JP2016066670A - Semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser capable of reducing working voltage.SOLUTION: The semiconductor laser includes: a semiconductor layer which is formed over a substrate including an active layer; a carrier injection layer which is formed on the semiconductor layer including a transparent conductive film for injecting a charge carrier into the active layer; an optical field adjustment layer which is disposed in a selectively area on the carrier injection layer for adjusting an optical field of a laser beam, and which has an insulation property; a first electrode electrically connected to a substrate; and a second electrode electrically connected to the carrier injection layer.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a semiconductor laser used in various electronic devices.

  In recent years, semiconductor lasers using a gallium nitride compound semiconductor and capable of emitting light from the green region to the ultraviolet region have been actively studied. The semiconductor laser that emits light from the green region to the ultraviolet region is an important device for increasing the storage capacity and achieving full color display devices.

  In order to reduce the power consumption of such a semiconductor laser, there is a method of reducing the thickness of a p-type semiconductor layer (p-type cladding layer) that mainly forms a series resistance component. However, when the p-type semiconductor layer is simply made thin, light leaked from the active layer is absorbed by the p-side electrode (metal) formed on the p-type semiconductor layer, and operating characteristics such as threshold current or operating current are obtained. Gets worse.

  Therefore, a technique for thinning the p-type semiconductor layer by replacing part or all of the p-type semiconductor layer with a transparent conductive film such as ITO (indium tin oxide) has been proposed (for example, Patent Documents 1 to 3). ).

JP 2009-94360 A JP 2013-38394 A JP 2013-42107 A

  However, even when a transparent conductive film is used as described above, for example, light absorption occurs in the p-side electrode, resulting in deterioration of operating characteristics. In order to avoid this, it is only necessary to secure the thickness of the transparent conductive film to some extent, but it is known that the light absorption coefficient increases as the thickness of the transparent conductive film increases. That is, there is an upper limit to the thickness of the transparent conductive film.

  Moreover, since a transparent conductive film such as ITO generally has a lower refractive index than other semiconductor layers, when such a transparent conductive film is used, the intensity distribution of the laser light field is higher than that of the active layer in the n-type semiconductor layer. Will shift to the side. Further, the degree becomes larger as the p-type semiconductor layer is made thinner. From the above, it is difficult to reduce the series resistance component by sufficiently thinning the p-type semiconductor layer.

  The present disclosure has been made in view of such problems, and an object thereof is to provide a semiconductor laser capable of reducing an operating voltage.

  A semiconductor laser according to an embodiment of the present disclosure includes a semiconductor layer formed on a substrate and including an active layer; a carrier injection layer provided on the semiconductor layer and injecting charge carriers into the active layer; a carrier injection layer including a transparent conductive film; Provided in a selective region on the injection layer to adjust the light field of the laser light, and to provide an insulating light field adjustment layer, a first electrode electrically connected to the substrate, and a carrier injection layer Connected first electrode, and a second electrode for applying a voltage to the semiconductor layer together with the first electrode.

  In the semiconductor laser of the present disclosure, a carrier injection layer including a transparent conductive film is provided on a semiconductor layer including an active layer, and an insulating light field adjustment layer is provided in a selective region on the carrier injection layer. ing. Thus, when a predetermined voltage is applied between the first electrode and the second electrode, charge carriers supplied from the first electrode are injected into the active layer from the lateral direction, for example, via the carrier injection layer.

  According to the semiconductor laser of the present disclosure, the carrier injection layer including the transparent conductive film is provided on the semiconductor layer including the active layer, and the light field adjustment layer having insulation is provided in a selective region on the carrier injection layer. Is provided. Thereby, carrier injection from the lateral direction from the first electrode to the active layer can be realized. In addition to realizing an element structure in which light leaking from the active layer is not easily absorbed by the first electrode, the optical field can be adjusted by the optical field adjustment layer. As a result, the semiconductor layer above the active layer can be thinned, and the series resistance component of the element can be reduced. Therefore, the operating voltage can be reduced.

  The above content is an example of the present disclosure. The effects of the present disclosure are not limited to those described above, and may be other different effects or may include other effects.

It is a sectional view showing composition of a semiconductor laser concerning a 1st embodiment of this indication. It is sectional drawing showing the structure of the semiconductor laser which concerns on the comparative example 1-1. It is sectional drawing showing the structure of the semiconductor laser which concerns on the comparative example 1-2. 6 is a cross-sectional view illustrating a configuration of a semiconductor laser according to Comparative Example 2. FIG. 10 is a cross-sectional view illustrating a configuration of a semiconductor laser according to Comparative Example 3. FIG. It is a cross-sectional schematic diagram for demonstrating the effect | action of the semiconductor laser shown in FIG. 7 is a cross-sectional view illustrating a configuration of a semiconductor laser according to Modification 1. FIG. It is sectional drawing showing the structure of the semiconductor laser which concerns on 2nd Embodiment of this indication. 10 is a cross-sectional view illustrating a configuration of a semiconductor laser according to Modification 2. FIG. It is sectional drawing showing the structure of the semiconductor laser which concerns on 3rd Embodiment of this indication.

Hereinafter, modes for carrying out the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order.

1. First Embodiment (an example of a semiconductor laser in which a light field adjustment layer is provided on a semiconductor layer via a carrier injection layer (transparent conductive film) and carriers are injected in the lateral direction and the light field is adjusted)
2. Modification 1 (example in which the upper electrode is also formed on the light field adjustment layer)
3. Second embodiment (an example of a semiconductor laser having a ridge portion as a current confinement structure)
4). Modification 2 (example in which the upper electrode is also formed on the light field adjustment layer)
5. Third Embodiment (Example of a semiconductor laser having a current confinement region by ion implantation in part of a semiconductor layer)

<First Embodiment>
[Constitution]
FIG. 1 illustrates an example of the configuration of the semiconductor laser (semiconductor laser 1) according to the first embodiment of the present disclosure. FIG. 1 schematically shows the configuration of the semiconductor laser 1 and is different from the actual size and shape. The semiconductor laser 1 is, for example, a so-called edge-emitting semiconductor laser, and has a structure in which the semiconductor layer 20 is sandwiched between a pair of resonator end faces (not shown) in the resonator direction (Z direction). The pair of resonator end surfaces are cleaved surfaces formed by cleavage, for example. One end surface is a surface from which laser light is emitted, and a multilayer reflection film set to a predetermined reflectance is formed on this end surface. As an example, when the semiconductor laser 1 is a blue-violet laser, it is a low reflection film having a reflectance of about 10%. However, the reflectance of this end face is set according to the emission wavelength, and is, for example, about 20% in the case of a blue laser. On the other end face, a highly reflective film (multilayer reflective film) having a reflectance of about 95% is formed. The semiconductor laser 1 is not particularly limited, but is a nitride semiconductor laser, for example.

  The semiconductor laser 1 includes a semiconductor layer 20 on a substrate 10, for example. The semiconductor layer 20 includes, for example, a lower cladding layer 11, an active layer 12, and an upper cladding layer 13 in order from the substrate 10 side. The semiconductor layer 20 may further be provided with layers other than these layers (for example, a buffer layer, a guide layer, an electron barrier layer, etc.). A carrier injection layer 15 is provided on the semiconductor layer 20 via a pair of current confinement films 14. The pair of current confinement films 14 are provided with a gap 14a therebetween, and each form a stripe shape along the resonator direction (Z direction). The carrier injection layer 15 is adjacent to the semiconductor layer 20 in the gap 14a. The light field adjustment layer 17 is formed in a selective region on the carrier injection layer 15 (region facing the gap 14a), and in other regions on the carrier injection layer 15 (regions exposed from the light field adjustment layer 17). Is provided with an upper electrode 16 (first electrode). A lower electrode 18 (second electrode) is formed on the back surface of the substrate 10 (the surface opposite to the surface on which the semiconductor layer 20 is formed).

  The substrate 10 is, for example, an n-type GaN (gallium nitride) substrate.

  The semiconductor layer 20 includes a so-called group III-V nitride semiconductor layer. The “III-V nitride semiconductor” includes at least one of the group 3B elements in the short period periodic table and at least N of the group 5B elements in the short period periodic table. pointing. Specifically, it is a gallium nitride compound containing Ga (gallium) and N (nitrogen). For example, GaN, AlGaN (aluminum nitride / gallium), AlGaInN (aluminum nitride / gallium / indium), etc. Is mentioned. For group III-V nitride semiconductors, n-type impurities composed of group IV and group VI elements such as Si (silicon), Ge (germanium), O (oxygen), Se (selenium), or Mg as necessary A p-type impurity composed of Group II and Group IV elements such as (magnesium), Zn (zinc), and C (carbon) is doped.

  The lower cladding layer 11 is made of, for example, n-type AlGaN. The active layer 12 has, for example, a multiple quantum well structure in which well layers and barrier layers respectively formed of GaInN having different composition ratios are alternately stacked. The upper cladding layer 13 is made of, for example, p-type AlGaN.

The current confinement film 14 constricts the current injected into the active layer 12 of the semiconductor layer 20. Examples of the constituent material of the current confinement film 14 include silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO), aluminum nitride (AlN), and oxynitride. Examples thereof include at least one of aluminum (AlO _x N _1-x ) and tantalum oxide (Ta ₂ O ₅ ). The current confinement film 14 may be a single layer film of any one of these insulating film materials, or a multilayer film in which two or more kinds are stacked. The current confinement film 14 is formed so as to extend along the resonator direction (Z direction), and a light emitting region 12A is formed in a region facing the gap 14a.

  The carrier injection layer 15 is configured to include a transparent conductive film, and constitutes a path for injecting carriers (charge carriers, charge carriers) into the active layer 12. As will be described later, the carrier injection layer 15 can inject carriers from the lateral direction (X direction). For example, indium tin oxide (ITO), zinc oxide (ZnO), graphene, carbon nanotube (CNT), silver nanowire, conductive polymer (PEDOT), CIGS compound, the carrier injection layer 15 is a transparent conductive film. Or the IGZO type compound is included. The CIGS compound is a compound mainly composed of copper (Cu), indium (In), gallium (Ga), and selenium (Se). An IGZO-based compound is a compound mainly composed of indium (In), gallium (Ga), zinc (Zn), and oxygen (O).

  The upper electrode 16 is a p-side electrode, for example, and is made of metal. As an example of the upper electrode 16, for example, a multilayer film (Ti / Pt / Au) in which titanium (Ti), platinum (Pt), and gold (Au) are sequentially laminated from the carrier injection layer 15 side can be cited. The upper electrode 16 may be electrically connected to the carrier injection layer 15 and may be formed on the entire upper surface of the carrier injection layer 15 and exposed from the light field adjustment layer 17. You may form only in part. Further, as will be described later, it may be formed on the upper surface of the light field adjustment layer 17. Here, the upper electrode 16 is formed over the entire surface exposed from the light field adjustment layer 17 on the carrier injection layer 15 and is adjacent to the side surface of the light field adjustment layer 17.

  The light field adjustment layer 17 adjusts the light field of the laser light generated in the active layer 12. Specifically, by appropriately setting the refractive index and thickness of the light field adjustment layer 17, the peak of the light field intensity distribution can be formed at an arbitrary position (for example, a position near the active layer 12). . Here, for example, when the thickness of the upper cladding layer 13 (p-type semiconductor layer) is reduced, the intensity peak shifts from the active layer 12 to the lower cladding layer 11 (n-type semiconductor layer) side (downward). Such a shift of the light field can be suppressed by setting the refractive index and the like. However, the intensity peak is not necessarily formed in the vicinity of the active layer 12 and may be formed slightly shifted from the active layer 12. For example, by design guidelines such as changing the refractive index difference in the lateral direction or improving the COD (Catastrophic Optical Damage) level, the intensity peak is intentionally formed at a position slightly shifted from the vicinity of the active layer. It doesn't matter.

The light field adjustment layer 17 has an insulating property. Examples of the material include silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO), aluminum nitride (AlN), and aluminum oxynitride (AlO _x N _{1). -X} ) and at least one of tantalum oxide (Ta ₂ O ₅ ). The light field adjusting layer 17 may be a single-layer film of any one of these insulating film materials, or a multilayer film in which two or more kinds are stacked. Since the light field adjustment layer 17 has insulating properties, carrier injection from the lateral direction using the carrier injection layer 15 becomes possible as will be described later. If the purpose is not carrier injection, the light field adjustment layer 17 may be made of, for example, a semiconductor.

  In the present embodiment, since the upper electrode 16 is not disposed on the light field adjustment layer 17, the material selection and film thickness design flexibility of the light field adjustment layer 17 are high. This is because the film thickness of the light field adjustment layer 17 hardly affects the presence or absence of light absorption by the upper electrode 16. In addition, this makes it easy to reduce the thickness of the upper cladding layer 13 and leads to suppression of the series resistance component.

  The lower electrode 18 is made of metal, and is, for example, a multilayer film (Ti / Pt / Au) in which titanium, platinum, and gold are sequentially stacked from the substrate 10 side. The lower electrode 18 may be electrically connected to the substrate 10 and may not be formed on the back surface of the substrate 10.

[Production method]
The semiconductor laser 1 can be manufactured, for example, as follows. That is, first, the lower clad layer 11, the active layer 12, and the upper clad layer 13 are grown in this order as the semiconductor layer 20 on the upper surface (crystal growth surface) of the substrate 10. When the compound semiconductor exemplified in the above configuration is used, the semiconductor layer 20 is formed by, for example, MOCVD (Metal Organic Chemical Vapor Deposition) method. At this time, for example, ammonia (NH ₃ ), trimethylaluminum (TMAl), trimethylgallium (TMGa), trimethylindium (TMIn), or the like is used as a raw material for the compound semiconductor. For example, monosilane (SiH ₄ ) is used as a source material for donor impurities, and biscyclopentadienyl magnesium (Cp ₂ Mg) or dimethyl zinc (DMZn) is used as source materials for acceptor impurities.

  Thereafter, the current constricting film 14 made of the above-described material is formed by, for example, a vapor deposition method and then patterned so as to have a predetermined stripe shape.

  Subsequently, the carrier injection layer 15 including the above-described transparent conductive film is formed by sputtering, for example, and then patterned by etching using, for example, photolithography. Thereby, the carrier injection layer 15 is formed on the current confinement film 14 so as to be in contact with the semiconductor layer 20 in the gap 14a.

  Next, the light field adjustment layer 17 is formed on the carrier injection layer 15. Specifically, the insulating material described above is formed on the carrier injection layer 15 by, for example, a vapor deposition method, and then patterned by, for example, etching using a photolithography method. At this time, the light field of the laser light can be adjusted by appropriately setting the material (refractive index) and thickness of the light field adjusting layer 17.

  Subsequently, the upper electrode 16 is formed in a region exposed from the light field adjustment layer 17 on the carrier injection layer 15. Specifically, the metal material described above is formed into a film by, for example, vapor deposition or sputtering, and then patterned into a desired shape by etching using, for example, photolithography.

  Thereafter, lapping is performed as necessary to adjust the thickness of the substrate 10, and then the lower electrode 18 is formed on the back surface of the substrate 10. Next, after forming a pair of resonator end faces by cleavage, dicing is performed. In this way, the semiconductor laser 1 of the present embodiment is completed.

[Action, Effect]
In the semiconductor laser 1 of the present embodiment, when a voltage higher than a predetermined threshold voltage is applied between the upper electrode 16 and the lower electrode 18, the current injection region (light emitting region 12A) of the active layer 12 of the semiconductor layer 20 is applied. ) Is injected, and light is emitted by recombination of electrons and holes. This light is repeatedly reflected between the pair of resonator end faces and then emitted from one end face as laser light having a predetermined wavelength. In this way, laser oscillation is performed.

  In this semiconductor laser 1, the upper cladding layer 13 (p-type semiconductor layer) mainly forms the series resistance component of the element. For this reason, in order to reduce the operating voltage by reducing the series resistance component, it is ideal to make the upper cladding layer 13 thinner.

  Here, FIG. 2 shows a configuration of a semiconductor laser (semiconductor laser 100A) according to a comparative example (Comparative Example 1-1) of the present embodiment. FIG. 3 shows a configuration of a semiconductor laser (semiconductor laser 100B) according to a comparative example (Comparative Example 1-2) of the present embodiment. In Comparative Example 1-1, as shown in FIG. 2, an n-type semiconductor layer 103 (GaN layer 103 a, cladding layer 103 b, guide layer 103 c), active layer 104, and p-type semiconductor layer 105 are formed on the substrate 102. (Electron blocking layer 105a, guide contact layer 105b) are laminated. A transparent electrode 106 made of ZnO is formed on the p-type semiconductor layer 105. An n-side electrode 107 is formed on the back surface of the substrate 102. In Comparative Example 1-2, as shown in FIG. 3, the n-type semiconductor layer 103, the active layer 104, and the p-type semiconductor layer 105 are stacked on the substrate 102, as in Comparative Example 1-1. An n-side electrode 107 is formed on the back surface of the substrate 102. However, in Comparative Example 1-2, the transparent electrode 107 is formed on the p-type semiconductor layer 105 through the insulating film 108 as a current constricting film.

  Further, FIG. 4 shows a configuration of a semiconductor laser (semiconductor laser 200) according to a comparative example (comparative example 2) of the present embodiment. FIG. 5 shows a configuration of a semiconductor laser (semiconductor laser 300) according to a comparative example (Comparative Example 3) of the present embodiment. In Comparative Example 2, as shown in FIG. 4, an n-type semiconductor layer 202 (cladding layer 202a and guide layer 202b), an active layer 203, and a p-type semiconductor layer 204 (guide layer) are formed on a substrate 201. Are stacked. Transparent electrodes 206 (206a, 206b) are formed on the p-type semiconductor layer 204 with an insulating film 205 interposed therebetween. A p-side electrode 207 made of metal is disposed on the transparent electrode 206. In Comparative Example 3, as shown in FIG. 5, an n-type semiconductor layer 302 (cladding layer 302 a and guide layer 302 b), an active layer 303, and a p-type semiconductor layer 304 (electron blocking layer 304 a, A guide contact layer 304b) is laminated. Transparent electrodes 306 (306a, 306b) are formed on the p-type semiconductor layer 304 with an insulating film 305 interposed therebetween.

  As in these comparative examples 1-1, 1-2, 2, and 3, by replacing part or all of the p-type semiconductor layer with a transparent electrode, the series resistance component is reduced as compared with the case where the transparent electrode is not used. Can be achieved. However, in any structure, for example, the resistance reduction effect is insufficient for the following reasons, and there is room for improvement. That is, in the structure of Comparative Examples 1-1, 1-2, 2, and 3, when the p-type semiconductor layer (105, 204, 304) was thinned, it leaked from the active layer (104, 203, 303). Light is easily absorbed by the transparent electrode (106, 206, 306) or the p-side electrode (207). This light absorption deteriorates operating characteristics such as threshold current or operating current.

  In particular, in Comparative Example 2, since the metal p-side electrode 207 is further disposed on the transparent electrode 206, light absorption is likely to occur in the p-side electrode 207. In this case, it is possible to suppress the light absorption at the p-side electrode 207 by increasing the thickness of the transparent electrode 206, but the light absorption coefficient at the transparent electrode 206 is increased.

  In addition, since a transparent conductive film such as ITO generally has a lower refractive index than other semiconductor layers, when such a transparent conductive film is used, the intensity distribution of the laser light field is increased by the active layer (104, 203, 303) to the n-type semiconductor layer (103, 202, 302) side (downward). This shift of the light field becomes larger as the p-type semiconductor layer (105, 204, 304) is made thinner.

  In Comparative Example 3, the transparent electrode 306 has a predetermined two-layer structure, so that the adjustment range of the intensity distribution of the light field can be expanded. However, in the configuration of Comparative Example 3, the resistance component increases as compared with the single-layer structure due to the two-layer structure, and thus the operating voltage cannot be sufficiently reduced.

  From the above, in a semiconductor laser using a transparent electrode (transparent conductive film), it is difficult to reduce the series resistance component by sufficiently thinning the p-type semiconductor layer.

  In contrast, in the present embodiment, a carrier injection layer 15 including a transparent conductive film is provided on the upper clad layer 13 of the semiconductor layer 20, and an insulating property is provided in a selective region on the carrier injection layer 15. A light field adjustment layer 17 is provided. Thereby, the charge carriers supplied from the upper electrode 16 are injected into the active layer 12 from the lateral direction (X direction orthogonal to the resonator direction) through the carrier injection layer 15 (arrow A1 in FIG. 6). . Specifically, the carrier injection layer 15 is provided on the semiconductor layer 20 via the current constriction film 14, and the light field adjustment layer 17 is provided in a region facing the gap 14 a on the carrier injection layer 15. Carrier injection from the lateral direction is realized.

  As described above, the light field adjustment layer 17 is provided in a selective region on the carrier injection layer 15 and preferably further includes the current confinement film 14 so that the carriers from the upper electrode 16 to the active layer 12 are laterally transmitted. Injection can be realized. Thereby, an element structure in which light leaking from the active layer 12 is difficult to be absorbed by the upper electrode 16 can be realized. Specifically, the upper electrode 16 can be disposed at a position shifted from immediately above the light emitting region 12 </ b> A of the active layer 12. Further, by providing the light field adjustment layer 17, the light field of the laser light can be adjusted.

  Further, since light absorption of the upper electrode 16 can be sufficiently reduced, it is not necessary to increase the thickness of the carrier injection layer 15 made of a transparent conductive film (thinning is possible). By reducing the thickness of the carrier injection layer 15, an increase in the light absorption coefficient in the carrier injection layer 15 can be suppressed.

  Further, as described above, there is a possibility that the light field shifts when the upper cladding layer 13 is thinned. In the present embodiment, the light field adjustment layer 17 is used to consider the shift of the light field. Design can be done. Therefore, it is possible to suppress the shift of the optical field accompanying the thinning of the upper cladding layer 13. The upper cladding layer 13 can be sufficiently thinned while suppressing the shift of the light field, and the series resistance component of the element can be reduced.

  In addition, the light field adjustment layer 17 has insulating properties, and carrier injection from the lateral direction into the active layer 12 is possible, thereby suppressing a series resistance change due to the thickness of the light field adjustment layer 17. Can do.

  Further, since the carrier injection layer 15 and the light field adjustment layer 17 can be formed at a lower temperature than the semiconductor layer 20, thermal damage given to the active layer 12 can be suppressed.

  As described above, in the present embodiment, the carrier injection layer 15 including a transparent conductive film is provided on the semiconductor layer 20, and an insulating optical field is formed in a selective region on the carrier injection layer 15. An adjustment layer 17 is provided. As a result, carrier injection from the lateral direction from the upper electrode 16 to the active layer 12 can be performed via the carrier injection layer 15. Light absorption by the upper electrode 16 is reduced, and the light field of the laser light can be adjusted. As a result, the upper cladding layer 13 can be thinned. Therefore, the series resistance component of the element can be reduced, and the operating voltage can be reduced.

  Next, a semiconductor laser according to another embodiment of the first embodiment will be described. Hereinafter, the same components as those of the semiconductor laser 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

<Second Embodiment>
FIG. 7 illustrates an example of a configuration of a semiconductor laser (semiconductor laser 2) according to the second embodiment of the present disclosure. FIG. 7 schematically shows the configuration of the semiconductor laser 2 and is different from the actual size and shape. Similar to the semiconductor laser 1 of the first embodiment, the semiconductor laser 2 is an edge-emitting semiconductor laser and has a predetermined resonator structure.

  Similar to the semiconductor laser 1 of the first embodiment, the semiconductor laser 2 includes the semiconductor layer 20 on the substrate 10. Carrier injection is performed on the semiconductor layer 20 via the current constriction film 14. Layer 15 is provided. A light field adjustment layer 17 is formed in a selective region on the carrier injection layer 15. An upper electrode (upper electrode 21) is provided in another region on the carrier injection layer 15, and a lower electrode 18 is formed on the back surface of the substrate 10.

  However, in the present embodiment, unlike the first embodiment, the upper electrode 21 is formed not only on the carrier injection layer 15 but also on the light field adjustment layer 17. The upper electrode 21 is formed so as to cover the carrier injection layer 15 and the light field adjustment layer 17 formed thereon. The upper electrode 21 can be made of the same material as the upper electrode 16 of the first embodiment.

  As in the present embodiment, the upper electrode 21 may be formed on the carrier injection layer 15 and the light field adjustment layer 17. Also in this case, the carrier injection layer 15 is provided on the semiconductor layer 20, and the light field adjustment layer 17 is provided in a selective region on the carrier injection layer 15, so that the upper electrode 21 to the active layer 12 Carrier injection from the lateral direction is possible. An element structure in which light is not easily absorbed in the upper electrode 21 can be realized. Specifically, since the light field adjustment layer 17 is interposed between the semiconductor layer 20 and the upper electrode 21, the upper electrode 21 can be arranged shifted from directly above the light emitting region 12 </ b> A. Therefore, light absorption at the upper electrode 21 can be suppressed and the light field can be adjusted, and the upper cladding layer 13 can be made thinner. Therefore, an effect equivalent to that of the first embodiment can be obtained.

<Third Embodiment>
FIG. 8 illustrates a configuration of a semiconductor laser (semiconductor laser 3) according to the third embodiment of the present disclosure. FIG. 8 schematically shows the configuration of the semiconductor laser 3 and is different from the actual size and shape. Similar to the semiconductor laser 1 of the first embodiment, the semiconductor laser 3 is an edge-emitting semiconductor laser and has a predetermined resonator structure.

  Similar to the semiconductor laser 1 of the first embodiment, the semiconductor laser 3 includes a semiconductor layer (semiconductor layer 20A) including a lower cladding layer 11, an active layer 12, and an upper cladding layer (upper cladding layer 31) on a substrate 10. ) And a carrier injection layer (carrier injection layer 33) is provided on the semiconductor layer 20A via a current constriction film (current confinement film 32). The light field adjustment layer 17 is formed in a selective region on the carrier injection layer 33, and the upper electrode 16 is provided in another region on the carrier injection layer 33. A lower electrode 18 is formed on the back surface of the substrate 10. The semiconductor layer 20A is made of, for example, a nitride semiconductor as described above, similarly to the semiconductor layer 20 of the first embodiment.

  However, in the present embodiment, unlike the first embodiment, the upper clad layer 31 has a striped ridge portion 31a. The ridge portion 31a functions as an optical waveguide and extends, for example, along the resonator direction (Z direction). A current constriction film 32 is formed so as to cover this side surface. The current constricting film 32 can be embedded in the vicinity of the side surface of the ridge portion 31a of the upper cladding layer 31, for example. As a constituent material of the current confinement film 32, the same material as that of the current confinement film 14 of the first embodiment can be cited. The carrier injection layer 33 is configured to include the same transparent conductive film as the carrier injection layer 15 of the first embodiment. The light field adjustment layer 17 is provided in a region facing the ridge portion 31 a of the upper clad layer 31. The light emitting region 12A is formed in a selective region facing the ridge portion 31a. Although only one ridge portion 31a is provided here, a plurality of ridge portions 31a may be formed.

  As in the present embodiment, the upper cladding layer 31 may have a ridge portion 31a. Also in this case, the carrier injection layer 33 is provided on the semiconductor layer 20A, and the light field adjustment layer 17 is provided in a selective region on the carrier injection layer 33, so that the upper electrode 16 is directed to the active layer 12. Thus, the carrier can be injected from the lateral direction through the carrier injection layer 33 and the ridge portion 31a. Therefore, it is possible to realize an element structure in which light is not easily absorbed in the upper electrode 16 and to adjust the light field, and to reduce the thickness of the upper cladding layer 13. Therefore, an effect equivalent to that of the first embodiment can be obtained.

<Fourth embodiment>
FIG. 9 illustrates a configuration of a semiconductor laser (semiconductor laser 4) according to the fourth embodiment of the present disclosure. FIG. 9 schematically shows the configuration of the semiconductor laser 4 and is different from the actual size and shape. Similar to the semiconductor laser 1 of the first embodiment, the semiconductor laser 4 is an edge-emitting semiconductor laser and has a predetermined resonator structure.

  Similar to the semiconductor laser 1 of the first embodiment, the semiconductor laser 4 includes a semiconductor layer 20A including a lower cladding layer 11, an active layer 12, and an upper cladding layer 31 on a substrate 10. A carrier injection layer 33 is provided on the semiconductor layer 20A via a current constriction film 32. A light field adjustment layer 17 is formed in a selective region on the carrier injection layer 33. An upper electrode 21 is provided electrically connected to the carrier injection layer 33, and a lower electrode 18 is formed on the back surface of the substrate 10. Similarly to the semiconductor laser 3 of the third embodiment, the upper cladding layer 31 has a ridge portion 31a, and a current constricting film 32 is formed so as to cover the side surface of the ridge portion 31a.

  Furthermore, in the present embodiment, as in the second embodiment, the upper electrode 21 is formed not only on the carrier injection layer 33 but also on the light field adjustment layer 17. The upper electrode 21 is formed so as to cover the carrier injection layer 33 and the light field adjustment layer 17 formed thereon.

  Also in the present embodiment, the carrier injection layer 33 is provided on the semiconductor layer 20A, and the light field adjustment layer 17 is provided in a selective region on the carrier injection layer 33. The carrier can be injected from the lateral direction. Therefore, it is possible to realize an element structure in which light is not easily absorbed in the upper electrode 21 and to adjust the light field, and to reduce the thickness of the upper cladding layer 13. Therefore, an effect equivalent to that of the first embodiment can be obtained.

<Fifth embodiment>
FIG. 10 illustrates a configuration of a semiconductor laser (semiconductor laser 5) according to the fifth embodiment of the present disclosure. FIG. 10 schematically shows the configuration of the semiconductor laser 5 and is different from the actual size and shape. Similar to the semiconductor laser 1 of the first embodiment, the semiconductor laser 5 is an edge-emitting semiconductor laser and has a predetermined resonator structure.

  Similar to the semiconductor laser 1 of the first embodiment, the semiconductor laser 5 is a semiconductor layer (semiconductor layer 20B) including a lower cladding layer 11, an active layer 12, and an upper cladding layer (upper cladding layer 41) on a substrate 10. The carrier injection layer (carrier injection layer 42) is provided on the semiconductor layer 20B. The light field adjustment layer 17 is formed in a selective region on the carrier injection layer 42, and the upper electrode 16 is provided in another region on the carrier injection layer 42. A lower electrode 18 is formed on the back surface of the substrate 10. The semiconductor layer 20B is made of, for example, a nitride semiconductor as described above, similarly to the semiconductor layer 20 of the first embodiment.

  However, in the present embodiment, a part of the upper clad layer 41 has a pair of current confinement regions 41a formed by ion implantation. These current confinement regions 41a are formed with a gap 41b in between, and each has a stripe shape extending along the resonator direction (Z direction). The light field adjustment layer 17 is formed in a region facing the gap 41b. The light emitting region 12A is formed to face the gap 41b.

  Also in the present embodiment, the carrier injection layer 42 is provided on the semiconductor layer 20B, and the light field adjustment layer 17 is provided in a selective region on the carrier injection layer 42. The carrier can be injected from the lateral direction. Therefore, it is possible to realize an element structure in which light is not easily absorbed in the upper electrode 16 and to adjust the light field, and to reduce the thickness of the upper cladding layer 13. Therefore, an effect equivalent to that of the first embodiment can be obtained.

  Although the present disclosure has been described with reference to the embodiment, the present disclosure is not limited to the above-described embodiment, and various modifications can be made. For example, in the above embodiment, a GaN substrate is used as an example of the substrate 10, but an insulating substrate such as a sapphire substrate may be used. However, in this case, the lower electrode 18 may be formed so as to be electrically connected to the lower cladding layer 11 instead of the substrate 10.

  In the above embodiment, the gallium nitride semiconductor laser is taken as an example, but the present invention is also applicable to other compound semiconductor lasers, for example, red semiconductor lasers such as AlGaInP, and II-VI group semiconductor lasers such as ZnCdMgSSeTe. Is possible. The present invention is also applicable to semiconductor lasers whose oscillation wavelength is not always in the visible range, such as AlGaAs, InGaAs, InP, and GaInAsNP.

  In the above embodiment, the present disclosure has been described by taking the semiconductor laser having the index guide structure as an example. However, the present disclosure is not limited to this, and other structures such as a semiconductor having a gain guide structure are provided. It can also be applied to lasers.

  Moreover, the effect demonstrated in the said embodiment etc. is an example, The effect of this indication may be other effects and may also contain other effects.

The present disclosure may be configured as follows.
(1)
A semiconductor layer formed on the substrate and including an active layer;
A carrier injection layer provided on the semiconductor layer and injecting charge carriers into the active layer, and including a transparent conductive film;
Provided in a selective region on the carrier injection layer to adjust the optical field of the laser light, and an optical field adjustment layer having insulation,
A first electrode electrically connected to the carrier injection layer;
A semiconductor laser comprising: a second electrode for applying a voltage to the semiconductor layer together with the first electrode.
(2)
The semiconductor laser according to (1), wherein the first electrode is formed in a region exposed from the light field adjustment layer on the carrier injection layer.
(3)
The semiconductor laser according to (1) or (2), wherein the first electrode is formed on the carrier injection layer and the light field adjustment layer.
(4)
The semiconductor laser according to any one of (1) to (3), further including a current confining film that is provided between the semiconductor layer and the carrier injection layer and confines a current injected into the active layer. .
(5)
A striped ridge is formed in a part of the semiconductor layer,
The semiconductor laser according to any one of (1) to (3), further including a current confining film that confines a current injected into the active layer on a side surface of the ridge portion.
(6)
The semiconductor laser according to any one of (1) to (3), wherein an ion implantation region for confining a current injected into the active layer is formed in a part of the semiconductor layer.
(7)
The carrier injection layer includes indium tin oxide (ITO), zinc oxide (ZnO), graphene, carbon nanotube (CNT), silver nanowire, conductive polymer (PEDOT), CIGS compound, or IGZO compound. The semiconductor laser according to any one of (1) to (6).
(8)
The light field adjusting layer includes silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO), aluminum nitride (AlN), aluminum oxynitride (AlO _x). N _1-X ) or tantalum oxide (Ta ₂ O ₅ ) The semiconductor laser according to any one of (1) to (6) above.

  DESCRIPTION OF SYMBOLS 1-5 ... Semiconductor laser, 10 ... Substrate, 11 ... Lower clad layer, 12 ... Active layer, 12A ... Light emitting region, 13, 31 ... Upper clad layer, 14, 32 ... Current constriction film, 14a ... Gaps, 15, 33 , 42 ... carrier injection layer, 16, 21 ... upper electrode, 17 ... light field adjustment layer, 20, 20A, 20B ... semiconductor layer, 31a ... ridge portion, 41a ... current confinement region, 41b ... gap.

Claims (8)

A semiconductor layer formed on the substrate and including an active layer;
A carrier injection layer provided on the semiconductor layer and injecting charge carriers into the active layer, and including a transparent conductive film;
Provided in a selective region on the carrier injection layer to adjust the optical field of the laser light, and an optical field adjustment layer having insulation,
A first electrode electrically connected to the carrier injection layer;
A semiconductor laser comprising: a second electrode for applying a voltage to the semiconductor layer together with the first electrode. The semiconductor laser according to claim 1, wherein the first electrode is formed in a region exposed from the light field adjustment layer on the carrier injection layer. The semiconductor laser according to claim 1, wherein the first electrode is formed on the carrier injection layer and the light field adjustment layer. The semiconductor laser according to claim 1, further comprising a current confining film provided between the semiconductor layer and the carrier injection layer and confining a current injected into the active layer. A striped ridge is formed in a part of the semiconductor layer,
The semiconductor laser according to claim 1, further comprising a current confining film for confining a current injected into the active layer on a side surface of the ridge portion. The semiconductor laser according to claim 1, further comprising an ion implantation region for confining a current injected into the active layer in a part of the semiconductor layer. The carrier injection layer includes indium tin oxide (ITO), zinc oxide (ZnO), graphene, carbon nanotube (CNT), silver nanowire, conductive polymer (PEDOT), CIGS compound, or IGZO compound. Item 2. The semiconductor laser according to Item 1. The light field adjusting layer includes silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO), aluminum nitride (AlN), aluminum oxynitride (AlO _X). The semiconductor laser according to claim 1, comprising N _1-X ) or tantalum oxide (Ta ₂ O ₅ ).

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