JPH03183681A - Manufacturing method of CdMnTe crystal - Google Patents

Abstract

PURPOSE:To obtain a crystal which suppresses the deposition of eutectics and decreases a light transmission loss by setting the temp. gradient at the solid- liquid boundary by the solidification of a melt to a specific value or above at the time of solidifying the melt to produce the CdMnTe crystal in a Bridggman furnace. CONSTITUTION:CdTe and MnTe are mixed at a prescribed ratio and the mixture is put into a boat. The boat is housed in a reaction tube and is vacuum sealed. A Cd lump is vacuum sealed at one end of the reaction tube in order to control the Cd vapor pressure in the reaction tube to a specified pressure. This reaction tube is housed in the Bridggman furnace having the prescribed temp. gradient and the raw materials in the boat are heated and melted. The melt is solidified by the Bridggman furnace to grow the CdMnTe crystal. The CdMnTe crystal is produced by setting the temp. gradient at the solid-liquid boundary by the solidification of the melt at >=3.5 deg.C/cm, further setting preferably the crystal growth speed at 0.8 to 3.5mm/h.

Description

[Detailed Description of the Invention] [P↑ Commercial Application 5) Field] The present invention relates to a method for producing Cd M n Te crystal by solidifying a melt in a Bridgman furnace.

[Prior Art] Conventionally, Cd M n Te crystals have been produced by the Bridgman method. The Bridgman method involves melting the raw material in the crucible in a furnace with a predetermined temperature gradient, and then moving the crucible at a slow speed toward the lower temperature distribution in the furnace. The first method is to solidify the melt inside and grow crystals. As the furnace, a horizontal Bridgman furnace or a vertical Bridgman furnace is used. For example, when using a horizontal Bridgman furnace, high-purity CdTe and M
nTe is blended to have a desired composition. This boat is placed in a thick-walled quartz reaction tube and sealed under vacuum. By controlling the Cd vapor pressure at the angle of the quartz reaction tube at a constant level,
^ In order to set the composition ratio to a desired value, a high-purity Cd lump is also vacuum sealed at one end of the quartz reaction tube. This quartz reaction tube is placed in a horizontal electric furnace, and after heating and melting the raw materials, the quartz reaction tube is moved at a slow speed to a low temperature section to crystallize from one end.

Conventionally, when a molten raw material is solidified and crystallized in a furnace, the temperature gradient and crystal growth speed in the longitudinal direction of the furnace at the solid-liquid interface have been set without any particular consideration.

[Problems to be Solved by the Invention] However, in such conventional methods, when producing a CdMnTe crystal with a large Mn composition ratio, for example, c
When producing a Cd MnTe crystal in which X exceeds 0.05 in the composition of d, -xMnxTe,
There was a problem in that the amount of eutectic gradually increased in the crystallization 1111, and when the wafer was made into a wafer with a thickness of about 1 mm, a characteristic pattern appeared on the surface, resulting in a large light transmission loss.

The purpose of this invention is to solve such conventional problems, to suppress the generation of eutectic in the crystal, and to suppress the generation of eutectic in the crystal, and to reduce the light transmission loss.
The purpose is to present a method for manufacturing dMnTe crystals.

[Means for Solving the Problems] In order to solve the above-mentioned conventional problems, the inventor of the present invention has conducted various studies, and as a result, the temperature gradient at the solid-liquid interface in the Bridgman reactor is as follows. It was discovered that this greatly affects crystal precipitation, and this invention was made.

That is, this invention reduces the temperature gradient in the direction of the furnace length at the solid-liquid interface where the melt solidifies in the Bridgman furnace to 3.5°C.
/ cm or more.

Furthermore, the present inventors have found that the crystal growth speed as well as the temperature gradient in the longitudinal direction of the furnace at the solid-liquid surface in the Bridgman furnace have a large effect on eutectic precipitation.

That is, in this invention, the temperature gradient at the solid-liquid interface where the melt solidifies in the Bridgman furnace is 3.5°C/
It is preferable that the crystal growth speed is set at cm or more and the crystal growth speed is 0.8 to 3.5 mm/h.

[Action] J, Cryst, Growth, 52,614 (198
According to 1), in the phase diagram of CdTe-MnTe mixed crystal, C
d, -X Mnx Te When X is around 0.75, a product is formed.In the range of Q<x<0.75, the segregation coefficient is less than 1, so during crystal growth, Mn There is always a tendency to be pushed in the direction of crystal growth.

According to this invention, when the temperature gradient in the direction of the furnace length at the solid-liquid interface is steep, such as 3.5°C/cm or more, M
When n is immediately pushed away, it solidifies and crystallizes at +17, so Mn is reliably pushed toward the crystal h° direction, and the generation of eutectic is suppressed. When the temperature gradient in the furnace longitudinal direction at the solid-liquid interface is gentle, Mn is not pushed away enough;
Regardless of the crystal growth speed, M forms a eutectic in the crystal.
r+ remains.

In addition, when the temperature gradient is set to 3.5°C/cm or more, the crystal growth speed is 0.8 to 3°5 m
Preferably m/h. When the crystal growth speed is faster than 3.5 mm/h, Mn is crystallized without being sufficiently pushed away, so Mn becomes a eutectic and tends to remain in the crystal. In addition, the crystal speed is 0.8
mm/h, and as it slows down to the ground, the subtle fluctuations in temperature that are originally observed at the solid-liquid interface become a coercive influence, and -
Once solidified and crystallized, microscopically 1.4 places +IG
H melts, and the difference in volume at this time causes pores to remain in the crystal.

[Example] Daisou I A total of 48 pieces of high-purity raw materials CdTe and MnTe were blended in a graphite boat at a molar ratio of 0.94:0.06, respectively. Got ready. They were separately placed in a thick-walled quartz reaction tube and vacuum sealed, and at the same time, a Cd lump was vacuum sealed at one end of the quartz reaction tube.

This quartz reaction tube was placed in a horizontal electric furnace, and after applying and melting the raw materials, it was held for about 12 hours, and then the quartz reaction tube was moved to a low temperature section. The speed of movement to the low temperature part is 0.
5;0.8.1.0.2゜0;3. O; 3.5; 4.0
;5. The speed was varied under eight conditions including Omm/h. In addition, the temperature gradient in the furnace longitudinal direction at the solid-liquid interface was set to 2.3°C/cm,
3. 0℃/cm, -3.5℃/cm, 4.0℃/
The temperature was varied under six conditions: cm, 5.0°C/cm, and 6.0°C/cm, and 2148 crystals were grown by combining the conditions with the speed of movement to the low temperature section.

Each crystal obtained has a width of 4 (1 mm and a length of 200 mm).

The depth was 15 mm. Cut out a wafer with a thickness of 2 mm from the center of the crystal length, polish both sides, and finish.
The sample was 1 mm thick. For each sample, a light transmission loss of 11111 was added for light at a wavelength of 850 nm. The measurement results for each sample are summarized in Table 1. In addition,
The movement speed of the quartz reaction tube to the low temperature section is 0.5 mm/h.
All of them had pores scattered over the entire length, and the light transmission loss /IpJ could not be determined.

Experiment ■ A total of 48 crystals were grown in the same manner as in Experiment I above, except that the mole ratio of CdTe and MnTe was 0.85:0, 15, respectively. Cut out a sample of the wafer and reduce the light transmission loss to 1lp1.
Established. The results are shown in Table 2.

Experiment ■ The composition ratios of CdTe and MnTe are each 0.0 in molar ratio. A:L 4g crystals were grown in the same manner as in Experiment I above, except that they were combined to become 78 + o, 22, and a sample of sea urchin I\ was cut out from the obtained crystals.
Light transmission loss was determined by aFI. The results are shown in Table 3.

Experiment ■ The composition ratio of CdTe and MnTe is 0 in terms of molar ratio.
．． A total of 48 crystals were grown in the same manner as in Experiment I above, except that the ratio was 70:0.30, and a sample of J-/\ was cut out from the obtained crystals to determine the optical transmission loss. was measured. The results are shown in Table 4.

Experiment V Except for blending CdTe and MnTe in a molar ratio of 0163:0.37,
A total of 148 crystals were grown in the same manner as in Experiment ① above, and samples of sea urchin/% were cut out from the obtained crystals, and the light transmission loss was determined by aF+. The results are shown in Table 5.

In addition, in experiments ① to V, all of the samples in which the movement speed to the low temperature part of the quartz reaction tube was 0 and 5 mrn/h had pores scattered over the entire length of the crystal, as in experiment I. Transmission loss could not be determined by API.

Table 1: Light transmission loss in Experiment I (dB/question) Cd + - x nx Tex -0,06 *) Since pores were scattered over the entire length of the crystal, the light transmission loss could not be determined by iMP+.

Table 2゜ Light transmission loss in experiment ■ (d137mm ) Cd +-x nx Te x −0,15 Light transmission loss could not be determined by aFI.

Table 3, Light transmission loss in experiment ■ (rill/++m) Cd +-x Mr＋×Te xmo, 22 The light transmission loss could not be determined at 4-1.

Table 4゜ Light transmission loss in experiment ■ (dll/n11) Cd +-x 　n　X Te x −0,30 The light transmission loss could not be determined.

Table 5゜ Light i in Experiment V! excess loss (rH3/open) Cd, -8 n　X Te x −0,37 Light transmission loss could not be measured.

As is clear from the results in Tables 1 to 5, the crystal grown according to the present invention with the temperature gradient at the wave interface set to 3.5°C/Cm or higher was found to have reduced optical transmission loss. .

Furthermore, crystals with crystal growth speeds of 0.8 to 3.5 mm/h showed particularly reduced light transmission loss.

[Effect of the invention] In this invention, the temperature gradient in the longitudinal direction of the furnace at the liquid boundary curve is reduced to 3.
．． By setting the temperature to 5° C./cm or higher, it is possible to suppress the precipitation of eutectic and grow a crystal with lower light transmission loss than before. Furthermore, by limiting the crystal growth speed to 0.8 to 3.5 mm/h for tIF, the optical transmission loss can be reduced to approximately 1/2 to 1/3 of that of the conventional method, and this crystal can be grown in an optical magnetic field. When used in a sensor, the performance as an optical magnetic field sensor can be almost doubled or tripled.

Claims (2)

[Claims] (1) Solidify the melt in the Bridgman furnace to produce CdMn
A method for producing a CdMnTe crystal, characterized in that the temperature gradient at the solid-liquid interface due to solidification of the melt is set to 3.5° C./cm or more. (2) Solidify the melt in the Bridgman furnace to produce CdMn
In the method for producing a Te crystal, the temperature gradient at the solid-liquid interface due to solidification of the melt is set to 3.5° C./cm or more, and the crystal growth speed is further increased from 0.8 to 3.5 m.
A method for producing a CdMnTe crystal, characterized in that the CdMnTe crystal is produced at m/h.