JPS61154123A - Liquid-phase epitaxial growth method - Google Patents

Abstract

PURPOSE:To obtain a GaAlAs epitaxial wafer whose luminous wavelength is constant and luminous effect is high by a method wherein turbulance on a surface of a GaAs single, crystal substrate is eliminated, and a smooth and uniform epitaxial growth layer is obtained. CONSTITUTION:At epitaxial growth, at first solvent or solute 2 not containing Al is placed on a substrate 1 and the surface of the GaAs substrate 1 is subjected to melt-back keeping at constant temperature and for constant period. After that, a p-type solvent 3 is placed on the substrate 1 sliding a slider 10 and is cooled at prescribed cooling speed, then epitaxial growth is performed to a p-type GaAlAs layer 2a or the surface of the GaAs substrate 1. Addition ally, an n-type solvent 4 is placed on the substrate sliding the slider 10, then an n-type growth layer 3a is obtained on the p-type layer 2a similarly. In this manner, when the GaAlAs layer is subjected to perform epitaxial growth after milt-back operation is performed by using the solute or the solvent not containing Al, turblence on the surface of the GaAs substrate does not generate then stable epitaxial growth can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to gallium aluminum arsenide (GaAJLAs).
This invention relates to a liquid phase epitaxial growth method.

[Conventional technology]

In recent years, semiconductors made of ■-v group compound semiconductors have been used as light emitting devices, microwave oscillation devices, or field effect transistors. A liquid phase epitaxial method is known as one of the methods used to manufacture such a -V group compound semiconductor crystal. In this method, a solute in a molten medium that has reached a predetermined temperature is brought into contact with a semiconductor crystal substrate, and by lowering the temperature by a predetermined amount, the supersaturated solute is deposited on the substrate to obtain an epitaxial growth layer. .

When performing liquid phase epitaxial growth on a single crystal substrate,
Usually, in order to remove a very thin oxide layer or thermally deformable layer formed on the surface of a substrate, a method called meltback is used in which an unsaturated solution is brought into contact with the substrate and the surface of the substrate is dissolved and removed.

When growing a GaAs layer on a GaAs single crystal substrate by the liquid phase epitaxial growth method, conventionally, a GaAJIAs solution containing unsaturated As is brought into contact with the GaAs substrate surface and held at a constant temperature for a certain period of time, and then a GaAs layer containing a large amount of oxygen is grown. Ga
The surface of the As substrate is melted back and removed, and then As
GaAfLAs was deposited on the GaAs substrate by contacting with a saturated GaAJIAg solution and lowering the temperature to a predetermined temperature.

[Problem that the invention seeks to solve]

However, in the liquid phase epitaxial growth of Ga AJLAs, if this meltback operation is performed in the usual manner, the surface of the GaAs substrate will not be a smooth surface, but will become a highly uneven surface. As shown in FIG. 2, the substrate surface 1a is not a straight line but a disordered line.

This disturbance indicates that the meltback phenomenon is not occurring uniformly within the plane, and the p-n junction formed by the subsequent epitaxial growth is not uniform. When a light emitting device is manufactured, the final product may have poor characteristics or variations in characteristics, such as a decrease in luminous efficiency or a shift in emission wavelength.

This is thought to be one of the reasons why the yield of products from GaAjLAs visible epitaxial wafers is said to be low at present.

[Means to solve the problem]

The purpose of this invention is to eliminate the above-mentioned disorder on the surface of a GaAs single crystal substrate and obtain a smooth and homogeneous epitaxial growth layer, thereby obtaining a GaAJIAs epitaxial wafer with a constant emission wavelength and high emission efficiency. It is.

The present inventor has found through various experiments that when performing the above-mentioned meltback operation using a solvent or solution that does not contain AfL, GaAs substrates and GaAJL
It has been found that no disturbance occurs at the interface with the As epitaxially grown layer. The reason why the interface is disturbed by the meltback caused by the A-containing solution is not yet clear, but it is thought to be related to the reaction between An, an element that is easily oxidized, in the solution and oxygen on the substrate surface.

In the present invention, when performing the meltback operation, A
A Q-free solvent or solution is used to remove only the oxide film on the surface of the substrate to keep the surface smooth, and then epitaxial growth is performed thereon.

The method of the present invention will be explained in detail with reference to the drawings.

Figure w41 is a diagram explaining the slide board type liquid phase epitaxial growth method according to the present invention. In Figure 0, a substrate holder 12 is provided on a board 11 made of graphite.
Inside this, mirror-polished Ga with a thickness of 330 to 340 pm was placed.
An As single crystal substrate 1 is placed.

A slidable slider 10 made of graphite is placed on the board 11, and the slider 10 is provided with 13a to 13c capable of accommodating three types of solutions. A solute or solution 2 that does not contain A5L for melting back is placed in the first solution tank 13a.

A solution containing An and p-type impurities for obtaining a p-type GaAlAs layer is placed in the next solution reservoir 13b.

A solution containing An and n-type impurities to obtain n-type GaAuAsM is placed in the last solution reservoir 13c. For epitaxial growth, first, a solvent or solute 2 that does not contain Ai is placed on the substrate l. Place the GaAs substrate on the substrate and hold it for a certain period of time at a constant temperature to melt the substrate surface into the solution 2.Next, slide the slider 10 to place the GaAs substrate on the substrate 1.
A mold solution 3 is placed and cooled at a predetermined cooling rate to epitaxially grow p-type GaAiAse 2a on the surface of the GaAs substrate 1. Then slide the slider 10 further,
An n-type solution 4 is placed on the substrate l, and an n-type epitaxial growth layer 3a is obtained on the p-type layer 2a in the same manner. Like this A
If a GaAfLAj layer is epitaxially grown after performing a meltback operation using a solvent or solution that does not contain n, stable epitaxial growth can be obtained without disturbing the surface of the GaAs substrate.

Next, the main points of the present invention will be explained.

The solvent-free solvent used in the present invention is a Ga melt that does not dissolve An or GaAs. When the temperature of Ga melt is 700℃, GaAs becomes Ga
1.4g can be dissolved per 100g.

The thickness of the GaAs substrate melted back is at most 11
Since the thickness is about 0.7L, it is sufficient for the Ga melt for meltback to be placed on the substrate surface with a thickness of several tens of pm.

In addition, a solution containing no Ai is a solution containing Gap in which Gaps is dissolved.
A solution does not need to be a saturated solution; for example, at 700°C, 30 g of Ga is mixed with 4 g of GaAs O.
You can use a solution containing . Any material may be used as long as it has solubility in GaAs at the temperature at which it melts back.

As a p-type Gaj14As layer growth solution, Ga and GaA are used.
This is a solution containing p-type impurities such as S, An, Zn, and Ge. In addition, the solution for the n-type GaA1As growth layer includes Ga, GaAs, An and St, Sn,
This is a solution containing n-type impurities such as Se and Te.

Meltback conditions are not particularly limited, and the temperature and time may be selected according to the thickness of the substrate surface to be melted back and the solution composition used.

Next, the present invention will be explained with reference to Examples.

(Example) A GaAJIAs layer was epitaxially grown on the surface of a GaAs single crystal substrate using a graphite slide board device as shown in Fig. 1, and a p-n junction was formed. Solution 2 contains 30g of Ga and 1.6g of GaA.
This is a solution of a. The solution reservoir 13b contains p-type Ga.
Contains solution 3 for growing AJLAs calendar,
Solution 3 is a solution of 308 Ga, 18 GaAs, 30 mg An, and 10 (leH) Zn.

Furthermore, the solution reservoir 4 contains a solution 4 for growing an n-type GaAMAs layer.
．． 3g GaAs, 100+gg An and 0.
This is a solution of 5 mg of Te.

First, after holding the temperature at 820° C. for 2 hours in the state shown in FIG. 1, the slider 10 was slid in the direction of the arrow, solution 2 was placed on the substrate 1, and the temperature was raised to 822° C. and held for 10 minutes.

Thereafter, the slider IO was further moved to sequentially place solutions 3 and 4 on the substrate 1, and the substrate was slowly cooled according to a predetermined program to grow p-type and n-type GaAJIAs epitaxial layers. The cooling conditions are those normally used for GaAJLAs growth.

When we examined the cross section of the GaA1As epitaxial wafer thus obtained, we found that the G
The thickness of the aAs substrate l is 300 l, and the original substrate is l
It is melted back to a thickness of 0.71m, and its surface 1a is smooth, and the GaAs substrate 1 and GaAs substrate 1a are smooth.
No disturbance at the interface of the jLAs epitaxially grown layer was observed.

Furthermore, the thicknesses of the p-type and n-type GaAJLAs epitaxial growth layers were both 30 pm.

Furthermore, when LED elements of 0.35 square meters were made from this wafer, the yield of elements satisfying the predetermined electrical characteristics was 81%, which was about twice as high as when using the conventional method.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a method of implementing the present invention, and FIG. 2 is a diagram showing a cross section of a wafer according to a conventional method. FIG. 3 is a cross-sectional view of a wafer according to the present invention.

Claims (1)

[Claims] When growing a gallium ariminium arsenide layer on a gallium arsenide single crystal substrate by liquid phase growth, the surface of the gallium arsenide single crystal substrate is melted back using a solution or solvent that does not contain aluminum, and then p-type or n-type A liquid phase epitaxial growth method characterized in that a gallium aluminum arsenide layer is grown.