JPH0769773A - Production of single crystal - Google Patents

Abstract

PURPOSE:To enable efficient growth of a Cd1-X-YMnXHgYTe, Cd1-X-Y-ZMnXHgYZnZTe and Cd1-X-YMnXHgYTe1-ZSeZ single crystals having high optical quality and free from twin crystal. CONSTITUTION:Metallic Cd, metallic Mn, metallic Te, metallic Zn, metallic Se, metallic Hg or an HgTe compound are used as starting raw materials and a sintered rod 6 having the target composition is produced from the raw materials as an intermediate crystal raw material. A molten liquid 4 charged with Te and Se somewhat excess to the target composition is prepared by the control of the temperature distribution and the movement of a quartz crucible 3 in a furnace and a single crystal 5 is crystallized from the molten liquid. The liquid corresponding to the crystallized material is continuously replenished from the above sintered rod 6 to the molten liquid 4 to keep the composition of the molten liquid to a definite state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical element for an optical isolator for an optical amplifier pumping light source (0.98 to 1.02 .mu.m) and an LD pumping SHG light source (0.83 to 0.86 .mu.m). Is Cd _1-XY Mn _X Hg _Y Te, C
d _1-XYZ Mn _X Hg _Y Zn _Z Te or Cd _1-XY Mn _X
The present invention relates to a method for producing a single crystal represented by Hg _Y Te _1-Z Se _Z.

[0002]

2. Description of the Related Art Conventionally, the above-mentioned Cd _1-XY Mn _X Hg _Y T
e, Cd _1-XYZ Mn _X Hg _Y Zn _Z Te or Cd
The manufacturing method of _1-XY Mn _X Hg _Y Te _1-Z Se _Z single crystal is C
A metal solid crystal raw material such as d, Mn, Te, or Se is vacuum-sealed in an ampoule-shaped crucible of a transparent quartz tube according to the composition ratio. By using the crucible and a heating device for converting the metal solid crystal raw material in the crucible into a melt, the relative positional relationship between the heating device and the crucible is continuously changed at a predetermined speed, thereby the crucible. The method corresponds to a method of solidifying a melt of the above-mentioned crystal raw material in the inside from below to produce a single crystal (hereinafter referred to as a conventional production method A), or a target composition produced by, for example, the quench method (high-pressure melting and quenching method). A polycrystalline raw material rod with a composition is vacuum sealed in an ampoule-shaped crucible,
There is a method for producing a single crystal by holding the crucible at a temperature lower than the melting point with a heating device to perform solid phase growth (hereinafter referred to as a conventional production method B).

[0003]

When the above-mentioned single crystal is manufactured using the conventional manufacturing method A, high temperature and high pressure (temperature:
1100 ° C., pressure: 20 atm) Expensive manufacturing equipment capable of setting conditions is required. In addition, since it melts at a melting point equal to or higher than the phase transformation point, it always passes through the phase transformation point in the crystallization process, so that there is a problem that twinning is likely to occur. When twins are present, it is necessary to use a specific crystal plane in order to achieve the practical characteristics of the optical isolator, which is not efficient in terms of yield and the like. Furthermore, when this manufacturing method is used, composition segregation increases with the progress of crystallization, and there is a problem that only a small amount of single crystal having a required composition can be obtained. On the other hand, when the above-mentioned single crystal was manufactured using the conventional manufacturing method B, the single crystallization rate was extremely low, and it was difficult to increase the diameter. Therefore, none of the manufacturing methods can be said to be the most suitable method for industrial production. An object of the present invention is to provide a manufacturing method suitable for mass-producing the above single crystal with high quality.

[0004]

The present invention solves the above-mentioned drawbacks and provides a method for mass-producing a high-quality single crystal. Therefore, a single crystal by a continuous traveling heater method (hereinafter abbreviated as THM method) is used. And a metal Cd,
A metal Mn, a metal Te, a metal Zn, a metal Se, a metal Hg, or a HgTe compound is used as a starting material, and a sintered body having a target composition is made from the starting material to be an intermediate crystal material.
A melt containing Te or Se in a larger amount than the target composition ratio is prepared, the single crystal is crystallized while gradually dissolving in the melt, and the component raw material corresponding to the crystallized portion is supplied to the melt. Thus, the composition in the melt is always kept constant, and the crystal is produced while reversing the rotation direction of the crucible so that the additional feed material does not cause a thermal change in the melt. That is, the present invention uses the continuous THM method to produce Cd _{1 -XY} Mn _X H
g _Y Te, Cd _1-XYZ Mn _X Hg _Y Zn _Z Te or C
In the method of making a _{d 1-XY Mn X Hg Y} Te 1-Z Se Z monocrystalline, metal Cd, metal Mn, which is prepared in proportions corresponding to the target composition, the metal Se, metal Zn, a metal Te, metal Hg Alternatively, a starting material of either metal HgTe is previously melted and reaction-solidified to prepare an intermediate raw material of a polycrystalline body, and the intermediate crystal raw material fixed to the upper part in the crucible and a single crystal is formed in the lower part in the crucible. In the middle of the melt to grow, Te
Is filled with a solvent, the temperature distribution in the furnace and the movement of the crucible melts the intermediate raw material of the polycrystalline body to form a melt having a composition in which Te is larger than the target composition, and a single crystal is formed from the melt. The method for producing a single crystal is characterized in that a single crystal is grown while continuously replenishing the component raw material amounts corresponding to the crystallized amount and keeping the composition of the melt within a predetermined range.

[0005]

In the case of the conventional production method A in which the above-mentioned single crystal is produced by the conventional Bridgman method, the melting point is higher than the phase transformation point, so that when the solidification occurs, the wurtzite-type crystal structure is used to form sphalerite. It passes through the phase transformation point where it changes into a crystal structure.
The strain generated at that time is considered to be a factor of twinning. That is, since it solidifies at a temperature higher than the phase transformation point, it is difficult to avoid twinning. Therefore, in order to achieve the practical characteristics of the optical isolator, it is necessary to use a specific surface, which is not efficient in consideration of yield and the like. Furthermore, when this manufacturing method is used, the composition segregation becomes large, so that there is a problem that only a small amount of the necessary composition can be taken. On the other hand, when the above-mentioned single crystal was manufactured by the conventional manufacturing method B, the single crystallization rate was extremely low, and it was difficult to increase the diameter. None of the manufacturing methods was the optimum method for industrial production.

Therefore, in the present invention, the problem of crystallinity has been solved by devising a device that enables crystal growth at a temperature below the phase transformation point. Also, by adopting a method of continuously supplying additional raw materials, composition segregation is eliminated, and in order to minimize the thermal change of the melt at this time, crystal growth is performed while reversing the rotation direction of the crucible. Perform. The seed crystal and the V-bottomed crucible are used to increase the probability of crystal growth in a specific orientation and improve the crystal yield. The reason why the melting zone containing excess Te is made equal to or smaller than the crystal diameter to be grown is to form an upward convex in-plane temperature distribution in order to make convection in the melting zone easy to crystallize.

The present invention will be described below with reference to examples.

[0008]

The development of Cd _0.72 Mn _0.15 Hg _{0. 13} semimagnetic semiconductor single crystals of Te will be described by way of example with reference to apparatus for producing the structure shown in FIG. 1 an embodiment of the embodiment of the present invention. High purity Cd, M
n, HgTe, Te are weighed to the target composition, and the quartz crucible 3
Melted in the electric furnace 1 of the high-pressure Bridgman furnace (melting point: about 1050 ° C, pressure: about 20 at)
After m), it is rapidly cooled to produce a polycrystalline sintered rod 6. After loading the polycrystalline sintered rod 6, the initial filling material, and the Te solvent into the quartz crucible 3 and vacuum-sealing, the quartz crucible 3 is installed in the electric furnace 1 and the quartz crucible 3 is set to 1 to 5 mm / day. The quartz crucible 3 is lowered at a speed of 1 to cause the crystal growth to be sequentially performed from the lower end of the quartz crucible 3. At the melting point (about 800 ° C.), the crystal is below the phase transformation point (about 950 ° C.), so that it has a sphalerite type crystal structure, and since it does not pass through the phase transformation point during the crystal growth process, twin crystals did not occur.

Cd _0.72 M is obtained by solidifying from below in the melt.
n _0.15 Hg _0.13 Te In order to constantly keep the composition in the melt constant by additionally supplying the raw material corresponding to the amount of crystallizing the single crystal, and to prevent the additional feed material from undergoing a thermal change. Sufficient stirring is performed by a device that can periodically reverse the rotation direction of the quartz crucible 3. The seed crystal and the V-bottom crucible are used to improve the crystal yield by increasing the probability of crystal growth in a specific orientation.
The reason why the melting zone H is grown to a crystal diameter or less is to form an upward convex in-plane temperature distribution so that the convection in the melting zone can be easily crystallized. A single crystal was grown by such a device. As a result, twin crystals did not occur in all the single crystals produced in this example, and a single crystal grown body was obtained at a yield of 90% or more.

(Conventional Example 1) FIG. 2 is an explanatory view showing a schematic cross section of a manufacturing apparatus used in a conventional manufacturing method A. The crystal raw material preloaded in the quartz crucible 3 is melted by using the temperature distribution of the electric furnace to form a melt 4, and then the quartz crucible 3 is lowered at a speed of 3 to 7 mm / hr,
A single crystal is obtained by sequentially growing crystals from the lower end of the quartz crucible 3 and then gradually cooling. Reference numeral H in FIG.
Indicates the melting zone.

In practice, the composition is Cd _0.72 Mn _0.15 H
A single crystal of g _0.13 Te was grown. Metal Cd, metal Mn,
After melting metal HgTe and a quartz crucible 3 in which metal Te is vacuum-sealed at a target composition ratio in an electric furnace 1 of a high-pressure Bridgman furnace (melting point: about 1050 ° C. pressure: about 20 atm) to form a melt 4. , Quartz crucible 3 3 to 7 mm / h
The quartz crucible 3 is lowered at a speed of r to sequentially grow crystals from the lower end of the quartz crucible 3. The crystal structure of the crystal becomes a wurtzite structure from the melting point (about 1050 ° C) to the phase transformation point (about 950 ° C), and becomes a sphalerite structure at a temperature below the phase transformation point (about 950 ° C). However, when this manufacturing method is adopted, twin crystals are always generated, and the obtained single crystal can be used only on a specific surface as a material for an optical device, resulting in poor crystal yield.

(Conventional Example 2) Next, a case of growing a Cd _0.72 Mn _0.15 Hg _0.13 Te single crystal using the conventional manufacturing method B will be described with reference to FIG. In FIG. 3, the vacuum-sealed quartz crucible 3 was once melted in the electric furnace 1 of the high-pressure Bridgman furnace (melting point: about 1050 ° C. pressure: about 20a
After tm), it is rapidly cooled to produce a polycrystalline sintered rod. Then, in the electric furnace 1, a solid phase reaction is performed at a temperature lower than the melting point by about 120 ° C. to grow crystals. Since the solid phase reaction temperature (about 930 ° C.) of the crystal is below the phase transformation point (about 950 ° C.), it has a sphalerite structure. Therefore, in this case, since the crystal does not pass through the phase transformation point in the course of crystal growth, twins are hardly generated. However, it was difficult to form the entire crystal into a single crystal because the solid phase reaction was used. Moreover, it was difficult to increase the diameter of the crystal.

Table 1 shows the growth conditions and the growth results according to the conventional method and the manufacturing method of the present invention.

[0014]

[Table 1]

[0015]

As described above, the present invention is used as an optical isolator for an optical amplifier pumping light source (0.98 to 1.02 μm) and an LD pumping SHG light source (0.83 to 0.86 μm). Optical element Cd _1-XY M
A single crystal capable of efficiently growing a twin-free high optical quality single crystal of n _x Hg _Y Te, Cd _1-XYZ Mn _x Hg _Y Zn _Z Te, and Cd _1-XY Mn _x Hg _Y Te _1-Z Se _Z. A method for producing crystals could be provided.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a schematic cross section of a crystal manufacturing apparatus used in the present invention.

FIG. 2 is an explanatory view showing a schematic cross section of a crystal manufacturing apparatus used in a conventional manufacturing method A.

FIG. 3 is an explanatory view showing a schematic cross section of a crystal manufacturing apparatus used in a conventional manufacturing method B.

FIG. 4 is a diagram showing a state of a crystal, FIG. 4 (a) is a diagram showing a crystal obtained by a conventional production method A, and FIG. 4 (b) is a diagram showing a crystal obtained by a conventional production method B. Figure, Figure 4
(C) is a figure which shows the crystal obtained by the manufacturing method of this invention.

[Explanation of symbols]

 1 Electric Furnace 2 Crucible Lifting Mechanism 3 Quartz Crucible 4 Melt 5 Single Crystal 6 Sintering Rod 8 Crucible Inversion Mechanism 9 Twinning Surface 10 Crystal Grain H Melting Zone

Claims (5)

[Claims] 1. A crucible and a heating device for converting a crystal raw material in the crucible into a melt, by moving the crucible downward in the heating device at a predetermined speed, The melt of the crystal raw material is solidified from below, and the composition is Cd _{1-X- Y} Mn _X Hg _Y Te, Cd _1-XYZ Mn _X Hg _Y
In the method for manufacturing a single crystal to grow a single crystal represented by Zn _Z Te or _{Cd 1-XY Mn X Hg Y} Te 1-Z Se Z,
Metal Cd and metal M adjusted to the ratio corresponding to the target composition
A starting material consisting of n, metal Te, and either metal Hg or a metal HgTe compound is previously dissolved and reactively solidified to prepare an intermediate raw material of a polycrystalline body, and the intermediate raw material is fixed to the upper part in the crucible. Then, a layer of Te as a solvent is formed between the crucible and the melt filled in the lower part of the crucible, and by combining the temperature distribution of the heating device and the movement of the crucible, an intermediate of the polycrystalline body is formed. The raw material is Te
Of the target composition to form a melt, and crystallize and grow a single crystal of the target composition from the melt, and crystallize as a single crystal with respect to the melt. 1. A method for producing a single crystal, which comprises continuously replenishing a component raw material corresponding to, and growing the single crystal while maintaining the composition of the melt within a predetermined range. 2. The method for producing a single crystal according to claim 1, wherein a single crystal having the same composition as the crystal to be grown is used as a seed crystal. 3. The method for producing a single crystal according to claim 1, wherein the bottom of the V-bottomed crucible is filled with a mixture having the same composition as the single crystal to be grown. 4. The method for producing a single crystal according to claim 1, 2, or 3, wherein the rotation direction of the crucible is reversed at a specific time interval during crystal growth. 5. The method for producing a single crystal according to claim 1, 2, 3 or 4, wherein the thickness of the Te layer is set to be equal to or smaller than a growing crystal diameter.