JPH0722136B2 - Method for producing compound semiconductor crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A method of vapor phase epitaxial growth of a mercury-cadmium-tellurium (HgCdTe) crystal layer on a spinel (MgAl ₂ O ₄ ) substrate without misfit dislocations, Zinc telluride (ZnTe) or ZnyC on spinel substrate
A compound semiconductor in which zinc element and at least one element of mercury, cadmium, and tellurium are combined on this substrate after forming d _1- yTe (0.5 <y <1) to a predetermined thickness that does not cause misfit transition. After forming the crystal into a multilayer structure,
A method of forming a Hg _1- xCdxTe crystal layer as the uppermost layer thereon by a vapor phase epitaxial growth method.

[Industrial application field]

The present invention relates to a method for producing a compound semiconductor crystal, and more particularly to a method for producing a compound semiconductor crystal of mercury, cadmium, tellurium on an insulating substrate such as spinel without causing lattice mismatch with the substrate.

As a material for forming the infrared detection element, a crystal in which a compound semiconductor crystal of mercury, cadmium, tellurium having a narrow energy band gap is formed in a thin layer state is used.

This thin-layer crystal has a problem such as weak strength in the element formation process. As a method for forming a thin-layer crystal, an insulating substrate such as a sapphire substrate is used so that it is convenient for element formation. A thin layer of mercury-cadmium-tellurium crystal is formed on the upper surface by using the vapor phase epitaxial growth method.

[Conventional technology]

Conventionally, as a method for producing a compound semiconductor crystal of mercury / cadmium / tellurium on such an insulating substrate, as shown in FIG. 3, sapphire (αAl ₂ O ₃ ) substrate 1 of cadmium tellurium (CdTe) After the compound semiconductor crystal layer 2 was previously formed by the vapor phase epitaxial method, the compound semiconductor crystal 3 of mercury cadmium tellurium (Hg _1- xCdxTe) was formed thereon by the vapor phase epitaxial method.

[Problems to be solved by the invention]

By the way, as shown in Table 1, the lattice constant of the (111) plane of hexagonal crystal such as sapphire is 4.763Å, and the zincblende crystal formed on it has CdTe ( 111) plane, and the lattice spacing is 4.583Å.

Here, when a heterogeneous crystal such as CdTe is formed on an insulating substrate such as sapphire, the crystal layer has misfit dislocations with respect to the substrate (the lattices of the respective crystals do not match between different crystals, that is, Assuming that the critical thickness of the crystal layer is hc so that the transition due to lattice mismatch) does not occur, the value of this hc is given in Reference 1 (US Patent, Patent No.
No. 3,788,890 Patented Jan.29,1974), it becomes as shown in the formula (1).

hc = b (1-ν) / 4f (1 + ν) cosλ1.1 / f (Å)…
(1) where hc is the critical thickness, f is the number of misfit dislocations, ν is the Poisson's ratio, λ is the direction of the slip plane of the crystal formed on the substrate, and the intersection of the slip plane and the original substrate. The angle formed by the normal line to the line and b indicates the magnitude of the Burgers vector.

Furthermore, the value of hc in the case of Hg _1- xCdxTe is given in Reference 2 (Phys.stat.so
l. (a) So, 663 (1983), Subject Classification: 1.5
and10.2; 22.4,4, by JHBasson and H. Booyens: Introd
Auction of Misfit Dislocation in HgCdTe) is shown by the equation (2).

hc1.8 / f (Å) ……… (2) When a crystal layer different from the substrate is formed on the substrate by combining the equations (1) and (2), the crystal layer that does not generate misfit dislocations is formed. The critical thickness hc is given by equation (3).

1.1 / f <hc <1.8 / f (3) Here, when a CdTe crystal layer is grown on a sapphire substrate as in the conventional method, as shown in Table 2,
The misfit number f = 3.7 × 10 ^-2 .

As a result, when the CdTe crystal layer is formed on the sapphire substrate as in the conventional method, the value of the critical thickness hc at which the CdTe crystal layer does not generate misfit dislocations is expressed by the formula (3). When calculated using, the thickness will be 29Å ~ 48Å.

This thickness has a lattice spacing of CdTe crystals of 7 layers or more.
It is difficult to manufacture such a thin crystal layer, which is equal to the thickness of 12 layers.

Therefore, with the conventional method of growing a CdTe crystal layer on a sapphire substrate, it is difficult to form a CdTe crystal layer without misfit dislocations.・ If a cadmium-tellurium crystal layer is formed, the crystal layer of the mercury-cadmium-tellurium crystal layer formed on the substrate will be inferior because of the crystal layer on the substrate where misfit dislocations occur. .

An object of the present invention is to solve the above problems and provide a method for producing a compound semiconductor crystal in which misfit dislocations do not occur in a substrate.

[Means for solving problems]

The method for producing a compound semiconductor crystal of the present invention is, in advance, on a spinel substrate, ZnTe, or after forming ZnyCd _1- yTe to a thickness that does not cause misfit dislocations, zinc element on this substrate, and mercury _- cadmium- After a compound semiconductor crystal layer made of at least one element of tellurium is laminated in a multilayer structure, a compound semiconductor crystal made of mercury, cadmium, tellurium is further formed in the uppermost layer.

[Action]

In the method for producing a compound semiconductor crystal of the present invention, a spinel substrate having an insulating property similar to that of a sapphire substrate is used as a substrate, and as shown in Table 2, the misfit number f = 7.0 × 10 ^{− with} respect to the spinel substrate. A ZnTe crystal layer having a value of ³ is formed beforehand with a thickness that does not cause misfit dislocations.

Then, when this ZnTe crystal layer is formed on this spinel substrate, the thickness of the crystal layer in which this crystal layer does not generate misfit dislocations, that is, the critical thickness hc is calculated using the above-mentioned equation (3). Then, it becomes 160Å to 260Å, and this thickness is a value equivalent to the lattice plane spacing in which 45 to 73 layers of lattice planes are laminated, and this thickness is a sufficiently realizable thickness.

When a crystal of mercury / cadmium / tellurium is further formed on the substrate and a crystal layer in which misfit dislocations do not occur, the crystal becomes a high-quality crystal.

〔Example〕

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

FIG. 1 is a sectional view of a compound semiconductor crystal formed by the method of the present invention, and FIG. 2 is a schematic view of an apparatus used in the method of the present invention.

As shown in FIG. 1, a metal-orga is formed on the spinel substrate 11.
nic-Chemical-Vapor-Deposition (hereinafter referred to as MOCVD)
By the method, a ZnTe crystal layer 12 made of zinc element and tellurium element is formed to a thickness of about 200Å.

In this case, since the critical thickness of the ZnTe crystal layer with respect to the spinel substrate 11 is 200 Å or more, misfit dislocations do not occur in the ZnTe crystal layer.

Then, on this ZnTe crystal layer 12, ZnyCd _1- yTe (y <1)
The crystal layer 13 is formed to a thickness such that misfit dislocations do not occur with the ZnTe crystal layer 12 thereunder.

If this thickness is calculated using the equation (4) derived from the equation (2), for example, ZnyCd _1- yTe with y = 0.9 is 290Å, y =
With a ZnyCd _1- yTe of 0.5, it becomes 58Å.

hc (ZnyCd _1- yTe / ZnTe) = 29 / (1-y) (Å) ……
(4) Next, on this ZnyCd _1- yTe crystal layer 13, ZnsCd _1- s _- tHg
The tTe crystal layer 14 is formed to a thickness such that misfit dislocations do not occur with the underlying ZnyCd _1- yTe crystal layer 13.

If the thickness is calculated using the equation (5) derived from the equation (2), for example, s = 0.1 Following ZnyCd _1- yTe of y = 0.5, ZnyCd _1- s of t = 0.3 _- the tHgtTe If forming, 7
It is 7Å.

_{hc (ZnsCd 1- s - tHgtTe /} ZnyCd 1- yTe) = | (583-34y) / {19 (y-s) -t} | (Å) ... (5) then this ZnsCd _1- s _- crystal THgtTe Hg _1- xCdxT on layer 14
The crystal layer 15 of e is formed as the uppermost crystal layer.

If the thickness is calculated using equation (6) derived from the equation (2), for example, s = 0.1, t = 0.3 of ZnsCd _1- s _- tHgtT
When the crystal layer 14 of e is subsequently formed and the crystal layer 15 of Hg _1- xCdxTe with x = 0.3 is formed, the distance is 398Å.

_{hc (Hg 1- xCdxTe / ZnsCd 1-} s - tHgtTe) = | (583- 34s-1.8t) / (19s + t + x-1) | (Å) .........
(6) In this way, since the Hg _1- xCdxTe crystal layer 15 formed in the uppermost layer does not generate misfit dislocations with respect to the substrate 11, a good semiconductor crystal can be obtained.

In order to obtain a crystal layer of Hg _1- xCdxTe having a desired thickness, the parameters y, s, t, x may be considered according to the equations (4) to (6).

In order to form such a semiconductor crystal, as shown in FIG.
A substrate 11 made of spinel is placed on top.

Next, a hydrogen gas supply valve 23, a valve 25 leading to a dimethylzinc storage container 24, and a diethyl tellurium storage container 26.
The hydrogen gas and the hydrogen gas carrying dimethylzinc and diethyl tellurium are introduced into the reaction tube 21 by opening the valve 27 leading to and the high frequency coil 28 provided in the reaction tube 21 is energized to heat the substrate. A ZnTe crystal layer 12 is formed on a substrate 11.

Then a valve leading to the container 29 of dimethyl cadmium
With 30 open, hydrogen gas carrying dimethylcadmium is introduced into the reaction tube 21 to form a ZnxCd _1- xTe crystal layer 13 on the substrate.

Next, the valve 32 leading to the mercury container 31 is opened, and hydrogen gas carrying mercury is introduced into the reaction tube 21 to obtain Zn.
A crystal layer 14 of HgCdTe is formed on the substrate.

Next, with only valve 25 closed, Hg _1-
A crystal layer 15 of xCdxTe is formed.

By doing so, a high-quality compound semiconductor crystal can be obtained without causing misfit dislocations on the substrate.

Besides this embodiment, instead of forming ZnTe on the spinel substrate, ZnyCd _1- yTe (however, 0.5 <y <1) may be formed. In this case, the critical thickness of the crystal layer in which misfit dislocations do not occur in the substrate in which these crystal layers are spinel can be calculated by the equation (7) derived from the equation (2).

hc = 26 / (1-0.9y) (Å) (7) This is thinner than 260 Å which is the critical thickness of ZnTe, but is a thickness that can be actually formed.

Therefore, in addition to ZnTe in the present embodiment, ZnyCd _1- yTe (however, 0.5
After forming a crystal layer of <y <1), Hg _1- xCdxTe is formed on the uppermost layer.
May be formed.

〔The invention's effect〕

As described above, according to the method of the present invention, since misfit dislocations do not occur in the compound semiconductor crystal formed on the substrate, a high-quality compound semiconductor crystal can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a semiconductor crystal formed by the method of the present invention, FIG. 2 is a schematic view of an apparatus used in the method of the present invention, and FIG. 3 is a structure of a semiconductor crystal formed by a conventional method. It is sectional drawing shown. In the figure, 11 is a spinel substrate, 12 is a ZnTe crystal layer, and 13 is ZnyCd _1- yTe.
Layer, 14 is ZnsCd _1- s _- tHgtTe layer, 15 is Hg _1- xCdxTe layer, 21 is reaction tube, 22 is substrate mount, 23, 25, 27, 30, 32 are valves, 24
Is a dimethylzinc container, 26 is a diethyl tellurium container, 29 is a dimethylcadmium container, and 31 is a mercury container.

Claims (3)

[Claims] 1. A crystal layer of zinc cadmium tellurium [ZnyCd ₁ -yTe (0.5 <y ≦ 1)] is formed on a spinel substrate (11) in advance, and then zinc element, mercury, cadmium and tellurium are formed on the substrate. Of the compound semiconductor crystal layer (12, 13, 14) containing at least one of the above elements, and then further stacking the compound semiconductor crystal layer of mercury, cadmium, tellurium (15) on the uppermost layer. A method for producing a compound semiconductor crystal, characterized in that 2. Zinc previously formed on the spinel substrate
When the composition of the crystal layer of cadmium tellurium (ZnyCd _1- yTe) is (y = 1), that is, ZnTe, the thickness of the crystal layer is 50Å
The method for producing a compound semiconductor crystal according to claim 1, wherein the compound semiconductor crystal has a thickness of about 260Å. 3. The composition of a crystal layer of zinc cadmium tellurium [ZnyCd _1- yTe] formed on the spinel substrate is 0.5 <
When y <1, the thickness of the crystal layer is 26 / (1-0.9 from 50Å).
y) (Å) Claims, characterized in that
Item 10. A method for producing a compound semiconductor crystal according to the item.