JPH02142145A - Method for growing compound semiconductor crystals - Google Patents

Abstract

PURPOSE:To fill the vacant lattices of a crystal with mercury by heat treatment in a short time and to make it possible to introduce mercury into the vacancies at a uniform concentration along the direction of the thickness of a crystal layer by heating a compound semiconductor substrate which is provided in a reaction tube, supplying the mercury and an epitaxially growing gas other than the mercury on the substrate, growing the epitaxial crystal, supplying only the mercury to the substrate, and heat- treating the crystal. CONSTITUTION:A substrate 3 is provided on a susceptor 2 in a reaction tube 1. Hydrogen gas as a carrier gas and the gases of dimethyl cadmium, diethyl tellurium and mercury which are supported by the hydrogen gas are introduced into the reaction tube 1 through a gas introducing pipe 19. An epitaxial crystal 31 of Hg1-xCdxTe is formed on the substrate. A valve 22 is opened. The hydrogen gas and the mercury gas are introduced into the reaction tube 1 under the state wherein the partial pressure of the mercury is made higher than that in epitaxial growing. With the substrate 3 being heated, heat treatment for filling the vacancies of the crystal 31 is performed. Thus the crystal 31 is transformed into an N-type epitaxial crystal 32. When this operation is repeated many times, the epitaxial crystal layer of Hg1-xCdxTe which is transformed into the N type having the specified thickness is obtained.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for growing a compound semiconductor crystal containing mercury, the present invention aims to provide a method for vapor phase growth of a compound semiconductor crystal containing water roots having a desired mercury vacancy concentration. a step of growing an epitaxial crystal of a compound semiconductor containing mercury on the substrate by supplying water and an epitaxial growth gas other than mercury to the substrate while heating the compound semiconductor substrate placed in the reaction tube; a step of heating the substrate having the grown epitaxial crystal, stopping the supply of the epitaxial growth gas except for mercury, and supplying only mercury to the substrate to heat-treat the epitaxial crystal to convert it into a desired conductivity type; The method includes the steps of growing a crystal on the substrate-L and sequentially repeating each step of heat treatment of the epitaxial crystal at least once to form a single crystal layer of a desired conductivity type on the substrate.

[Industrial Application Field] The present invention relates to a method for vapor phase growth of compound semiconductor crystals containing mercury.

Mercury, cadmium,
A compound semiconductor crystal such as tellurium (Ig+□CdTe) is used.

[Conventional technology]

Conventionally, when a crystal of t1g+-+v C+J+ Te is grown by vapor phase epitaxial growth on a substrate such as cadmium tellurium (CdTe), a CdTe substrate placed on a susceptor 2 in a reaction tube 1 is grown as shown in FIG. 3 is applied to the high frequency coil 4 provided around the reaction tube 1 to heat the substrate while heating the susceptor 2, and at the same time, the substrate is heated with mercury (TLG) gas and dimethyl cadmium ((C113)). Epitaxial growth gases such as zcd ) gas and diethyl tellurium ((C2115) zTe ) gas are supplied, and two o, - [Bitter 1-Sha 11 layers are grown in vapor phase.

By the way, in this epitaxial crystal layer of IIg+-x CdX Te, since mercury is an easily evaporable element, it is easy to extract from the lattice point position of the crystal, and the epitaxial growth conditions such as the growth temperature and mercury partial pressure during epitaxial crystal growth can be changed. As a result, vacancies are formed in the crystal from which the mercury atoms are extracted, and since these vacancies serve as acceptors, the crystal generally exhibits P-type conductivity.

By the way, N is generally used as a crystal for forming an infrared sensing element.
There is a demand for crystals having a conductivity type of P-type or P-type crystals with a low acceptor concentration.

Therefore, in order to obtain such a crystal, as shown in FIG. 4, a substrate 5 on which the epitaxial crystal of t1g+-x CdXTe is formed is placed in a quartz jig 6 in a reaction tube 1, and a mercury 7 is placed in the reaction tube 1. After evacuating the reaction tube 1 to empty, the reaction tube 1 is heated to fill the container with mercury 7 vapor, and the substrate is heated for a long time in this mercury atmosphere. The vacancies of the epitaxial crystal thus formed are filled with mercury atoms to form an N-type conductivity type,
Alternatively, it is a P-type crystal having a desired acceptor concentration.

[Problem to be solved by the invention]

However, in the conventional method described above, it takes a long time of about 24 hours for the mercury atoms to fill the vacancies.
In particular, when the epitaxial crystal layer becomes thick, there is a problem that it takes a long time for mercury atoms to diffuse and permeate to the lower part of the crystal layer.

In addition, when the thickness of the epitaxial crystal layer is thick, mercury atoms in the upper part of the crystal layer tend to diffuse and permeate, so the concentration of mercury atoms fluctuates between the upper and lower parts of the crystal layer, and the concentration of mercury atoms changes along the thickness direction of the crystal layer. There is a problem that a uniform mercury concentration cannot be obtained.

The present invention solves the above-mentioned problems, does not require a long heat treatment time to fill the vacancies in the crystal with mercury, and mercury fills the vacancies at a uniform concentration along the thickness direction of the epitaxial crystal layer. An object of the present invention is to provide a method for vapor phase growth of compound semiconductor crystals.

[Failure to solve the problem]

The method for vapor phase growth of a compound semiconductor crystal of the present invention which achieves the above object includes heating a compound semiconductor substrate placed in a reaction tube while supplying mercury and an epitaxial growth gas other than mercury to the substrate. a step of growing an epitaxial crystal of a compound semiconductor containing mercury, then heating the substrate having the grown epitaxial crystal, stopping the supply of the epitaxial growth gas excluding mercury, and supplying only mercury to the substrate; At least one step each of heat-treating the epitaxial crystal, growing the epitaxial crystal on a substrate, and heat-treating the epitaxial crystal.
The method is characterized in that it includes a step of forming a single crystal layer on a substrate by repeating the steps one or more times.

[For production]

In the vapor phase growth method of the present invention, an epitaxial layer is formed in advance to a thickness of about 0.1 μm on a substrate, and then the same reaction tube as that used for epitaxial growth is carried out with the supply of epitaxial growth gases other than mercury stopped. The substrate on which the epitaxial layer has been formed is heat-treated in a mercury atmosphere using a tube. By repeating such an epitaxial growth step and a heat treatment step in sequence, an epitaxial crystal having a desired thickness and a desired conductivity type can be obtained.

In this way, since the epitaxial layer is thin, the heat treatment process to fill the vacancies with mercury atoms can be carried out in a short time, and the concentration of mercury diffused into the upper and lower parts of the epitaxial layer becomes uniform, and the epitaxial layer becomes thinner. A uniform mercury concentration is obtained along the thickness direction of the layer, and since the same reaction tube is used, there is no risk of contamination of the crystals.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

1(a) to 1(C) are cross-sectional views of a compound semiconductor crystal formed by the method of the present invention, and FIG. 2 is an explanatory diagram of an apparatus used in the method of the present invention.

As shown in FIG. 1(a) and FIG. 2, a reaction tube 1
A substrate 3 for epitaxial growth is placed in a susceptor 2 inside the reaction tube 1, and after evacuating the inside of the reaction tube 1, the susceptor 2 inside the reaction tube 1 is heated by energizing a high frequency induction coil 4, and the substrate 3 is heated to 400℃. A valve 11 for supplying hydrogen gas, a valve 13 connected to an evaporator 12 containing dimethyl cadmium, a valve 15 connected to an evaporator 14 containing diethyl tellurium, and a valve 15 connected to an evaporator 14 containing diethyl tellurium. The valve 17 connected to the evaporator 16 is connected to the valve controller 18.
hydrogen gas as a carrier gas and the gases of dimethyl cadmium, diethyl tellurium and mercury supported by the hydrogen gas are introduced into the reaction tube 1 through the gas introduction tube I9, and this is applied to the substrate. -J by supplying gas such as
- Due to the gas phase chemical reaction of the above gas, l1g is added to the substrate -L,
An epitaxial crystal layer of Cd and Te is formed.

After a predetermined period of time has elapsed in this way, as shown in FIG. 1(a), IIg, -, 1CdX
A Te epitaxial crystal 31 is formed to have a diameter of 0.1 μm.

Next, the valves 13, 15, and 17 are closed, and the valve 22 connected to the evaporator 21 containing the mercury for heat treatment is opened to supply hydrogen gas and mercury gas in a state where the partial pressure of mercury is higher than that during the above-mentioned evitigmental growth. The substrate 3 is introduced into the reaction tube 1.
As shown in FIG. 1(b), while heating the 11g1□CdXTe epitaxial crystal 31, a heat treatment is performed to fill the vacancies in the 11g1□CdXTe epitaxial crystal 31, thereby forming the t+g+-,,Cd
The x're epitaxial crystal 31 is converted into an N-type epitaxial crystal 32.

Next, the valve 23 was closed, and the valves 13, 15, and 17 were opened to supply water, dimethyl cadmium, and diethyl tellurium supported by hydrogen gas to the substrate on which the N-type epitaxial crystal 32 was formed. As shown in C), additional 0.1 μm of HP, , -8Cd on the substrate
An epitaxial crystal 33 of XTe is formed.

Since this epitaxial growth is performed in mercury vapor at a high partial pressure, the mercury atoms buried in the vacancies of the epitaxial crystal do not evaporate.

Next, the valves 13, 15, and 17 are closed, and the valve 22 connected to the evaporator 21 containing the mercury for heat treatment is opened to introduce hydrogen gas and mercury gas into the reaction tube 1 to remove the epitaxial crystal 33 formed above. Convert to N-type layer.

By repeating the above operation many times, an epitaxial crystal layer of lIg+-x cciXTe converted to N-type with a desired thickness is obtained on the substrate.

In this way, since mercury gas is introduced into the epitaxial crystal layer, which is very thin, the heat treatment time for filling the vacancies in the epitaxial crystal with water jfQ can be shortened, and the thickness of the epitaxial crystal layer can be reduced. Because of its thinness, the concentration of mercury introduced into the upper and lower parts of the crystal layer becomes uniform, resulting in a crystal layer in which mercury is added at a uniform concentration.

Furthermore, since the same reaction tube is used for epitaxial growth and heat treatment, contamination of the epitaxial crystal can be prevented.

Although this embodiment has been described using 11g1□Cd-Te crystal as an example, the present invention is also applicable to mercury-manganese-tellurium (lIgMnTe), mercury-zinc-tellurium (HgZn).
It can be applied to compound semiconductor crystals containing mercury such as Te), and in addition to the vapor phase epitaxial growth method of the present invention, a molecular beam epitaxial growth method or a hot wall epitaxial growth method may be used as the crystal growth method.

[Effects of the Invention] As is clear from the above description, according to the present invention, the vacancies in the epitaxially grown P-type Ilg, Cd, and Te crystals are filled with mercury atoms in a short time, so that N It has the effect that it is converted into a mold and a crystal for forming an infrared sensing element can be easily obtained.

1(a) to 1(C) are cross-sectional views of a compound semiconductor crystal formed by the method of the present invention, FIG. 2 is an explanatory diagram of the apparatus used in the method of the present invention, and FIG. 3 is a conventional An explanatory diagram of the vapor phase growth method, and FIG. 4 is an explanatory diagram of the conventional heat treatment method.

In the figure, 1 is the reaction tube, 2 is the susceptor, 3 is CdTeJ, 5 is temporary, 4 is
is a coil, 11 is a hydrogen gas supply valve, 12 is a dimedium cadmium evaporator, 13.15.17.22 is a valve,
14 is a diethyl tellurium evaporator, 16 is a water root evaporator, 18
21 is a mercury evaporator for heat treatment; 31. is a valve control device;
33 is Ilg, -, CdXTe epitaxial crystal, 3
2 shows an N-type 1+8X Cdw Te epitaxial crystal.

[Brief explanation of the drawing]

(Ql (b) (C) -1 month Mitro month 48 → Te is 1; [Pin□5hi[]L
Figure 2 Figure 1

Claims (1)

[Claims] While heating a compound semiconductor substrate (3) placed in a reaction tube (1), mercury and an epitaxial growth gas other than mercury are supplied to the substrate (3) to form mercury on the substrate. Next, the substrate (3) having the grown epitaxial crystal (31) is heated, the supply of epitaxial growth gas excluding mercury is stopped, and only mercury is grown. A step of supplying the epitaxial crystal to a substrate and heat-treating the epitaxial crystal to convert it into a crystal of a desired conductivity type (32), a step of growing the epitaxial crystal on the substrate, and a step of heat-treating the epitaxial crystal are performed at least once each at least once. A method for growing a compound semiconductor crystal, the method comprising the step of repeatedly forming a single crystal layer having a desired conductivity type on a substrate.