JPS62283893A - Method for growing compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To inhibit the shift of the position of a solid-liquid interface and to secure the stable growth of crystal by descending the temp. of a melt in coincidence with the growth of crystal in a horizontal Bridgman's method. CONSTITUTION:In the growth of compd. semiconductor single crystal by a horizontal Bridgman's method, the concn. of impurities incorporated in a melt is made high as the growth of crystal is progressed and m.p. of the melt is lowered and the position of the interface of crystalline growth is shifted to a low-temp. side. As a result, the growth of crystal is made unstable. Therefore the temp. of the melt is continuously or intermittently lowered in coincidence with the growth of crystal and the fluctuation of the position of a solid-liquid interface is made small and thereby the growth of crystal is made stable. As a result, single crystal such as GaAs which has little crystalline flaw and good quality can be obtained.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for growing compound semiconductor single crystals by the horizontal Bridgman method, and in particular, to a method for growing compound semiconductor single crystals doped with impurities. Regarding the method.

[Conventional technology]

FIG. 1 is a conceptual diagram of manufacturing a '9 GaA single crystal by the horizontal Bridgman method. In the crystal growth furnace, a heater 2 is embedded in a cylindrical heat insulator 1, a viewing window 7 is opened in the middle of the furnace to observe the solid-liquid interface of the crystal, and a television camera 8 is installed.
This is fixed so that it can be observed on the image processing storage device 10. By energizing the heater 2, a temperature distribution 9 in the furnace is formed such that the solid-liquid interface is located below the viewing window 7. On the other hand, a GaAs raw material is placed in a boat, and the boat is sealed in a quartz sealed tube S.

The quartz sealed tube 3 is introduced into the furnace to melt the raw material in the boat to form a GaAe melt 6, and then gradually moves in the moving direction 4 to grow a GaA11l 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 decreases, and the position of the crystal growth interface moves to the lower temperature side. Figure 5 shows Part 1
As an example, the variation of the solid-liquid interface position in the conventional method is shown in relation to the solidification rate. This movement of the solid-liquid interface changes the crystal growth rate, making crystal growth unstable and facilitating the generation of crystal defects.

[Problems to be solved by the present invention]

The present invention is a method for growing compound semiconductor single crystals with fewer crystal defects by eliminating the drawbacks of conventional compound semiconductor single crystal growth methods and ensuring stable crystal growth by suppressing the movement of the solid-liquid interface position. This is what we are trying to provide.

[Means for solving problems]

The present invention provides a method for growing compound semiconductor single crystals using the horizontal Bridgman method, in which continuous growth is performed in accordance with crystal growth.
Alternatively, the method for growing a compound semiconductor single crystal is characterized in that the position of the solid-liquid interface in the furnace is kept substantially unchanged by lowering the melt temperature intermittently.

[Operation] The melting point drop ΔT due to impurity segregation during crystal growth of GaAs single crystal is derived as follows.

(Shin Akai, “Low Defect Density C1aAs Using Three Temperature Zone Method”
Research on the preparation of single crystals) n (G) −
El (1-x) ---(5
)N(1): Number of mo'l of impurities N(G): Number of moles of GaAs m(1): Weight of impurities introduced n(1): Weight of impurities taken into the GaAs single crystal during growth M( Takumi: Atomic weight of impurities m (G): GaAa input weight n (G): GaA daily single crystal weight during growth M (G):
Molecular weight of GaAs Co: Impurity concentration k at the forefront of GaAs single crystal
: Impurity segregation coefficient S in GaAs
: Cross-sectional area of GaAa single crystal ρ : GaAs
Specific gravity of single crystal Q: Solidification rate x: Position from the rear end of GaAs single crystal/
: Total length of GaAa 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 5-112M! −
FIG. 4 shows a theoretical curve in which Δτ during growth of a 51-5 cm GaAs single crystal is plotted against the solidification rate of the single crystal.

The present invention is characterized in that the temperature of the melt is lowered in accordance with the melting point drop of the melt due to crystal growth, so that the solid-liquid interface position does not change, and this is determined by the solidification rate Q of the crystal. Figure 2 shows the relationship step by step. among them,
The diagram of Q-0 shows the state immediately after crystal growth starts. Naturally, the melting point depression ΔT is also zero. Crystal growth is 5
In the diagram of Q-α5, which has progressed by 60%, ΔT below the melting point is 17°C, and the temperature of the melt is also lowered by that amount from the dotted line by actual IvJ''1. Q = Q when crystal growth has progressed by 60%, In the figure 6, the melting point drop ΔT is 'L4℃, and in the figure Q,=[18, the melting point drop ΔT is 5.5℃, and the melt temperature is also drastically lowered as shown in the figure. By reducing the fluctuation in the solid-liquid interface position by reducing the temperature 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] Chromium content 9.12 for gallium arsenide 4.550 t
A semi-insulating gallium arsenide single crystal was grown by adding F and using the horizontal Bridgman method. After growing to half of the expected crystal growth length at a crystal growth rate of 5°C/hour and a melt cooling rate α of 03°C/hour, the crystal growth in the second half was performed by increasing the melting temperature cooling rate to Q, 08°C/hour. I did it.

As a result, the variation in the solid-liquid interface position was ±2fi within 80% of the tip of the growing crystal, as shown in FIG. The crystal grown in this way is a single crystal and has semi-insulating properties, and has crystal defects of 1×103 to 5×1 o”cln.
-”, which was extremely low.

[Example 2] Chromium &52 was added to gallium arsenide 2000F, and a semi-insulating gallium arsenide single crystal was grown by the horizontal Bridgman method. Two crystal growths were carried out at a crystal growth rate of 1 OW/hour and a melt cooling rate of 109° C./hour in the first half and 119° C./hour in the second half.

As a result, the variation in the solid-liquid interface position was good within ±3 wa, and the number of crystal defects was small at 5×10 2 to 5×10″3.

[Comparative example]

What about not lowering the melt temperature due to crystal growth? Crystal growth was performed according to the conditions of Example 1 except for the following. At a solidification rate of about 115, the solid-liquid interface became distorted, lineage occurred, and finally polycrystalline formation occurred. The solidification interface has moved in the range of 0 to aom.

〔Effect of the invention〕

By adopting the above configuration, the present invention has been able to substantially eliminate movement of the solid-liquid interface position and ensure stable crystal growth conditions, thereby growing a good compound semiconductor single crystal with few crystal defects. We were able to.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram showing the situation in which a F) GaAs single crystal is grown using the horizontal Bridgman method. Figure 2 is a conceptual diagram illustrating the crystal growth and the temperature drop of the melt. Figure 5 The diagram is
A graph showing the fluctuation of the solid-liquid interface position in Example 1, Fig. 4 is a graph showing the relationship between melting point depression and solidification rate according to equation (6), and Fig. 5 shows the solidification caused by crystal growth by the conventional method. FIG. 3 is a diagram showing an example of variation in the position of a liquid surface.

Claims (2)

[Claims] (1) In the method of growing compound semiconductor single crystals by the horizontal Bridgman method, the position of the solid-liquid interface in the furnace is substantially reduced by lowering the melt temperature continuously or intermittently in accordance with crystal growth. A method for growing a compound semiconductor single crystal characterized by keeping it unchanged. (2) Growing a chromium-added gallium arsenide single crystal at a crystal growth rate of 1 to 100 mm/hour, and lowering the temperature of the melt at a rate of 0.01 to 1.0°C/hour in accordance with the growth. A method according to claim 1, characterized in that: