JPH078759B2 - Method for growing compound semiconductor single crystal - Google Patents

Description

The present invention relates to a method for growing a compound semiconductor single crystal by a liquid-encapsulated Czochralski method (LEC method).

[Conventional technology]

The LEC method is one of typical methods for growing a single crystal of a III-V group compound semiconductor such as GaAs, GaP, InP, InAs or a II-VI group compound semiconductor such as CdTe. In the LEC method, B ₂ O ₃ is usually used as the liquid sealant. This plays a role of sealing the liquid level in order to prevent the element having a high vapor pressure contained in the constituent elements of the compound from volatilizing from the liquid level of the raw material melt.

On the other hand, the characteristics of the compound semiconductor single crystal are affected by the impurity concentration in the crystal. In some cases, impurities are positively added to improve the crystal characteristics, but in general, it is desirable that the impurity concentration be low.

By the way, the liquid sealant B ₂ O ₃ has a function of preventing impurities from being mixed into the crystal. It is known that its inhibitory effect depends on the amount of water contained in B ₂ O ₃ . For example, Rumsby et al., When growing a GaAs single crystal by LEC method using B ₂ O ₃ in water content 2000 ppm, compared with the case of growing with B ₂ O ₃ in water content 290 ppm, of Si B Concentration decreases by 2 digits M
It has also been reported that the concentrations of g, Al, P, and S also decreased significantly (Pro
c.Int.Symp.Gallium Arsenide and Related Compounds,
P. 573 (1981)). Also Oliver et al.
_When a GaAs single crystal was grown by the LEC method using ₂ O ₃ , the Si concentration was 5 × 10 ₁₅ cm ⁻³ or more and the semi-insulating property was not obtained,
It was reported that a semi-insulating material was obtained by using B ₂ O ₃ having a water content of 1000 ppm (Electron. Lett. Vol. 17, No. 22P.
839 (1981)). Impurities suppression effect of B ₂ O ₃ such as described above, B ₂ O ₃ is Getsuta impurities, considered to be because it imported as an oxide.

As described above, many B ₂ O ₃ of the amount of water, there is a great effect in suppression of the impurities, while the water content is large the raw material melt B ₂
A large amount of scum is generated in the interface with O ₃ and in B ₂ O ₃ , and it becomes a raw material for twinning in the growing single crystal.Because B ₂ O ₃ is turbid, it is difficult to observe the crystal growth state. Become. Therefore, when growing a compound semiconductor single crystal by the usual LEC method, 100
B ₂ O ₃ with a low water content around ppm has been used.

[Problems to be solved by the invention]

The present invention is high while the water content of B ₂ O ₃ with utilizing impurity suppressing action, the interface and B in ₂ O ₃ of the raw material melt and the B ₂ O ₃ prevents scum occurs growing crystal An object of the present invention is to provide a growth method capable of growing a high quality compound semiconductor single crystal under certain observation without generating twin crystals therein.

[Means for solving problems]

The present invention simply seals the raw material melt in the crucible with the boron oxide melt, immerses the seed crystal in the raw material melt under a high-pressure inert gas atmosphere, and then pulls it while rotating it. In the method for growing a compound semiconductor single crystal for growing a crystal, a raw material and boron oxide containing 1000 ppm to 3000 ppm of water are housed in a crucible, and after heating and melting under a high-pressure inert gas atmosphere, and sufficiently holding them. , 850 ℃ to 9 after cooling
Reduce the pressure to 0.3 Torr or less at a temperature of 50 ° C and hold for 30 minutes or more,
Then, the compound semiconductor single crystal is grown by heating and melting again in a high-pressure inert gas atmosphere and seeding to grow the single crystal.

[Action]

The method of the present invention will be described by taking the growth of a GaAs compound semiconductor single crystal as an example.

Using B ₂ O ₃ with a water content of 1000 to 3000 ppm as a liquid sealant, put it in a crucible together with GaAs, heat and melt it in a high-pressure inert gas (Ar, N ₂ etc.) atmosphere of 10 atm or more for 1 hour. Hold above. During this time, the impurities in the GaAs raw material melt were changed to B ₂ O ₃
The raw material melt is highly purified by being gettered therein.
The gettering pressure and temperature are preferably the growth conditions of the normal LEC method in order to prevent compositional deviation of the raw materials.

Then, the temperature is lowered to a temperature of 850 to 950 ° C. At this temperature
GaAs is solidified, but B ₂ O ₃ thereon a liquid, reducing the pressure in the furnace to below 0.3 Torr, 30 minutes or more, preferably by keeping at least 1 hour, in B ₂ O ₃ Remove water and impurities. This state is called bubbling. During this time, B ₂ O ₃
The water content will be reduced to less than 100 ppm.

Then, the raw material is heated and melted again in a high-pressure inert gas atmosphere, and a GaAs single crystal is grown by the conventional LEC method. The water content in the B ₂ O ₃ is at fostering even less turbidity of B ₂ O ₃ in order lower than that of the prior art, it is possible to reliably observe the growing conditions of the single crystal, also suppressing occurrence of scum Therefore, twin crystals are hardly generated, and a good single crystal can be grown.

〔Example〕

A GaAs single crystal was grown by the method of the present invention. Normal LEC
Using a furnace, a crucible with HB method 3 kg of polycrystal and water content of 2300 p
I charged 700g of B ₂ O _{3 at} pm. Then, with high-purity N ₂ gas
The crucible was heated to 1350 ° C. under a pressure of 20 atm to melt the raw material. At this time, it was confirmed that the B ₂ O ₃ melt completely covered the raw material melt. Hold this state for 2 hours
The gettering action of B ₂ O ₃ promoted the uptake of impurities from the raw material melt. It was observed that scum, which seems to be various oxides, floated on the surface of the raw material melt, and the turbidity of B ₂ O ₃ increased. Next, the temperature of the furnace was lowered to 950 ° C. to solidify the raw material, and the pressure was reduced to 0.2 Torr. At this time, B ₂ O
₃ Vigorous bubbling of the melt was confirmed. After maintaining this state for 1 hour, the pressure of the high-purity N ₂ gas was returned to 20 atm, and the temperature was raised again to remelt the raw material. It was confirmed that in the seeding state in which the melt was stable, the B ₂ O ₃ melt had no turbidity and most of the scum had disappeared. After that, seeding was performed to grow a GaAs single crystal. Upper shaft speed is 5r
pm, lower shaft rotation speed is 20 rpm (reverse rotation), pulling speed is 4 mm
It was / hr. Automatic diameter control is performed by monitoring the crystal weight signal, and the diameter of GaAs is 3 inches and 2.1 kg.
A single crystal was obtained.

It was confirmed that the obtained single crystal had no twins and the concentration of impurities such as Si and B was reduced to about 1/2 to 2/3 as compared with the conventional one. Further, the specific resistance also showed a large value of 3 × 10 ⁸ Ωcm, and the effect of high purification could be confirmed.

〔The invention's effect〕

The present invention is based on adopting the above-mentioned constitution, and by utilizing the gettering action and the bubbling action due to the high water content in B ₂ O ₃ , impurities are suppressed, scum generation is avoided, and twins are prevented. A high-quality compound semiconductor single crystal could be grown under sufficient observation.

Continuation of the front page (56) References JP-A-59-83999 (JP, A) JP-A-59-102899 (JP, A) JP-A-61-236690 (JP, A) JP-B-62-51239 (JP , B2)

Claims (2)

[Claims] 1. A raw material melt in a crucible is sealed with a boron oxide melt, a seed crystal is immersed in the raw material melt under a high-pressure inert gas atmosphere, and then pulled while rotating. In a method for growing a compound semiconductor single crystal for growing a single crystal, a raw material and boron oxide containing 1000 ppm to 3000 ppm of water are contained in a crucible, and after heating and melting under a high-pressure inert gas atmosphere and sufficiently holding the boron oxide. 850 ℃ to 950 ℃
The pressure is reduced to 0.3 Torr or less at the temperature of 30 minutes or more, and then heated and melted again under a high-pressure inert gas atmosphere, and seeded to grow a single crystal. Training method. 2. The method according to claim 1, wherein a compound semiconductor single crystal of GaAs, GaP, InP, InAs or CdTe is grown.