JPH0613697A - Semiconductor device - Google Patents

Abstract

PURPOSE:To select the best Al composition ratio and doping concentration and improve the injection efficiency of an electron by forming a third layer formed of GaAlAs which has the Al ratio larger than a first layer and smaller than a second layer between the first and the second layers. CONSTITUTION:A first layer is formed of a p-clad layer 14 composed of GaAlAs with relatively small Al composition ratio or GaAs and an activating layer 15 formed of GaAlAs, and a second layer is composed of an n-clad layer 17 formed of (n)<+> type GaAlAs doped with group VI elements such as selenium and tellurium with relatively large Al composition ratio and a cap layer 18. A melt back preventing layer 16 is provided between the activating layer 15 and the n-clad layer 17. The melt back layer 16 is formed of n-GaAlzAs and the Al composition ratio (z) is larger than the Al composition ratio (y) of the activating layer 15 and is smaller than the composition ratio (x) of the n-clad layer 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to GaAlAs or GaA having a relatively small Al composition ratio.
and a second layer made of GaAlAs having a relatively large Al composition ratio doped with a Group VI element formed on the first layer by liquid phase crystal growth. The present invention relates to a semiconductor device, for example, a semiconductor laser device.

[0002]

2. Description of the Related Art Conventionally, for example, an inner stripe type semiconductor laser device is constructed as shown in FIG.

That is, in FIG. 3, a semiconductor laser device 1 includes a substrate 2 made of p ^{+ -type} GaAs and an n ⁺ -type GaA.
a current confinement layer 3 made of s, a p-cladding layer 4 made of p ⁺ -type GaAlxAs, an active layer 5 made of GaAlyAs, and an n-type made of n ⁺ -type GaAlxAs doped with a group VI element such as selenium or tellurium. Clad layer 6,
and a cap layer 7 made of n ^{+ type} GaAs.

Electrode layers (not shown) are provided on the lower surface of the substrate 2 and the upper surface of the cap layer 7, respectively, and a stripe-shaped groove 8 is formed in a V shape from the upper surface of the current confinement layer 3. Beyond the boundary between layer 3 and substrate 2 said substrate 2
It is provided to reach inside. However, x is y
Have been selected larger than.

In manufacturing the semiconductor laser device 1 having the above-described structure, the current confinement layer 3 is crystal-grown on the surface of the substrate 2 by the LPE (Liquid Phase Crystal Growth) method, and then etched. A stripe-shaped groove 8 that extends from the surface of the current constriction layer 3 to the inside of the substrate 2 is formed, and then the p-clad layer 4, active layer 5, n-
The clad layer 6 and the cap layer 7 are sequentially crystal-grown, and finally electrodes are formed on the lower surface of the substrate 2 and the upper surface of the cap layer 7 to manufacture the structure.

[0006]

However, according to the semiconductor laser device 1 having such a configuration, the Al composition obtained by doping the group VI element on the active layer 5 made of GaAlyAs having a relatively small Al composition ratio y is used. When liquid phase crystal growth of the n-clad layer 6 made of n ⁺ -type GaAlxAs having a relatively high ratio x occurs, the interface between the active layer 5 and the n-clad layer 6 becomes rough due to meltback. Will end up. On the other hand, (xy)
It has been known that the above-mentioned meltback can be prevented by decreasing the value of n or the dope concentration of the n-clad layer 6, but the electron injection efficiency is reduced, so that a semiconductor laser device is obtained. However, this is not a preferable method because it reduces the efficiency of.

In view of the above points, the present invention has an active layer and an n-type.
A first layer composed of GaAlAs or GaAs having a relatively small Al composition ratio, such as the relationship of the clad layer, and an Al composition doped with a group VI element formed by liquid phase crystal growth on the first layer. GaAlAs with relatively large ratio
By preventing the melt-back at the interface with the second layer composed of Al, the Al composition ratio, the doping concentration, etc. are selected to the optimum values, the electron injection efficiency is improved, and the semiconductor such as a semiconductor laser device having high efficiency is obtained. The purpose is to provide a device.

[0008]

The above object is to provide a first layer made of GaAlAs or GaAs having a relatively small Al composition ratio, and a group VI element formed on the first layer by liquid crystal growth. In a semiconductor device including a second layer made of GaAlAs having a relatively large Al composition ratio doped with Al, the Al ratio between the first layer and the second layer is larger than that of the first layer. And smaller than the second layer GaA
A semiconductor device, characterized in that a third layer of 1As is formed.

[0009]

According to the above construction, even when the difference in Al composition ratio between the first layer and the second layer is relatively large, the difference between the first layer and the second layer is large. In addition, since the third layer exists, the difference in Al composition ratio between the first layer and the third layer and between the third layer and the second layer becomes relatively small. Therefore, when the third layer is formed on the first layer and when the second layer is formed on the third layer, meltback may occur at each interface. Therefore, since each interface is kept smooth, the Al composition ratio, the doping concentration, etc. can be selected to the optimum values, so that the electron injection efficiency can be improved, and thus good efficiency can be obtained. Becomes

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. FIG. 1 shows an embodiment of an inner stripe type semiconductor laser device constructed according to the present invention.

The semiconductor laser device 10 is a p ^{+ type} GaA.
On the surface of the substrate 11 made of s, n ⁺
After crystal growth of the current confinement layer 12 made of GaAs, a stripe-shaped groove 13 extending from the surface of the current confinement layer 12 into the substrate 11 is formed by etching or the like.

Then, p ⁺ GaAl was formed by the LPE method.
x-As p-cladding layer 14 and GaAlyAs
An active layer 15 composed of n, a meltback prevention layer 16 having a structure described below, an n-clad layer 17 composed of n ^{+ type} GaAlxAs doped with a group VI element such as selenium, tellurium, and n ^{+ type} GaAs. Then, the cap layer 18 and the cap layer 18 are sequentially grown.

Thereafter, the lower surface of the substrate 11 and the upper surface of the cap layer 18 are provided with electrode layers (not shown), respectively.

Here, the meltback prevention layer 16 is made of n-
It is composed of GaAlzAs, and the Al composition ratio z is
It is selected to be larger than the Al composition ratio y of the active layer 15 and smaller than the Al composition ratio x of the n-clad layer 17, and the doping concentration is preferably n-clad layer 1.
It is lower than 7, or the doping material is an n-type material other than Group VI.

The semiconductor laser device 10 according to the present invention is
Since the meltback prevention layer 16 is provided between the active layer 15 and the n-clad layer 17, the active layer 15 and the n-clad layer 17 are structured as described above.
Even when the difference (xy) in the Al composition ratio between the active layer 15 and the melt-back preventing layer 1 is large due to the presence of the melt-back preventing layer 16 therebetween.
6, the melt-back prevention layer 16 and the n-clad layer 1
Since the differences (x-z) and (z-y) in the Al composition ratio between the active layer 15 and 7 are relatively small, even when the meltback prevention layer 16 is formed on the active layer 15, Even when the n-clad layer 17 is formed on the meltback prevention layer 16, meltback does not occur at each interface.

Therefore, each interface is kept smooth, and the active layer 15 and the n-clad layer 17 can be selected to have optimum Al composition ratios x and y, respectively, and the doping concentration is also optimized. Can be selected. Thus, the electron injection efficiency can be improved, so that a good semiconductor laser device 10 having high efficiency can be obtained.

FIG. 2 illustrates a CS constructed according to the present invention.
1 shows a P-type semiconductor laser device, in which the semiconductor laser device 20 is a substrate 2 made of n ^{+ -type} GaAs.
1. A groove 22 is formed on the surface of No. 1, and a melt-back prevention layer 23 made of n-GaAlzAs similar to that described above, an n-clad layer 24 made of n ⁺ -type GaAlxAs, and GaAlyAs are formed on the groove 22 by the LPE method. The active layer 25, the p-clad layer 26 made of p ⁺ -type GaAlxAs, and the cap layer 27 made of n ^{+ -type} GaAs are sequentially grown so that each layer has a predetermined thickness.

Thereafter, the lower surface of the substrate 21 and the upper surface of the cap layer 27 are provided with electrode layers (not shown), respectively.

Here, the meltback prevention layer 23 is made of Al.
The composition ratio z is selected to be larger than the Al composition ratio of the substrate 21 made of GaAs, that is, zero, and smaller than the Al composition ratio x of the n-clad layer 24.

In this case, the substrate 21 and the n-clad layer 2
Since the meltback prevention layer 23 is provided between the substrate 21, the meltback prevention layer 23, and the meltback prevention layer 23, the meltback prevention layer 23 and the n-clad layer 2 are similarly formed.
No meltback occurs at the interface between the substrate 4 and 4 and therefore each interface is kept smooth, so that the shape of the groove 22 provided on the surface of the substrate 21 is deformed by the meltback. It will not happen that the efficiency will be improved.

[0021]

As described above, according to the present invention, a first layer made of GaAlAs or GaAs having a relatively small Al composition ratio, such as an active layer and an n-clad layer,
GaAl having a relatively large Al composition ratio formed by liquid crystal growth on the first layer and doped with a group VI element
By preventing the melt-back at the interface with the second layer made of As, the Al composition ratio, the doping concentration, etc. were selected to be the optimum values, and the electron injection efficiency was improved. Further, a semiconductor laser device can be provided.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an embodiment of a semiconductor laser device according to the present invention.

FIG. 2 is a partial cross-sectional view showing another embodiment of the semiconductor laser device according to the present invention.

FIG. 3 is a partial cross-sectional view showing an example of a conventional semiconductor laser device.

[Explanation of symbols]

 10 semiconductor laser device 11 substrate 12 current confinement layer 13 stripe-shaped groove 14 p-clad layer 15 active layer 16 meltback prevention layer 17 n-clad layer 18 cap layer 20 semiconductor laser device 21 substrate 22 groove 23 meltback prevention layer 24 n -Clad layer 25 Active layer 26 p-Clad layer 27 Cap layer

Claims (1)

[Claims] 1. GaAlAs having a relatively small Al composition ratio
Alternatively, a first layer made of GaAs and a second layer made of GaAlAs having a relatively large Al composition ratio doped with a group VI element formed by liquid phase crystal growth on the first layer are included. In the semiconductor device, a third layer made of GaAlAs having an Al composition ratio higher than that of the first layer and lower than that of the second layer is formed between the first layer and the second layer. A semiconductor device characterized by: