JPS6287499A - Heat treatment of single crystal cdte - Google Patents

Abstract

PURPOSE:To heat-treat a single crystal CdTe and readily control it at desired conduction type and resistivity, by containing the single crystal CdTe and a specific vapor-producing substance in communicating separate vessels and respectively heating the single crystal and substance at desired temperatures. CONSTITUTION:A quartz tube 7 is provided in an electric furnace 6 having two parts (6a) and (6b) capable of independently controlling heating temperatures and a heat-treating chamber 9 for containing a single crystal CdTe and a vapor- producing chamber 10 for containing at least one vapor-producing substance of Cd, Te and CdTe are provided in the quartz tube 7. The heat-treating chamber 9 and vapor-producing chamber 10 are communicated with a vapor feed pipe 11. The single crystal CdTe in the heat-treating chamber 9 and vapor- producing substance in the vapor-producing chamber 10 are respectively heated at given temperatures in an inert gas stream to heat-treat the single crystal CdTe and control the single crystal at desired conduction type and/or resistivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a single crystal CdTe0 heat treatment method in which single crystal CdTe is heat treated by an open tube method.

[Summary of the invention]

The present invention provides a single-crystal CdTe0 heat treatment method in which single-crystal CdTe is heat-treated by an open-tube method, in which the single-crystal CdTe and at least one substance selected from Cd, Te, and CdTe are connected to a first and heating the single crystal CdTe and the at least one substance contained in the first and second containers to a predetermined temperature in a reducing or inert gas flow; This makes it possible to easily control the conductivity type and/or resistivity to a desired value at the same time as heat treating the single crystal CdTe.

[Conventional technology]

Conventionally, the conductivity type and resistivity of single crystal CdTe have been controlled by the following so-called sealed tube method.

The first method, as described in JP-A-51-35086, is to put Cd and Te in an amount corresponding to the stoichiometric ratio in a quartz ampoule, and then add a predetermined amount of Cd in excess. After adding, a quartz plug is inserted into the ampoule so that the volume of the space inside the ampoule reaches a predetermined value, and the ampoule is vacuum sealed.
This quartz ampoule is then heated in a Bridgman furnace, and by controlling the amount of excess Cd added, the conductivity type and resistivity of the single crystal CdTe can be controlled simultaneously with the growth of the single crystal CdTe.

The second method uses single crystal CdT as shown in FIG.
A susceptor 2 carrying an e-substrate 1 and a reservoir 4 containing, for example, granular Cd3 are vacuum-sealed in a quartz ampoule 5, and this is inserted into an electric furnace 6.
This method heat-treats the single-crystal CdTe substrate 1 in a Cd vapor atmosphere by heating the substrate 1 and Cd3 to predetermined temperatures. By using Te or CdTe instead of Cd3 in the reservoir 4, that is, by changing the type of substance put into the reservoir 4, the conductivity type and resistivity of the single crystal CdTe substrate 1 can be controlled.

[Problem that the invention seeks to solve]

However, the first method described above is based on single crystal □CdTe
Although the conductivity type and resistivity can be determined during the manufacturing process, heat treatment must be performed separately to remove crystal defects such as vacancies and dislocations that exist in the crystal, and to eliminate compositional gradients. Therefore, it is not efficient. Furthermore, depending on the conditions during this heat treatment, there is a possibility that the characteristics may differ from those during growth of single crystal CdTe. In addition, although the second method described above can reduce the amount of Cd3 consumed compared to the open tube method, it is possible to reduce the amount of Cd3 consumed during heat treatment.
Since the constituent elements of the substrate 1, particularly Cd, are likely to evaporate, it is difficult to control the heat treatment atmosphere, and therefore it is difficult to control the conductivity type and resistivity. Not only the above-mentioned first and second
Both methods are unsuitable for industrial production because they require time and cost to vacuum seal the quartz ampoule.

An object of the present invention is to provide a novel compound semiconductor heat treatment method that corrects all of these drawbacks of the prior art.

[Means for solving problems]

The heat treatment method for single crystal CdTe according to the present invention is a method for heat treatment of single crystal CdTe.
Single crystal Cd made by heat treating dTe using open tube method
In the Te heat treatment method, the above single crystal CdTe and Cd
, Te and CdTe, the first and second containers are connected to each other (for example, the heat generation chamber 9 and the steam generation chamber 1 are connected by a steam supply pipe 11).
0) and heating the single crystal CdTe and the at least one substance contained in the first and second containers to predetermined temperatures in a reducing or inert gas flow, respectively. At the same time as the single crystal CdTe is heat treated, its conductivity type and/or resistivity are controlled.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

First, the structure of the heat treatment apparatus using the open tube method used in this example will be explained.

As shown in FIG. 1, in the heat treatment apparatus used in this embodiment, a quartz tube 7 is placed in an electric furnace 6 consisting of two parts 5a and 5b whose heating temperature can be controlled independently of each other.
is provided, and a heat treatment instrument 8 is provided within this quartz tube 7.

As shown in FIGS. 2A and 2B, this heat treatment apparatus 8 includes a heat treatment chamber 9 for accommodating and performing heat treatment on a single crystal CdTe substrate 1 to be heat treated, and a steam chamber for generating Cd vapor. For example, a cylindrical steam supply pipe 1 is connected to the generation chamber 10.
It has a structure that is connected by a construction. The outer circumferential surfaces of both ends of this steam supply pipe 11 are joined to the inner circumferential surfaces of circular openings 9b and 10b provided in mutually opposing side walls 9a and 10a of the heat treatment chamber 9 and steam generation chamber 10, respectively. The heat treatment chamber 9 and the steam generation chamber 10 are integrally connected. The heat treatment chamber 9, the steam generation chamber 10, the steam supply pipe 11, and the lids 12 and 13 described below are made of an airtight, heat-resistant material such as carbon, quartz, and boron nitride (BN).

The heat treatment chamber 9 has a rectangular parallelepiped shape, and a lid 12 is provided on one open side. A protruding portion 12 a that is slightly smaller in size than the planar size of the interior of the heat treatment chamber 9 is provided on one surface of the lid 12 . Then, by bringing the peripheral portion 12b of the above-mentioned surface of the lid 12 into contact with the upper end surface of the side wall 9a of the heat treatment chamber 9 with the protruding portion 12a protruding inside the heat treatment chamber 9, the heat treatment chamber 9 is almost completely sealed. I'm starting to get it. The degree of sealing is selected so that Cd vapor can escape from the heat treatment chamber 9 to the outside while the heat treatment chamber 9 is covered with the lid 12. Furthermore, within this heat treatment chamber 9, a susceptor 2 for holding the single crystal CdTe substrate 1 to be heat treated is provided.
is provided. Note that this susceptor 2 is capable of accommodating a plurality of single-crystal CdTe substrates 1 in alignment.

On the other hand, the steam generation chamber 10 has a smaller volume than the heat treatment chamber 9, and has a rectangular parallelepiped shape with a planar shape close to a square. A lid 1 is provided on one open side of the steam generation chamber 10.
3 is provided. A protrusion 13a that is the same as the cover 12 is provided on one surface of the lid 13, and when the protrusion 13a protrudes inside the steam generation chamber 10,
The peripheral portion 13b of the above surface of No. 3 is connected to the side wall 10 of the steam generation chamber 10.
By contacting the upper end surface of a, the steam generation chamber 10 can be almost completely sealed.

Note that it is preferable that the degree of sealing of the steam generation chamber IO by the lil, 3 is higher than the degree of sealing of the heat treatment chamber 9 by the lid 12. Furthermore, inside this steam generation chamber 10,
A glue reservoir 4 is provided for accommodating Cd.

On one open side of the reservoir 4, a circular steam supply port 14 with a small diameter of, for example, about 1 φ is provided in the center of the reservoir 4.
A lid 14 with a diameter a is provided, with which the reservoir 4 can be sealed almost completely.

Next, a method for heat-treating the single-crystal CdTe substrate 1 using the heat-treating apparatus and heat-treating equipment configured as described above will be described.

As shown in FIGS. 2A and 2B, first, a required number of single-crystal CdTe substrates 1 are placed on the susceptor 2 in the heat treatment device 8, and then the heat treatment chamber 9 is covered with the lid 12 and sealed. Similarly, after putting a sufficient amount of Cd3 into the reservoir 4, the steam generation chamber 10 is covered with a lid 13 and sealed.

Next, as shown in FIG. 1, the entire heat treatment instrument 8 is inserted into the quartz tube 7. Next, after reducing the pressure inside the quartz tube 7 to a predetermined pressure using a vacuum pump, while flowing a reducing or inert gas such as hydrogen, argon, or nitrogen into the quartz tube 7 in the direction shown by arrow A, The generation chamber 10 is heated to the heat treatment temperature of the single crystal CdTe substrate 1 and the generation temperature of Cd3, respectively.

The gas flowing into the quartz tube 7 described above is preferably hydrogen in which the oxygen concentration in the gas is as low as IQ-Is to 10-'' atmospheric pressure.

Due to this heating, Cd evaporates from Cd3 in the reservoir 4 at a rate according to the heating temperature, and as a result, Cd vapor is injected into the steam generation chamber 10 from the steam supply port 14a of the lid 14 of the reservoir 4. The inside of the steam generation chamber 10 is filled with Cd steam. This Cd vapor is supplied from the steam generation chamber 10 through the steam supply pipe 11 into the heat treatment chamber 9, and this heat treatment chamber 9 is also filled with Cd vapor. Therefore, single crystal CdT
The e-substrate 1 is heat-treated in a Cd vapor atmosphere.

Note that when the steam pressure inside the heat treatment chamber 9 rises to an extent that exceeds the external pressure, the Cd vapor exceeding the external pressure is released to the outside from the gap between the lid 12 and the heat treatment chamber 9. The maximum vapor pressure within the heat treatment chamber 9 is approximately equal to the pressure within the quartz tube 7.

After performing the heat treatment for a predetermined time in this manner, the entire heat treatment instrument 8 is taken out of the furnace to complete the intended heat treatment.

The heat treatment of the single crystal CdTe substrate 1 as described above was carried out by varying the heat treatment temperature and the temperature of the reservoir 4, and the conductivity type and resistivity of the single crystal CdTe substrate 1 after the heat treatment were measured. The results shown in FIG. 4 were obtained.

For heat treatment, hydrogen gas is introduced into the quartz tube 7 at a flow rate of 17! / minutes.

As shown in Figure 3, when the heat treatment temperature is 800°C, the conductivity type is p-type when the temperature of the reservoir 4 is in the range of 400 to 530°C, and as the temperature increases, the resistivity decreases from 100cm to The conductivity type increases to about 3 x 105 Ωcm, while the conductivity type is n within the range of 570 to 720°C.
type, and as the temperature increases, the resistivity decreases to 3 x 105
It can be seen that the resistance decreases from Ωcm to about 10 Ωcm.

Further, as shown in Fig. 4, when the heat treatment temperature is 700°C, the conductivity type is p-type when the temperature of the reservoir 4 is in the range of 400 to 430°C, and as the temperature increases, the resistivity decreases to 100 cm. The conductivity type increases from 480 to 730 degrees Celsius to 3
type, and as the temperature increases, the resistivity increases to 10'G
It can be seen that the resistance decreases from about 5Ωcm to about 5Ωcm. Furthermore, the third
In the figure and FIG. 4, in the temperature range of the reservoir 4 where the conductivity type is neither p-type nor n-type, an intrinsic, i.e., i-type wheel crystal CdTe substrate 1 was obtained. Single crystal CdT
Since the conductivity type and resistivity of the e-substrate 1 change depending on the heat treatment temperature and the temperature of the server 4 as shown in FIGS. It can be seen that it is possible to control the conductivity type and resistivity of the crystalline CdTe substrate 1. Therefore, by appropriately combining the heat treatment temperature and the temperature of the reservoir 4, it is possible to obtain a single crystal CdTe substrate 1 having a desired conductivity type and resistivity.

As described above, according to the above embodiment, by appropriately selecting the heat treatment temperature and the temperature of the server 4 and performing the heat treatment, crystal defects in the single crystal CdTe substrate l can be removed and composition gradients can be eliminated. At the same time, it is possible to easily control the conductivity type and resistivity to desired values. Furthermore, in the above embodiment, since the open tube method is used and the heat treatment device 8 is used, the heat treatment can be easily performed, and the reaction tube 7 and the heat treatment device 8 can be used repeatedly. Therefore, economical industrial production is possible.

Furthermore, since the Cd vapor generated from the reservoir 4 is efficiently and reliably supplied into the heat treatment chamber 9 through the steam supply pipe 11, the composition of the single crystal CdTe substrate 1 deviates from the stoichiometric ratio due to the heat treatment. It is possible to effectively prevent this. Furthermore, since the heat treatment chamber 9 and the steam generation chamber 10 can be separated by the length of the steam supply pipe 11,
It is easy to independently control the temperature of the heat treatment chamber 9 and the temperature of the steam generation chamber 10. Not only that, but also by heat treatment,
Chlorine (CI) contained in the single crystal CdTe substrate 1,
It is also possible to volatilize and remove volatile impurities such as arsenic (As).

Although one embodiment of the present invention has been described above, the invention is not limited to the above-described embodiment, and various modifications can be made based on the technical idea of the present invention. For example, the heat treatment temperature and the heating temperature of the server 4 can be appropriately selected as necessary. The heat treatment temperature is 500 to 90
It is possible to use a temperature in the range of 0°C, but if the temperature is too low, the diffusion rate of Cd is not high enough and the heat treatment takes time (e.g. 800°C takes only 2 hours, whereas 700°C takes only 2 hours). If the temperature is too high, the vapor pressure of Cd will exceed 1 atm, making it difficult to carry out the open tube method. It is preferred to use a temperature within the range of 750 to 850°C. Also, the heat treatment temperature is 500 to 9
When the temperature is in the range of 00℃, the heating temperature of the glue reservoir 4 is 4
It is possible to set it as the range of 00-800 degreeC.

Furthermore, the material, dimensions, shape, structure, etc. of the heat treatment instrument 8 can be selected as necessary. Furthermore, it is also possible to put Te or CdTe in the reservoir 4 instead of Cd3, if necessary.

In particular, when Te is used, the monocrystalline CdTe substrate is heat-treated in an atmosphere of Te vapor, so there is an advantage that the temperature range of the reservoir can be widened when producing p-type CdTe. In addition, when using CdTe, single crystal (JTe) is heat-treated in an atmosphere where Cd vapor and Te vapor coexist, and at the same reservoir temperature, the Cd vapor pressure is lower than when using Cd, so the same conductivity type In order to control the resistivity, it is sufficient to make the reservoir temperature higher than in the case of Cd.

〔Effect of the invention〕

According to the present invention, by selecting the heating temperatures of the single crystal CdTe and the predetermined substance housed in the first and second containers, the single crystal CdTe0 heat treatment is simultaneously performed and the desired conductivity type and/or resistivity is achieved. It can be easily controlled. Furthermore, since the open tube method is used, economical industrial production is possible. In addition, since the first and second containers are communicated with each other, the vapor of the substance generated in the first container can be efficiently and reliably supplied into the second container,
Therefore, it is possible to heat treat single crystal CdTe in this vapor atmosphere.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining a heat treatment method for single crystal CdTe according to an embodiment of the present invention, and FIGS. 2A and 2B are plan views of a heat treatment tool used in an embodiment of the present invention, and its B- A cross-sectional view taken along line B, Figures 3 and 4 are graphs showing the conductivity type and resistivity of single crystal CdTe when the heat treatment temperature is 800°C and 700°C, respectively, and the dependence of the resistivity on the reservoir temperature. Single crystal Cd by conventional sealed tube method
FIG. 3 is a cross-sectional view for explaining a method of heat treatment of Te. In addition, in the symbols used in the drawings, 1.
Te substrate 2--------------Susceptor 3--------・-------Cd4--・--・
−−−−−−11−−−−−Reservoir 6～・−・−−
−−−−1・−・・−Electric furnace 7−−−−−−−−−1−−−−Quartz tube C 8−−−−−−−−・−−−−11−− Heat treatment equipment 9
−−−−−−−−−−−−−−−・Heat treatment chamber 10−
−−−−−−−−−−−−−−・−Steam generation chamber 11−
・−・−−−−−−−1−・−Steam supply pipes 12, 13
．． 14---One lid.

Claims (1)

[Claims] 1. In a method for heat treatment of single crystal CdTe in which the single crystal CdTe is heat treated by an open tube method, the single crystal CdTe is
dTe and at least one substance selected from Cd, Te, and CdTe are accommodated in first and second containers communicated with each other, and the first and second substances are placed in a reducing or inert gas flow.
The single crystal CdTe and the at least one substance housed in the container are heated to predetermined temperatures, thereby simultaneously heat treating the single crystal CdTe and controlling its conductivity type and/or resistivity. Crystal Cd
Heat treatment method for Te. 2. The heating temperature of the above single crystal CdTe is 500 to 900°C
and the heating temperature of the at least one substance is 400
The method for heat treatment of single crystal CdTe according to claim 1, wherein the temperature is 800°C. 3. The method for heat treatment of single crystal CdTe according to claim 1 or 2, wherein the reducing or inert gas is hydrogen, argon, or nitrogen.