JPH0710674A - Method for growing inorganic compound signal crystal - Google Patents

Abstract

PURPOSE:To obtain a single crystal of high quality by controlling the solid-liquid interface so as to provide a curved surface of an upward curved convex form in a method for growing an inorganic compound single crystal containing a volatile element according to a vertical boat growth method. CONSTITUTION:A hermetically sealed type crucible having a volatile element holding part capable of producing a volatile element atmosphere in the upper part and a seed crystal holding part at the lower end is used to grow an inorganic compound single crystal while forcedly cooling the lower end of the crucible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing an inorganic compound single crystal having a high quality volatile element, which is suitable for manufacturing a device such as a light emitting diode or a laser diode.

[0002]

2. Description of the Related Art Inorganic compound single crystals containing volatile elements such as III-V group compounds and II-VI group compounds are usually produced by the Czochralski method (Cz method) or the temperature gradient method (GF method). It is manufactured by a horizontal boat growth method such as the horizontal Bridgman method (HB method). Of these growth methods, C
Although the z method can obtain a single crystal having a circular cross section, it has a drawback that the dislocation density becomes large because the single crystal is grown under the condition of a high temperature gradient. Although it can be obtained, it has a drawback that the raw material yield decreases when a circular substrate is cut out because the cross section becomes a semicircle.

Therefore, in order to obtain a single crystal having a circular cross section under the condition of a low temperature gradient, a vertical boat growth method has been developed in which the single crystal growth boat is held substantially vertically (Japanese Patent Publication No. 2-3).
Japanese Patent No. 3680, Japanese Patent Publication No. 64-500020, Japanese Patent Laid-Open No. 64-37486, Japanese Patent Laid-Open No. 63-85082.
Issue).

[0004]

However, in the vertical boat growth method, it is not easy to maintain the solid-liquid interface on the curved surface of the upward convex shape, and as a result, dislocation density increases, twinning occurs, etc. There was a problem.

[0005]

The inventors of the present invention have developed a method for growing a high quality single crystal by holding a solid-liquid interface on an upward convex curved surface in a vertical boat growth method. The present invention has been achieved as a result of intensive research conducted for the purpose of The above-mentioned object of the present invention is to produce an inorganic compound single crystal containing a volatile element, in a method of growing it in a volatile element atmosphere using a crucible held substantially vertically, in which a volatile element atmosphere is generated in the upper part. This can be achieved by a method of growing an inorganic compound single crystal while forcibly cooling the lower end of the crucible using a closed crucible having a volatile element holding part and a seed crystal installation part at the lower end.

The method of the present invention will be described with reference to FIG. FIG. 1 is a schematic vertical sectional view of an example of an apparatus used for carrying out the method of the present invention. In FIG. 1, 1 is a crucible. The crucible 1 has a closed structure. This is to keep the atmosphere of volatile elements and prevent them from leaking out of the crucible. In order to make the crucible 1 a closed type structure, it is preferable to provide a lid portion for rubbing on the upper end of the crucible. By growing in the atmosphere of a volatile element, it is possible to prevent the volatile element from volatilizing from the melt and the surface of the single crystal during the growth of the single crystal to cause crystal defects such as dislocation. When the crucible 1 is made of pyrolytic boron nitride (pBN), if the rubbed portion is exposed to a high temperature, the rubbed portion may sinter.
It is preferable to maintain the temperature at 1100 ° C. or lower, more preferably 1000 ° C. or lower.

To grow a single crystal, a crucible 1 is provided with a polycrystal of a desired inorganic compound. Alternatively, each constituent element may be placed in a crucible and the synthetic reaction and single crystal growth may be performed in the same crucible. In order to form the atmosphere of the volatile element in the crucible 1, the volatile element holding portion 2 is provided on the upper part of the crucible. If 2 is provided in the lower part of the crucible, the lower end of the crucible cannot be forcibly cooled, which is not preferable. It is preferable that the volatile element holding portion 2 and the main body of the crucible 1 are connected via a thin tube 3, and a heat insulating material 4 is arranged around the thin tube 3 so as to be thermally insulated. This is because the temperature at which the vapor pressure of the volatile element is optimal and the temperature suitable for single crystal growth are different. For example, when growing a GaAs single crystal, arsenic is installed in the volatile element holding portion 2. Since the atmosphere of arsenic is appropriately about 1 atm, the temperature of the volatile element holding unit 2 is adjusted to 600 to 700 ° C. As the heat insulating material, a block of graphite, a fiber, a block of silicon carbide, silicon, or the like is used.

The volatile element means a group V element in the case of a III-V group compound and a group VI element in the case of a II-VI group compound. The material of the crucible 1 may be quartz or the like, but it is preferable to use pyrolytic boron nitride (pBN) which hardly elutes impurities such as Si. 5 is a melt. Further, 6 is a single crystal. If the interface between the melt 5 and the single crystal 6 is a curved surface that is convexly curved upward, it does not develop even if a crystal defect such as a dislocation occurs, so that a high quality single crystal can be obtained.

Reference numeral 7 is a seed crystal installation portion of the crucible 1. When a thin rod-shaped crystal is used as the seed crystal, the seed crystal installation portion is thinned as shown, but when a thick crystal is used,
It does not necessarily have to be thin. 8 is a heat insulating material used for the purpose of preventing melting of the seed crystal. The heat insulating material 8 prevents radiant heat from a heater arranged around the crucible 1 from reaching the seed crystal 7.

Reference numeral 9 is a cooling section for forcibly cooling the lower end of the crucible 1. By forcibly cooling the lower end of the crucible, the solid-liquid interface can be controlled to have an upward convex shape. As shown in FIG. 1, the forced cooling is preferably performed by passing a gas such as nitrogen through a block made of graphite or the like. Reference numeral 10 denotes a quartz sealed tube in which necessary members such as the crucible 1 and the heat insulating materials 4 and 8 are enclosed. The quartz sealed tube 10 prevents arsenic and other group V elements and group VI elements from being deposited outside.

Forced cooling is preferably carried out by placing the quartz sealed tube 8 on the cooling section 9. In order to grow a single crystal, the quartz sealed tube 10 is installed in a heater and the electric power of the heater is controlled to move the solid-liquid interface upward, or the heater is mechanically moved to grow the single crystal.

[0012]

According to the method of the present invention, since the solid-liquid interface can be easily controlled, a high-quality single crystal with few crystal defects can be obtained, which is of great industrial utility value.

[0013]

EXAMPLES The present invention will be specifically described based on Examples and Comparative Examples. Example A GaAs single crystal was grown using the apparatus shown in FIG. pB
A 4 mm × 4 mm × 50 mm seed crystal was placed at the lower end of an N crucible (inner diameter 56 mm, straight barrel length 200 mm), and 2 kg of separately synthesized GaAs polycrystal was placed in the crucible. 5 g of arsenic was placed in the volatile element holder. After covering the crucible made of pBN with a lid having a lap, the quartz crucible was placed in a quartz sealed tube together with a heat insulating material, and the inside of the sealed tube was evacuated to 100 to 50.
It was heated to 0 ° C., treated, and then sealed.

This quartz sealed tube was placed in an electric furnace, and nitrogen was passed through the cooling section at a rate of 5 l / min to cool it. After heating the electric furnace to melt the polycrystal, control the electric furnace to 6 ° C / c
A temperature gradient of m (upper side is hot side) was formed. The quartz sealed tube was moved downward together with the cooling section at a speed of 2 mm / min to grow crystals.

The resulting single crystal has a straight body length of about 16c.
m, the single crystal length was 12.8 cm. Etch pit density (EPD) is 7 × 103c at a position 1 cm after the constant diameter.
m-2, at a position 5 cm after the constant diameter, 5 × 103 cm-2,
Further, it was 6 × 10 3 cm −2 at the position of 10 cm. Comparative Example A GaAs single crystal was grown in the same manner as in Example except that the cooling part was omitted.

In the obtained crystal, grain boundaries (boundaries) were formed from the latter half of the cone-shaped portion, and the straight body portion was not a single crystal. As is clear from the above Examples and Comparative Examples, the yield of single crystals was dramatically increased by cooling the lower end of the crucible as in the method of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view of an example of a single crystal growth apparatus used for carrying out the method of the present invention.

[Explanation of symbols]

 1 ・ ・ Closed crucible 2 ・ ・ Volatile element holding part 3 ・ ・ ・ ・ Small tube 4 ・ ・ Heat insulation material 5 ・ ・ ・ ・ ・ ・ ・ ・ Melting liquid 6 ・・ ・ ・ ・ ・ Single crystal 7 ・ ・ ・ Seed crystal installation part 8 ・ ・ ・ ・ ・ ・ Insulating material 9 ・ ・ ・ ・ Cooling part 10 ・ ・ ・ Quartz sealed tube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Okada 1000 Higashihuinana-cho, Ushiku-shi, Ibaraki Mitsubishi Kasei Co., Ltd.Tsukuba Plant (72) Inventor Shinichiro Kawabata 1000 Higashihuinaka-cho, Ushiku-shi, Ibaraki Mitsubishi Kasei Co., Ltd. Tsukuba factory

Claims (2)

[Claims] 1. A method for growing an inorganic compound single crystal containing a volatile element in a volatile element atmosphere using a crucible held substantially vertically, in which volatile element atmosphere for generating a volatile element atmosphere Using a closed crucible having a holding portion and a seed crystal installation portion at the lower end, a method for growing an inorganic compound single crystal while forcibly cooling the lower end of the crucible . 2. An inorganic compound containing a volatile element is III-
The method of claim 1 which is a Group V compound.