JPH09249479A - Method for growing compound semiconductor single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for growing a compound semiconductor single crystal in high yield while suppressing the generation of polycrystal and twin crystal in the growth of a compound semiconductor single crystal doped with n-type or p-type dopant, especially a GaAs single crystal doped with Si by a vertical temperature-gradient method. SOLUTION: A temperature gradient 10 is formed in a molten raw material. The gradient starts from a high-temperature zone having a temperature higher than the melting point of the molten liquid through a solid-liquid interface temperature zone near the melting point to a low-temperature zone lower than the melting point and has a high-temperature peak between the high-temperature zone and the interface temperature zone. The temperature gradient is maintained to effect the uniform distribution of a dopant in the molten liquid. Thereafter, a temperature gradient 10 for crystal growth starting from the high-temperature zone higher than the melting point of the molten liquid 3 through a solid-liquid interface temperature zone maintained at about the melting point and controlling the solid-liquid interface 7 to a low-temperature zone maintained below the melting point is formed to effect the growth of a compound semiconductor single crystal doped with a dopant.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a growth of a compound semiconductor single crystal capable of growing a high quality n-type or p-type dopant-added compound semiconductor single crystal by a vertical slow cooling method (hereinafter abbreviated as VGF method). It is about the method.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a compound semiconductor single crystal such as GaAs, a liquid sealing pulling method (hereinafter referred to as LE
C method), horizontal Bridgman method (hereinafter abbreviated as HB method), and vertical annealing method. The LEC method has a drawback that the dislocation density in the single crystal is high and the diameter of the grown single crystal needs to be controlled because the single crystal is grown with a high temperature gradient. H
The method B has an advantage that the dislocation density in the obtained single crystal is low because the single crystal can be grown with a low temperature gradient. However, in order to obtain a circular wafer, it is necessary to process the crystal into a circular shape and the yield is poor. Have. On the other hand, VGF
The method has both advantages, and it is possible to obtain a crystal having a circular cross section with a low dislocation. Therefore, the method attracts attention as a method for producing a compound semiconductor single crystal. III-V by the conventional VGF method
A method for growing a group compound semiconductor will be described with reference to FIG.

A seed crystal 2 and a polycrystal raw material are put in a crucible 1 having a funnel-shaped bottom, and the seed crystal 2 is placed in a furnace having a cylindrical heater 5, and the cylindrical heater 5 is supplied with electric power to supply the seed crystal 2. Form a temperature gradient such that the upper part is above the melting point,
Hold the temperature gradient for several days until the melt stabilizes. afterwards,
The temperature is gradually lowered and this temperature gradient is moved to grow the single crystal 6 from the melt 3. The temperature gradient 10 has a gentle temperature distribution in the gravity direction from a high temperature region above the melting point to a low temperature region below the melting point through a solid-liquid interface temperature region near the melting point.

[0004]

SUMMARY OF THE INVENTION A compound semiconductor single crystal doped with an n-type or p-type dopant by a conventional method, particularly a GaAs single crystal doped with Si or a GaA doped with Zn.
When an s single crystal or the like was grown, a dopant was partially precipitated during the crystal growth, and a polycrystal or a twin crystal was generated from that portion. For this reason, the yield of single crystals was very poor.

[0005]

The inventor of the present invention has considered that the cause of this is that the distribution of the dopant in the melt during crystal growth is not uniform, and as a result of intensive studies, the present invention has been accomplished.

That is, according to the present invention, after the dopant in the crucible and the compound semiconductor raw material are melted to form a melt, the solid-liquid interface in the vicinity of the melting point for controlling the solid-liquid interface from the high temperature region above the melting point forming the melt. In the method of growing a compound semiconductor single crystal in which a temperature gradient for crystal growth is formed through the temperature region to a low temperature region lower than the melting point, and the temperature gradient is moved to gradually grow the single crystal, the raw material is melted after melting. , A temperature gradient having a high temperature peak between the high temperature region and the interface temperature region in the temperature gradient from the high temperature region above the melting point forming the melt to the low temperature region below the melting point through the solid-liquid interface temperature region near the melting point The temperature for crystal growth from the high temperature region above the melting point forming the melt to the low temperature region below the melting point through the solid-liquid interface temperature region near the melting point controlling the solid-liquid interface after forming and holding Distribution is formed, a method of growing a compound semiconductor single crystal, characterized by growing the dopant additive compound semiconductor single crystal, also the dopant is S
i. The method for growing a compound semiconductor single crystal, wherein the compound semiconductor single crystal is a GaAs single crystal.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION When a single crystal is grown by the VGF method, since the temperature of the upper part of the melt is high and has a gradual temperature distribution, natural convection does not easily occur, and it is difficult for the dopant to be homogeneous in the melt. is there. So, after melting the raw materials,
As described above, between the high temperature region and the solid-liquid interface temperature region, a portion 11 (peak temperature Th) in which the lower portion of the melt has a higher temperature than the upper portion (hereinafter referred to as high temperature peak 11) is provided, and natural convection 4 Then, the dopant is homogeneously distributed in the melt, and then the temperature distribution is changed to a temperature gradient for crystal growth to start crystal growth. As a result, a homogeneous compound semiconductor single crystal can be grown with a high yield.

Seed crystal 2 from high temperature peak 11 in the temperature distribution
The distance L from the melt to the solid-liquid interface 7 is determined by the balance between the temperature of the solid-liquid interface 7 and the convection of the melt. Distance L
Is too close, the seed crystal 2 is melted and the growth of the compound semiconductor single crystal becomes difficult. On the other hand, if the distance L is too long, the effect of homogenizing the dopant due to the convection of the melt 3 is reduced, and a homogeneous compound semiconductor is obtained. A single crystal cannot be grown with a high yield.

If the peak temperature Th in the temperature distribution is too high, volatile components (for example, As component in the growth of GaAs single crystal) will escape from the melt and the composition of the melt will shift, causing twinning and the like. Become. On the other hand, if it is too low, convection of the melt does not occur sufficiently, and the effect of making the dopant homogeneous becomes low.

As the compound semiconductor single crystal added with an n-type or p-type dopant, GaA added with Si is used.
There are s single crystal, Zn-added GaAs single crystal, S-added InP single crystal, and the like.

[0011]

【Example】

Example 1 An example of the present invention is silicon-doped Ga.
The growth of As single crystal (melting point; 1238 ° C.) will be described (used single crystal growing apparatus; FIG. 2). The crucible 1 used is p
Made of BN, diameter 80 mm, total length 180 mm, raw material GaA
The charge amount of s polycrystal is 3000 g, and the addition amount of silicon as a dopant is 1.6 g. The raw material and the dopant were charged into the crucible 1, and the heater 5 was energized to form a temperature gradient in the furnace vertical direction such that the upper portion of the seed crystal 2 was above the melting point, and the raw material was melted.

Next, the sub-heater 8 is energized, and the high temperature region (1250 ° C to 1260 ° C) to the solid-liquid interface temperature region (about 12 ° C).
40 ° C.) to low temperature region (1100 ° C. to 1220 ° C.) and a temperature gradient in which a high temperature peak was partially formed between the high temperature region and the solid-liquid interface temperature region were maintained for 1 hour, and the melt 3 was stirred by natural convection. The distance L from the high temperature peak to the seeding position is 40 mm
And the peak temperature Th was 1280 ° C. In the case of GaAs single crystal growth, the peak temperature Th of the high temperature peak is 1
It is preferably 250 ° C or higher and lower than 1300 ° C. If the temperature is lower than 1250 ° C, the effect of convection of the melt is small, and if the temperature is higher than 1300 ° C, As volatilizes from the melt at normal pressure.

Next, a high temperature region (1250 ° C. to 1260)
℃) ~ solid-liquid interface temperature range (about 1240 ℃) ~ low temperature range (110
The temperature gradient in the melt was changed to a temperature distribution for crystal growth of 5 ° C / cm. After this temperature distribution was stabilized, the mixture was cooled at a growth rate of 2 mm / h. GaAs after growth
As the single crystal, a complete single crystal was obtained from the seed crystal over the entire length of 100 mm.

(Comparative Example) The temperature distribution having a high temperature peak after melting the raw material is not maintained, and the high temperature region (1250 ° C to 1260 ° C) to the solid-liquid interface temperature region of the temperature distribution for crystal growth is maintained.
(About 1240 ° C) to low temperature region (1100 ° C to 1220 ° C),
After maintaining the temperature distribution from the high temperature region to the solid-liquid interface temperature region, a GaAs single crystal was grown in the same manner as in Example 1. The obtained crystals had twins in the increased diameter portion (cone portion) of the crucible.

Although the sub-heater 8 is used to form the high temperature peak in Example 1, the high temperature peak may be formed using a crystal growth furnace having a plurality of heaters.

[0016]

Industrial Applicability According to the present invention, after the raw material is melted, a temperature gradient is formed between the high temperature region and the solid-liquid interface temperature region in which the lower part of the melt has a higher temperature part than the upper part, and once held, crystal growth is performed. Since the crystal is grown by the use temperature gradient, it is possible to prevent the generation of polycrystal or twin crystal which is considered to be caused by the partial nonuniformity of the dopant in the melt. Therefore, a compound semiconductor single crystal added with an n-type or p-type dopant, for example, a Si-added GaAs single crystal, a Zn-added GaAs single crystal, an S-added InP single crystal, or the like can be grown with high yield. .

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a temperature before the start of crystal growth in a compound semiconductor single crystal growth method according to the present invention.

FIG. 2 is a diagram schematically showing a single crystal growth apparatus for growing a compound semiconductor single crystal according to an example of the present invention.

FIG. 3 is a diagram schematically showing an example of compound semiconductor single crystal growth by a vertical slow cooling method.

[Explanation of symbols]

 1 crucible 2 seed crystal 3 melt 4 natural convection 5 heater 6 single crystal 7 solid-liquid interface 8 sub-heater 10 temperature gradient 11 high temperature peak

Claims (2)

[Claims] 1. After melting a dopant in a crucible and a compound semiconductor raw material to form a melt, a high-temperature region above the melting point that forms the melt passes through a solid-liquid interface temperature region near the melting point that controls the solid-liquid interface. In the method for growing a compound semiconductor single crystal in which a temperature gradient for crystal growth reaching a low temperature region lower than the melting point is formed and the temperature gradient is moved to gradually grow the single crystal, the melt is temporarily melted after melting. After forming and maintaining a temperature gradient with a high temperature peak between the high temperature region and the interface temperature region in the temperature gradient from the high temperature region above the melting point to the low temperature region below the melting point through the solid-liquid interface temperature region near the melting point Forming a temperature gradient for crystal growth from a high temperature region above the melting point forming the melt to a low temperature region lower than the melting point through a solid-liquid interface temperature region near the melting point controlling the solid-liquid interface, and adding a dopant A method for growing a compound semiconductor single crystal, which comprises growing a compound semiconductor single crystal. 2. The method for growing a compound semiconductor single crystal according to claim 1, wherein the dopant is Si and the compound semiconductor single crystal is GaAs single crystal.