JPH0840800A - Production of single crystal - Google Patents

Abstract

PURPOSE:To stably obtain single crystal having excellent optical performance while controlling precipitation of Te by preparing polycrystal excessively premixed with Te and controlling the temperature of a crucible under specific conditions in production of the single crystal in producing specific single crystal by THM method using Te as flux. CONSTITUTION:Single crystal of the chemical formula (Cd1-x-yMnxHgy)Te, (Cd1-x-y-zMnxHgyZnz)Te and (Cd1-x-yMnxHgy)(SeuTe1-u) [(x), (y), (z) and (u) are each 0-1] is produced by a method (THM method) for moving polycrystal while melting in a belt-like state by using Te as flux under a fixed temperature gradient. In the production, Cd, Mn, Zn, Se, Hg, Te or HgTe are used as a raw material, the blending molecular ratio of the raw materials is regulated and Te is made in a ratio 1-10% higher than a fixed ratio to manufacture polycrystal. In production of the single crystal, the whole inner space of a crucible for housing the polycrystal is kept at a temperature >= the melting point of Te (450 deg.C).

Description

Detailed Description of the Invention

[0001]

The present invention relates to the chemical formula (Cd _1-xy M
n _x Hg _y ) Te, (Cd _1-xyz Mn _x Hg _y Zn _z ) T
e, and (Cd _1-xy Mn _x Hg _y ) (Se _u Te
_1-u ), (x, y, z and u are all values of 0 to 1, hereinafter the same). These single crystals are used as a pumping light source (wavelength 0.98 to 1.02 μm) for optical amplifiers used in long-distance transmission of optical communication, and a semiconductor laser (LD) pumping SHG light source (wavelength 0.83 to 0.83 μm).
86 μm) and is used as a material for the magneto-optical element of the optical isolator.

[0002]

2. Description of the Related Art Among many methods for producing single crystals, a method called THM (Travelling Heating Method) uses a flux (solvent) to move a polycrystal while melting it in a band shape. This is a method for producing a single crystal by This method has characteristics that it can be applied to a complex component system and that a relatively long single crystal can be produced with little variation in composition. The crucible is filled with the blended raw materials, vacuum sealed, heated and melted, and then rapidly cooled to prepare a polycrystalline body, and then Cd _1-y Hg _y Te single crystal is prepared by the THM method using Te as a flux. It is known that can be made.

(Cd _1-xy Mn _x Hg _y ) Te, (Cd used as a material for a magneto-optical element such as an optical isolator
_1-xyz Mn _x Hg _y Zn _z ) Te, and (Cd _1-xy M
This method can be basically applied to the production of a single crystal represented by n _x Hg _y ) (Se _u Te _1-u ). However, there is a problem that the crucible is easily damaged due to a rise in internal pressure due to the vapor pressure of Hg during high-temperature heating, especially when producing single crystals of these systems containing Hg. Is true. Nevertheless, the current situation is that this problem has not been fundamentally resolved.

Further, in the crystals obtained by this method,
One of the problems is that many Te phase particles are precipitated.
When these crystals are used as a magneto-optical element such as an optical isolator, Te particles deposited in the crystals cause light scattering, resulting in a remarkable decrease in transmittance.

[0005]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to solve the above-mentioned problems, to stably produce a single crystal, and to suppress the precipitation of Te and to have good optical performance. A method for manufacturing a single crystal is provided.

[0006]

According to the present invention, when Te is used as a flux to produce a polycrystal used in the process of producing a single crystal by the THM method, Cd, M
Using n, Zn, Se, Hg, Te, or HgTe as a raw material, the blending molar ratio of the raw materials is (Cd _{1-x- y} Mn _x
Hg _y ): Te = 1: 1.01 to 1.10, (Cd _1-xyz
Mn _x Hg _y Zn _z ): Te = 1: 1.01 to 1.10, and (Cd _1-xy Mn _x Hg _y ) :( Se _u Te _1-u ) =
A polycrystal body adjusted to have a ratio of 1: 1.01 to 1.10 was prepared, and a polycrystal having a chemical formula (Cd _1-xy Mn _x Hg _y ) Te, (Cd
d _1-xyz Mn _x Hg _y Zn _z ) Te, and (Cd _1-xy
Mn _x Hg _y ) (Se _u Te _1-u ) is a method for producing a single crystal.

Further, according to the present invention, the crucible containing the polycrystal obtained by the above method and Te is sealed in a vacuum, and the entire filling space in the crucible is always kept at a temperature equal to or higher than the melting point of Te, and in the vertical direction. Temperature gradient in the range of 5 to 50 ° C
According to the M method, the chemical formula (Cd _1-xy Mn _x Hg _y ) Te,
(Cd _1-xyz Mn _x Hg _y Zn _z ) Te, and (Cd _1
-xy Mn _x Hg _y ) (Se _u Te _1-u ).

According to the present invention, in addition to the above, at least at the start of the above-mentioned single crystal manufacturing process, a melt of Te at the bottom of the filling space in the crucible and a polycrystalline body located above the melt. Is a method for producing a single crystal by providing a space of a predetermined size between

As described above, according to the present invention, the chemical formula (Cd _1-xy) is obtained by using Te as a flux under a predetermined temperature gradient and moving the polycrystal while melting it in a band _shape.
Mn _x Hg _y ) Te, (Cd _1-xyz Mn _x Hg _y Zn _z ) T
e, and (Cd _1-xy Mn _x Hg _y ) (Se _u Te
_1-u ), (where x, y, z and u are all values of 0 to 1), Cd, Mn, Z
n, Se, Hg, Te, or HgTe is used as a raw material, and the mixing molar ratio of the raw materials is (Cd _{1 -xy} Mn _x Hg
_y ): Te = 1: 1.01 to 1.10, (Cd _1-xyz Mn
_x Hg _y Zn _z ): Te = 1: 1.01 to 1.10, and (Cd _1-xy Mn _x Hg _y ) :( Se _u Te _1-u ) = 1:
A method for producing a single crystal, comprising the step of producing a polycrystal having a composition in the range of 1.01 to 1.10, wherein the polycrystal is produced in the method for producing a single crystal described above. A method for producing a single crystal, characterized in that the entire inner space of the crucible to be housed is maintained at a temperature equal to or higher than the melting point of Te, in the method for producing a single crystal described above, the upper and lower portions in the vicinity of a place where the crystal is grown. Direction temperature gradient is 5-5
The method for producing a single crystal is characterized in that the temperature is 0 ° C./cm, and in the method for producing a single crystal described above, Te existing at the bottom of the filling space in the crucible is at least at the start of the single crystal production process. A liquid surface of the melt of, and a method for producing a single crystal, characterized in that a space is provided between the polycrystalline body located on the melt, in the method for producing a single crystal described above, In the method for producing a single crystal, the height range of the space between the liquid surface of the Te melt and the polycrystal is between the inner diameter of the crucible and a quarter of the inner diameter. .

[0010]

The three types of materials targeted by the present invention, (Cd
_1-xy Mn _x Hg _y ) Te, (Cd _1-xyz Mn _x Hg _y Zn
_z ) Te, and (Cd _1-xy Mn _x Hg _y ) (Se _u Te
Each of the melting points of _{1- u} ) exceeds 1,000 ° C. TH
In the process of producing a single crystal by the M method, in order to produce a polycrystal of these systems, a quartz crucible is simply filled with a raw material blended with a target composition, vacuum-sealed, and then melted. When heated to a temperature of 1,050 ° C, there are many problems in which the crucible is damaged. As a result of pursuing this cause, it was found that the crucible was damaged due to vapor pressure of a part of the raw materials charged in the crucible which remained unreacted. Based on this result, the present inventor reacted with Hg by excessively blending Te as a raw material, and reacted with unreacted Hg.
It was devised to avoid the rise in internal pressure due to the vapor pressure by eliminating the existence of the above.

On the other hand, the melting point of the Cd _x Hg _1-x Te system of the crystal, which has been reported to be more numerous than before, is about 800.
C., and crucible failure was less of a problem in this system. The reason is that the melting of this material is about 850 ° C.
Since it is carried out at the temperature of, the H that is slightly unreacted at that time
It is considered that even if g was present, it was far from the melting temperature (about 1,050 ° C.) of the system targeted by the present invention, and therefore the vapor pressure did not rise so high that the crucible was broken. .

Next, reference will be made to Te particles in a single crystal. In the case of producing a single crystal by the general THM method, the flux is concentrated in a narrow region under a steep temperature gradient. However, application of a commonly used THM method device to the subject material of the present invention resulted in the presence of a large number of Te particles in the crystal.

It is inferred that the cause thereof is a result of emphasizing a steep temperature gradient in a narrow area. Therefore, according to the present invention, in the process of producing a single crystal, the entire inner space of the quartz crucible is always set to the melting point of Te (450 ° C.) or higher, and the THM method is applied on the inner space of the quartz crucible. Is to be manufactured. This mechanism is not clear, but if we infer this, would it be as follows.

In the process of producing a single crystal, by keeping the inside of the quartz crucible at a temperature of 450 ° C. or higher, which is the melting point of Te, Te does not precipitate on the inner wall of the crucible and always functions as an effective flux. Furthermore, it is considered that the diffusion rate of Te in the solid is high, and that Te can easily move under a temperature gradient to effectively function.

Further, at the time of crystal formation, an appropriate space is provided between the lowermost portion of the polycrystal and the liquid surface of the melt of Te, which is the flux, and heating is started to produce a single crystal. It was also found as a result of the experiment that it is effective in reducing Te particles in the inside.

In this case, the T located at the bottom of the quartz crucible
The e melts, a part of it evaporates, and it condenses on the bottom of the polycrystal, and this becomes a flux to melt a part of the polycrystal. After that, by descending the quartz crucible, the melted portion forms a band shape and sequentially moves to the upper part of the polycrystalline body, and after passing through this, a single crystal is formed. That is, under a certain condition, the amount of Te required for melting the polycrystalline body to form the band shape can be reproducibly incorporated by this method.

The contents of the present invention will be further described below with reference to examples.

[0018]

Example 1 Using Cd, Mn, Hg, and Te as raw materials, the composition was (Cd _0.66 Mn _0.17 Hg _0.17 ) Te _1.05.
The total amount of about 60 g is weighed so as to obtain a quartz crucible having an inner diameter of the filling space of 20 mm and a length of about 100 mm, and vacuum-sealed. This is heated in a pressure furnace at about 18 atm and 1,100 ° C. to melt the raw material filled in the crucible, hold it for 5 hours, and then turn off the heating power source to quench it. By adopting this method, there is no unreacted residue other than at least Te in the filled raw material, and therefore there is no trouble that the quartz crucible is damaged due to an excessive internal pressure due to the vapor pressure. Can take out a uniform polycrystalline ingot. The thus obtained polycrystal is used as a starting material for the subsequent single crystal production process.

This polycrystal and about 20 g of Te are filled in a quartz crucible having an inner size of 20 mm and a length of about 100 mm, which is vacuum-enclosed and subjected to a single crystal production process.

The single crystal is produced by arranging a quartz crucible vertically and heating it under atmospheric pressure. FIG. 1 is a diagram schematically showing the single crystal growth apparatus used in this example. The quartz crucible 1 is always at a temperature higher than 450 ° C., which is the melting point of Te, and locally has a maximum temperature of about 860 ° C. and 800 ° C.
In the vicinity of ° C, a single crystal is produced by the electric furnaces 2 and 3 that form a temperature profile having a temperature gradient of about 25 ° C / cm and the crucible moving mechanism 5.

If the electric furnaces 2 and 3 having a relatively flat temperature profile and the electric furnace 4 having a relatively steep temperature profile for local heating are combined,
Such a temperature profile can be obtained.

At the time of starting the production of the single crystal, the position of the quartz crucible is adjusted in the above temperature profile so that the lowest temperature of the quartz crucible 1 containing the melt of Te, which is the flux, becomes the highest. The lowermost part of the polycrystalline body is partially dissolved by Te. After that, by continuously descending the quartz crucible at a speed of 8 mm / day, the melted portion forms a band shape and sequentially moves to the upper portion of the polycrystalline body, and a single crystal is formed after passing through the polycrystalline body. FIG. 2A schematically shows a state in which the single crystal 13 is being produced in the quartz crucible 1. After the quartz crucible has moved a sufficient distance, the temperature is lowered to room temperature and the single crystal is collected.

Te of the flux remains at the upper end of the single crystal. Except for this portion, the single crystal has a uniform composition over almost the entire area, and almost no Te particles are found inside the single crystal. The one that can sufficiently withstand the use as an element was obtained.

[0024]

Example 2 Using Cd, Mn, Zn, Hg and Te as raw materials, the composition was (Cd _0.64 Mn _0.16 Hg _0.15 Zn
_A total amount of about 60 g was weighed so as to be _0.05 ) Te _1.05, and a polycrystal was prepared by the same method as described in Example 1.

This polycrystal and about 20 g of Te are filled in a quartz crucible having an inner size of 20 mm and a length of about 100 mm, which is vacuum-enclosed to be used in a single crystal production process.

The single crystal is produced by arranging the quartz crucible vertically and heating it under atmospheric pressure. FIG. 1 is a diagram schematically showing the single crystal growth apparatus used in this example. The quartz crucible 1 is always at a temperature higher than the melting point of Te, 450 ° C., and locally has a maximum temperature of about 850 ° C. and 800 ° C.
In the vicinity of ° C, a single crystal is produced by the electric furnaces 2 and 3 that form a temperature profile having a temperature gradient of about 30 ° C / cm and the crucible moving mechanism 5.

If the electric furnaces 2 and 3 having a relatively flat temperature profile and the electric furnace 4 having a relatively steep temperature profile for local heating are combined,
Such a temperature profile can be obtained.

At the start of single crystal production, the position of the quartz crucible is adjusted in the temperature profile so that the lowest temperature of the quartz crucible 1 containing the melt of Te, which is the flux, becomes the highest. The lowermost part of the polycrystalline body is partially dissolved by Te. After that, by continuously descending the quartz crucible at a speed of 7 mm / day, the melted portion forms a band shape, sequentially moves to the upper portion of the polycrystalline body, and a single crystal is formed after passing through the polycrystalline body. FIG. 2A schematically shows a state in which the single crystal 13 is being produced in the quartz crucible 1. After the quartz crucible has moved a sufficient distance, the temperature is lowered to room temperature and the single crystal is collected.

Te of the flux remains at the upper end of the single crystal. Except for this portion, the single crystal has a uniform composition over almost the entire area, and Te particles are almost absent inside the single crystal. The one that can sufficiently withstand the use as an element was obtained.

[0030]

Example 3 Using Cd, Mn, Hg, Te, and Se as raw materials, the composition was (Cd _0.66 Mn _0.17 Hg _0.17 ).
(Se _0.05 Te _0.95 ) _1.06 in total so that it becomes _1.05
0 gram is weighed, and a polycrystal is produced by the same method as described in Example 1.

As shown in FIG. 2B, the inner size is 20 mm in diameter and about 100 mm in length, and about 20 m from the lower end.
A quartz crucible 1 having a collar 11 of 1 to 2 mm preliminarily provided on the inner wall of m for the entire circumference is used for producing a single crystal. About 50 grams of Te12 was added to the bottom of the quartz crucible 1, and
Fill 5 sequentially. Due to the presence of the brim, the polycrystalline body 15 has a space formed between it and the Te 12, which do not directly contact with each other (when Te is melted to form a melt,
A space of about 10 mm will be formed between the liquid surface and the bottom of the polycrystalline body). Then, the quartz crucible is vacuum-sealed and subjected to a single crystal production process.

A single crystal is produced by placing a quartz crucible vertically and heating it under atmospheric pressure. FIG. 1 is a diagram schematically showing a situation of producing a single crystal. The quartz crucible 1
Always at a temperature above 450 ° C, the melting point of Te,
A single crystal 13 is produced by an electric furnace that forms a temperature profile having a temperature gradient of about 35 ° C./cm and a crucible moving mechanism 5 at a location locally at a maximum of about 840 ° C. and near 800 ° C. .

If the electric furnaces 2 and 3 having a relatively flat temperature profile and the electric furnace 4 having a relatively steep temperature profile for local heating are combined,
Such a temperature profile can be obtained.

At the time of starting the production of the single crystal, the position of the quartz crucible 1 is adjusted in the above temperature profile so that the lowermost part of the quartz crucible 1 having the melt 12 of Te, which is the flux, has the highest temperature. To do.

After holding at this position for 5 hours, the quartz crucible 1 is continuously lowered at a speed of 7 mm / day to produce a single crystal 13. After the quartz crucible 1 has moved a sufficient distance, the temperature is lowered to room temperature to collect the single crystal.

Te of the flux remains at the upper end of the single crystal. Except for this portion, the single crystal has a uniform composition over almost the entire area, and no Te particles are found inside the single crystal. As a use as an optical element, a very excellent one was obtained.

In the above examples, Cd _1-xu Mn _x H
g _u, the molar ratio of Te with respect to _{Cd 1-xuz Mn x Hg u} Zn z _{or, (Se u Te 1-u} ) is 1: results 1.05, of an experiment conducted for various molar ratios, The range of the molar ratio of Te or (Se _u Te _1-u ) is 1: 1.01.
The region of ˜1.10 has been found to be suitable. 1.01
When it is smaller than this, unreacted Hg is generated, and when it is larger than 1.10, Hg segregation occurs.

The temperature gradient in the vertical direction during growth in the examples is 25 to 35 ° C./cm, but various experiments have shown that the range of 5 to 50 ° C./cm is appropriate. I understood. At a temperature gradient smaller than or larger than this range, Te precipitation was observed in the grown crystal. In Example 3, the height of the space between the liquid surface of the Te melt and the bottom of the polycrystalline body is, as a result of various experiments, equal to the inner diameter, or a range between 1/4 of the inner diameter is suitable. It was clear. If the height of the space is higher than the inner diameter, it becomes difficult to melt the polycrystalline body, and if it is lower than 1/4 of the inner diameter,
Precipitation of Te was observed in the crystal.

[0039]

As described above, according to the present invention, (Cd
_1-xy Mn _x Hg _y ) Te, (Cd _1-xyz Mn _x Hg _y Zn
_z ) Te, and (Cd _1-xy Mn _x Hg _y ) (Se _u Te
It has made it possible to produce a single crystal that suppresses the precipitation of Te particles, which has long been desired for a _1-u ) single crystal.

Therefore, these single crystals are used as a pumping light source for an optical amplifier (wavelength 0.98 to 1.02 μm) used in long-distance transmission of optical communication, and a semiconductor laser (LD).
As a magneto-optical element such as an optical isolator mounted on an excitation SHG light source (wavelength 0.83 to 0.86 μm), it becomes possible to supply a single crystal of sufficient quality in the future.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline and a temperature profile of a single crystal growth apparatus used in an example of the present invention. 1 (a) is a central cross-sectional view of the furnace body, and FIG. 1 (b) is a view showing a temperature distribution in the central part of the furnace.

FIG. 2 is a sectional view showing a quartz crucible used for carrying out the present invention. FIG. 2 (a) is a diagram showing a quartz crucible used in this example, which is filled by a conventional filling method, and FIG. 2 (b) is
The figure which shows the quartz crucible used by the present Example filled with the filling method of this invention.

[Explanation of symbols]

 1 quartz crucible 2 electric furnace 3 electric furnace 4 electric furnace (for local heating) 5 crucible lifting mechanism 6 crucible support 11 collar 12 Te melt 13 single crystal 14 melting zone 15 polycrystal

Claims (5)

[Claims] 1. A chemical formula of (Cd _1-xy Mn _x Hg _y ) T is obtained by using Te as a flux under a predetermined temperature gradient to move a polycrystalline body while melting it in a band shape.
e, (Cd _1-xyz Mn _x Hg _y Zn _z ) Te, and (C
d _1-xy Mn _x Hg _y ) (Se _u Te _1-u ), (where x, y, z and u are each a value of 0 to 1), Cd, Mn, Zn, Se, Hg, T
e or HgTe as a raw material, and the blending molar ratio of the raw materials is (Cd _1-xy Mn _x Hg _y ): Te = 1: 1.
_{01~1.10, (Cd 1-xyz Mn} x Hg y Zn z): T
e = 1: 1.01 to 1.10, and (Cd _1-xy Mn _x H
g _y ) :( Se _u Te _1-u ) = 1: 1.01 to 1.10, which is a method for producing a single crystal. 2. The method for producing a single crystal according to claim 1, wherein the entire inner space of the crucible for containing the polycrystalline body is maintained at a temperature equal to or higher than the melting point of Te. . 3. The method for producing a single crystal according to claim 2, wherein the temperature gradient in the vertical direction near the place where the crystal is grown is 5 to 50 ° C./cm. 4. The method for producing a single crystal according to claim 2, wherein at least at the start of the single crystal production process, the surface of the melt of Te existing at the bottom of the filling space in the crucible and the melt. A method for producing a single crystal, characterized in that a space is provided between the polycrystal located above. 5. The method for producing a single crystal according to claim 4, wherein the range of the height of the space between the liquid surface of the Te melt and the polycrystal is equivalent to the inner diameter of the crucible or 4 minutes of the inner diameter. 1. The method for producing a single crystal, characterized in that