficient thickness for providing a microstructure (here, as an example, the plurality of different refractive index regions 113b) can be provided below the active layer 114 (i.e., between the active layer 114 and the semiconductor substrate 110). Therefore, the formation of the microstructure (the plurality of different refractive index regions 113b) roughens the crystal surface of the layer (n-type guide layer 113) directly below the active layer 114 (on the semiconductor substrate 110 side). Therefore, when the semiconductor laser element 100 is manufactured by growing each layer on the semiconductor substrate 110 through the process described in the manufacturing process of the semiconductor laser element 1A, the manufacturing difficulty of forming the active layer 114 with high precision on the n-type guide layer 113 with a roughened surface becomes high. This is different from forming the diffraction grating 15c as a fine structure portion on the n-type guide layer 113 (see Figure 10 ) is the same as the case of the semiconductor laser element 100. In the semiconductor laser elements 1A and 1C described above, by using a p-type semiconductor substrate 10, a guide layer (n-type guide layer 15) capable of ensuring a layer thickness for forming a fine structure can be provided on the upper side of the active layer 14 (i.e., on the side of the semiconductor substrate 10 opposite to the side where the active layer 14 is located). Therefore, Figure 2 As shown in (A), after the active layer 14 is easily and accurately formed, a process for forming a microstructure portion on the n-type guide layer 15 above the active layer 14 can be performed. Therefore, according to semiconductor laser devices 1A and 1C, when the microstructure portion is provided on the guide layer, the manufacturing process can be simplified and the yield can be improved compared to semiconductor laser device 100.

[0160] [Fourth embodiment]

[0161] Reference Figures 13 to 15 , a semiconductor laser element 1D according to a fourth embodiment will be described. Figure 13 As shown, semiconductor laser element 1D differs from semiconductor laser element 1A primarily in that it includes semiconductor substrate 10D, semiconductor stack 11D, and electrode 19D instead of semiconductor substrate 10, semiconductor stack 11, and electrode 19. Semiconductor laser element 1D is configured as a surface-emitting laser diode, similar to semiconductor laser element 1A.

[0162] The semiconductor substrate 10D is an n-type semiconductor substrate, which differs from the p-type semiconductor substrate 10. The other structures of the semiconductor substrate 10D, such as the shape, are the same as those of the semiconductor substrate 10. The semiconductor substrate 10D can be formed, for example, from an InP substrate doped with S (sulfur) or an InP substrate doped with Sn (tin).

[0163] The semiconductor stack 11D is different from the semiconductor stack 11 in that it also includes a p-type contact layer 22. The p-type contact layer 22 is provided in such a manner as to be in contact with the p-type cladding layer 12. In the present embodiment, the p-type contact layer 22 is arranged between the main surface 10a of the semiconductor substrate 10D and the p-type cladding layer 12. In addition, the p-type contact layer 22 is not limited to a shape formed by one layer, and may also be formed by a plurality of layers. For example, the p-type contact layer 22 may also include a layer (also referred to as a buffer layer) provided in such a manner as to be in contact with the p-type cladding layer 12 as part of the p-type contact layer 22 to reduce the resistance between the p-type cladding layer 12 and the p-type cladding layer 12.

[0164] The semiconductor stack 11D is provided with a groove portion G1 extending from the surface of the semiconductor stack 11D on the side opposite to the semiconductor substrate 10D (in this embodiment, the upper surface of the n-type cladding layer 16) to the surface 22a (first surface) of the p-type contact layer 22 on the side opposite to the semiconductor substrate 10D. Figure 14 and Figure 15 As shown, in this embodiment, as an example, the groove portion G1 is provided in an L-shape when viewed from the Z-axis direction. The semiconductor stack 11D is separated into a light-emitting portion P1 (first portion) and a non-light-emitting portion P2 (second portion) by the groove portion G1. The light-emitting portion P1 is a portion configured to output laser light (surface emission) and is formed in a substantially square shape when viewed from the Z-axis direction. The non-light-emitting portion P2 is a portion that does not output laser light and is formed in an L-shape along the outer periphery of the groove portion G1. The width of the light-emitting portion P (width in the X-axis direction or the Y-axis direction) is, for example, approximately 500 μm.

[0165] In the semiconductor laser element 1D, an insulating film 20 is provided on the upper surface of the light-emitting portion P1 (n-type cladding layer 16), the inner surface of the groove G1 (the side surfaces of the light-emitting portion P1, the side surfaces of the non-light-emitting portion P2, and the upper surface of the p-type contact layer 22), and the upper surface of the non-light-emitting portion P2 (n-type cladding layer 16). An opening 20a is formed in the insulating film 20 at the portion corresponding to the bottom of the groove G1 (i.e., the upper portion of the p-type contact layer 22) to expose the surface 22a of the p-type contact layer 22. As an example, the opening 20a is provided throughout the entire L-shaped groove G1. That is, when viewed from the Z-axis direction, the opening 20a is formed in an L-shape along the groove G1.

[0166] In the semiconductor stack 11D, an electrode 19D, which opposes the electrode 18, is provided so as to extend from the surface of the non-light-emitting portion P2 on the side opposite to the semiconductor substrate 10D side, along the side surface of the non-light-emitting portion P2, to the surface 22a of the p-type contact layer 22. Specifically, in this embodiment, the electrode 19D is provided on the insulating film 20 formed on the upper surface and side surfaces of the non-light-emitting portion P2, and extends to the opening 20a in the insulating film 20, thereby being provided in contact with the surface 22a of the p-type contact layer 22 exposed through the opening 20a.

[0167] Next, refer to Figure 14 and Figure 15 An example of a method for manufacturing a semiconductor laser element 1D is described below. Figure 14 and Figure 15 This is a schematic diagram, so in reality, for a part of a component with thickness, there are parts whose thickness is not shown. Figure 14 As shown in FIG. 1 , a semiconductor stack 11D is crystal-grown on a semiconductor substrate 10D, and a groove G1 is formed by etching or the like. Figure 15 As shown in FIG. 1 , the insulating film 20 and the electrodes 18 and 19D are formed in sequence, and the anti-reflection film 21 is formed. Figure 13 Semiconductor laser device 1D having the structure shown.

[0168] In the semiconductor laser element 1D, by using an n-type semiconductor substrate 10D, when the semiconductor laser element 1D is constructed as a surface emitting laser that emits laser light from the surface (back surface 10b) of the semiconductor substrate 10D opposite to the semiconductor stack 11D side, the absorption loss of the laser light in the semiconductor substrate 10D can be reduced compared to the case of using a p-type semiconductor substrate 10, thereby increasing the laser output.

[0169] In addition, in the semiconductor laser element 1D, the electrode 18 is provided on the n-type contact layer 17 of the light emitting portion P1, and the electrode 19D is provided so as to extend from the surface of the non-light emitting portion P2 on the side opposite to the semiconductor substrate 10D to the surface 22a of the p-type contact layer 22. According to the above structure, when the n-type semiconductor substrate 10D is used, the electrode 19 for driving the semiconductor laser element 1D can be appropriately arranged. More specifically, as Figure 13 As shown, the electrode 18 and the electrode 19D are arranged on substantially the same plane so as to be spatially separated with the groove G1 interposed therebetween. Figure 16 As shown in FIG. 1 , the semiconductor laser element 1D can be easily mounted on the wiring substrate 50 by so-called epitaxial side down mounting. Figure 16In the example shown, the wiring substrate 50 is formed into a rectangular plate shape. Furthermore, the wiring substrate 50 includes a surface 50a on which the semiconductor laser element 1D is mounted, and an electrode 51 (cathode electrode) and an electrode 52 (anode electrode) that are insulated from each other on surface 50a. Electrode 51 has an area A1 that overlaps with electrode 18 on light-emitting portion P1, and electrode 52 has an area A2 that overlaps with electrode 19D on non-light-emitting portion P2. With the semiconductor laser element 1D, the surface of the semiconductor stack 11D opposite the semiconductor substrate 10D can be easily mounted on surface 50a of the wiring substrate 50, with electrodes 18 and 19D overlapping areas A1 and A2.

[0170] [Fifth embodiment]

[0171] Reference Figure 17 , a semiconductor laser element 1E according to a fifth embodiment will be described. Figure 17 As shown, semiconductor laser element 1E differs from semiconductor laser element 1A primarily in that it includes a semiconductor substrate 10D, a semiconductor stack 11E, and electrodes 18E and 19E instead of semiconductor substrate 10, semiconductor stack 11, and electrodes 18 and 19. Semiconductor laser element 1E is configured as a surface-emitting laser diode similar to semiconductor laser elements 1A and 1D. Furthermore, semiconductor laser element 1E does not include insulating film 20, but may include the same insulating film as semiconductor laser elements 1A and 1D.

[0172] The semiconductor stack 11E is provided with a groove G2 extending from the surface of the semiconductor stack 11E on the side opposite to the semiconductor substrate 10D to a position located inside the p-type cladding layer 12 and away from the semiconductor substrate 10D. Figure 17 In the example, the groove G2 is formed as a notch groove having a shape that notches one edge of the semiconductor stack 11E in the X-axis direction along the Y-axis direction. Alternatively, the groove G2 may be provided along the edge of the semiconductor stack 11E in the Y-axis direction.

[0173] The thickness (length in the Z-axis direction) of the portion 12a between the bottom surface B of the groove G2 in the p-type cladding layer 12 and the main surface 10a of the semiconductor substrate 10D is smaller than the thickness of the portion of the p-type cladding layer 12 where the groove G2 is not formed (the portion corresponding to the light-emitting portion P1 of the semiconductor laser element 1D). In the semiconductor laser element 1E, a p-type contact layer 22E is disposed (laminated) within the groove G2. In this embodiment, the p-type contact layer 22E is disposed on the upper surface of this portion 12a (i.e., on the bottom surface B of the groove G2). Furthermore, an electrode 18E is provided on the n-type contact layer 17, and an electrode 19E is provided on the surface 22a (the surface opposite the bottom surface B) of the p-type contact layer 22E.

[0174] The semiconductor laser element 1E can be manufactured, for example, as follows. First, a semiconductor stack 11E (a stack without the groove G2) is formed on a semiconductor substrate 10D. Then, a groove G2 is formed on the semiconductor stack 11E by etching or the like so that a portion 12a of the p-type cladding layer 12 remains. Then, a p-type contact layer 22E is formed on the portion 12a. Then, electrodes 18E, 19E and an anti-reflection film 21 are formed. By the above, a semiconductor laser element 1E having Figure 17 Semiconductor laser element 1E having the structure shown.

[0175] The semiconductor laser device 1E does not require the formation of a p-type contact layer 22 between the semiconductor substrate 10D and the p-type cladding layer 12 as in the structure of the semiconductor laser device 1D. This avoids absorption loss of laser light in the p-type contact layer 22, thereby further increasing the laser output.

[0176] [Sixth embodiment]

[0177] Reference Figure 18 and Figure 19 , a semiconductor laser element 1F according to a sixth embodiment will be described. Figure 18 and Figure 19 As shown, in addition to the electrodes 18 and 19D, the semiconductor laser element 1F also has an electrode 23 (third electrode) formed on the back side 10b of the semiconductor substrate 10D (the surface of the semiconductor substrate opposite to the semiconductor stack side) in the same way as the electrode 19 of the semiconductor laser element 1A. It is mainly different from the semiconductor laser element 1D in this point.

[0178] In semiconductor laser device 1F, electrode 18 connected to electrode 51 of wiring substrate 50 functions as an emitter electrode, electrode 19D connected to electrode 52 of wiring substrate 50 functions as a base electrode, and electrode 23 functions as a collector electrode. This allows semiconductor laser device 1F to operate as a high-speed transistor laser. More specifically, by causing carriers injected from the emitter electrode (electrode 18) to be extracted by the collector electrode (electrode 23), high-speed carrier supply to active layer 14 is achieved. Consequently, semiconductor laser device 1F can function as a high-speed modulated transistor laser.

[0179] While the embodiments and several variations of the present disclosure have been described above, the present disclosure is not limited to the structures shown in the above embodiments and variations. The materials and shapes of the various structures are not limited to the specific materials and shapes described above; various materials and shapes other than those described above may be employed. Furthermore, some of the structures included in the above embodiments and variations may be omitted or modified as appropriate. For example, the above embodiments describe several characteristic structures included in the semiconductor laser element and the effects exhibited by each structure. However, the semiconductor laser element of the present disclosure need not necessarily be configured to exhibit all of the effects described in the above embodiments; it may be configured to exhibit only a portion of the effects described in the above embodiments. In the latter case, the semiconductor laser element only needs to include the structures necessary to exhibit at least a portion of the effects, and structures that are not necessary to exhibit the effects may be omitted or modified as appropriate. Furthermore, when focusing on a single effect, the structure necessary to exhibit that effect should be appropriately understood by those skilled in the art based on common technical knowledge and the descriptions in this specification. Several specific variations of the semiconductor laser element of the present disclosure are illustrated below, but the variations of the semiconductor laser element are of course not limited to the specific embodiments illustrated below.

[0180] For example, the fourth embodiment and the fifth embodiment may be combined. That is, in the semiconductor laser element 1E of the fifth embodiment, a groove portion identical to the groove portion G1 of the fourth embodiment may be provided instead of the groove portion G2, and a light-emitting portion P1 and a non-light-emitting portion P2 may be provided. Moreover, the electrode 19E may be formed in a manner extending to the upper surface of the non-light-emitting portion P2. In this case, the effect of the fifth embodiment (i.e., the effect of suppressing light absorption loss by not providing the p-type contact layer 22 between the semiconductor substrate 10D and the p-type cladding layer 12) can be obtained, and the effect of the fourth embodiment (i.e., the effect of being able to easily perform Figure 16 effect of epitaxial mounting as shown).

[0181] Furthermore, the electrode 23 of the sixth embodiment may be additionally provided to the semiconductor laser element 1E of the fifth embodiment. With such a configuration, the semiconductor laser element 1E can also be operated as a transistor laser, similar to the semiconductor laser element 1F of the sixth embodiment.

[0182] In addition, in the semiconductor laser element 1D of the fourth embodiment, the shape of the groove G1 does not necessarily need to be formed into an L-shape along two adjacent sides of the light-emitting portion P1. For example, two independent (separate) grooves may be formed along two sides of the light-emitting portion P1 that are opposite to each other when viewed from the Z-axis direction (for example, two sides that are opposite to each other in the X-axis direction or two sides that are opposite to each other in the Y-axis direction). In addition, an I-shaped groove may be formed along only one side of the light-emitting portion P1, a U-shaped groove may be formed along three sides of the light-emitting portion P1, or a four-sided annular groove may be formed along four sides of the light-emitting portion P1. In this way, the shape of the groove G1 is not limited to a specific shape. However, as in the present embodiment, by forming the groove G1 into an L-shape, the area of the light-emitting portion P1 and the area of the mounting surface of the non-light-emitting portion P2 (that is, the contact area between the electrode 19D and the electrode 52) can be ensured in a balanced manner. Furthermore, from the perspective of appropriately injecting current into the light-emitting portion P1, the shapes of the groove portion G1 are preferably, in order, a four-sided ring, a U-shape, an L-shape, and an I-shape. That is, from the perspective described above, the most preferred shape of the groove portion G1 is a four-sided ring, enabling current injection from all four sides of the light-emitting portion P1. The next most preferred shape is a U-shape, enabling current injection from three sides of the light-emitting portion P1. The next most preferred shape is an L-shape, enabling current injection from two sides of the light-emitting portion P1. The next most preferred shape is an I-shape, enabling current injection from one side of the light-emitting portion P1. On the other hand, from the perspective of miniaturizing the mounting area of the semiconductor laser element 1D (i.e., the width of the semiconductor laser element 1D in the X-axis and Y-axis directions), the shapes of the groove portion G1 are preferably, in order, an I-shape, an L-shape, a U-shape, and a four-sided ring. That is, when the shape of the groove G1 is set to a four-sided ring surrounding the four sides of the light-emitting portion P1, the installation area is maximized. In contrast, when the shape of the groove G1 is set to an I-shape set only along one side of the light-emitting portion P1, compared with the case where the groove G1 is formed into a four-sided ring, the installation area can be reduced by the amount of reduction along the remaining three sides.

[0183] Furthermore, the semiconductor laser elements 1D to 1F may be configured as end-emission laser diodes by including the same n-type guide layer 15B as the semiconductor laser element 1B.

Claims

1. A semiconductor laser element, wherein: A semiconductor substrate and a semiconductor stack formed on the semiconductor substrate are provided. The semiconductor stack comprises: active layer; A p-type cladding layer disposed between the semiconductor substrate and the active layer; a non-doped guide layer, disposed between the p-type cladding layer and the active layer; An n-type guide layer is arranged on the side opposite to the side where the non-doped guide layer is located relative to the active layer; as well as an n-type cladding layer disposed on the side opposite to the active layer relative to the n-type guide layer; The p-type cladding layer is doped with Zn, The non-doped guide layer is made of InAl x Ga 1-x As is formed, where 0 <x≤1, The thickness of the n-type guide layer in the stacking direction of the semiconductor stack is greater than the thickness of the undoped guide layer in the stacking direction.

2. The semiconductor laser element according to claim 1, wherein The semiconductor substrate is of p-type.

3. The semiconductor laser element according to claim 2, wherein The semiconductor stack further includes an n-type contact layer, the n-type contact layer being arranged on the side opposite to the side where the n-type guide layer is located with respect to the n-type cladding layer. The semiconductor laser element further comprises: A first electrode is provided on the n-type contact layer; and The second electrode is provided on a surface of the semiconductor substrate on the side opposite to the semiconductor stack.

4. The semiconductor laser element according to claim 1, wherein The semiconductor substrate is n-type, The semiconductor stack includes a p-type contact layer provided in contact with the p-type cladding layer.

5. The semiconductor laser element according to claim 4, wherein The p-type contact layer is disposed between the semiconductor substrate and the p-type cladding layer. The semiconductor stack is provided with a groove portion, the groove portion extending from a surface of the semiconductor stack on the side opposite to the semiconductor substrate to a first surface of the p-type contact layer on the side opposite to the semiconductor substrate, and separating the semiconductor stack into a first portion and a second portion, An n-type contact layer is provided in the first portion, and the n-type contact layer is arranged on the side opposite to the side where the n-type guide layer is located with respect to the n-type cladding layer. The semiconductor laser element further comprises: a first electrode disposed on the n-type contact layer; and The second electrode is provided so as to extend from the surface of the second portion on the side opposite to the semiconductor substrate to the first surface.

6. The semiconductor laser element according to claim 4, wherein The semiconductor stack further includes an n-type contact layer, the n-type contact layer being arranged on the side opposite to the side where the n-type guide layer is located with respect to the n-type cladding layer. The semiconductor stack is provided with a groove portion extending from a surface of the semiconductor stack on the side opposite to the semiconductor substrate to a position located inside the p-type cladding layer and away from the semiconductor substrate. The p-type contact layer is arranged inside the groove portion, The semiconductor laser element further comprises: A first electrode is provided on the n-type contact layer; and The second electrode is disposed on the p-type contact layer.

7. The semiconductor laser element according to claim 5 or 6, wherein A third electrode is further provided on a surface of the semiconductor substrate on the side opposite to the semiconductor stack.

8. The semiconductor laser element according to any one of claims 1 to 6, wherein The n-type guide layer and the n-type cladding layer are doped with Si.

9. The semiconductor laser element according to any one of claims 1 to 6, wherein The thickness of the n-type guide layer in the stacking direction is 2 μm or less.

10. The semiconductor laser element according to any one of claims 1 to 6, wherein The thickness of the non-doped guide layer in the stacking direction is 30 nm to 150 nm.

11. The semiconductor laser device according to any one of claims 1 to 6, wherein A fine structure portion having a fine concavo-convex structure is provided on the n-type guide layer.

12. The semiconductor laser element according to claim 11, wherein The n-type guide layer includes a base layer having a first refractive index and a plurality of different refractive index regions having a second refractive index different from the first refractive index. The fine structure portion is composed of the plurality of different refractive index regions arranged two-dimensionally when viewed from the stacking direction.

13. The semiconductor laser element according to claim 11, wherein The fine structure portion has a diffraction grating distributed along a resonance direction of the active layer that is orthogonal to the stacking direction.

14. The semiconductor laser element according to claim 11, wherein The thickness of the n-type guide layer in the stacking direction is 1.5 times or more the thickness of the undoped guide layer in the stacking direction.

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