JPS61106498A - Method for growing cdte crystal - Google Patents

Abstract

PURPOSE:To obtain the titled crystal having uniform resistivity by eliminating a temp. gradient in a furnace after the CdTe crystal is grown, and cooling slowly the furnace while keeping a uniform temp. distribution in the Bridgman furnace having a temp. gradient between the upper and the lower part. CONSTITUTION:Cd and Te3 in a stoichiometric ratio are charged in a vessel 2, then allowed to react with each other at a low temp. of about 800 deg.C, and alloyed. The alloy is charged into a Bridgman furnace 4 having such a temp. gradient that the temp. of the upper furnace (a) is regulated to 1,150 deg.C and that of the lower furnace (b) is regulated to about 950 deg.C, and allowed to react at about 1,150 deg.C for several hours. Then the vessel 2 is moved to the lower furnace (b) at 950 deg.C, the temp. of the upper furnace (a) is equalized to the temp. of the lower furnace (b), and then the temp. of the upper and the lower furnace is reduced at 10 deg.C/hr cooling velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for growing CdTe crystals using a Bridgman furnace, and particularly to improving the uniformity of resistivity of the crystals.

<Prior art> Fig. 2 (a), (b), and (c) are in the conventional example.
Fig. 2(a) shows a crystal growth method for Te. In Fig. 2(a), a cylindrical container (for example, a quartz ampoule) 2 with a hook 1 on the top is filled with a material having a purity of 5N to 6N (99°999 to 99.9%).
CD and Te crystals 3 of approximately 999%) are housed in a chemical equivalent ratio and sealed under a vacuum degree of approximately 104 Pascals (Pa). Figure 1(b) is Figure 1(a)
This figure shows the state in which the container 2 is inserted into the Bridgman furnace 4, where 5 is a furnace core tube and 6 is a heater provided on the outer wall of the furnace core tube 5. These heaters are controlled by a control section (not shown), and, for example, the upper part A forms an upper furnace, and the lower mouth part forms a lower furnace. 7 is a wire for hanging the container 2 and positioning it at a predetermined location or moving it by a control device (not shown).

Figure 2<C,) shows the temperature distribution of the furnace core tube 5 in Figure 2 (1)), where the horizontal axis is the temperature and the vertical axis is the temperature at each rental of the furnace core tube 5. The lower furnace above approximately the center of furnace 4 is 1150°C, and the lower furnace below the center is 950°C.
℃, 1092℃ between the lower furnace and the lower furnace
This shows that point A exists.

In the Bridgman furnace configured as above, the crystals of C(l and Te' stored in container 2 are alloyed by a lower part reaction σ at around 800°C, and reacted at 1150'C for several hours in the upper furnace A). Then, the container 2 is lowered toward the lower furnace opening at a rate of several mm per hour, and the CdTe crystal growth ends when the entire container 2 reaches a temperature range of 950° C. Conventionally, at this point, the heater Power supply to 6 was stopped and natural cooling was performed.

However, in this conventional example, if all parts of the container 2 do not reach the 950°C region of the lower furnace mouth,
It is not possible to uniformly cool the entire crystal ingot due to growth erosion. In addition, since the temperature drop during cooling is rapid due to natural cooling to room temperature, the cooling temperature becomes uneven even within the crystal ingot, which has the disadvantage that the specific resistance of the cdTe crystal tends to become uneven. .

<Object of the invention> The present invention has been made in view of the drawbacks of the above-mentioned prior art.
The purpose of this method is to obtain crystals with uniform resistivity by devising a temperature pattern in the furnace after CdTe crystal growth and slow cooling while maintaining a uniform temperature.

It is.

<Configuration of the Invention> The configuration of the present invention that achieves this object is based on cadmium (Cd).
) and tellurium (Chinese) crystals are stored in a container in a chemically equivalent ratio, and after the lower part reacts and becomes alloyed at around 800°C, the lower furnace is heated to a temperature of approximately 1150°C and the lower furnace to a temperature of approximately 950°C. The alloyed Cd and Te are placed in a Bridgman furnace with a gradient and reacted at about 1150°C for several hours, and then transferred to a lower furnace at about 950°C to cool down and form a monomer of cadmium telluride (CdTe). In the Cd Te crystal growth method to obtain crystals, after crystal growth, the temperature of the lower furnace is made to match the lower furnace temperature of about 950°C, and then the temperature of the upper and lower parts is adjusted at a rate of several tens of degrees Celsius. The structural feature is that the temperature is lowered by .

<Embodiment> FIGS. 1(a) and 1(b) show an embodiment of the present invention. In the second factor (a), CD and Te are stored and sealed in the container 2, inserted into the furnace 4, and heated to a temperature of 1150 in the upper furnace part.
Let the reaction take place at ℃ for several hours, then change the container several meters per hour.
The process is the same as the conventional method until the entire container 2 is moved to a region of 950° C. and crystal growth of tICd Te is performed. The present invention is characterized by a processing method after crystal growth, and in contrast to conventional methods in which the heater is de-energized and natural cooling is performed after crystal growth, the control unit 7 performs processing as shown in FIG. 1(b). As shown in (,115
From the state of ■ where there is a temperature gradient between 0°C and 950°C, the humidity in the upper furnace A is lowered to a temperature of around 950°C, the humidity at the upper furnace A and the lower furnace mouth are made to be the same, and the temperature gradient in ■ is shown by the dotted line. The temperature is then gradually cooled, for example, at a temperature drop rate of about 40° C. for 1 hour. According to the above method, since the entire container 2 is slowly cooled to a uniform temperature, it is possible to obtain crystals with uniform resistivity.

Figures 3(a) to 6(a) compare the resistivity states of a conventional crystal plate and a crystal plate according to the present invention. Table 0 of the disc-shaped sample of (c) and the plate-shaped sample of (2) cut into a rectangular shape from the center of the crystal ingot 20.
N poles with a diameter of about 0.4 mm were provided on the surface in a lattice-like position with a pitch of 1 mm, and a 4-terminal probe was applied to these electrodes to measure the specific resistance over the entire surface. Figure 3(a)
Figure 4 (a) shows the strength and weakness of resistivity in each part of the sample prepared using the conventional example using color shading, and the numbers on the left side and the top of the figure specify the position of each part. It is for. Figure 3(b) and Figure 4(1)) are graphs of the degree of resistivity in Figures 3(a) and 4(a), with the degree of resistivity on the vertical axis and the degree of resistivity on the horizontal axis. The axis shows the degree of resistivity of the sample, and it can be seen that the outer part of the ingot 20 has a higher resistivity and the inner part has a lower resistivity, indicating that the crystal is not uniform.

FIGS. 5(a) and 6(a) show the degree of strength of resistivity in each part of the sample prepared by the method of the present invention by color shading, as in the conventional example,
The numbers on the left side and the top of the figure are for identifying the position of each part. Figure 5 (1)) and Figure 6 (b) are graphs of the degree of resistivity in Figure 5 <a> and Figure 6 <a), with the degree of resistivity plotted on the vertical axis. The horizontal axis shows the degree of resistivity of the sample, and it can be seen that the difference in resistivity between the outer part and the inner part is lower than that of the conventional example, indicating that the crystals are growing uniformly.

Effects> As specifically explained above in conjunction with the examples, according to the present invention, a crystal with uniform resistivity can be obtained.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) show an embodiment of the present invention, FIG. 1(a) is an explanatory diagram showing the configuration of a Bridgman furnace, and FIG. Explanatory diagram showing humidity distribution, 3rd
FIG. 4 shows the degree of resistivity in each part of a crystal prepared according to a conventional example. 2... Container, 3... Cadmium (Cd) and tellurium (Te) crystals, 4... Bridgman furnace, 5...
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Claims (1)

[Claims] Cadmium (Cd) and tellurium (Te) crystals are stored in a container in a chemically equivalent ratio, and after being reacted and alloyed in the lower part at around 800°C, the upper furnace is around 1150°C and the lower furnace is around 950°C. The alloyed Cd and Te are placed in a Bridgman furnace with a temperature gradient of 1,150°C for several hours, and then transferred to a lower furnace at around 950°C to cool down, resulting in the formation of cadmium telluride (CdTe). In the CdTe crystal growth method to obtain a single crystal, after crystal growth, the temperature of the upper furnace is made to match the temperature of the lower furnace of about 950°C, and then the temperature of the upper and lower furnaces is kept at several tens of degrees Celsius for one hour.
A CdTe crystal growth method characterized by lowering the temperature at a rate of approximately .