JPH075427B2 - Method for growing compound semiconductor single crystal - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for growing a compound semiconductor single crystal by a horizontal Britzmann method, and more particularly to a method for growing an impurity-doped compound semiconductor single crystal.

[Conventional technology]

FIG. 1 is a conceptual diagram of manufacturing a GaAs single crystal by the horizontal Britzmann method. In the crystal growth furnace, a heater 2 is embedded in a cylindrical heat insulating material 1, a viewing window 7 for observing a solid-liquid interface of crystals is opened in an intermediate portion of the furnace, and a television camera 8 is fixed and an image processing storage device 10 is provided. To be able to observe with. By energizing the heater 2, an in-furnace temperature distribution 9 is formed so that the solid-liquid interface is located under the observation window 7. on the other hand,
The GaAs raw material is housed in a boat, and the boat is sealed in the quartz sealed tube 3. The quartz sealed tube 3 is introduced into the furnace to melt the raw material in the boat to form the GaAs melt 6, and then gradually moved in the moving direction 4 to grow the GaAs single crystal 5. Let

As the crystal growth progresses, the impurity concentration in the melt 6 increases due to segregation. As a result, the melting point of the melt 6 is lowered, and the position of the crystal growth interface moves to the low temperature side. Fig. 1
As an example, the variation of the solid-liquid interface position in the conventional method is shown in relation to the solidification rate. The movement of the solid-liquid interface causes a change in the crystal growth rate to make the crystal growth unstable and facilitate the generation of crystal defects.

[Problems to be Solved by the Present Invention]

The present invention is a method for growing a compound semiconductor single crystal with few crystal defects by solving the drawbacks of the conventional method for growing a compound semiconductor single crystal and suppressing the movement of the solid-liquid interface position to ensure stable crystal growth. Is to provide.

[Means for solving problems]

The present invention provides (1) a method for growing a compound semiconductor single crystal doped with impurities by the horizontal Bridgman method,
In order to prevent the solid-liquid interface position in the furnace from fluctuating substantially by decreasing the melt temperature continuously or stepwise in response to the melting point drop due to the increase of the impurity concentration in the melt accompanying the crystal growth. A method for growing a compound semiconductor single crystal doped with impurities, and (2) a gallium arsenide single crystal doped with chromium having a crystal growth rate of 1 to 10 mm.
The method for growing a compound semiconductor single crystal according to claim 1, wherein the temperature of the melt is lowered at a rate of 0.01 to 1.0 ° C./hour according to the growth. .

[Action]

The melting point drop ΔT due to impurity segregation in the crystal growth of GaAs single crystal is derived as follows.

(From "Study on Preparation of Low Defect Density GaAs Single Crystal by Three Temperature Zone Method" by Shinichi Akai) n (G) = S (l−x) (5) N (I): mol number of impurities N (G): mol number of GaAs m (I): input weight of impurities n (I): growing Impurity weight taken into GaAs single crystal M (I): Atomic weight of impurities m (G): GaAs input weight n (G): Growing GaAs single crystal weight M (G): GaAs molecular weight Co: GaAs Impurity concentration at the front of the single crystal k: Impurity segregation coefficient in GaAs S: Cross section of GaAs single crystal ρ: Specific gravity of GaAs single crystal Q: Solidification rate x: Position from the end of GaAs single crystal l: Total length of GaAs single crystal From the above equations (1), (2) and (3), ΔT can be expressed as the following equation.

Here, Cr is added as an impurity and S = 15.2 cm ² l = 56.5 cm
FIG. 4 shows a theoretical curve obtained by plotting .DELTA.T during the growth of GaAs single crystal with respect to the solidification rate of the single crystal.

The present invention is characterized in that the melt temperature is lowered along with the drop of the melting point of the melt accompanying the crystal growth so that the solid-liquid interface position is not changed. FIG. 2 shows the relationship in a stepwise manner. inside that,
The state immediately after the start of crystal growth is shown in the figure of Q = 0. The melting point drop ΔT is naturally zero. Crystal growth is 3
In the figure of Q = 0.3, which has progressed relatively, the temperature ΔT below the melting point is 0.7 ° C., and the temperature of the melt is also reduced by that amount from the dotted line to the solid line. In the figure of Q = 0.6 where the crystal growth progressed 60%, the melting point drop △ T was 2.4 ° C, and in the figure of Q = 0.8, the melting point drop △
T becomes 5.5 ° C, and the melt temperature is greatly lowered as shown in the figure. By reducing the fluctuation of the solid-liquid interface position due to such temperature drop of the melt, crystal growth can be stabilized, and as a result, a good single crystal with few crystal defects can be obtained.

Example 1 9.12 g of chromium was added to 4.550 g of gallium arsenide and a semi-insulating gallium arsenide single crystal was grown by the horizontal Britzmann method. The crystal growth rate is 5 mm / hour, the melt temperature is 0.03 ° C / hour, and the melt temperature is increased to 0.08 ° C / hour, and then the latter half of the crystal is grown. It was

As a result, the variation of the solid-liquid interface position was ± 2 mm within the range of 80% from the tip of the grown crystal as shown in FIG. The crystal thus grown was a single crystal and had a semi-insulating property, and crystal defects were extremely small at 1 × 10 ^{3 to} 5 × 10 ³ cm ⁻³ .

Example 2 6.5 g of chromium was added to 2000 g of gallium arsenide, and a semi-insulating gallium arsenide single crystal was grown by the horizontal Britzmann method. The crystal growth rate was set to 10 mm / hour, and the crystal growth rate was set to 0.09 ° C./hour in the first half and 0.19 ° C./hour in the second half.

As a result, the variation of the solid-liquid interface position was favorable within ± 3 mm, and the crystal defects were small at 5 × 10 ^{2 to} 5 × 10 ⁻³ .

[Comparative example]

Crystal growth was carried out according to the conditions of Example 1 except that the melt temperature was not lowered with crystal growth. At the solidification rate of about 1/3, the solid-liquid interface became distorted, lineage was generated, and finally it became polycrystalline. The solidified interface moved within the range of 0 to 80 mm.

〔The invention's effect〕

According to the present invention, by adopting the above configuration, the movement of the solid-liquid interface position is substantially eliminated, and stable crystal growth conditions can be secured, so that a good compound semiconductor single crystal with few crystal defects is grown. I was able to.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a situation in which a GaAs single crystal is grown by the horizontal Britzmann method, FIG. 2 is a diagram for explaining the crystal growth and the temperature lowering state of the melt descending liquid, and FIG. Example 1
Fig. 4 is a graph showing the variation of the solid-liquid interface position of Fig. 4, Fig. 4 is a graph showing the relationship between the melting point drop and the solidification rate according to equation (6)
FIG. 5 is a diagram showing an example of the variation of the solid-liquid interface position caused by the crystal growth by the conventional method.

Claims (2)

[Claims] 1. A method for growing an impurity-doped compound semiconductor single crystal by the horizontal Bridgman method, which is continuous or stepwise in response to a melting point drop due to an increase in impurity concentration in a melt accompanying crystal growth. A method for growing a compound semiconductor single crystal doped with impurities, characterized in that the position of the solid-liquid interface in the furnace is kept substantially unchanged by lowering the melt temperature. 2. A gallium arsenide single crystal doped with chromium is grown at a crystal growth rate of 1 to 10 mm / hour, and the temperature of the melt is lowered at a rate of 0.01 to 1.0 ° C./hour according to the growth. The method for growing a compound semiconductor single crystal according to claim 1.