JPH069290A - Method for growing compound semiconductor single crystal - Google Patents

Abstract

(57) [Summary] [Purpose] The carbon concentration in a compound semiconductor single crystal can be significantly reduced. A novel and inexpensive method for growing a compound semiconductor single crystal is provided. [Structure] Graphite, which is the material of the hot zone constituent, was coated with pyrolytic graphite (high temperature heat separation graphite), and the concentration of carbon mixed in the compound semiconductor single crystal was significantly reduced.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method for growing an ultra-high purity compound semiconductor single crystal.

[0002]

2. Description of the Related Art An example is a gallium arsenide (hereinafter abbreviated as GaAs) crystal, which has been the largest scale in the production and development of III-V group compound semiconductor crystals in the conventional method of growing a compound semiconductor single crystal. Will be described with reference to FIG.

In the main chamber high-pressure container 1, a pedestal 3 is attached to a lower shaft 2, and the pedestal supports a susceptor 4. A crucible 5 made of pyrolytic boron nitride (hereinafter abbreviated as PBN) is placed in the susceptor, and a GaAs polycrystalline raw material 6 12, is further placed in the crucible.
Add 000 g and 1,000 g of liquid sealant B ₂ O ₃ 7. After evacuation, use an inert gas such as nitrogen or argon for 10
The pressure is increased to about atmospheric pressure, and then the main heater 8 is energized to raise the temperature inside the high-pressure container, especially inside the PBN crucible. 500 ° C
If it exceeds, the encapsulant B ₂ O ₃ softens and melts to cover the polycrystalline raw material. Then, the temperature inside the crucible is raised to GaAs.
The melting point is 1238 ° C. or higher to melt the polycrystalline raw material. At the tip of the seed crystal holder 10 attached to the upper shaft 9, there is a seed crystal having a desired crystal orientation, and a <100> seed crystal 11 which is a commonly used orientation. After setting the pressure in the high-pressure container to 5 to 20 atm, the seed crystal is grated and the tip thereof is immersed in the melt to perform seeding. After that, while lowering the temperature of the heater, pulling up the upper shaft at a speed of 9 to 12 mm / h, attach 1 to the upper shaft weight sensor attached to the upper shaft.
2 detects the crystal weight and controls the heater output to GaA
s grow crystals.

[0004]

2. Description of the Related Art In the above-described conventional method for growing a compound semiconductor single crystal, the main heater 8, the pedestal 3 and the susceptor 4 are not shown in FIG. It is called a hot zone (hereinafter abbreviated as HZ).
Is usually high-purity graphite.

The characteristics of the GaAs single crystal are largely related to the concentration of carbon mixed in the crystal, and the carbon mixed in the crystal is considered to be mixed from the HZ member. Therefore, the concentration of carbon mixed in the crystal changes greatly depending on the material of the graphite used as HZ. Usually, about 30% of the volume of graphite is hollow, and the surface of the graphite is sparse when viewed microscopically, and the surface area is very large. Therefore, it is very difficult to control the concentration of carbon mixed in the crystal. Especially as the length of the crystal becomes longer, that is, the single crystal growth time becomes longer,
The concentration of carbon mixed in the single crystal becomes large, and there is a tendency for a large difference in carbon concentration between the seed side and the tail side of the crystal.

Twenty GaAs single crystals were grown in the same manner as in the above-mentioned prior art, and the concentration of mixed carbon was measured at the seed side, the intermediate portion and the tail side, and was 2.0 × 10 ¹⁵ cm ^-3.
It was difficult to control the variation and the mixed carbon in the range of 20.0 × 10 ¹⁵ cm ^-3 .

[0007] Conventionally, there is a technique of applying PBN coating to a graphite HZ member in order to reduce the carbon concentration and obtain a high-purity crystal. However, in the case of PBN coating, the price is about 15 times as effective as the graphite HZ member. Yes,
Also, the PBN coating changes the thermal environment in the furnace,
There is a problem that it is difficult to obtain a single crystal by applying the growth conditions of graphite HZ.

[0008]

OBJECT OF THE INVENTION The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to greatly reduce the carbon concentration in the compound semiconductor single crystal. A new and inexpensive compound semiconductor single crystal growth method is provided.

[0009]

The gist of the present invention resides in the use of graphite obtained by coating pyrolytic graphite (high-temperature heat-separated graphite; hereinafter abbreviated as PG) on graphite which is a material of the hot zone constituent member. The concentration of carbon mixed in the semiconductor single crystal is greatly reduced.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described with reference to the case of gallium arsenide. The explanation is shown in FIG.
To use. First, the main heater 8, which is an HZ member, the pedestal 3, the susceptor 4, and the HZ member are not shown in FIG.
The surface of the other graphite member was coated with PG to a thickness of about 300 μm, and a GaAs single crystal was grown using this HZ member. GaAs in the PBN crucible 5
About 12,000 g of polycrystalline raw material 6 and liquid sealant B ₂
O ₃ 7 placed 1,000 g, G in the prior art the same method as
About 12,000 g of aAs melt was prepared. Crystal orientation <1
The seed crystal 11 of 00> was used for seeding, and then the upper axis was pulled up at about 9 mm / h while controlling the heater temperature to obtain a GaAs single crystal with an outer diameter of about 90 mm, a crystal length of about 300 mm, and a crystal weight of about 300 mm. 9000 g was obtained.

With the same method and apparatus as above, GaAs
20 single crystal boxes were grown. The mixed carbon concentration of the grown GaAs single crystal was measured on the seed side, the middle part and the tail side of each crystal, and it was <1 × 10 ¹⁵ cm ⁻³ in all 20 crystals, and the variation was also It was few and controllable.

[0012]

[Other Embodiments] In the above-mentioned embodiments, the high carbon concentration GaAs single crystal with a mixed carbon concentration of <1 × 10 ¹⁵ cm ⁻³ or less was described, but for example, with a concentration of 1 × 10 ¹⁵ cm ⁻³ or more. When it is desired to obtain a crystal having an arbitrary mixed carbon concentration, the mixed carbon concentration may be adjusted by introducing carbon dioxide gas into the furnace.

The method for adjusting the carbon concentration is as follows. When the crystal before adjusting the carbon concentration is a high-purity crystal of <1 × 10 ¹⁵ cm ⁻³ , the adjustment range of the carbon concentration is 1 × 10 ¹⁵ cm ^−3. While the adjustment can be made as described above, in the case of the crystal prepared by the conventional method, the adjustment can be made only within the range of the carbon concentration of the crystal or more, and the adjustment range is narrowed.

Therefore, also in the method such as carbon dioxide gas dope for controlling the carbon concentration, the higher the purity of the crystal before the carbon dioxide gas dope is, the wider the carbon concentration control range is. Is the basis of not only the technology for obtaining ultra-high purity but also the technology for controlling carbon concentration.

Although only the GaAs single crystal growth method has been described in the embodiment, the same effect can be obtained by applying the single crystal growth method of InP, GaP, InAs or the like.

[0016]

The present invention described above has the following effects and has great industrial value.

(1) By applying PG coating to the HZ member, a compound semiconductor single crystal having a significantly reduced carbon concentration can be obtained. In addition, it is possible to provide a technology that is a basis of the technology for controlling the concentration of carbon mixed in the crystal.

(2) A compound semiconductor single crystal having a significantly reduced carbon concentration can be obtained by applying an inexpensive PG coating (price about 1/5) as compared with the conventional PBN coating on the HZ member.

(3) In the case of the conventional PBN coating on the HZ member, the thermal environment in the furnace changes due to the PBN coating on the graphite, and the single crystal growth conditions when using the graphite HZ cannot be applied as they are. Compared to P
In the case of G coating, since the graphite is coated on the graphite, the thermal environment in the furnace does not change, and the single crystal growth conditions when using HZ made of graphite can be applied as they are, and the crystal growth conditions are easier. There is an effect that a high-purity crystal can be obtained without changing.

[Brief description of drawings]

FIG. 1 is a sectional view of a device for explaining a conventional technique and an embodiment of the present invention.

[Explanation of symbols]

1 Main Chamber High Pressure Container 2 Lower Axis 3 Pedestal 4 Susceptor 5 PBN Crucible 6 GaAs Polycrystal 7 B ₂ O ₃ 8 Main Heater 9 Upper Axis 10 Seed Crystal Holder 11 Seed Crystal 12 Upper Axis Weight Sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Tahara 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Hidaka Factory

Claims (1)

[Claims] 1. A method for growing a single crystal by containing a raw material melt and a liquid sealant in a heated crucible housed in a pressure-resistant container filled with an inert gas, the hot zone constituting member. A method for growing a compound semiconductor crystal characterized by growing a single crystal by using graphite obtained by coating pyrolytic graphite (high temperature pyrolytic graphite) on graphite.