JPH04293289A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent shortening of a life of an element for deteriorating characteristics by diffusing Zn in an active layer from a p-type AlGaInP semiconductor layer in a semiconductor laser using an AlGaInP material. CONSTITUTION:An active layer 3 is doped with Se or Si, or an (AlzGa1-z)0.52 In0.48P(0<=z<=1) layer 12 doped with Se or Si and having 10-500 Angstroms of thickness is inserted between the active layer and a p-type semiconductor layer 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser using an AlGaInP material, and more particularly to a semiconductor laser having good initial characteristics and a long device life.

0002

2. Description of the Related Art FIG. 5 is a diagram showing a semiconductor laser using a conventional AlGaInP-based material. In the figure, 1 is an n-type (hereinafter referred to as n-) GaAs substrate;
n-(AlGa)0.52In0.48 which is lattice matched with
P lower cladding layer 2 is arranged on substrate 1 . An undoped In0.48Ga0.52P active layer 4 lattice-matched to GaAs is disposed on the lower cladding layer 2 and is p-type (hereinafter p-
) (AlGa)0.52In0.48P light guide layer 5 is disposed on the active layer 4 and is made of p-In0.48Ga0
．． A 52P etch stopper layer 6 is disposed on the light guide layer 5. The thickness of the etching stopper layer is extremely thin, about 100 angstroms. p-(AlGa)0.
52In0.48P upper cladding layer 7 and p-In0.4
The 8Ga0.52P band discontinuous relaxation layers 8 are sequentially arranged on the etching stopper layer 6, and are etched into a striped ridge shape in the cavity length direction. n-G
The aAs current blocking layer 15 is arranged on a region of the etching stopper layer 6 other than the region where the ridge is formed so as to bury the ridge. A p-GaAs contact layer 9 is arranged on the band discontinuity relaxation layer 8 and on the block layer 15. The electrode 10 is connected to the back surface of the substrate 1 and the contact layer 9
provided above.

Next, the manufacturing process will be explained. First, by the first crystal growth on the substrate 1, the lower cladding layer 2,
The active layer 4, the optical guide layer 5, the etching stopper layer 6, the upper cladding layer 7, and the band discontinuity relaxation layer 8 are successively crystal-grown. Next, a striped mask pattern in the cavity length direction is formed on the band discontinuity relaxation layer 8, and selective etching is performed using the etching stopper layer 6 to form the band discontinuity relaxation layer 8 and the upper cladding layer 7 into a ridge shape. Shape. After that, the n-GaAs current blocking layer 15 is grown using the mask pattern used for the etching as a selective growth mask.
A crystal is grown so as to embed a ridge consisting of the upper cladding layer 7 and the band discontinuous relaxation layer 8. After removing the mask pattern, the p-GaAs contact layer 9 is grown on the band discontinuity relaxation layer 8 and the block layer 15 by third crystal growth.
Finally, electrodes 10 are formed on the contact layer 9 and the back surface of the substrate 1 to complete the device.

0004

[Problem to be solved by the invention] Conventional AlGaInP
A semiconductor laser using the above-mentioned materials is constructed as described above.

[0005] Usually, Zn is used as the p-type impurity of AlGaInP used as the optical guide layer and the upper cladding layer. Since Zn-doped AlGaInP has a low electrical activation rate of impurities (approximately 40%), excessive Zn needs to be added to obtain the desired conductivity. Further, the diffusion rate of impurities in AlGaInP is higher than that in GaAs, etc., and abnormal diffusion is likely to occur. As a result, p-AlGaI
Excess Zn in the nP layer diffuses and eventually becomes InGa.
In many cases, the P active layer is no longer undoped. When a large amount of p-type impurity diffuses into the InGaP active layer,
Crystal defects are formed that serve as recombination centers for photocarriers, and the characteristics of the device deteriorate. Further, excessive Zn in the p-AlGaInP layer easily diffuses during operation of the device, resulting in deterioration of characteristics and shortening of device life.

The present invention was made to solve the above-mentioned problems, and by preventing Zn diffusion from the p-AlGaInP layer to the active layer, it has good initial characteristics and shortens the device life. The object of the present invention is to obtain an AlGaInP semiconductor laser having a long length.

[0007]

[Means for solving the problem] AlGa according to the present invention
InP-based semiconductor lasers have an active layer doped with Se or Si.

Further, the AlGaInP semiconductor laser according to the present invention has an undoped active layer and a p-AlGaInP semiconductor laser.
Se or Si doped layer thickness 10~
A 500 angstrom AlGaInP layer is provided.

[0009]

[Operation] In this invention, Se or S is added in the active layer.
Since it is doped with i, Zn in the p-type AlGaInP layer can be prevented from diffusing into the InGaP active layer during crystal growth and subsequent thermal processing, or during device operation.

Further, in the present invention, a layer of Al doped with Se or Si and having a thickness of 10 to 500 angstroms is provided between the undoped active layer and the p-AlGaInP layer.
Since the structure includes an lGaInP layer, p-type AlGa
Zn in the InP layer can be prevented from diffusing into the InGaP active layer during crystal growth and subsequent thermal processing, or during device operation.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1(a) is a cross-sectional structural diagram showing a semiconductor laser according to a first embodiment of the present invention, and in the figure, 1 is n-
It is a GaAs substrate, and n-(A
A lower cladding layer 2 of lGa)0.52In0.48P is placed on the substrate 1. A Se-doped n-In0.48Ga0.52P active layer (n-type impurity concentration 1 x 1018 cm-3) 3 lattice-matched to GaAs is disposed on the lower cladding layer 2, and a p-(AlGa)0.52In0.48P light guide is formed on the lower cladding layer 2. Layer 5 is disposed on active layer 3 and is made of p-In0.48Ga
A 0.52P etch stopper layer 6 is disposed on the light guide layer 5. The thickness of the etching stopper layer is extremely thin, about 100 angstroms. p-(AlGa)0
．． 52In0.48P upper cladding layer 7 and p-In0.
The 48Ga0.52P band discontinuous relaxation layers 8 are sequentially arranged on the etching stopper layer 6, and are etched into a striped ridge shape in the cavity length direction. n-
The GaAs current blocking layer 15 is the etching stopper layer 6
The p-GaAs contact layer 9 is disposed on the band discontinuity relaxation layer 8 and the block layer 15 so as to bury the ridge above the region other than the region where the ridge is formed. The electrode 10 is connected to the back surface of the substrate 1 and the contact layer 9.
provided above.

FIG. 4(a) is an enlarged view of the vicinity of the active layer 3 of this embodiment. Next, the manufacturing process will be explained. First, the lower cladding layer 2, the active layer 3, the optical guide layer 5, the etching stopper layer 6, the upper cladding layer 7, and the band discontinuity relaxation layer 8 are sequentially crystal-grown on the substrate 1 by the first crystal growth. . Next, a striped mask pattern in the cavity length direction is formed on the band discontinuity relaxation layer 8, and selective etching is performed using the etching stopper layer 6 to form the band discontinuity relaxation layer 8 and the upper cladding layer 7 into a ridge shape. Shape. Thereafter, using the mask pattern used in the etching as a selective growth mask, the n-GaAs current blocking layer 15 is grown to bury the ridge formed by the upper cladding layer 7 and the band discontinuity relaxation layer 8. After removing the mask pattern, p-GaAs is grown by the third crystal growth.
A contact layer 9 is grown on the band discontinuity relaxation layer 8 and the block layer 15, and finally an electrode 10 is formed on the contact layer 9 and the back surface of the substrate 1 to complete the device.

In the AlGaInP semiconductor laser according to this embodiment, since the InGaP active layer is doped with Se, diffusion of Zn, which is a p-type impurity in the optical guide layer 5, into the active layer can be suppressed. FIG. 2 shows an example of measurement by SIMS of Zn concentration profiles of a semiconductor laser whose active layer is doped with Se and a semiconductor laser whose active layer is undoped. As shown in FIG. 2(b), when the active layer is undoped, Z in the p-AlGaInP optical guide layer
The n concentration decreases near the active layer, and Zn diffuses into the active layer. However, when the active layer is doped with Se, there is no Zn diffusion from the p-AlGaInP optical guide layer near the active layer to the active layer. The active layer is Se-doped (
n=1×1018 cm−3), Zn doped (p=3×1
017 cm-3), and the laser oscillation threshold current density of an undoped element is shown in FIG. As shown in Figure 3, AlG
By doping the active layer of an aInP-based semiconductor laser with Se, a semiconductor laser with a low threshold current density and small variation was obtained. In the above example, as shown in FIG. 4(a), S was applied to the entire GaInP active layer.
Although a material doped with e is shown, a material doped with Si may also be used.

FIG. 1(b) is a sectional view showing the structure of an AlGaInP semiconductor laser according to a second embodiment of the present invention. In the figure, 1 is an n-GaAs substrate;
n-(AlGa)0.52In0. which is lattice matched to As.
A 48P lower cladding layer 2 is disposed on the substrate 1. GaA
Undoped In0.48Ga0.52 lattice matched to s
P active layer 4 is arranged on lower cladding layer 2 . active layer 4
On top is a Se-doped (Alz
Ga1-z )0.5 In0.5 P (0≦z≦1)
A layer 12 is disposed. p-(AlGa)0.52In0
．． The 48P light guide layer 5 is disposed on the Se-doped layer 12, and the p-In0.48Ga0.52P etch stopper layer 6 is disposed on the light guide layer 5. p-(AlGa
)0.52In0.48P upper cladding layer 7 and p-In
The 0.48Ga0.52P band discontinuous relaxation layers 8 are sequentially arranged on the etching stopper layer 6, and are etched into a striped ridge shape in the cavity length direction. The n-GaAs current blocking layer 15 is disposed on the etching stopper layer 6 in a region other than the region where the ridge is formed so as to bury the ridge. A p-GaAs contact layer 9 is formed on the band discontinuity relaxation layer 8 and on the block layer 1.
5. Electrode 10 is provided on the back surface of substrate 1 and contact layer 9 .

FIG. 4(b) shows the active layer 4 and S of this embodiment.
It is an enlarged view of the e-doped layer 12 and its vicinity.

Next, the manufacturing process will be explained. First, by the first crystal growth on the substrate 1, the lower cladding layer 2,
The active layer 4, the Se-doped layer 12, the optical guide layer 5, the etching stopper layer 6, the upper cladding layer 7, and the band discontinuity relaxation layer 8 are successively crystal-grown. Next, a striped mask pattern in the cavity length direction is formed on the band discontinuity relaxation layer 8, and selective etching is performed using the etching stopper layer 6 to form the band discontinuity relaxation layer 8 and the upper cladding layer 7 into a ridge shape. Shape. After this, the mask pattern used for the above etching was used as a selective growth mask to grow n-GaAs.
The current blocking layer 15 is crystal-grown so as to bury the ridge formed by the upper cladding layer 7 and the band discontinuous relaxation layer 8. After removing the mask pattern, a p-GaAs contact layer 9 is grown on the band discontinuity relaxation layer 8 and the block layer 15 by third crystal growth, and finally an electrode 10 is formed on the contact layer 9 and the back surface of the substrate 1. is formed to complete the device.

In this embodiment, the Se-doped layer 12 prevents Zn from diffusing from the p-AlGaInP layer near the active layer to the active layer, and the same effect as in the embodiment shown in FIG. 1A can be obtained.

In the first and second embodiments described above, the case of P-on-N type was explained, but the same effect as in the above-mentioned embodiment can be obtained also in the case of N-on-P type.

Furthermore, in the first and second embodiments described above, In0.48Ga0.52P was used as the active layer, but (Alx Ga1-x )0.5 In
It may be 0.5 P (0≦x≦0.7). However, in this case, the (AlGa) of the light guide layer and upper and lower cladding layers
The Al composition ratio of 0.52In0.48P needs to be set higher than that of the active layer.

[0020]

[Effects of the Invention] As described above, according to this invention, AlG
In an aInP-based semiconductor laser, since the active layer is doped with Se or Si, Zn in the p-type AlGaInP layer diffuses into the InGaP active layer during crystal growth and subsequent thermal processing, or during device operation. AlGaI with good initial properties and long life.
This has the effect of providing a semiconductor laser using nP-based materials.

According to the present invention, an Al layer doped with Se or Si and having a thickness of 10 to 500 angstroms is formed between the undoped active layer and the p-AlGaInP layer.
Since the structure includes a GaInP layer, p-type AlGaI
During crystal growth and subsequent thermal processing, Zn in the nP layer
Alternatively, it is possible to suppress diffusion into the InGaP active layer during operation of the device, and to obtain a semiconductor laser using an AlGaInP-based material that has good initial characteristics and has a long life.

[Brief explanation of drawings]

[Fig. 1] AlGa according to first and second embodiments of the present invention
FIG. 2 is a cross-sectional view showing the layer structure of an InP-based semiconductor laser.

FIG. 2 is a diagram showing the relationship between doping of an active layer and Zn diffusion.

FIG. 3 is a diagram showing the relationship between active layer doping and threshold current density.

FIG. 4 AlGa according to the first and second embodiments of the present invention
FIG. 2 is a diagram showing the vicinity of an active layer of an InP-based semiconductor laser.

FIG. 5 is a cross-sectional view showing the layer structure of a conventional AlGaInP semiconductor laser.

[Explanation of symbols]

1 n-GaAs substrate 2 n-AlGaInP lower cladding layer 3
n-InGaP active layer 4 Undoped GaInP active layer 5 p-
AlGaInP optical guide layer 6 p-InGaP etching stopper layer 7 p-AlGaInP upper cladding layer 8 p-InGaP band discontinuity relaxation layer 9 p-GaAs contact layer 10 electrode 12 n-(AlzGa1-z)0.5 In0
．． 5 P (0≦z≦1) layer 15 n-GaAs current blocking layer

Claims (2)

[Claims] Claim 1: A semiconductor laser constructed using an AlGaInP-based material, in which (Alx Ga1-x ) InP (0≦x≦0) doped with Se or Si is used.
．． 7) An active layer and (AlyGa1-y)I containing Zn as a p-type impurity provided in close proximity to the active layer.
A semiconductor laser comprising: an nP (y>x) p-type semiconductor layer. [Claim 2] In a semiconductor laser constructed using an AlGaInP-based material, (Alx Ga1-x )
An InP (0≦x≦0.7) undoped active layer and a 10-500 angstrom thick (Alz
a1-z) InP (0≦z≦1) layer and (A) containing Zn as a p-type impurity provided closely to the doped layer.
ly Ga1-y ) InP (y>x) p-type semiconductor layer.