JPH06316500A - Production of cdmnte single crystal - Google Patents

Abstract

PURPOSE:To obtain a high-quality single crystal in a high yield at the time of producing a cadmium manganese tellurium single crystal by the Bridgman technique by making the Te in the mixed material composition excess over stoichiometry. CONSTITUTION:A quartz ampule and a heater for melting a solid single crystal material vacuum-sealed in the ampule are used, the heater and ampule are continuously moved with respect to each other at a specified speed, and hence the molten material in the ampule is solidified from the lower part to produce the cadmium manganese tellurium single crystal (Bridgman technique). The composition of the material is shown by Cd1-xMnxTe1+y (where 0.1<=x<=0.5 and 0.01<=y<=0.10). The melting temp. and saturated vapor pressure are lowered in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is about 0.6 .mu.m to 0.
The present invention relates to a method for producing a cadmium-manganese-tellurium (CdMnTe) single crystal used as a material for an optical isolator having a short wavelength of 8 μm.

[0002]

2. Description of the Related Art Conventional CdMnTe single crystals for optics are manufactured by using a cadmium (Cd) raw material having a purity of 99.9999%, a manganese (Mn) raw material having a purity of 99.99%, and a purity of 99.9999%. Tellurium (Te) raw material is placed in a transparent quartz ampoule according to the composition ratio, and the degree of vacuum is about 1 × 10 ^-5 Tor.
In a state of r, the ampoule and a heating device for converting the solid crystal raw material in the ampoule into a melt are vacuum-sealed, and the relative positional relationship between the heating device and the ampoule is continuously set to a predetermined value. It was produced by the so-called Bridgman method in which the melt of the crystal raw material in the ampoule is solidified from below by changing the speed to produce a single crystal.

[0003]

Using the conventional technique, C
When a d _{1 -x} Mn _x Te single crystal is manufactured, the Mn concentration x ≧
In the case of 0.1, the ampoule made of quartz often bursts when melted. Therefore, there is a problem that the crystal cannot be manufactured or the crystal does not crack, but the grown crystal does not satisfy the practical characteristics (insertion loss <1 dB, extinction ratio> 35 dB). An object of the present invention is to solve the above problems and provide a method for producing a high quality single crystal of Cd _1-x Mn _x Te with a high yield.

[0004]

In order to solve the above-mentioned problems, the present invention is a method for growing a single crystal by the Bridgman method. In order to reduce the vapor pressure in a quartz ampoule, Te is used in a stoichiometric amount. Over the theoretical composition, ie C
In the composition formula represented by d _1-x MnxTe _{1 + y} , y is made excessive by an amount defined by 0.01 ≦ y ≦ 0.10 to lower the melting temperature, and as a result, the vapor pressure is lowered,
A method for mass producing high quality single crystals was obtained.

That is, the present invention uses a quartz ampoule and a heating device for making a solid single-crystal raw material vacuum-sealed in the ampoule into a melt, and the relative positional relationship between the heating device and the ampoule. Cd _1-x in the method for producing a single crystal by the Bridgman method in which the melt of the raw material for a single crystal in the ampoule is solidified from below by continuously changing the Cd _1-x In the chemical formula represented by Mn _x Te _{1 + y} , 0 ≦ x ≦ 0.5, 0.01 ≦ y
Cd _1-x M when blended to the composition ratio specified by ≦ 0.10
Cd _1-x Mn characterized by growing n _x Te single crystal
a method for producing _x Te single crystal.

[0006]

When a CdMnTe single crystal is produced by the conventional Bridgman method, the transparent quartz ampoule is cracked during the growth to make it unmanufacturable, or the crystal which is grown without cracking has practical characteristics (insertion loss <1 dB. The problem of not satisfying the extinction ratio> 35 dB) is considered to be that the surface oxidation of the Mn raw material and the surface oxidation of MnTe or the presence of MnTe ₂ promotes the reaction with the transparent quartz ampoule. The author previously mentioned that the method for removing dissolved oxygen in the Mn raw material (Japanese Patent Application No. 3-35978).
No. 1) was proposed.

According to the present invention, it has become possible to solve the phenomenon that the quartz ampoule reacts with the crystal melt to deteriorate the quartz ampoule. However, often the quartz ampoule ruptured as soon as the melting started. The cause of this is considered to be insufficient removal of dissolved oxygen.

However, it has been reported that the removal of manganese oxide (MnO) once formed requires a hydrogen (H ₂ ) reduction treatment at a temperature of 2,000 ° C. and a pressure of 150 atm (E). . Newbury an
d J. N. Pring, Proc. (London)
A92 (1910) 276). Thus, it is difficult to dissociate O _{2 from} manganese oxide (MnO) once formed experimentally. This incomplete removal of dissolved oxygen depends on TeO.
_In the form of insufficient Te, which actually promotes the generation of ₂ and forms a compound, as a result, the unreacted melting point is low, and cadmium (Cd), which is a constituent with a high vapor pressure, exists independently, and in the vicinity of the melting point It was interpreted that the pressure of the above rose to -20 atm and the quartz ampoule became dead.

In order to improve this point, there is no problem if the thickness of the quartz ampoule is ≧ 3.5 mm. However, if the ampoule thickness is ≥3.5 mm or more, the quartz ampoule is vulnerable to temperature shock, so it is necessary to pay close attention to the handling in the vacuum encapsulation process. There was a problem that the grown crystal was easily cracked due to the strain from the container. Further, in the case of producing crystals, an increase in the thickness of the quartz ampoule has a drawback that the cost (ampoule cost) increases and the crystal yield decreases.

Therefore, by taking measures to reduce the saturated vapor pressure in the equilibrium state during crystal growth, the wall thickness becomes 2 mm.
It was possible to grow a good quality crystal using a quartz ampoule of a certain degree.

In order to reduce the saturated vapor pressure, it is effective to lower the growth temperature. The saturated vapor pressure near the melting point of Cd _1-x Mn _x Te is estimated to be about 5 to 8 atm. However, when cadmium becomes excessive in some way and unreacted cadmium vapor exists in the crystal growth step, a saturated vapor pressure of -20 atm is applied. On the other hand, C
When d _1-x Mn _x Te is dissolved in a Te solvent, the melting point and the saturated vapor pressure decrease. This is because the absolute values of the saturated vapor pressure of cadmium and the saturated vapor pressure of tellurium are 100 times different, so that the solvent of Te is increased and at the same time, Cd _1-x Mn _x T
The saturated vapor pressure curve of e shifts toward the saturated vapor pressure curve of tellurium.

As described above, the above problem can be solved by crystal growth from a melt containing Te in excess. However, there is a problem in view of industrial application because the crystal growth rate is significantly slowed by the amount of Te excess. That is, the crystal growth rate in consideration of industrial production ~ 1 mm /
By setting the lower limit of hr and limiting the excess from the Te stoichiometric composition to achieve the intended purpose (lowering of melting point and accompanying reduction of saturated vapor pressure), high-quality CdMn is obtained.
A Te single crystal is produced with good yield.

[0013]

EXAMPLES The present invention will be described below with reference to examples. FIG. 1 shows a comparison of saturated vapor pressure-temperature curves obtained by the conventional manufacturing method and the manufacturing method of the present invention.

With reference to FIG. 1, Cd is manufactured by the conventional manufacturing method._0.5
Mn_0.5A case of producing a Te single crystal will be described. Raising temperature
The saturated vapor pressure in the quartz ampoule at 1100 ° C is ~ 8a.
estimated to be tm. For example, some form of melt
Therefore, when Cd evaporates, saturated steam of ~ 20 atm
Pressure will be applied. Until now, if you train
Is an ampoule within 0.5 to 2 hours after melting the crystal raw material.
Often burst. This factor is
It is thought that it is as follows, so Cd will never become excessive
And lower the growth temperature.
Good. To do so, grow crystals from the Te-rich melt.
The growth temperature and the saturated vapor pressure in the quartz ampoule.
Should be lowered. In the manufacturing method of the present invention, referring to FIG.
Cd_0.5Mn_{0 .Five}A case of producing a Te single crystal will be described.
Preparation composition Cd_0.5Mn_0.5Te_{1 + 0.05}In case of
At 1050 ° C, the internal pressure of the ampoule can be suppressed to ~ 4 atm
As a result, the growth rate can be set to ~ 1.5 mm / hr. Also, T
eSince it is in excess, Cd with high saturated vapor pressure is in excess.
Never be. Preparation composition Cd_0.5Mn_0.5Te
_{1 + 0.1}In the case of, the internal temperature of the ampoule at a growth temperature of 1000 °
Is suppressed to ~ 2 atm, and the growth rate is ~ 1.0 mm / h.
It can be r. Also, since Te is in excess, saturated steam
Cd having high atmospheric pressure is not excessive. Excess Te
The lower limit is the composition Cd_{0. Five}Mn_0.5Te_{1 + 0.01}Limited to
You are Te_{1 + 0.001}If it is over the above range, the saturated vapor pressure is high.
This is because there is no excess Cd. Set the upper limit
Only composition Cd_0.5Mn0.5Te_{1 + 0.1}Only limited to training
It means that crystals could be grown at a speed of 1 mm / hr or more.
Stipulated. In Table 1, the conventional method and the manufacturing method of the present invention are used.
The quartz ampoule used to manufacture the crystal.
The crack rate, devitrification rate and crystal yield are shown in comparison.

[0015]

[Table 1]

The reduction of the devitrification rate of the quartz ampoule in Table 1 is
This is due to the lowering of the growth temperature, and the lowering of the rupture rate of the quartz ampoule is due to the lowering of the saturated vapor pressure.

[0017]

As described above, in the method for growing a Cd _1-x Mn _{x Te} single crystal by the Bridgman method,
In order to lower the vapor pressure in the quartz ampoule, Te in the raw material blending composition is set to be in excess of the stoichiometric composition to lower the melting temperature and the saturated vapor pressure to achieve the above object.

[Brief description of drawings]

FIG. 1 Cd _1-x Mn _x Te _{1 + y-} based compound, Cd and T
3 shows a saturated vapor pressure-temperature curve of e.

[Explanation of symbols]

A Cd _0.5 Mn _0.5 Te saturated vapor pressure-temperature curve B Cd _0.5 Mn _0.5 Te _{1 + 0.05} saturated vapor pressure-temperature curve C Cd _0.5 Mn _0.5 Te _{1 + 0.1} saturated vapor pressure-temperature curve D Cd saturated vapor Pressure-Temperature Curve E Te Saturated Vapor Pressure-Temperature Curve T Absolute Temperature

Claims (1)

[Claims] 1. A quartz ampoule and a heating device for converting a solid single-crystal raw material vacuum-sealed in the ampoule into a melt are used, and the relative positional relationship between the heating device and the ampoule is continuous. Cadmium by the Bridgman method for producing a single crystal by solidifying the melt of the single crystal raw material in the ampoule from below by changing at a predetermined speed to
In the method for producing a manganese-tellurium single crystal, the raw material composition of the cadmium manganese tellurium single crystal is represented by the chemical formula C
d _1-x Mn _x Te _{1 + y} , 0.1 ≦ x ≦ 0.5,
A method for producing a cadmium-manganese-tellurium single crystal, characterized in that the range is 0.01 ≦ y ≦ 0.10.