JPH0510315B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for vapor phase growth of crystals, and in particular to bulk growth of - group compound semiconductors (ZnS, ZnSe, etc.) using a sublimation method or a halogen transport method. It relates to a crystal growth method.

<Prior art and its problems> A crystal growth apparatus conventionally used in crystal growth methods such as sublimation and halogen transport methods is used, for example, in a vertical arrangement as shown in FIG. The powder is placed in the lower part of the growth container 11, and the seed crystal 14
is installed in the upper part of the growth container 11 connected to a support rod 12, and the raw material 13 in the lower part is heated to a high temperature _T1 and transported to the crystal growth section which is a low temperature _T2 region in the upper part. In such an arrangement, there is a temperature difference between the lower part of the growth container 11 at a high temperature and the upper part of the growth container 11 at a low temperature.
Material transport occurs due to vapor diffusion and convection due to T ₁ -T ₂ or a temperature gradient, and growth of the crystal 15 progresses in the low temperature region. However, in single crystal growth, which aims to obtain a high-quality, uniform single crystal, it is a necessary condition that mass transport be steady, and for this purpose, the above-mentioned diffusion and convection, which are the driving forces for transport, must be steady. There must be. However, convection itself due to heat originally changes its shape depending on the shape of the container, blocks the flow like crystals that gradually grow inside the container, and changes the boundary conditions for the flow over time. In the following, it is not possible to reliably reproduce the same convection even if containers with the same shape are set up, and furthermore, its constancy cannot be assumed at all. Reflecting this situation, crystal growth in a crystal growth apparatus as shown in FIG. 2 often has low reproducibility, and moreover, part of the crystal often contains irregularities in shape. Furthermore, even if we assume steady uniformity of convection, if a growing crystal continues to grow covered by its unique crystal planes (i.e., the shape in which its unique crystal planes are developed), then In the flow field, different surfaces have different degrees of supersaturation, and it is easy to predict that the growth state will differ depending on the region even within the same crystal. Therefore, it is reasonable to assume that a turbulent flow exists that is not constant in time and space in a growth apparatus where convection exists, and this is the reason why a completely controlled single crystal growth method has not yet been established. This is one of the major causes.

<Object of the invention> The present invention has been made in view of the above points, and
When growing single crystals of - group compound semiconductors such as ZnS and ZnSe based on vapor phase transport, by excluding convection, the transport of vapor evaporated from the raw material proceeds only by a specific transport mechanism, and the flow in the process from transport to growth. After eliminating the effects of The purpose is to provide a method for perfectly preserving the shape of.

<Summary of the Invention> The crystal growth method of the present invention is characterized in that the crystal growth region (low temperature section) and the raw material region (high temperature section) are set at a constant flat temperature, and the low temperature crystal growth region is located at the bottom of the growth apparatus. By placing the high-temperature raw material region at the top and setting the temperature difference between them steeply, only the difference between the steam pressure based on the raw material temperature and the steam pressure based on the crystal region temperature drives crystal growth. This is a point that was made to be a source of strength. In this method, the pressure of the vapor in the growth vessel is determined by the temperature of the raw material, and a certain supersaturation state is achieved throughout the growth region, and no precipitation occurs on the inner wall of the vessel in this region. It is easy to achieve a temperature difference (that is, supersaturation degree) within a range that does not cause nucleation, and to sufficiently clean and stabilize the inner wall of the container to prevent spontaneous nucleation. By means of such a method, the transport of substances is precisely set by means of temperature differences only, and thus the crystal growth is precisely controlled.

<Example> An example of the present invention will be described using a method for growing a single crystal of ZnS and ZnSe, which are − group compound semiconductors, by a halogen transport method. FIG. 1 is a block diagram of a crystal growth apparatus using a halogen transport method for explaining an example of the present invention. A quartz growth container 1 in which a single crystal is grown is a hollow cylindrical container with a diameter of 30 mm and a length of several 100 mm, and a seed crystal 6 is provided above the raw material container 2 and below the interior. Growth container 1 above raw material container 2
There is a raw material 5 consisting of - group compounds such as ZnS and ZnSe, a seed crystal 6, and a filling port 3 for transport medium halogen.
is located. After the filling port 3 is filled with raw materials and the like, it is hermetically sealed or fused. The growth container 1 has a holding rod 4 at the center of the upper part and is held in the heating furnace. During growth, the raw material 5 side in the upper part of the growth container 1 (part A in the figure) is kept at a high temperature (temperature T ₁ ), and the seed crystal 6 and the growth side in the lower part of the growth container 1 (part B in the figure) are kept at a low temperature (temperature T _{2 )} . ), each is heated to a uniform temperature. Temperature difference ΔT in the growing part (part B)
Supersaturation of the vapor pressure difference based on (=T ₁ −T ₂ ) occurs and is maintained constant everywhere, and is the driving force for transport and single crystal growth. Nucleation does not occur on the inner wall of the growth container 1 which has been sufficiently cleaned and stabilized, and therefore the single crystal 7 grows only on the seed crystal 6. Since no vapor flow occurs near the single crystal 7, the vapor pressure on the surface of the single crystal 7 is constant, and the growth occurs at a constant growth rate without disturbance.
For example, ZnS
In this case, the result is a single crystal with widely developed (111) and (100) planes, but due to the constancy and steadiness of the vapor pressure on the crystal surface, there is no shape disturbance, and the crystal has a uniform shape corresponding to the seed crystal 6. A high quality single crystal 7 is obtained.

The temperature distribution of the growth container 1 can be easily controlled, for example, by independently installing high-frequency induction heating coils or resistance heating furnaces in parts A and B, and heating the growth container using the coils or furnaces. will be achieved. When the evaporation temperature of the raw material 5 is low, it may be heated by a heat ray irradiation method. The temperature difference ΔT is formed with a steep slope near the boundary between parts A and B, but
The temperature T ₂ and the temperature difference ΔT are set so that precipitation does not occur on surfaces other than the seed crystal 6 such as the inner wall of the growth container in the B portion.

Steam from the raw material 5 heated to a temperature _T1 is transported using halogen gas as a medium, and when moving from part A to part B, passes through a region of temperature difference ΔT, and the extraction driving force corresponding to this temperature difference ΔT is generated. will be granted.
Therefore, precipitation occurs in the seed crystal 6 from the gas of the raw material 5 that has contacted the seed crystal 6 in the B portion, and a single crystal 7 grows based on the precipitation driving force.

Note that the present invention is not limited to the above-mentioned - group compound semiconductors, but is effective when growing various crystals in a vapor phase.

<Effects of the Invention> As explained in detail above, according to the present invention, transport is controlled by a temperature difference strictly set steeply after removing the flow effect (irregularity) associated with mass transport for crystal growth. Since single crystal growth can be controlled in a constant supersaturated atmosphere, the crystal grows at a growth rate specific to its individual plane orientation, and no morphological disorder is introduced. In this way, it is possible to obtain a bulk single crystal of high quality and a regular shape with industrially sufficient dimensions, making it possible to realize crystalline materials such as compound semiconductor devices and crystal growth substrates.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a growth apparatus used to explain one embodiment of the present invention. FIG. 2 is a schematic diagram of a growth apparatus used in the conventional halogen transport method. 1... Growth container, 2... Raw material container, 3... Filling port, 4... Holding rod, 5... Raw material, 6... Seed crystal,
7...Single crystal.

Claims (1)

[Claims] 1 In a crystal growth method in which a raw material for crystal growth is heated and its vapor is transported to a crystal growth region, and the vapor is brought into a supersaturated state to grow a crystal, the raw material is heated in an upper high temperature region and the crystal growth region is lowered. A crystal growth method characterized in that the crystals are placed in low temperature regions, and a steep temperature difference is formed at the boundary between the high temperature region and the low temperature region.