JPS60176225A - Liquid-phase epitaxial crowth method - Google Patents

Abstract

PURPOSE:To enable to form a layer of flat surface on a substrate having protrusions by a method wherein a layer growing method is performed under the state having a specific temperature of supersaturation. CONSTITUTION:A layer is grown at the supersaturation temperature of 4 deg.C or above. For exaple, on the surface of a P type GaAs substrate 1 whereon protrusions of 2.2mum in height and 10mum in width are formed by etching, an N type GaAs blocking layer 2 is grown at the growing temperature of 845 deg.C and the supersaturation temperature of 5 deg.C by performing a liquid-phase epitaxial method in such a manner that the layer 2 will be formed at 0.7mum in thickness on the protrusions. On the surface of the substrate whereon the first growing process has been finished. After a ridge erecting in parallel with the surface of the substrate, whereon the first growing of layer was finished, has been formed astriding a groove by performing an etching, the first layer of P type Ga1-yAlyAS clad layer 3, the second layer of non-doped Ga1-xAlxAS active layer 4, the third layer of N type Ga1-yAlyAS clad layer 5, the fourth layer of N type GaAs electrode forming layer 6 are continuously grown by performing a liquid-phase epitaxial method again.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid phase epitaxial growth method.

2. Description of the Related Art Structures and Problems Therein, in recent years, semiconductor laser devices have been attracting attention as light sources for recording and reproducing in disk file devices, as they are capable of producing high output with a low threshold and low noise. In order to meet this demand, the present inventors proposed an internal stripe type TR3 laser.
, Its cross-sectional view is shown in Fig. 1. In the same figure, 1 is p-type G
aAs substrate, 2 is n-type GaAs blocking layer, 3 is p
Type G2LI yAβyAs cladding layer, 4 is non-doped Ga, 1A6xAs active layer, 5 is n-type Fa, ,he
yhs cladding layer, 6 is an n-type GaAs electrode forming layer, 7 is a metal film for n-side ohmic electrode, and 8 is a metal film for p-side ohmic electrode. P-type Ga with striped protrusions
An n-type GaAs blocking layer 2 is grown on an As substrate 1, in which two parallel ridges are formed. The current injected from the p-side electrode 8 is intensively injected into the active layer 4 above the groove by the action of the blocking layer 2. Since the active layer 4 is very thin due to the action of the ridge, the light generated in the active layer 4 due to this current leaks into the cladding layer 3 to a large extent. In this beam part, the light is absorbed by the substrate and is consequently confined in the groove part, where stable fundamental transverse mode oscillation is obtained.

However, in the conventional internal stripe type TRS laser, when the blocking layer 2 is formed by the first growth, the growth surface is often not flat and undulated, as shown in FIG. 2a. When such undulation occurs, the second
As shown in the figure, the etching during ridge formation reaches the substrate size even in areas other than the grooves, and as a result, when the laser is configured as shown in Figure 2C, current leakage occurs outside the grooves as shown by the arrow. will occur. This becomes a major obstacle in improving the oscillation rate of the device.

OBJECTS OF THE INVENTION In view of the above-mentioned drawbacks, the present invention provides a liquid phase epitaxy/pitaxial growth method capable of forming a layer with a flat surface on a substrate provided with projections.

Structure of the Invention In order to achieve this object, the liquid phase epitaxial growth method of the present invention is characterized in that growth is performed with a supersaturation degree of 4° C. or higher.

DESCRIPTION OF EMBODIMENTS 1 An embodiment of the present invention will be described below with reference to the drawings. FIGS. 3a to 3d are cross-sectional views at each step of an embodiment of the present invention.

On the surface of a p-type GaAs substrate 1 (FIG. 3a) on which protrusions of 2.2 μm in height and 10 μm in width have been formed by etching, an n-type GaAs blocking layer 2 is formed on the protrusions by a liquid phase epitaxial method. Growth was carried out under the conditions of a growth temperature of 845° C. and a supersaturation degree of 5° C. to obtain a thickness of 7 μm (FIG. 3b). A layer with a height of 1.5μ22z was placed on the surface of the substrate after this first growth.

Two parallel ridges with a width of 20 μm are connected to a width of 4 μm.
It is formed by etching across the m groove.

The groove between the ridges is located directly above the protrusion, and its bottom reaches the p-type substrate 1. On the other hand, the blocking layer 2 remains on the flat portion outside the ridge even after etching (FIG. 3C). A first layer of p-type GtL + 1Aey A is then applied to the surface of the substrate 10 on which the ridge has been formed by the liquid phase epitaxial method again.
The S crack layer 3 is placed on the ridge with a thickness of about 0.2 μm, the second layer is made of non-doped Ga, the ZHEXHS active layer 4 is made of about 0.05 li 77K, and the third layer is made of n-type Ga.
, the A6yAS cladding layer 5 is also approximately 1.6 μm thick.
Similarly, the n-type GaAs electrode forming layers 6 are continuously grown to a thickness of about 2.0 μm (FIG. 3d).

In addition, in the above example, 7=0.43, X=0.0
It is 8.

A metal for the n-side electrode is deposited on the fourth electrode forming layer 6 and alloyed to form an n-side ohmic electrode 7f, and a metal for the p-side electrode is deposited on the substrate 1 side and alloyed. Processing is performed to form the p-side ohmic electrode 8.

FIG. 4 shows the relationship between the degree of supersaturation Δ and the flatness of the growth surface during growth of the blocking layer. As is clear from FIG. 4, if the degree of supersaturation Δ is 4°C or more, the growth surface becomes completely flat. Therefore, the semiconductor laser device manufactured according to this example had no current leakage, the oscillation rate was dramatically improved, and a high output of 5 QmW was achieved with good reproducibility.

As described in detail, the liquid phase epitaxial growth method of the present invention provides a flat growth surface even on a substrate provided with protrusions, so that it has great industrial utility.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of an internal stripe type TRS laser;
Figures a-c are cross-sectional views of each step in a conventional manufacturing method for this laser, Figures 3 a-d are cross-sectional views of each step in a manufacturing method according to an embodiment of the present invention, and Figure 4 is a cross-sectional view of the growth of a blocking layer. FIG. 3 is a diagram showing the relationship between the degree of supersaturation and the growth surface. 1...p-type GaAs substrate, 2...n-type GaAs blocking layer, 3...p-type GA 1
y A eyA s crat layer, 4...Non-doped Ga1, 1xAs active layer, 5...n-type Ga
, , hey, s cladding layer, 6...n-type GI
LAS electrode forming layer, R: Metal film for n-side ohmic electrode, 8: Metal film for p-side ohmic electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3v4

Claims (1)

[Claims] A liquid phase epitaxial growth method characterized in that growth is performed on a substrate having protrusions with a supersaturation degree of 4°C or higher.