JPH08139414A - Semiconductor laser - Google Patents

Abstract

PURPOSE: To provide a semiconductor laser having a new resonator structure which can make easily high quality crystal of semiconductor forming a light emitting part compatible with high reflectivity of a reflecting part. CONSTITUTION: A semiconductor laser is provided with a laminate S formed by laminating a plurality of semiconductor layers containing a light emitting part 2 on a crystal substrate 1, and a pair of reflecting parts 3a, 3b formed by directly or indirectly sandwiching the laminate S in the lamination direction. A pair of the reflecting parts constitutes a resonator structure which makes a light emitted from the light emitting part resonate in the lamination direction. When the light emitting part is a multilayered structure composed of InGaAlN based compound semiconductor, sapphire, GaN, SiC, ZnO, etc., are desirable as the material of the crystal substrate. As the reflecting part, a multilayered structure composed of InGaAlN based compound semiconductor or a dielectric multilayered film is preferable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting semiconductor laser.

[0002]

2. Description of the Related Art An edge-emitting type semiconductor laser has a crystal substrate 1 as shown in FIG.
The light emitting layer 2a is formed on the surface a by a double heterojunction, and the opposite side end faces of the light emitting layer 2a are formed on the reflecting surface 3c
3d, thereby forming a Fabry-Perot type resonator structure and emitting the laser beam L1 from the side end face. However, incidental parts such as electrodes are omitted in the drawing. Further, the light emitting portion and the crystal substrate are hatched to emphasize them (hereinafter the same). The formation of this reflective surface is G
A laminated structure using a general semiconductor material such as aAs can be easily achieved by cleaving the side end face together with the crystal substrate. However, a single crystal of an InGaAlN-based compound semiconductor, a crystal serving as a crystal substrate on which the crystal can grow, and the like have many substances that exhibit a property of being difficult to cleave, and a laminated structure using these semiconductor materials has a reflective surface. Is not easy to form.

On the other hand, a surface emitting semiconductor laser (also called "vertical cavity surface emitting laser") is known as one having a resonator structure in which the side end surface of the light emitting layer is not used as a reflecting surface. FIG. 3B is a diagram schematically showing an example of the structure. The reflection surface of this type is formed as the reflection layers 3e and 3f with the light emitting portion 2b including the light emitting layer sandwiched in the stacking direction, and the emitted light resonates in the direction perpendicular to the stacking and laser light is emitted from the outermost surface of the stacking. It is released as L2. Such a resonator structure is a structure useful for forming a semiconductor laser for the above-described substance whose side end face is difficult to cleave. Further, in such a resonator structure, since the reflective layer, the light emitting portion, and the reflective layer are sequentially crystal-grown and laminated on the crystal substrate 1b, the parallelism between the reflecting surfaces can be easily made highly accurate. be able to.

[0004]

However, a superlattice is formed on the reflecting surface of the surface emitting resonator structure.
In many cases, a multilayered reflective surface such as a layer formed by laminating a desired number of pairs of crystal layers or a dielectric multilayer film is used, and particularly a reflective surface having a structure using a superlattice. The following problems become noticeable. That is, when a superlattice is used, in order to increase the reflectance of the reflecting surface, the number of pairs of two layers forming the superlattice may be increased. However, as the number of pairs increases, the light emission formed on the superlattice increases. The crystal quality of the part deteriorates, and high-efficiency light emission cannot be obtained. Conversely, in order to improve the crystallinity of the light emitting portion in order to obtain highly efficient light emission, the number of superlattice pairs on the crystal substrate side with respect to the light emitting portion had to be reduced. .

In the surface emitting semiconductor laser, a layer to be a light emitting portion is directly formed on the crystal substrate, and the surface of the crystal substrate opposite to the side where the light emitting portion is formed is changed to the crystal substrate. There is also known a structure in which a through hole is formed, a light emitting portion is exposed in the hole, and a reflective layer is formed therein, but such a structure requires a complicated and sophisticated processing step. In addition, when the area of the reflecting surface is increased, there is a problem that the mechanical strength of the device centering on the crystal substrate is impaired.

An object of the present invention is to provide a semiconductor laser having a novel resonator structure which can easily achieve both good crystal quality of the semiconductor forming the light emitting portion and high reflectance of the reflecting portion. That is.

[0007]

The semiconductor laser of the present invention has the following features. (1) having a laminated body in which a plurality of semiconductor layers including a light emitting portion are laminated on a crystal substrate, and a pair of reflecting portions formed by directly or indirectly sandwiching the laminated body in the laminating direction, A surface emitting semiconductor laser, wherein the pair of reflecting portions has a resonator structure that resonates the light emitted from the light emitting portion in the stacking direction. (2) The semiconductor laser according to (1), wherein the light emitting portion has a multi-layer structure made of InGaAlN-based crystal, and the crystal substrate is made of a material capable of transmitting the light emitted from the light emitting portion. (3) The semiconductor laser according to (2), wherein the material of the crystal substrate that allows the light emitted from the light emitting portion to pass therethrough is any one of sapphire, GaN, SiC, and ZnO. (4) At least one of the pair of reflecting portions is I
The semiconductor laser according to (1), which has a multilayer structure made of nGaAlN-based crystals or a dielectric multilayer film.

[0008]

The semiconductor laser of the present invention has a surface emission type structure, and the reflecting portion on the crystal substrate side of the pair of reflecting portions forming the resonator structure is provided between the light emitting portion and the crystal substrate. Instead of being provided, it is provided directly or through another layer on the surface opposite to the surface on the side where the light emitting portion is present among the two surfaces in the stacking direction of the crystal substrate. Hereinafter, this “surface of the two surfaces of the crystal substrate in the stacking direction opposite to the surface on the side where the light emitting portion is present” is referred to as “the back surface of the crystal substrate”. On the other hand, the surface on the side where the light emitting portion is present is referred to as the “front surface of the crystal substrate”.

Due to the resonator structure of the semiconductor laser of the present invention, light traveling from the light emitting portion toward the crystal substrate passes through the crystal substrate and is provided at the interface of the back surface of the crystal substrate or the back surface side of the crystal substrate. The reflected light is reflected by the reflected portion and laser oscillation is generated between the reflected portion and the other reflected portion. Further, such a resonator structure enables the light emitting portion to be formed directly on the crystal substrate (including layers related to formation of a buffer layer etc.), and the semiconductor material forming the light emitting portion can be formed. The crystal quality can be independently improved without being affected by the reflection part. Similarly, the reflection portion on the back side of the crystal substrate can be freely improved to improve the reflectance without affecting the light emitting portion.

Further, an example of the conventional surface emitting semiconductor laser as described above (that is, a through hole is formed in the laser crystal substrate from the back side thereof, a light emitting portion is exposed in the hole, and a reflection layer is provided there. It does not require complicated and sophisticated processing steps for the crystal substrate as compared with the one formed.

[0011]

EXAMPLES The present invention will be described in more detail with reference to examples. FIG. 1 is a diagram schematically showing an example of the structure of the semiconductor laser of the present invention. The structural example in the figure is a crystal substrate 1.
The light emitting unit 2 (or a plurality of semiconductor layers including the light emitting unit 2) is stacked on top to form a stacked body S, and the pair of reflecting units 3a and 3b are formed with the stacked body S sandwiched in the stacking direction. ing. The pair of reflecting portions 3a and 3b has a resonator structure that resonates the light emitted from the light emitting portion 2 in the stacking direction, and the laser light L is emitted from the outermost surface of the stack. However, in the figure, the additional parts such as electrodes are omitted. The plurality of semiconductor layers including the light emitting section 2 include all the incidental layers for providing a buffer layer and other functions in addition to the light emitting section. Further, the light emitting portion and the crystal substrate are hatched. The outermost surface of the stack from which the laser light L is emitted may be either of the two surfaces.

With such a structure, as described in the above operation, the light emitting portion 2 can be directly formed on the crystal substrate 1 by, for example, epitaxial growth, and the semiconductor forming the light emitting portion can be formed. The crystals are of high quality. On the other hand, with respect to the reflecting portion 3a on the back surface side of the crystal substrate, improvements for improving the reflectance, such as increasing the number of pairs of superlattices, can be freely performed without affecting the crystal quality of the light emitting portion. Can be applied to.

The crystal substrate serves as a basis for providing a semiconductor layer including a light emitting portion on one surface and a reflecting portion on the other surface by crystal growth or another forming method. As the material of the crystal substrate, as long as it is a crystal having a good lattice constant matching with the semiconductor crystal to be grown, a semiconductor made of a single element, a compound semiconductor, an insulator such as sapphire, and the like, It can be anything. The specific material will be described later together with an example of the semiconductor material forming the light emitting unit.

The light emitting portion is a portion that emits light to be resonated. The principle and method for emitting light are not limited, but the following methods (a) and (b) are mainly exemplified. (A) Injecting electrons or holes into the active layer of the pn junction,
A method of emitting light by recombining electrons and holes (injection type). In this case, the structure of the light emitting portion is a so-called double heterojunction structure in which an active layer is sandwiched by p-type and n-type cladding layers, or an SQW (Single Quantum) having a superlattice structure.
Well), MQW (Multi Quantum Well) and the like. (B) A method in which a laser beam having energy larger than the desired wavelength (wavelength corresponding to the bandgap of the light emitting section) to be lased is externally applied to the light emitting section for excitation to emit light of the desired wavelength. (Photoexcitation type). The structure of the light emitting part is basically the same as that of the injection type, and the structure of a double heterojunction in which the active layer is sandwiched by two cladding layers and the SQ
W, MQW, etc. are illustrated. However, in the case of the photoexcitation type, it is not necessary to control the conduction type of each layer, and it is preferable that the conduction type is undoped.

In the structure of the semiconductor laser of the present invention,
In order that the light emitted from the light emitting portion is reflected at least at the interface of the back surface of the crystal substrate, preferably at the predetermined reflection portion provided on the back surface of the crystal substrate,
It is necessary for the light to pass through the crystal substrate. The term "passage" as used herein does not mean that 100% of the light incident on the crystal substrate passes, but if laser oscillation is achieved, the incident light may undergo some attenuation within the crystal substrate. It may be accompanied or part of the wavelength band of the incident light may be absorbed. Therefore, when selecting the material of the crystal substrate and the material of the light emitting portion, it is necessary to consider the material so that the light emitted from the light emitting portion passes through the crystal substrate. From this point of view, as the material of the light emitting portion, a compound semiconductor composed of a representative element and nitrogen Group III are preferred, among them, an In _x Ga _y A
A compound semiconductor determined by l _1-xy N, (0 ≦ x ≦ 1, 0 ≦ y ≦ 1), that is, an InGaAlN-based compound semiconductor is preferable.

The InGaAlN-based compound semiconductor is a material capable of emitting light mainly in a wavelength band from green to blue and further to ultraviolet light, and is currently commercially available InGaA.
It is possible to form an element capable of emitting light of a shorter wavelength than a light emitting element made of an s-based, GaAlAs-based, or InGaAlP-based material. A laser with such a short wavelength region is used as a light source for a pickup such as an optical disc,
Applications such as various sensor light sources for medical purposes are expected. Further, in the semiconductor laser of the present invention, the light emitted from the light emitting portion can pass through the crystal substrate as described above, which is an essential condition for establishing the resonator structure. Also in this respect, by selecting the InGaAlN-based compound semiconductor as the material of the light emitting portion, it becomes easy to select the material of the crystal substrate through which the light emitted from the light emitting portion can pass.

As a specific structural example of the light emitting portion using the above InGaAlN compound semiconductor, n-type AlGaN is used.
Cladding layer, undoped InGaN active layer, p-type Al
Examples include a double heterojunction structure formed by sequentially growing a GaN cladding layer, and a structure such as SQW and MQW.

The reflecting portion includes all means capable of reflecting light so that the light can resonate. For example, a mirror surface, an interface having different refractive index, and these surfaces are multiply formed. A laminated body in which the material substances are laminated in this manner is included. Among them, a multilayer structure made of a compound semiconductor or a dielectric multilayer film is preferable, and in particular, two crystal layers forming a superlattice such as a strained superlattice are regarded as one pair, and this is used as a desired number of pairs. It is preferable that only these layers are laminated because they have high reflectance.

If the reflecting portion has a structure in which light is made incident on the inside of the reflecting portion itself in order to reflect the light, the material allows the light emitted from the light emitting portion to pass through, like the crystal substrate. Use the one of the nature. For example, when the material of the active layer in the light emitting portion is InGaN among InGaAlN-based compound semiconductors, and if the reflecting portion has a structure of a multilayer reflecting layer of the superlattice, the material forming the superlattice is AlN / Al _0.1 Ga _0.9 N, AlN / Al
_0.2 Ga _0.8 N, AlN / GaN, InGaAlN
A combination selected from InGaAlN-based compound semiconductors such as / GaN is exemplified. Further, as the dielectric multilayer film, those made of a preferable material may be appropriately selected and used.

Among the structures of the reflecting portion, AlN / A
structure of the superlattice by l _0.1 Ga _0.9 N is higher a structure of a multilayer having a reflectivity, which is an example of a reflection portion that can most prominently indicate the utility of the present invention the active layer of InGaN. The number of pairs is 10 to 50 pairs, preferably 20 to 40 pairs per one reflecting portion. When the number of pairs is 10 pairs or less, sufficient reflectance cannot be obtained, and when the number of pairs is 50 pairs or more, the reflectance saturates near 100%, and it becomes difficult to obtain more reflectance. Achieving such a high reflectance in a reflective layer using a superlattice and not affecting the crystal quality of the light emitting portion by the superlattice can be easily achieved by the structure of a conventional semiconductor laser. It wasn't. The reflecting portion is a laminated body including a crystal substrate and a light emitting portion,
It may be formed by directly sandwiching it, or a mode in which the laminate is indirectly sandwiched, that is, a layer having a desired function is laminated on the outermost layer of the laminate as necessary, and this is reflected. A mode in which the parts are sandwiched and formed may be used. The area of the reflecting portion is not limited and is determined according to the structure.

As described above, the InGaAlN-based compound semiconductor is preferable as the material forming the light emitting portion and the reflecting portion. However, the material of this system often has severe crystal growth conditions such as high temperature and high pressure. To grow high quality single crystals of such materials, ZnO, BeO, MgO,
Oxides of Group II elements such as CaO, SrO, CdO, BaO, HgO and their compounds, AlN, GaN, A
It is preferable to use a method in which lGaN or the like is formed as a buffer layer and the desired InGaAlN-based compound semiconductor is grown as a single crystal on the buffer layer. Further, as the material of the crystal substrate in that case, sapphire, SiC, ZnO, GaN and the like are exemplified as preferable materials.

As a method for crystal-growing the semiconductor layer forming the light-emitting portion and the reflection portion, a film-forming method capable of epitaxial growth on a crystal substrate is preferable, and VPE (Vapor) is used.
Phase Epitaxy), MOVPE (Metal Organic VP)
E), HVPE (Hydride VPE), MBE (Molecula
r Beam Epitaxy), GS-MBE (Gas Sourse MB)
E), CBE (Chemical Beam Epitaxy), LPE (Li
quid Phase Epitaxy).

When the reflecting portion is formed on the back surface side of the crystal substrate and the light emitting portion is formed on the front surface side by crystal growth, either surface may be grown first, but the light emitting portion may be grown first. Since it is necessary that the crystal of (3) has a high quality, it is preferable to grow the reflecting portion on the back surface side first. As a result, the crystal of the light emitting portion is not exposed to the high temperature during crystal growth of the reflecting portion, and high crystal quality is maintained.

The emission direction of the laser light is not limited, and it may be emitted from either side of the pair of reflecting portions. Further, as described above, the emission method of the semiconductor laser of the present invention may be injection type, photoexcitation type, or the like, but in the case of injection type, a known structure may be used for the incidental structure of the electrodes and the like, It is provided according to the emission direction of the laser light and the intended specifications. FIG. 2 is a diagram schematically showing an example of an electrode structure in the case where the light emitting method is the injection type in the structure of the semiconductor laser according to the present invention. In the figure, only the electrodes are hatched. In the example of the figure, a columnar reflecting portion 3a is formed in the center of the back surface of the n-type GaN single crystal substrate 1, and an electrode 4 is formed so as to surround the periphery thereof. Reflector 3
a is a stack of superlattices made of AlN / Al _0.1 Ga _0.9 . In addition, the front surface of the crystal substrate 1 has n
Type Al _0.15 Ga _0.85 N cladding layer 2a, undoped I
n _0.1 Ga _0.9 N active layer 2c, p-type Al _0.15 Ga _0.85 N
Emitting portion 2 of the double heterojunction formed by sequentially growing a clad layer 2b is formed is further formed reflective portion 3b of the p-type in the middle of its upper surface in a columnar shape from SiO _2, SiN, or the like so as to surround the periphery An insulating layer 5 is formed,
The structure is such that the electrode 6 is formed on these upper layers.
The structure of the reflecting portion 3b can form a pair with the reflecting portion 3a, but may be undoped. In such a structure,
When a forward voltage is applied between the electrodes 4 and 6, holes (electrons depending on the selection of the conduction type) are injected through the reflecting portion 3b, so that the light emitting portion 2 emits light and the reflecting portions 3a and 3b.
Laser oscillation is obtained, and the laser light L is emitted from the reflecting portion 3a side to the outside world.

The shape of the cross section perpendicular to the stacking direction of the reflecting portions 3a and 3b is not limited, and may be circular, rectangular, strip-shaped or the like. Further, in the structural example of FIG. 2, the reflection portion 3b is a laminated body of p-type doped semiconductors and serves as a path for concentrated passage of holes or electrons. As another example of such a structure, doping is not performed in order to increase the reflectance of the reflection portion 3b, but instead, a current path between the electrode 6 and the p-type cladding layer 2b is provided near the center of the reflection portion. An example is a structure in which a columnar p-type semiconductor to be formed is formed so as to penetrate the reflecting portion in the stacking direction.

[Performance Confirmation Experiment] In order to confirm the performance of the semiconductor laser of the present invention, a surface emission type semiconductor laser according to the present invention and a surface emission type having a conventional structure are used by using a light emitting portion having the same structure. Also, edge emitting semiconductor lasers were manufactured, and the threshold values of the respective laser oscillations were compared. The structure of the light emitting unit is the same as that of the present invention and the prior art.
Both had a double heterojunction structure composed of Al _0.15 Ga _0.85 N / Ga _0.9 In _0.1 N (active layer) / Al _0.15 Ga _0.85 N. Hereinafter, it is referred to as a "common specification light emitting unit". Further, the light emitting system was a photoexcitation type, and the excitation light source was an N ₂ laser. As a method of confirming the performance of each sample, the input power [kW / cm ² ] of the pumping light source (N ₂ laser) when the laser oscillation was started was examined and compared to confirm.

(1) Structural Example 1 According to the Present Invention A semiconductor laser having the structure shown in FIG. 1 described in the above embodiment was manufactured. The order of forming the light emitting portion and the reflecting portion with respect to the crystal substrate will be described with reference to FIG. 1. First, one side of the crystal substrate 1 made of sapphire crystal is provided with a buffer layer (not shown) made of AlN interposed therebetween. The reflecting portion 3a is formed, and then the light emitting portion 2 having a common specification is provided on the front surface side of the crystal substrate 1 via a buffer layer (not shown) made of AlN.
And the other reflecting portion 3b is further formed thereon. The reflectors 3a and 3b have an AlN layer and an A
This is a structure in which 40 pairs of 1 _0.1 Ga _0.9 N layers and a layer of _0.1 Ga _0.9 N are laminated to form a superlattice. The formation of each layer including the buffer layer is based on a method capable of epitaxial growth. The threshold value of this semiconductor laser is shown below together with the results of other examples.

(2) Structural Example 2 According to the Present Invention Exactly the same as Structural Example 1 except that the reflecting portions 3a and 3b both have a structure in which 40 pairs of superlattices of an AlN layer and a GaN layer are laminated. A semiconductor laser sample was manufactured.
The threshold value of this semiconductor laser is shown below together with the results of other examples.

(3) Comparative Example 1 According to Prior Art In this comparative example, among the semiconductor lasers according to the prior art, an edge emitting sample having the structure shown in FIG. 3A was manufactured. As an outline of the manufacturing process, a buffer layer (not shown) made of AlN is formed on a sapphire crystal substrate 1a, a light emitting portion having a common specification is formed on the buffer layer, and the side end surfaces 3c and 3d of the light emitting layer 2a are formed. A reflective surface was formed by etching. The threshold value of this semiconductor laser is shown below together with the results of other examples.

(4) Comparative Example 2 of the Prior Art A sample of edge emitting semiconductor laser which is exactly the same as Comparative Example 1 except that the processing for making the side end surface of the light emitting layer 2a a reflecting surface is performed by polishing. Was produced. The threshold value of this semiconductor laser is shown below together with the results of other examples.

(5) Comparative Example 3 of the Prior Art Among the semiconductor lasers of the prior art, a surface emission type sample having a conventional structure shown in FIG. 3B was manufactured. The order of forming the light emitting portion and the reflecting portion with respect to the crystal substrate will be described with reference to the same figure. First, a buffer layer made of AlN (not shown) is formed on the surface of the sapphire crystal substrate 1b.
In this order, one reflecting portion 3e is formed via the, then the light emitting portion 2 of the common specification is formed, and the other reflecting portion 3f is further formed thereon. The reflection parts are 3N and 3F, and are made of AlN.
The layer and the Al _0.1 Ga _0.9 N layer are laminated so as to form a superlattice, and one pair constitutes 20 pairs. The number of superlattice pairs was set to 20 in consideration of the fact that the crystal quality of the light emitting portion deteriorates as the reflectance increases due to the increase. The formation of each layer including the buffer layer is based on a method capable of epitaxial growth. The threshold value of this semiconductor laser is shown below together with the results of other examples.

The outlines and threshold values of the reflecting portions of the above-mentioned structure examples 1 and 2 of the present invention and the comparative examples 1 to 3 of the prior art are as follows. (1) Structural example 1 according to the present invention Reflecting portion; AlN / Al _0.1 Ga _0.9 N superlattice 40 pairs each, threshold value; 15 kW / cm ² (2) Structural example 2 according to the present invention Reflecting portion; AlN / GaN superlattice 40 pairs each, threshold value: 20 kW / cm ² (3) Comparative example 1 according to prior art Method of forming reflective surface (end face emission type); etching, threshold value; 30 kW / cm ² (4) Comparative example according to conventional technology 2 Method of forming reflective surface (edge emission type); polishing, threshold value; 150 kW / cm ² (5) Comparative example 3 according to conventional technology Reflecting part; AlN / Al _0.1 Ga _0.9 N superlattice 20 pairs each, threshold value 50 kW / cm ²

From the above confirmation experiments, it was confirmed that the structure of the semiconductor laser according to the present invention can obtain laser oscillation with a lower input than the conventional structure.

[0034]

The semiconductor laser of the present invention has a surface emission type structure, and in addition to its conventional characteristics, one of a pair of reflecting portions constituting the resonator structure, which is closer to the crystal substrate than the light emitting portion. Is provided on the back surface side of the crystal substrate. Due to this feature, the light emitting portion can be directly molded on the crystal substrate, and the same method as the crystal growth method used in manufacturing the current high-brightness light emitting diode can be used. As a result, regardless of the injection type or the photoexcitation type, in the light emitting portion, the same level of crystal quality and internal quantum efficiency as that of the high brightness light emitting diode can be obtained. Similarly, in the reflecting portion on the back side of the crystal substrate, the improvement for improving the reflectance can be given priority and freely without considering the crystallinity deterioration of the light emitting portion. In particular, when the reflection part is composed of a large number of pair layers of superlattice,
In order to improve the reflectance, it is possible to form the layers up to the limit. Further, since it is not necessary to process the through hole in the substrate, it is possible to provide an efficient surface emitting semiconductor laser at low cost.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an example of a structure of a semiconductor laser of the present invention.

FIG. 2 is a diagram schematically showing an example of an electrode structure in the case where the emission method is an injection type in the structure of the semiconductor laser of the present invention.

FIG. 3 is a diagram schematically showing an example of a structure of a conventional semiconductor laser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crystal substrate 2 Light emission part 3a Reflection part 3b Reflection part S Laminated body L Laser light emitted

Claims (4)

[Claims] 1. A laminated body having a plurality of semiconductor layers including a light emitting portion laminated on a crystal substrate, and a pair of reflective portions formed by directly or indirectly sandwiching the laminated body in the laminating direction. The pair of reflecting portions has a resonator structure that resonates the light emitted from the light emitting portion in the stacking direction. 2. The semiconductor laser according to claim 1, wherein the light emitting portion has a multi-layer structure made of an InGaAlN-based compound semiconductor, and the crystal substrate is made of a material capable of transmitting the light emitted from the light emitting portion. . 3. The material of the crystal substrate that allows the light emitted from the light emitting portion to pass through is sapphire, GaN, SiC, Zn.
The semiconductor laser according to claim 2, which is any one of O. 4. The semiconductor laser according to claim 1, wherein at least one of the pair of reflecting portions has a multilayer structure made of an InGaAlN compound semiconductor or a dielectric multilayer film.