JP2003146794A - Method of refining gallium for liquid phase epitaxial growth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of refining gallium for liquid phase epitaxial growth which can easily reduce the Al concentration in Ga used for epitaxial growth. SOLUTION: The concentration of the Al in a Ga solution can be lowered by a simple method of adding GaAs to the used Ga solution having the residual Al, melting the same by temperature rising in an electric furnace and lowering the temperature to deposit the residual Al as AlGaAs, then removing the same.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying gallium for liquid phase epitaxial growth.

[0002]

2. Description of the Related Art Compound semiconductor materials such as GaAs and AlGaAs are widely used as light emitting devices such as infrared or visible light emitting diodes (LEDs) by taking advantage of their light emitting function. Epitaxial wafers used as materials for these light-emitting diodes are n-type or p-type GaAs layers or A
It is manufactured by forming an lGaAs layer. Ga used as a solvent for these liquid phase epitaxial growth
Is rare and expensive, and it is desired that it can be easily reused repeatedly.

[0003]

By the way, AlGaA
The Al used as the epitaxial growth raw material remains in the Ga used for the epitaxial growth of the s layer, but as a means for using this Ga again, A in Ga is used.
The target AlA is adjusted by adjusting the weight of Al newly added as a raw material after estimating the l concentration as a constant amount.
A method for obtaining an epitaxial layer having an s mixed crystal ratio is adopted.

However, A actually remaining in Ga
Since the l concentration varies by about 5 to 10% for each epitaxial growth, A of the epitaxial layer obtained by the above method is
It has been a problem that the lAs mixed crystal ratio also fluctuates.

Therefore, in order to obtain an epitaxial layer having a desired AlAs mixed crystal ratio with good reproducibility, it is necessary to remove Al in Ga by a simple method.

Therefore, an object of the present invention is to solve the above problems and to provide a method for purifying gallium for liquid phase epitaxial growth which can easily reduce the Al concentration in Ga used for epitaxial growth.

[0007]

In order to achieve the above object, a method for purifying gallium for liquid phase epitaxial growth according to the present invention is characterized in that when Ga is repeatedly used as a growth solvent for liquid phase epitaxial growth of an AlGaAs epitaxial wafer, GaAs was added to the used Ga solution containing Al.
Is added, and the temperature is raised in an electric furnace to be melted, and then the temperature is lowered to remove the deposited AlGaAs to reduce the Al concentration of used Ga.

Further, the method for purifying gallium for liquid phase epitaxial growth of the present invention uses G as a growth solvent for liquid phase epitaxial growth of AlGaAs epitaxial wafers.
Used G containing Al when repeatedly used a
a solution was transferred into a graphite container, 33 mg / g Ga or more of GaAs was added to the graphite container, the graphite container was set in a quartz reaction tube, and the air in the reaction tube was evacuated. It is introduced, heated to 800 ° C. in an electric furnace to be melted, and then cooled to remove the deposited AlGaAs to reduce the Al concentration of used Ga.

According to the present invention, GaAs is added to a used Ga solution containing Al and the temperature is raised in an electric furnace to produce G.
The solution in which aAs is dissolved is cooled to remove residual Al from AlG.
The concentration of Al in the Ga solution can be lowered by removing it after it is precipitated as aAs. The used Ga solution having residual Al can be purified by such a simple method.

The upper limit of GaAs added here is not set because if GaAs is excessively added, it will remain undissolved, and this will not particularly affect the purification of Ga. is there.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a sectional view of a growth jig (slide boat) used in an epitaxial growth apparatus for explaining a method for purifying gallium for liquid phase epitaxial growth of the present invention.

This slide boat has a Ga solution 201,
Solution chamber 21 for accommodating 202, 203 and solution recovery parts 301, 302, 3 formed in the lower part of the solution chamber 21.
And a recess 24 for holding the GaAs single crystal substrate 23 at the upper part of one end (the left end in the figure) of the graphite board 22 and a substrate holder 2 made of graphite capable of horizontally penetrating the lower part of the graphite board 22.
5, a quartz holder 26 that moves the substrate holder 25 in the direction of arrow A, and a graphite cover 27 that covers the solution chamber 21.
It consists of and.

A case of carrying out liquid phase epitaxial growth by reusing the Ga solution used for liquid phase epitaxial growth using such a slide boat will be described with reference to FIG.

It is to be noted that what was intended to grow here is Al of the epitaxial wafer for red light emitting diode.
GaAs window layer (surface AlAs mixed crystal ratio is 0.6
0).

(1) When high-purity Ga that is not reused is used, the solution chamber 21 of the graphite board 22 of the slide boat
GaAs polycrystal: 28mg / gGa, Al: 5mg
The Ga solutions 201, 202, and 203 containing / gGa are set, and the GaAs single crystal substrate 23 is set in the substrate holder 25.

This slide boat is set in a quartz reaction tube (not shown), the air in the reaction tube is exhausted, and then hydrogen gas is introduced. In that state, the temperature of the electric furnace (not shown) was raised to 860 ° C., and Ga was added to the Ga solution.
A raw material solution is prepared by melting As polycrystal and Al. afterwards,
Start cooling. In the meantime, the substrate holder 25 is brought into contact with the GaAs single crystal substrate 23 and the raw material solutions 201, 202 and 203 successively to grow an AlGaAs layer having a thickness of about 40 μm.

(2) Reuse of Ga with Adjusted Al Addition Amount of Ga used for epitaxial growth is reused.
Newly added GaAs polycrystal: 28 mg / gGa, Al:
Epitaxial growth similar to the above (1) is performed using a solution added with 4.1 mg / g Ga.

(3) G purified by the purification method of the present invention
When a is reused, the Ga solutions 201 to 203 used for the epitaxial growth are transferred to a graphite container (not shown), and GaAs polycrystal: 33 mg / gGa or more is added. This graphite container is set in a quartz reaction tube (not shown), air in the reaction tube is exhausted, and then hydrogen gas is introduced. In this state, the temperature of an electric furnace (not shown) is raised to 800 ° C. to melt the GaAs polycrystal, and then the temperature is lowered. Residual Al is removed by removing the AlGaAs crystals precipitated in this temperature lowering step. Epitaxial growth is performed by reusing this purified Ga.

FIG. 2 shows the result of measuring the surface AlAs mixed crystal ratio of the AlGaAs epitaxial layer obtained by performing the above (1) to (3) 10 times.

FIG. 2 is a diagram showing the measurement results of the AlAs mixed crystal ratio on the surface of the epitaxial layer to which the method for purifying gallium for liquid phase epitaxial growth of the present invention is applied, in which the horizontal axis represents the epi growth lot and the vertical axis represents. The surface AlAs mixed crystal ratio is shown. In the figure, the polygonal line L1 shows the surface AlAs mixed crystal ratio of the epitaxial layer to which the purification method of the present invention is applied, the polygonal line L2 shows the surface AlAs mixed crystal ratio of the epitaxial layer to which the conventional purification method is applied, and the polygonal line L3 shows. Surface A of epitaxial layer using high-purity Ga that is not reused
The 1As mixed crystal ratio is shown.

From FIG. 2, it can be seen that the variation of the AlAs mixed crystal ratio is the largest in the case of (2), and the same as (1) and (3).

In the above, GaAs was added to the Ga solution containing residual Al and the temperature was raised and lowered in the electric furnace to obtain AlGa.
By precipitating Al as As, the Al concentration in the Ga solution can be reduced. As a result, AlA
The variation of the s mixed crystal ratio is the same as that of the AlGaAs layer obtained by epitaxial growth using high-purity Ga that is not reused, and thus epitaxial growth using purified Ga is possible.

[0024]

In summary, according to the present invention, the following excellent effects are exhibited.

A in Ga used for epitaxial growth
It is possible to provide a method for purifying gallium for liquid phase epitaxial growth that can easily reduce the l concentration.

[Brief description of drawings]

FIG. 1 is a sectional view of a growth jig (slide boat) used in an epitaxial growth apparatus for explaining a method for purifying gallium for liquid phase epitaxial growth of the present invention.

FIG. 2 AlAs on the surface of an epitaxial layer to which the method for purifying gallium for liquid phase epitaxial growth of the present invention is applied.
It is a figure which shows the measurement result of a mixed crystal ratio.

[Explanation of symbols]

21 Solution chamber 22 Graphite board 23 GaAs single crystal substrate 24 recess 25 substrate holder 26 Quartz holder 27 Graphite cover 201, 202, 203 Ga solution

Claims (2)

[Claims] 1. When Ga is repeatedly used as a growth solvent for liquid phase epitaxial growth of an AlGaAs-based epitaxial wafer, GaAs is added to a used Ga solution containing Al, and the temperature is raised in an electric furnace to melt. A method for purifying gallium for liquid phase epitaxial growth, characterized in that the Al concentration of used Ga is reduced by removing the deposited AlGaAs by lowering the temperature. 2. When repeatedly using Ga as a growth solvent for liquid phase epitaxial growth of an AlGaAs-based epitaxial wafer, a used Ga solution containing Al is transferred into a graphite container and 33 mg is put in the graphite container. / GGa or more of GaAs is added, the graphite container is set in a quartz reaction tube, air in the reaction tube is exhausted, hydrogen gas is introduced, and the temperature is raised to 800 ° C. in an electric furnace to melt. After that, the method is a method for purifying gallium for liquid phase epitaxial growth, characterized in that the Al concentration of used Ga is reduced by removing the AlGaAs that has been precipitated by lowering the temperature.