JPH10294524A - Semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser which has excellent temperature characteristics by suppressing the overflow of electrons from an active layer to a p clad layer. SOLUTION: This semiconductor laser 10 is an AlGaInP-based semiconductor laser formed on a GaAs substrate 12 and has an electron stopper layer 20 with 2% expansion strain between the active layer 18 and p type clad layer 22. Consequently, the overflow of electrons from the active layer 18 to the p clad layer 22 is suppressed to improve the temperature characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, and more particularly, to a semiconductor laser having good temperature characteristics and a wavelength of 600 nm.
The present invention relates to a visible light semiconductor laser oscillating in a band.

[0002]

2. Description of the Related Art In order to facilitate adjustment of optical systems of various laser-applied devices such as large-capacity optical disks and optical measuring devices, attempts have been made to employ a visible light semiconductor laser oscillating in the 600 nm band as a light source. There is a growing demand for a visible light laser that oscillates at a shorter wavelength in order to improve the beam focusing property and visibility of the laser light. 60
The 0 nm band visible laser uses AlGaIn on a GaAs substrate.
This is realized by a laser having a P-based mixed crystal semiconductor laminated structure, and an active layer in which tensile strain is introduced into GaInP or an AlGaInP active layer in which Al is added is used. Furthermore, oscillation at a shorter wavelength has been obtained by using a quantum well structure of these substances as the active layer.

However, with the shortening of the oscillation wavelength, Al
In a GaInP-based visible light semiconductor laser, p
Deterioration of temperature characteristics due to overflow of electrons into the mold cladding layer is a problem. In order to suppress the overflow of electrons, it is necessary to take measures to increase the band gap difference between the active layer and the p-cladding layer or to shift the band edge of the cladding layer by high concentration doping of the p-cladding layer. It is said to be effective. By the way, in the AlGaInP system, in order to increase the band gap difference between the active layer and the p clad layer, an attempt is made to increase the band gap of the clad layer by increasing the Al composition ratio in the AlGaInP mixed crystal used as the clad layer. Also, (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P becomes a boundary between the direct transition type semiconductor and the indirect transition type semiconductor, and even if the Al composition ratio is further increased, the electron confinement effect is substantially increased. Can not be done. Therefore, as the oscillation wavelength becomes shorter and the band gap of the active layer becomes larger, the band gap difference between the active layer and the cladding layer becomes smaller, and the phenomenon that electrons overflow into the p-cladding layer cannot be ignored.

Therefore, the equivalent barrier height for electrons depends on the dopant concentration of the p-cladding layer, and based on the principle that the higher the dopant concentration, the equivalent barrier for electrons is higher. Attempts have been made to suppress the overflow phenomenon of electrons into the p-cladding layer by increasing the doping concentration. Also, as another technique for increasing the doping concentration of the p-cladding layer, a very thin multilayer film is inserted between the active layer and the p-cladding layer, and the p-cladding layer utilizes the interference effect of electrons on the p-cladding layer. A so-called multiple quantum barrier (MQB) structure has been attempted in which electrons overflowing into the cladding layer are reflected, electrons are efficiently confined in the active layer, and the barrier height is equivalently increased.

[0005]

However, AlGaIn
It is technically difficult to dop the p-type dopant at a high concentration in the AlGaInP mixed crystal p-cladding layer with a P-based 600 nm band visible laser, and it is technically difficult, and at most 1 × 10 ¹⁸ c
A concentration of about m ^-3 is the upper limit. However, at such a dopant concentration, there is a limit to the effect of equivalently increasing the height of the barrier, and the effect of suppressing the electron overflow phenomenon is poor. Although multiple quantum barriers are expected to produce a very large effect in theory, it is difficult to form an ultra-thin multilayer structure as designed in practice. At present, the same effect has not been obtained. That is, in the range of the prior art, the problem of electron overflow peculiar to the AlGaInP-based laser structure has not been sufficiently solved.

Similarly, with respect to an infrared laser oscillating in the 1300 nm band, deterioration of temperature characteristics due to an electron overflow phenomenon is a problem for the following reason. That is,
Since lasers in this wavelength band are used in optical subscriber systems, it is important to realize low-cost modules for practical use. Attempts have been made to omit features. However, when the temperature adjustment function is omitted, 600 nm
As in the case of the visible light laser in the band, an overflow phenomenon of electrons from the active layer to the p-type clad occurs, which causes an increase in the threshold current. It was difficult to sufficiently solve the electron overflow problem by the method.

An object of the present invention is to provide a semiconductor laser having good temperature characteristics by suppressing the overflow of electrons from the active layer to the p-cladding layer.

[0008]

The present inventors have studied the mechanism of the overflow of electrons from the active layer to the p-cladding layer. As a result, the energy at the conduction band X is higher than the energy at the conduction band Γ. By making the semiconductor layer, which is a low indirect transition type mixed crystal, having a lattice constant smaller than that of the substrate and introducing tensile strain, function as an electron stopper between the active layer and the p-cladding layer. With the idea of suppressing the overflow of electrons, the present invention has been completed.

Hereinafter, the phenomenon underlying the present invention will be described in more detail. Conventionally, most of the mixed crystal semiconductor materials used in semiconductor lasers are so-called direct transition type mixed crystals in which the energy at the conduction band Γ is lower than the energy at the point X, as shown in FIG. . In recent years, the use of a semiconductor material having a lattice constant different from that of a substrate intentionally in a layered structure has also become popular, but this is also mainly used as a quantum well active layer in which strain is introduced. The active layer having a quantum well structure into which is introduced is a direct transition type semiconductor layer.
In rare cases, indirect semiconductor layers may be used,
The semiconductor layer was lattice-matched to the substrate as shown in FIG.

Under such circumstances, although the behavior at the point Γ of the conduction band of the indirect transition type mixed crystal in which strain is introduced has been investigated, the characteristics of the point X in the conduction band of the mixed crystal in which strain is introduced are not known. Not been. In general, when strain is introduced, the energy of the conduction band of the indirect transition type mixed crystal changes. The magnitude of the change is determined by the magnitude of the strain and the magnitude of the deformation potential, and the deformation potential under hydrostatic pressure is involved in the conduction band. The energy at the Γ point of the conduction band increases during compressive strain and decreases during stretch strain. In general, a composition in which a compressive strain is introduced has a small band gap, and a composition in which an extensional strain is introduced has a large band gap.Therefore, in a strained quantum well structure, for example, in order to improve electron confinement, a band gap is required. Even when a composition having a large value is used, the conduction band energy is reduced due to the effect of strain, and the effect is not so large.

In the indirect transition type mixed crystal in which the extensional strain is introduced, the change in the deformation potential under the above-mentioned hydrostatic pressure differs between that for the point と and that for the point X, and the signs are opposite. In the composition having a large band gap where the tensile strain is introduced, the point 伝 導 of the conduction band decreases and the point X increases as shown in FIG. 1 (c). Will do. Since the indirect transition type mixed crystal has lower energy at the X point than at the Γ point, this increase in the energy at the X point increases the band edge discontinuity ΔEc of the conduction band of the extensional indirect transition type semiconducting layer. This increases the band gap and increases the electron confinement effect, and is suitable as a barrier layer for suppressing overflow of electrons.

On the other hand, the valence band energy always has a maximum at the Γ point. The energy level of the valence band is split into energies for heavy holes and energies for light holes due to the introduction of strain, as shown in FIG. In the case of a composition having a large band gap where a tensile strain is introduced, the direction of the change in the valence band energy level due to the strain decreases the band edge discontinuity ΔEv because the energy for light holes increases. To reduce the band gap. Therefore,
The indirect transition type mixed crystal in which the above-described tensile strain is introduced serves as an energy barrier for electrons but hardly a barrier for holes.

Based on the above findings, the semiconductor laser according to the present invention is characterized by having an indirect transition type mixed crystal semiconductor layer having an extensional strain between an active layer and a p-type cladding layer. Preferably, the composition of the mixed crystal semiconductor layer is configured such that the magnitude of the extensional strain of the indirect transition type mixed crystal semiconductor layer is 3% or less. A preferred embodiment is an AlGaInP-based semiconductor laser on a GaAs substrate, wherein the substrate and the active layer are GaAs and (Al) GaInP, respectively, and the indirect transition type mixed crystal semiconductor layer is AlGaInA.
sP, AlGaInP, AlInP, GaInP and G
aAsP. Another preferred embodiment is an InP-based semiconductor laser lattice-matched on an InP substrate, wherein the substrate and the active layer are each made of InP.
P and GaInAs (P), wherein the indirect transition type mixed crystal semiconductor layer is composed of AlGaInAs, AlInAs and Al
Any of InAsP.

GaInAs deposited on a GaAs substrate
With respect to P mixed crystal, AlInAsP mixed crystal, AlGaAsP mixed crystal and AlGaInP mixed crystal, an isostrain line and a boundary line between a direct transition type and an indirect transition type were obtained by calculation, and FIG. 2 (a) and FIG. , FIG. 4 (a) and FIG. 5 (a). Also, a lattice-matched GaInAsP mixed crystal, AlInAsP mixed crystal, Al
Concerning the GaAsP mixed crystal and AlGaInP mixed crystal, the lower energy lines of the conduction point energy between the Γ point and the X point of the conduction band energy were obtained by calculation.
(B), FIG. 3 (b), FIG. 4 (b) and FIG. 5 (b). In the drawing, the range indicated by oblique lines indicates a range where the extensional strain is 3% or less. Incidentally, among the mixed crystals lattice-matched to the GaAs substrate, the composition having the highest energy in the conduction band is (A
l _0.7 Ga _0.3 ) _0.5 In _0.5 P, and the energy of the conduction band is 1.85 e on the basis of the valence band of GaAs.
On the other hand, in any of the mixed crystals shown in FIGS. 2 to 5, the indirect transition type mixed crystal region in which the tensile strain is introduced has a region where the energy of the conduction band is larger than 1.85 eV. Exists. Therefore, by using the mixed crystal in this region, the overflow of electrons can be effectively suppressed as compared with the related art.

FIG. 6 (a) shows an isostrain line and a boundary line between a direct transition type and an indirect transition type for an AlGaInAs mixed crystal lattice-matched on an InP substrate. FIG. 6 (b)
It is a contour line showing a lower energy point between the Γ point and the X point of the conduction band energy of the AlGaInAs mixed crystal on the InP substrate. Meanwhile, in the case of an InP substrate, among mixed crystals lattice-matched to InP, the composition having the highest energy in the conduction band is Al _0.48 In _0.52 As, and the energy in the conduction band is based on the valence band of GaAs. In contrast, in the mixed crystal shown in FIG. 6, in the indirect transition type mixed crystal region into which the tensile strain is introduced, there is a region where the energy of the conduction band is larger than 1.6 eV. Exists. Therefore, by using the mixed crystal in this region, the overflow of electrons can be effectively suppressed as compared with the related art.

As the extensional strain becomes larger, the energy level of the conduction band becomes higher and the effect of suppressing the overflow of electrons is larger, but it is difficult to grow a layer having a large amount of strain and having a large film thickness well. To increase the amount of distortion, it is necessary to reduce the film thickness. Generally, in order to prevent dislocations due to strain from occurring, the film thickness × the amount of strain should be 30 nm%.
It is desirable to be about the following. On the other hand, even if an energy barrier exists, if the thickness of the barrier is small, electrons pass through by tunneling, so that the film thickness needs to be about 10 nm or more to suppress the tunneling. Therefore, in order to suppress the overflow of the electrons while suppressing the tunneling, it is desirable that the amount of the extensional strain is set to 3% or less.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings by way of examples. Embodiment 1 This embodiment is an embodiment in which the configuration of the semiconductor laser according to the present invention is applied to an AlGaInP-based semiconductor laser,
FIG. 7 is a cross-sectional view of a substrate showing a layer structure of the semiconductor laser of the present embodiment, FIG. 8A is a schematic diagram of a conduction band energy near an active layer of the semiconductor laser of Embodiment 1, and FIG.
FIG. 5 is a schematic diagram of a conduction band energy near an active layer of a semiconductor laser having a conventional structure corresponding to FIG. As shown in FIG. 7, the semiconductor laser 10 of the present embodiment is an AlGaInP-based semiconductor laser fabricated on a GaAs substrate 12 and has a magnitude of a tensile strain between the active layer 18 and the p-type cladding layer 22. Has a 2% electron stopper layer 20.

This semiconductor laser 10 is an n-GaAs substrate which is epitaxially grown on an n-type GaAs substrate 12 sequentially.
Buffer layer 14, n- (Al _0.7 Ga _0.3 ) _0.5 In
_0.5 P lower cladding layer 16, intrinsic GaInP active layer 1
8. Al _0.81 In _0.19 P tensile-strained electron stopper layer 20 with a tensile strain of 2% and a thickness of 10 nm, p- (Al _0.7 Ga _0.3 ) _0.
5 In _0.5 P first upper cladding layer 22 and p-GaI
An nP etching stop layer 24 is provided. Thereon has a mesa structure _{p- (Al 0.7 Ga 0.3) 0.5} In 0. 5 P second upper cladding layer 26, and p-GaInP intermediate layer 28, on both sides of the mesa structure n-GaAs current A blocking layer 30 is formed. Furthermore, the p-
An upper electrode 34 is provided via the GaAs contact layer 32, and a lower electrode 36 is provided below the substrate 12 as an electrode.

Hereinafter, a method of manufacturing the semiconductor laser 10 will be described. The method for manufacturing the present semiconductor laser 10 is as follows.
Except that the electron stopper layer 20 is formed on the substrate 8, the method is the same as that of the conventional semiconductor laser. First, on an n-type GaAs substrate 12, a buffer layer 14, a lower cladding layer 16, an active layer 18, and an extension strained electron stopper layer 2 are sequentially formed.
0, first upper cladding layer 22, etching stop layer 2
4. The second upper cladding layer 26 and the intermediate layer 28 are
Epitaxial growth is performed by the VD method. Next, an insulating film such as SiN is deposited on the intermediate layer 28, and the second upper cladding layer 26 is formed by photolithography and chemical etching.
Then, the intermediate layer 28 is etched to the etching stop layer 24 to form a mesa structure. 2
The current blocking layer 30 is formed by the second MOCVD growth to bury the mesa structure. Next, the insulating film is removed, and 3
The contact layer 32 is grown on the entire surface by the second MOCVD growth. Further, the upper electrode 34 on the contact layer 30,
The lower electrode 36 is formed below the substrate 12 to complete the semiconductor laser 10 as shown in FIG.

Measurements were made to evaluate the semiconductor laser 10 of Example 1. As a result, the threshold current was 40 mA, and the oscillation wavelength was 652 nm. When the characteristic temperature T0 was measured to evaluate the temperature dependence of the threshold current, T0 was about 120K. The potential near the active layer is shown in FIG.
This is as shown in FIG.

For comparison, a conventional semiconductor laser having the same configuration as the semiconductor laser 10 of the first embodiment except that no electron stopper layer is formed between the active layer and the first upper cladding layer. Was prepared as a comparative example. The first upper cladding layer of the comparative example is the semiconductor laser 1 of the first embodiment.
It has a thickness equal to the sum of the thicknesses of the electron stopper layer 20 and the first upper cladding layer 22. When the characteristics of the semiconductor laser of the comparative example were measured, the threshold current was 45 mA and the oscillation wavelength was 652 nm. When the characteristic temperature T0 was measured in order to evaluate the temperature dependence of the threshold current, T0 was about 60K. The potential near the active layer is shown in FIG.
This is as shown in FIG.

Embodiments 2 to 4 Embodiments 2 to 4 are other embodiments of the semiconductor laser according to the present invention. Each of the electron stopper layers has a thickness of 10 nm and a p- ( al _0.15 Ga _{0. 85) 0.8}
In _0.2 P layer, p-GaAs _0.25 P having a tensile strain of 2.5%
Semiconductor lasers having the same configuration as in Example 1 were produced in the same manner as in Example 1 except that a _0.75 layer and a Ga _0.8 In _0.2 P layer having a tensile strain of 2% were used. . When the laser characteristics of the semiconductor lasers of Examples 2 to 4 were measured in the same manner as in Example 1, the threshold currents were all 40 m.
A, and the characteristic temperature T ₀ ranges from 120 K to 130
It was K. The energy structures near the active layers in Examples 2 to 4 were as shown in FIGS. 9A, 9B, and 9C.

As is clear from the comparison with the comparative example, the semiconductor lasers of Examples 1 to 4 can prevent the overflow of electrons to the p-cladding layer by using the indirect transition type semiconductor layer having a tensile strain as the electron stopper layer. As a result, the characteristic temperature T0 is significantly higher than that of the comparative example, and it can be seen that the temperature characteristic of the laser is greatly improved. Also, the threshold current value is lower than the comparative example.

Embodiment 5 Embodiment 5 is an embodiment in which the configuration of the semiconductor laser according to the present invention is applied to an InP-based semiconductor laser. FIG. 10 is a sectional view showing the layer structure of the semiconductor laser of this embodiment. It is.
As shown in FIG. 10, the semiconductor laser 40 of the present embodiment
This is an InP-based semiconductor laser fabricated on an InP substrate 42, and has an electron stopper layer 52 having an extensional strain of 2% between an active layer 48 and a p-type cladding layer 54. As shown in FIG. 10, a semiconductor laser 40 according to the present embodiment includes an n-type InP substrate 42, an n-InP lower cladding layer 44, and a GaIn
AsP-SCH layer 46, GaInAsP active layer 48, G
aInAsP-SCH layer 50, 10 nm thick, tensile strain 2
% Of the Al _0.8 In _0.2 As electron stopper layer 52, the upper part of the lower cladding layer 44, the SCH layer 46, the active layer 48,
The SCH layer 50 and the electron stopper layer 52 are formed as a mesa structure. On the top and both sides of the mesa structure, p-In
It has a P upper cladding layer 54, and an n-InP current blocking layer 56 has entered the upper cladding layer 54 toward the mesa structure. On the upper cladding layer 54, p-InGa
An upper electrode 60 is formed on the entire surface via a contact layer 58 made of As, and a lower electrode 62 is formed below the substrate 42 as an electrode.

Hereinafter, a method of manufacturing the semiconductor laser 40 will be described. The method of manufacturing the semiconductor laser 40 is as follows.
Except that an electron stopper layer 52 is formed on the substrate 8 via an SCH layer 50, the method is the same as the conventional method for manufacturing a semiconductor laser. On the n-type InP substrate 42, the lower cladding layer 44, the SCH layer 46, the active layer 48, the SCH layer 50, and the electron stopper layer 52 are sequentially grown epitaxially by MOCVD. Next, Si is deposited on the electron stopper layer 52.
An insulating film of N or the like is deposited and removed by photolithography and chemical etching except for a part of the region up to the upper portion of the lower cladding layer 44 to form a mesa structure. Subsequently, the upper cladding layer 54 and the current blocking layer 56 are formed by the second MOCVD growth while leaving the insulating film. The insulating film is removed, an upper clad layer 54 is further grown on the entire surface by the third MOCVD growth, and then a contact layer 58 is grown. Next, the upper electrode 60 and the lower electrode 62 are manufactured, and the semiconductor laser 40 is completed.

When the characteristics of the semiconductor laser 40 were measured in order to evaluate the semiconductor laser 40 of Example 5, the threshold current was 15 mA and the oscillation wavelength was 1310 nm. When the characteristic temperature T0 was determined in order to evaluate the temperature dependence of the threshold current, T0 was about 180K. For comparison, a semiconductor laser having a conventional structure having the same configuration as that of the semiconductor laser 40 of Example 5 except that an electron stopper layer is not formed between the active layer and the upper cladding layer is manufactured as a comparative example. When the characteristics of the semiconductor laser of the comparative example were measured, the threshold current was 15 mA and the characteristic temperature T0 was about 80K. As is clear from the comparison with the comparative example, in the semiconductor laser of Example 5, the overflow of electrons to the p-cladding layer was suppressed by using the indirect transition type semiconductor layer having the extensional strain as the electron stopper layer, and the characteristic temperature was reduced. T0 is significantly higher than that of the comparative example, and it can be seen that the temperature characteristics of the laser are greatly improved.

In the above embodiment, the active layer has a bulk structure. However, it is needless to say that the same effect can be obtained even if the active layer has a quantum well structure.

[0028]

According to the structure of the present invention, an indirect transition type mixed crystal semiconductor layer having an extensional strain is interposed between the active layer and the p-side cladding layer as an electron stopper, so that the p-cladding layer can be separated from the active layer. It is possible to suppress the overflow of electrons to the layer and obtain a semiconductor laser device having good temperature characteristics.

[Brief description of the drawings]

1 (a), (b) and (c) are respectively
It is a schematic diagram for demonstrating the energy level of the indirect transition type mixed crystal which introduced the extensional strain.

FIGS. 2 (a) and 2 (b) show GaAs, respectively.
The strain line of GaInAsP mixed crystal lattice-matched to the boundary line of direct transition type / indirect transition type, and the contour line of the lower energy of Γ point and X point of the conduction band are displayed. Indirect transition indicates a region where the extensional strain is 3% or less.

FIGS. 3 (a) and 3 (b) show GaAs, respectively.
The strain lines of the AlInAsP mixed crystal lattice-matched to the boundary lines of the direct transition type and the indirect transition type, and the contour lines of the lower energies of the 帯 point and the X point of the conduction band are displayed. Indirect transition indicates a region where the extensional strain is 3% or less.

FIGS. 4A and 4B show GaAs, respectively.
The strain lines of the AlGaAsP mixed crystal lattice-matched to the boundary lines of the direct transition type and the indirect transition type, and the contour lines of the lower energies of the 帯 point and the X point of the conduction band are displayed. Indirect transition indicates a region where the extensional strain is 3% or less.

FIGS. 5A and 5B show GaAs, respectively.
The strain lines of the AlGaInP mixed crystal lattice-matched to the boundary lines of the direct transition type and the indirect transition type, and the contour lines of the lower energies of the 帯 point and the X point of the conduction band are displayed. Indirect transition indicates a region where the extensional strain is 3% or less.

FIGS. 6 (a) and 6 (b) are respectively a strain line of an AlGaInAs mixed crystal lattice-matched to InP, a boundary line of a direct transition type / indirect transition type, and a Γ point / X of a conduction band. The contour line of the lower energy among the points is displayed, and the shaded area indicates an area of 3% or less in extensional strain due to indirect transition.

FIG. 7 shows an AlGaInP system 6 formed on a GaAs substrate.
1 is a cross-sectional view of a first embodiment of a 00 nm band semiconductor laser.

FIGS. 8 (a) and (b) show Example 1 respectively.
FIG. 4 is a schematic diagram of conduction band energy near the active layer of the semiconductor laser of FIG.

9 (a), 9 (b) and 9 (c) show Examples 2 to 9;
FIG. 9 is a schematic diagram of the conduction band energy near the active layer of the semiconductor laser of No. 4;

FIG. 10 shows an InP-based 1300n fabricated on an InP substrate.
It is sectional drawing of an m-band semiconductor laser.

[Explanation of symbols]

Reference Signs List 10 Semiconductor laser of Example 1 12 n-type GaAs substrate 14 n-GaAs buffer layer 16 n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P lower cladding layer 18 intrinsic GaInP active layer 20 extension strain 2% Al _0.81 In _0.19 P electron Stopper layer 22 p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first upper cladding layer 24 p-GaInP etching stop layer 26 p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P second upper cladding layer 28 p-GaInP intermediate Layer 30 n-GaAs current blocking layer 32 p-GaAs contact layer 34 upper electrode 36 lower electrode 40 semiconductor laser of Example 5 n-type InP substrate 44 n-InP lower cladding layer 46 GaInAsP-SCH layer 48 GaInAsP active layer 50 GaInAsP -SCH layer 52 tensile strain 2% Al _0.8 In _0.2 As electron Stopper layer 54 p-InP upper cladding layer 56 n-InP current blocking layer 58 p-InGaAs contact layer 60 upper electrode 62 lower electrode

Claims (4)

[Claims] 1. A semiconductor laser comprising an indirect transition type mixed crystal semiconductor layer having extensional strain between an active layer and a p-side cladding layer. 2. The semiconductor laser according to claim 1, wherein the magnitude of the extensional strain of the indirect transition type mixed crystal semiconductor layer is 3% or less. 3. The substrate and the active layer are made of GaAs and (Al) GaInP, respectively, and the indirect transition type mixed crystal semiconductor layer is made of AlGaInAsP, AlGaInP, and AlI.
The semiconductor laser according to claim 1, wherein the semiconductor laser is one of nP, GaInP, and GaAsP. 4. The substrate and the active layer are made of InP and GaInAs (P), respectively, and the indirect transition type mixed crystal semiconductor layer is made of AlGaInAs, AlInAs and AlInA.
2. The method according to claim 1, which is any one of sP.
Or the semiconductor laser according to 2.