JP2001233699A - Method for thermally treating group ii to vi compound semiconductor crystal substrate and the substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for thermally treating a low resistant ZnSe crystal and its mixed crystal substrate having a prescribed specific resistance value without deteriorating crystallinity, and to provide the ZnSe crystal and its mixed crystal substrate thermally treated by the method. SOLUTION: This method for thermally treating the ZnSe crystal and its mixed crystal substrate, characterized by forming one or more Al films and one or usore Zn films, or one or more Al-Zn alloy films on the surface of a substrate of ZnSe crystal or its mixed crystal represented by formula: Zn1-xAsSe, ZnBySe1-y [A is an element in the group II; B is an element in the group VI; 0<(x)<=0.2; 0<(y)<=0.2], placing the ZnSe crystal or its mixed crystal substrate and Zn in a closed vessel, and then thermally treating both the materials in a state that both the materials do no contact with each other, and the substrate obtained by the treating method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ZnS crystal doped with Al which is a donor impurity for ZnSe crystals.
The present invention relates to a heat treatment method for an e-crystal and a mixed crystal substrate thereof, and a substrate heat-treated by the method.

[0002]

2. Description of the Related Art Light-emitting elements such as lasers and LEDs having short wavelengths such as blue, green, and blue-green light are attracting attention. These light-emitting elements can be manufactured on a substrate such as GaAs. However, from the viewpoint of improving the element characteristics, it is preferable to manufacture the ZnSe-based crystal thin film on a ZnSe substrate of the same material by homoepitaxial growth.

Recently, a technique has been developed for producing a white LED in which the long-wavelength emission of the ZnSe substrate itself excited by the emission from the active layer on the substrate is mixed with the short-wavelength emission from the active layer. In this case, a ZnSe substrate is essential.

As described above, ZnS is used as a light emitting element substrate.
Although an e-single crystal substrate is used, a conductive low-resistance substrate is indispensable to simplify the element structure and improve the element characteristics. However, ordinary PVT (Physical Vapor)
A ZnSe bulk single crystal manufactured by a manufacturing method such as a Transport (Transport) method or a GG (Grain Growth) method is undoped and has high resistance.

Conventionally, as a method of reducing the resistance of a ZnSe single crystal, there has been proposed a method of heat-treating a ZnSe single crystal in a Zn—Al melt. (J. Phys. D: Appl. Phy
s.vol.9, 1976, p.799-810, G. Jones et al.) In this method, Al diffuses into the ZnSe crystal and acts as a donor impurity, and at the same time, the Zn vacancy concentration decreases. The activation rate of Al can be increased, and the desired resistivity can be obtained by increasing the n-type carrier concentration.

However, this heat treatment method cannot prevent the melt from adhering to the ZnSe single crystal at the time of cooling.
Due to the stress generated by the difference in thermal expansion coefficient between Se and the Zn-Al melt, the dislocation density of the ZnSe single crystal increases,
There is a problem that crystallinity is significantly deteriorated. In order to solve this problem, a method has been proposed in which an Al thin film is formed on the surface of a ZnSe single crystal and heat-treated in a sealed container in a Zn atmosphere (Japanese Patent No. 2839027). By this method, remarkable deterioration in crystallinity was suppressed, and an increase in the dislocation density could be substantially suppressed for a substrate having a dislocation density of 5 × 10 ⁴ cm ⁻² or more before heat treatment.

However, when heat treatment is performed on a substrate having a low dislocation density and good crystallinity under the same conditions, the problem remains that the dislocation density increases as the Al film thickness increases. That is, it has been clarified that the increase in the dislocation density cannot be completely suppressed at a level of 5 × 10 ⁴ cm ⁻² or less when the Al film thickness is 400 ° or more by this method. But,
The carrier density of the ZnSe substrate after the heat treatment is A
When the Al film thickness is less than 400 °, only a substrate having a carrier density of 6 × 10 ¹⁷ cm ⁻³ or less can be manufactured.

[0008]

Therefore, in the present invention,
Solving the above problems, a method of heat-treating a low-resistance ZnSe crystal having a predetermined specific resistance value without deteriorating crystallinity and a mixed crystal substrate thereof, and ZnSe heat-treated by the method
It is intended to provide a crystal and a mixed crystal substrate thereof.

[0009]

The present invention has succeeded in solving the above-mentioned problems by adopting the following constitution. (1) ZnSe crystal or Zn _1-x A _x Se, ZnB _y Se
_1-y (A is a group II element, B is a group VI element, 0 <x ≦ 0.
(2, 0 <y ≦ 0.2)
After forming at least one film and at least one Zn film, the ZnSe crystal or a mixed crystal thereof and Zn are placed in a closed container, and heat treatment is performed while keeping both in a non-contact state.
Heat treatment method for nSe crystal and its mixed crystal substrate.

(2) ZnSe crystal or Zn _1-x A _x Se,
ZnB _y Se _1-y (A is a group II element, B is a group VI element,
0 <x ≦ 0.2, 0 <y ≦ 0.2), after forming an Al—Zn alloy film on the surface of the mixed crystal substrate, the ZnSe crystal or the mixed crystal thereof and Zn And heat-treating the ZnSe crystal and the mixed crystal substrate thereof in a state where they are not in contact with each other.

(3) The total weight of the Al film and the Zn film or the ratio of the weight of Zn to the weight of the Al—Zn alloy film is 10%.
(1) or the above-mentioned (1), wherein
(2) The heat treatment method for the ZnSe crystal and the mixed crystal substrate described in (2). (4) the total thickness of the Al film and the Zn film or the Al-Zn
The Zn according to any one of the above (1) to (3), wherein the thickness of the alloy film is in the range of 50 to 5000 °.
Heat treatment method for Se crystal and its mixed crystal substrate.

(5) The heat treatment temperature in the heat treatment is 66
The temperature is set in the range of 0 to 1200 ° C.
The heat treatment method for a ZnSe crystal and a mixed crystal substrate thereof according to any one of (1) to (4). (6) The heat treatment method for a ZnSe crystal and a mixed crystal substrate thereof according to any one of (1) to (5), wherein a heat treatment time in the heat treatment is set in a range of 1 to 800 hours.

(7) The cooling rate after the heat treatment is 1 to 200
(1)-characterized in that the temperature is set in the range of ° C / min.
(6) The heat treatment method for a ZnSe crystal and a mixed crystal substrate thereof according to any one of (6). (8) In the cooling process after the heat treatment, the temperature of the portion where the ZnSe crystal or the mixed crystal exists is 1 to 100 higher
The Zn according to any one of the above (1) to (7), wherein a portion having a temperature lower by 0 ° C. is provided in the closed container.
Heat treatment method for Se crystal and its mixed crystal substrate. (9) The (1) to (8), wherein the Al film and the Zn film, or the Al-Zn alloy film are formed by a vacuum evaporation method.
4. The heat treatment method for a ZnSe crystal and a mixed crystal substrate thereof according to any one of the above.

(10) Two substrates made of the ZnSe crystal or a mixed crystal thereof are prepared, and the Al film and the Zn film or the Al—Zn alloy film is formed on at least one of them.
The heat treatment is performed after the two substrates are brought into close contact with each other so as to sandwich the Al film and the Zn film or the Al-Zn alloy film, and then the heat treatment is performed. A heat treatment method for a ZnSe crystal and a mixed crystal substrate thereof according to any one of the above. (11) The Zn according to any one of the above (1) to (10), wherein the surface to be opposed is polished flat in advance.
Heat treatment method for Se crystal and its mixed crystal substrate. (12) A ZnSe crystal or a mixed crystal substrate thereof, which is heat-treated by the heat treatment method according to any one of (1) to (11).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, "heat treatment"
Unless otherwise specified, it refers to the entire process including all the series of steps of heating, maintaining high temperature, and cooling. The high-temperature holding includes not only the case where the temperature is changed to a certain temperature, but also the case where the temperature is changed in the middle and the temperature is sequentially held at a plurality of temperatures, and the case where the temperature is continuously changed with time.

In the process of forming an Al thin film on a ZnSe substrate and raising the temperature, since the melting point of Al is 660 ° C., solid Al is in close contact with solid ZnSe at a temperature lower than the melting point. The linear expansion coefficients of both are 7.5 × 10 ⁻⁶ / deg for ZnSe and 2.3 × 10 ⁻⁵ / de for Al.
greatly different from g. Therefore, if the Al film thickness is increased in order to increase the Al diffusion amount, ZnSe and A
1 due to the difference in thermal expansion coefficient of ZnSe
The crystallinity of the substrate deteriorates. It has been difficult to increase the Al diffusion amount without deteriorating the crystallinity and further reduce the resistivity.

FIG. 4 shows a binary phase diagram of Al—Zn (Consti
tution of Binary Alloys, M. Hansen, McGraw-Hill, 19
58). Al and Zn form a eutectic, and the eutectic point is 382 ° C. In the present invention, the melting temperature of a thin film on ZnSe can be reduced by forming an Al-Zn binary compound instead of forming an Al film alone on a ZnSe substrate. It has become possible to suppress the stress due to the difference in the coefficient of thermal expansion with the thin film formed thereon.

As a method of forming an Al-Zn binary compound, a method of forming an Al / Zn multilayer film as shown in FIG. 1, a method of forming an Al-Zn alloy film as shown in FIG. Can be adopted. In the case of the Al—Zn alloy film, the alloy film starts melting when the temperature reaches the solidus line of the alloy composition in the phase diagram of FIG. In the case of an Al / Zn multilayer film, the multilayer films react with each other and start melting near the solidus temperature in the Al-Zn alloy composition corresponding to the weight ratio of the Al film and the Zn film.
Therefore, in either case, the melting temperature of the thin film can be reduced as compared with the case of using the Al film alone, and the stress caused by the difference in the coefficient of thermal expansion between ZnSe and the thin film can be suppressed. Since the critical shear stress of ZnSe decreases sharply as the temperature rises, it is extremely effective in suppressing the deterioration of ZnSe crystallinity.

As apparent from FIG. 4, the upper limit of the eutectic composition of Zn in the Al—Zn binary compound is 95% by weight.
It is. Effectively lower the melting temperature and convert Al to ZnS
In order to diffuse into e, the proportion of Zn needs to be 95% by weight or less. On the other hand, when the Zn content is less than 10% by weight, the melting temperature decreases only by 30 ° C. from the Al melting point, and the effect of lowering the melting point is small. Therefore, Zn
Is desirably 10% by weight or more. Here, the weight percent of Zn refers to the total weight of the Al film and the Zn film or the ratio of the weight of Zn to the weight of the Al—Zn alloy film.
Since the specific gravity of Al is about 2.7 and the specific gravity of Zn is about 7.14, when Zn weight% suitable for the present invention is represented by Zn volume%, it is in the range of 4-88 volume%.

The total thickness of the Al film and the Zn film or Al-Zn
The alloy film thickness is desirably in the range of 50 to 5000 °. If the film thickness is less than 50 °, the diffusion amount of Al into ZnSe is low, and the resistance of the ZnSe crystal cannot be sufficiently reduced. On the other hand, if the film thickness exceeds 5000 °, Al or Al—Zn alloy that could not be diffused remains on the ZnSe substrate surface, exerts stress on the ZnSe crystal during cooling, and causes deterioration of crystallinity. The total thickness of the Al film and the Zn film or the more preferable range of the Al-Zn alloy film thickness is 100 to 10
00 °.

The heat treatment temperature of the present invention is 660 to 1200 ° C.
Is desirable. If the temperature is lower than 660 ° C., Al cannot be effectively diffused into the ZnSe crystal because Al exists as a solid. If the temperature exceeds 1200 ° C., the crystallinity of ZnSe deteriorates. Note that a more preferable range of the heat treatment temperature is 800 to 1100 ° C.

The heat treatment time of the present invention is preferably in the range of 1 to 800 hours. If the time is less than 1 hour, Al cannot be completely diffused into ZnSe, remains on the ZnSe surface, exerts stress on the ZnSe crystal at the time of cooling, and deteriorates crystallinity. On the other hand, if the heat treatment time exceeds 800 hours, Al diffuses completely into ZnSe, and conversely, outward diffusion in which the ZnSe surface volatilizes and diffuses into the gas phase becomes remarkable.
There is a problem that the Al concentration in e decreases with time. The more preferable range of the heat treatment time is 10 to 400.
Time.

The cooling rate after the heat treatment is preferably in the range of 1 to 200 ° C./min. Rapid cooling at over 200 ° C / min results in Zn
The temperature distribution inside the Se crystal increases, and the crystallinity deteriorates during the cooling process. In addition, if the cooling rate is less than 1 ° C./min, the time required to pass through the low temperature region becomes longer, so that the peeling of ZnSe approaches the thermal parallel state at a low temperature, the activation rate of Al decreases, and the carrier density decreases. , The resistivity increases. A more preferable range of the cooling rate after the heat treatment is 10 to 1
00 ° C./min.

Usually, the heat treatment is performed in a quartz airtight container, but since quartz reacts with Al, A diffuses into the crystal.
The controllability of the amount 1 decreases. If Al is set in the container in advance, during the heat treatment, the inside of the container can be maintained at the Al equilibrium vapor pressure, the Al film can be prevented from decreasing due to the reaction with quartz, and the diffusion amount of Al into the crystal can be controlled. Performance can be improved.

At the time of cooling, ZnSe crystal and Zn, Al or Z
When it comes into contact with the n-Al alloy, the difference in thermal expansion coefficient
Greatly deteriorates crystallinity. Zn in the reaction vessel during cooling
If the temperature other than the position where the Se crystal substrate is set is adjusted to be the lowest temperature, Zn, Al, and Zn-Al alloy are transported to the lowest temperature part and solidified.
Contact with a crystal substrate can be prevented, and deterioration of crystallinity can be prevented. It is desirable that the temperature difference between the lowest temperature part and the part where the ZnSe crystal substrate exists is in the range of 1 to 100 ° C. If the temperature difference is less than 1 ° C., there is no effect of setting the lowest temperature part, and if the temperature difference exceeds 100 ° C., ZnSe
The crystal itself is transported to the lowest temperature, and deterioration of crystallinity cannot be ignored. During the high-temperature holding, there may be some temperature distribution within a range where the transport of the ZnSe crystal itself does not become significant even when the inside of the reaction vessel is completely soaked. The lowest temperature part and Zn
The preferred range of the temperature difference in the existing portion of the Se crystal substrate is 5 to 5.
20 ° C.

When heat treatment is performed only by forming an Al / Zn multilayer film or an Al—Zn alloy film on the ZnSe crystal surface, Al and Zn are dissipated during the heat treatment, and Al
There is a problem that the diffusion amount of Al decreases and the controllability of the Al concentration decreases. It is effective to improve the controllability of the amount of Al diffusion by adhering some anti-dissipation material on the formed thin film. However, if another material is used, stress may be newly generated due to a difference in thermal expansion coefficient. There is.

Therefore, it is necessary to form the ZnSe film on the Al / Zn multilayer film or the Al—Zn alloy film, or to adhere another ZnSe crystal substrate to the Al / Zn multilayer film or the Al—Zn alloy film to dissipate Al. This is effective for achieving both prevention and deterioration of crystallinity. In particular, when a ZnSe crystal substrate is used, Al can be diffused into the ZnSe crystal substrates on both sides of the thin film, which is effective from the viewpoint of productivity. At this time, the Al / Zn multilayer film or the Al—Zn alloy film
It may be formed only on the surface of the nSe crystal substrate, or may be formed on both sides.
It may be formed on the surface of the nSe crystal substrate, and arranged so that both films are in close contact with each other. Also, an Al / Zn multilayer film or Al
It is also possible to perform heat treatment by stacking ZnSe crystals on which a Zn alloy film is formed in multiple stages.

As described above, the Al / Zn multilayer film or Al
-When heat treatment is performed by sandwiching a Zn alloy film between ZnSe crystal substrates, it is important to make the surface of the ZnSe crystal substrate as flat and smooth as possible in order to suppress Al dissipation. If the surface warpage or roughness is large, the adhesion will decrease,
The effect of preventing the dissipation of Al is small, and the controllability of the amount of Al diffusion into the crystal is reduced. When the in-plane average value of the surface unevenness height difference is 5000 ° or less, the dissipation of Al can be sufficiently suppressed.

In the above description, ZnSe is used as a crystal.
Only II-VI mainly composed of ZnSe
In the mixed crystal of the group III compound semiconductor, the critical shear stress is low and the dislocation tends to increase.
The method of the present invention can be applied. Such II-V
As mixed crystals of Group I compound semiconductors, Zn _1-x Cd _x Se,
ZnS _y Se _1-y , ZnSe _1-y Te _{y and the} like can be mentioned. At this time, x and y are respectively 0 <x ≦ 0.2,
It must be in the range of 0 <y ≦ 0.2. If x and y are larger than 0.2, the difference in physical properties from simple ZnSe increases, and the method of the present invention cannot be applied.

[0030]

EXAMPLES (Comparative Example 1) A 10 mm square, 1 mm thick (1
A heat treatment was performed on two ZnSe single crystal wafers having the (00) plane. The specific resistance of the ZnSe single crystal before the heat treatment was a high resistance of 10 ⁵ Ωcm or more, which is the upper limit of the measurable range of the hole measurement. Also, the surface of the wafer is mirror-polished, and Br
-The dislocation density of the crystal measured by etching with methanol was 5 × 10 ³ to 2 × 10 ⁴ cm ⁻² . On this etched surface, 800 mm thick Al
A film was formed. The in-plane average value of the unevenness height difference of the surface before vapor deposition was 8000 °. As shown in FIG. 3, the Al films of the two wafers are arranged facing each other so as to be in close contact with each other.
It was set in a quartz ampoule together with 0.1 g of Zn, evacuated to a vacuum of 2 × 10 ⁻⁸ Torr, and sealed.

The ampoule was set in a vertical tube furnace, the wafer was heated to a uniform temperature of 1000 ° C., and the lower end of the ampoule was heated to 98 ° C.
After heating to 0 ° C and heat-treating for 7 days, 10 ° C
/ Min at room temperature. After cooling, Zn had settled on the lower end of the ampoule. Two ZnS sheets facing each other
The e-wafers could be easily separated without being integrated with each other. The Al deposited on the wafer surface cannot be visually observed on the surface, but seems to have diffused into the crystal or dissipated outside. The surface of the heat-treated wafer on the side where the Al film was deposited was polished again by 50 μm and evaluated. Although the specific resistance was reduced to 0.04 Ωcm,
The increase in dislocation density is about 2 × 10 at the local maximum in the wafer plane.
^{It was 4} cm ^-2 , confirming that the heat treatment increased the dislocation density of the crystal.

Example 1 A heat treatment was performed in the same process as in Comparative Example 1 except for the thin film forming process. The thin film is formed by a vacuum evaporation method, and as shown in FIG.
Four layers were alternately stacked at 0 °, and the total film thickness was 1600 °. Assuming that both the Al film and the Zn film are sufficiently dense, the Zn weight ratio at this time is about 73% by weight. Al and Zn vapor-deposited on the wafer surface in the same manner as in Comparative Example 1 cannot be visually observed on the surface, and are presumed to have diffused into the crystal or diffused outside. The surface of the heat-treated wafer on the side where the Al / Zn multilayer film was deposited was polished again by 50 μm and evaluated. Specific resistance is 0.04Ωc
m, and the increase in dislocation density is as low as about 2 × 10 ³ cm ^-2 at the local maximum in the wafer surface, and this value is confirmed to not increase within the measurement error range. Was.

Example 2 A heat treatment was performed in the same process as in Example 1 except for the process of forming a thin film. The thin film is formed by a vacuum evaporation method, and as shown in FIG.
A thin film having a film thickness of 2000 ° made of the Al—Zn alloy was formed. Al-Z deposited on the wafer surface in the same manner as in Example 1.
The n-alloy cannot be visually observed on the surface and seems to have diffused inside the crystal or dissipated outside.
The surface of the heat-treated wafer on which the Al—Zn alloy film was deposited was polished again by 50 μm and evaluated. The specific resistance is as low as 0.04 Ωcm, and the increase in dislocation density is as low as about 1.5 × 10 ³ cm ^-2 at the local maximum value within the wafer surface, and this value is within the measurement error range. It was confirmed that there was no increase.

Comparative Example 2 A heat treatment was performed in the same process as in Example 1 except for the process of forming a thin film. The thin film is formed by a vacuum evaporation method, and Al and Zn are alternately formed by
The layers were stacked and the total film thickness was 6000 °. Assuming that both the Al film and the Zn film are sufficiently dense,
The weight ratio amounts to about 73% by weight. A thin film residue was observed on the wafer surface after the heat treatment. A of heat-treated wafer
The surface on which the 1 / Zn multilayer film was deposited was polished again by 50 μm and evaluated. Although the specific resistance was as low as 0.02 Ωcm, the increase in dislocation density was as high as about 1.2 × 10 ⁴ cm ^-2 at the local maximum in the wafer surface, and the heat treatment increased the dislocation density of the crystal. It was confirmed that.

(Embodiment 3) The ZnSe crystal wafer in which the resistance was reduced by diffusing Al in Embodiments 1 and 2 had a rough surface due to damage during heat treatment.
It was unsuitable as a substrate for forming a thin film. Then, the same heat treatment as in Example 1 was performed on two 10 mm square, 1 mm thick, (100) plane ZnSe single crystal wafers having almost the same characteristics as those used in Example 1, and then Al Is polished on the surface on which
It was removed to a thickness of μm, and the surface was finished by mirror polishing.
Next, the wafer was etched with a dichromic acid solution to remove the wafer surface layer by a thickness of 3 μm. The obtained wafer was set in an MBE (Molecular Beam Epitaxy) apparatus, and a ZnSe thin film having a thickness of 1.5 μm was grown.

The grown ZnSe thin film had good surface morphology. The dislocation density of the epitaxial film was measured by etching with a Br-methanol solution. Although the number of dislocations newly increased by about 3 × 10 ³ cm ⁻² during epitaxial growth, the total dislocation density including the dislocations inherited from the ZnSe substrate was 8 × 10 ^{3 to} 2.2 × 10 ⁴ c
Good crystallinity of m ^-2 was maintained. Further, the back surface of the epitaxially grown substrate is polished, and the substrate thickness is reduced to 25.
The thickness was reduced to 0 μm. Carrier density on the back of wafer is C-
When evaluated by V measurement, it was confirmed that the carrier density was about 1 × 10 ¹⁸ cm ^−3, which was high enough to form an n-electrode.

[0037]

According to the present invention, by adopting the above structure, in the heat treatment method for diffusing Al into the ZnSe substrate, the stress in the temperature increasing process can be reduced.
It has become possible to obtain a conductive ZnSe crystal having excellent crystallinity and a mixed crystal substrate thereof.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an ampule structure used in Example 1.

FIG. 2 is a schematic cross-sectional view of an ampule structure used in Example 2.

FIG. 3 is a schematic cross-sectional view of the ampule structure used in Comparative Example 1.

FIG. 4 shows a binary system diagram of Al—Zn (Constitution of
Binary Alloys, M. Hansen, McGraw-Hill, 1958).

Claims (12)

[Claims] 1. ZnSe crystal or Zn _1-x A _x Se, Z
nB _y Se _1-y (A is a group II element, B is a group VI element, 0
<X ≦ 0.2, 0 <y ≦ 0.2) After forming at least one Al film and at least one Zn film on the surface of the mixed crystal substrate, the ZnSe crystal or the mixed crystal thereof is placed in a closed container. And a ZnSe crystal and a mixed crystal substrate thereof. 2. ZnSe crystal or Zn _1-x A _x Se, Z
nB _y Se _1-y (A is a group II element, B is a group VI element, 0
(X ≦ 0.2, 0 <y ≦ 0.2), after forming an Al—Zn alloy film on the surface of the mixed crystal substrate, the ZnSe crystal or the mixed crystal thereof and Zn are placed in a closed container. And heat-treating them while keeping them in contact with each other.
Heat treatment method for nSe crystal and its mixed crystal substrate. 3. The weight ratio of Zn to the total weight of the Al film and the Zn film or the weight of the Al—Zn alloy film is 10 to 10.
The heat treatment method for a ZnSe crystal and a mixed crystal substrate thereof according to claim 1 or 2, wherein the heat treatment is in a range of 95%. 4. The method according to claim 1, wherein a total thickness of the Al film and the Zn film or a thickness of the Al—Zn alloy film is in a range of 50 to 5000 °. A heat treatment method for the ZnSe crystal and the mixed crystal substrate described in the above. 5. The heat treatment temperature in the heat treatment is 660.
The heat treatment method for a ZnSe crystal and a mixed crystal substrate thereof according to any one of claims 1 to 4, wherein the temperature is set in a range of from 1 to 1200 ° C. 6. The heat treatment time in said heat treatment is 1 to 8
The time is set within a range of 00 hours.
6. The heat treatment method for a ZnSe crystal and a mixed crystal substrate thereof according to any one of the above items 5. 7. The cooling rate after the heat treatment is 1 to 200 ° C.
The method for heat treating a ZnSe crystal and a mixed crystal substrate thereof according to any one of claims 1 to 6, wherein the heat treatment is performed in a range of / min. 8. In the cooling step after the heat treatment, a portion having a temperature lower by 1 to 100 ° C. than a temperature of a portion where the ZnSe crystal or the mixed crystal substrate exists is provided in the closed container. A heat treatment method for the ZnSe crystal and the mixed crystal substrate thereof according to claim 1. 9. The Al film and the Zn film, or the Al-Z
The heat treatment method for a ZnSe crystal and a mixed crystal substrate thereof according to any one of claims 1 to 8, wherein the n-alloy film is formed by a vacuum deposition method. 10. The ZnSe crystal or a mixed crystal substrate thereof is prepared in two sheets, and the Al film and the Zn film or the Al—Zn alloy film are formed on at least one of them.
The heat treatment is performed after the two substrates are brought into close contact with each other so as to sandwich a film, a Zn film or an Al-Zn alloy film, and the heat treatment is performed. Heat treatment method for ZnSe crystal and mixed crystal substrate thereof. 11. The heat treatment method for a ZnSe crystal and a mixed crystal substrate thereof according to claim 1, wherein the surface to be opposed is polished flat in advance. 12. A ZnSe heat-treated by the heat treatment method according to claim 1. Description:
Crystal or its mixed crystal substrate.