JPS60161399A - Manufacture of low dislocation single crystal - Google Patents

Abstract

PURPOSE:To manufacture low dislocation single crystal wherein low dislocation has been performed effectively by adding two kinds of the specified elements to the raw material of GaAs single crystal and growing up the crystal. CONSTITUTION:An element of th group III (e.g. In) and an element of the group IV(e.g. Sb) excepting Ga and As which have not effect on electrical characteristics are added by 0.02-1.0mol% to the raw material of GaAs single crystal respectively, and the GaAs single crystal is grown up by a horizontal type boat method or a pickup method.

Description

[Detailed Description of the Invention] [Background and Objectives of the Invention] The present invention relates to a method for producing a low dislocation single crystal, and particularly relates to a method for producing a low dislocation single crystal suitable for effectively reducing dislocation. be.

Methods for producing GaAs single crystals can be roughly divided into horizontal boat methods and pulling methods. The horizontal boat method can obtain a single crystal with low dislocations compared to the pulling method, but crystals with a dislocation density (EPD) ≦500/cyn2, which is used for semiconductor lasers, can be reliably obtained only in 81-doped crystals. It is still in the process of being sold, and the yield is poor. Also,
In the pull-up method, FET, I
Each company develops and manufactures undoped semi-insulating raw crystals for C, but in terms of dislocation density, EPD≦100,
000 pieces/am'' can be manufactured, but EPD
≦50,000 cells/am2 seems to be difficult to manufacture.

There is an urgent need to reduce dislocations in semi-insulating main crystals using the pulling method.
≦1000 pieces/cr? If you can't do it, IC.

It is said that there is no hope for the development of LSI.

As an attempt to reduce dislocations, it has been considered to lower the temperature gradient at the crystal growth interface to prevent the generation of dislocations due to thermal strain.
Efforts are beginning to be made to increase the thickness of the compound or to crystallize it in capsules.

Another attempt was to increase the strength of the crystal itself,
Efforts have been made to prevent the introduction of dislocations. So-called impurity hardening (Impurity1+arden)
This is a method of adding Group III and Group II elements other than Ga and As, which do not affect the electrical characteristics. Regarding this, I'
There are reports of adding single elements such as 1 (indium), Sb (antimony), and B (boron). In particular, the effect of adding In seems to be the greatest, with an outer diameter of 20 mm and a length of 40 mm.
There are reports that dislocation-free crystals of about mm size have been obtained. However, for practical crystals with a diameter of 50 mm or more, EP
D≦to, oo.

Almost no one has been obtained.

Also, attempts have been made to add In using the boat method;
It has been revealed that addition of more than mol % has no effect and, on the contrary, causes defects that are thought to be caused by In precipitation. °Also, it is clear that due to segregation, In is pushed out to the rear end of the crystal, making it difficult to enter the crystal, and that it has drawbacks such as "wetting" of the extruded In and the quartz boat. has been done.

The present invention has been made in view of the above, and an object thereof is to provide a method for producing a low dislocation single crystal that can effectively reduce dislocations by an impurity hardening method.

[Summary of the invention]

A feature of the present invention is that when producing a GaAs single crystal by a horizontal boat method or a pulling method, at least one of each of group Ⅰ and group Ⅰ elements other than Ga and As, which do not affect the electrical properties, is used. is added to the raw material of the GaAs single crystal for crystal growth.

〔Example〕

An embodiment of the manufacturing method of the present invention will be described in detail below with reference to FIGS. 1 and 2.

(1) Example 1 (by horizontal boat method) A seed crystal and 800 g of Ga as a raw material were placed at one end of a quartz glass reaction tube, and In
2.5 g (0.1 mol%), Sb 2.7 g (sail 1
After placing a quartz boat containing mol%) and welding A3890g at the other end, I X 10-'
Use the vacuum bow for at least 1 hour under Torr, then seal it off.

This reaction tube is installed in a double electric furnace, and the boat side (high temperature furnace) is heated to 1200°C or higher, and the As side (low temperature furnace) is heated to 610°C. After the GaAs synthesis reaction is completed, the temperature of the high-temperature furnace is further raised while keeping the temperature of the low-temperature furnace constant, and the temperature of the seed part is raised to 1238°C, which is the GaAs melting point, and the boat body side is brought to an even higher pz temperature. The temperature difference is 1.0
Adjust to dig/Cm. After a portion of the seed crystal inserted in this manner is dissolved, the temperature is lowered at a rate of about 1.0 dig/llr while keeping the temperature gradient constant. Then, after confirming that the entire crystal had solidified (+00 di
Cool to room temperature at a rate of 2 g/llr and remove the crystals.

By the above method, a GaAs single crystal weighing about 1600 g was obtained. The obtained crystal was of type II, with a carrier concentration of η==IX10'' to 3.5×10@Cm−', and there were no particular problems in terms of electrical properties. When etched and measured, the entire crystal had a density of EPP≦500PP-500, except for the part about 5 mm inward from the part that was in contact with the boat wall.Figure 1 shows that the obtained crystal wafer is In the figure showing the in-plane dislocation density distribution, the numerical values shown in each frame are numerical values (unit: x 100 cells/cm'') indicating the dislocation density.

In addition, the experiment was repeated more than 30 times, and In.

When compared with the case where sb was not added, it was found that the yield was more than twice as high and crystals with EPD≦500'7/cm'' could be obtained.

(2) Example 2 In Example (1), In 0.50g (0,0
2 mol%), SbO, 52g (0.02 mol%)
Similar single crystal growth was performed with the addition of . As a result, E.P.
It was found that single crystals with D≦500 crystals/cm” were obtained, and the yield was 20 to 30% better than when nothing was added.

(3) Example 3 (by pulling method) P B N
(T'yrolitic Boron N1tride
,) Ga1O,00g, As1100g in a crucible
, In 3.3g (0.1 mol%), Sb 3.5
g (0.1 mol%), and further placed 500 g of +3zOi (boron oxide) capsules, placed in a lifting device, and carried out the GaAs synthesis reaction at 700°C and 70 atm, and then at 20 atm. The GaAs single crystal was pulled by lowering the pressure to . As a result, 1500 g of a single crystal with an outer diameter of 65 to 75 cm was obtained. The obtained single crystal is HOO)
After slicing it on the surface and etching it with molten KOH, the center portion with a diameter of about 50 mm had an EPD ≦100.
It was a semi-insulating crystal with a low dislocation density of 0.00'7/cm". Figure 2 shows the in-wafer dislocation density distribution of the obtained crystal, and the numbers shown in each frame indicate the dislocation density. It is a numerical value (unit: X100'z/cm"). Next, a comparative example will be explained.

(4) Comparative example In Example (1), 25 g (1 mol %) of In.

A similar single crystal growth was performed by adding 27 g (1 mol %) of Sb. As a result, it was found that although the dislocation density was reduced, it had the following drawbacks.

(a) Defects that appear to be caused by In precipitation occur during the latter half of crystal growth.

(D) In exceeds the solid solubility limit and precipitates around the crystal, causing "wetting" with the boat and causing sliding dislocations.

(c) Twins are likely to occur in conjunction with "male".

Furthermore, when In and Sb are added individually, if it is less than 1 mol %, it has almost no effect on reducing dislocation density, and if it is added more than 1 mol %, it becomes InxG rather than Ga As crystal.
a (1-x) As or GaAs (1-x)
It becomes an Sbx mixed crystal, and the lattice constant and other properties may change. In addition, realistically, In is 1 mol%
If the above amount is added, defects likely to be caused by In precipitation tend to occur in the latter half of crystal growth, making the GaAs single crystal unusable.

By the way, when In and sb are added at the same time as in the production method of the present invention, a remarkable effect on lowering dislocations appears with just 0.1 mol% of each added, and when 0.02 mol% of each is added, This is the boundary area between whether or not there is an effect. Note that when In and Sb are added at 1 mol% each, defects that appear to be In precipitation occur in the latter half of crystal growth, as in the case of In alone, so it is necessary to avoid adding such large amounts. There is 1 power.

As described above, according to the embodiment of the method of the present invention, when applying the impurity curing method, In and sb were added at the same time, resulting in the following effects due to the synergistic effect.

(a) Compared to the case where only a single element is added, a smaller amount is required, so the characteristics of the Ga AS crystal are less likely to change.

(b) Precipitation of impurities added at the same time or occurrence of "wetting" when using the horizontal boat method can be suppressed.

(C) Due to the synergistic effect, the effect is significantly greater than when the same amount of a single element is added.

In the above-mentioned example, In and sb were added, but as a group Ⅰ element that does not affect the electrical characteristics, In
In addition, there are B (boron), AI (aluminum), etc.
In addition to sb, group (2) elements include N (nitrogen), P (phosphorus), etc., and it goes without saying that a combination of these may also be used.

In addition, although the case of GaAs single crystal has been explained, two other examples of III-V group compound semiconductors are I
The same applies to nP, Gar', etc.

〔Effect of the invention〕

As explained above, according to the present invention, there is an effect that dislocation can be effectively reduced by the impurity hardening method.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the in-plane dislocation density distribution of a crystal obtained according to the present invention using the horizontal boat method. FIG. 2 is a diagram showing the in-plane dislocation density distribution of a crystal obtained according to the present invention using the pulling method.

Claims (2)

[Claims] (1) GaAs by horizontal boat method or pulling method
When manufacturing a single crystal, crystal growth is performed by adding at least one type of each of Group 1 and Group 2 elements other than Ga and As, which do not affect electrical characteristics, to the raw material of the GaAs single crystal. A method for producing a low dislocation single crystal characterized by: (2) The above-mentioned group Ⅰ element is In, and the above-mentioned group Ⅰ element is sb, which is 0.02 mol% or more and 1.0 mol% or more, respectively.
The method for producing a low dislocation single crystal according to claim 1, wherein the addition amount is mol % or less.