JPH0752737B2 - Method for producing compound semiconductor crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A method of vapor phase epitaxially growing a crystal layer of mercury-cadmium-tellurium (HgCdTe) on a gallium arsenide (GaAs) substrate without causing misfit dislocations.
Zinc selenide tellurium [Zn Se _1-y Te _y
(0 ≦ y <0.43)] is formed on the GaAs substrate to a predetermined thickness that does not cause misfit dislocations, and at least zinc element, selenium, cadmium, tellurium, and mercury are formed on this substrate. After forming a compound semiconductor crystal that combines one element into a multilayer structure, Hg
_A method for forming a crystal layer of _1-X Cd _X Te by vapor phase epitaxial growth.

[Industrial application field]

The present invention relates to a method for manufacturing a compound semiconductor crystal, and particularly to GaAs
On a compound semiconductor substrate such as that described above without producing a lattice mismatch with the substrate, a method for producing a compound semiconductor crystal of mercury, cadmium and tellurium.

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 problems such as weak strength in the element formation process, which is convenient for element formation, and in order to increase the withstand voltage of the formed element, a method for forming this thin layer crystal As sapphire (α-Al ₂ O ₃ ) and spinel (MgO
-A thin layer of mercury / cadmium / tellurium crystals is formed on an insulating substrate such as Al ₂ O ₃ ) by a vapor phase epitaxial growth method.

In particular, a compound semiconductor crystal of mercury, cadmium, and tellurium is formed in a thin layer state on a semi-insulating compound semiconductor substrate such as GaAs, and using this, an infrared sensing element integrated at high density is formed, FET for operating this sensing element
There is formed a high-performance semiconductor device in which semiconductor elements such as the above are formed on the GaAs substrate described above, and an element for detecting infrared rays and a semiconductor element for operating the detection element are collectively formed on the same substrate.

[Conventional technology]

Conventionally, as shown in FIG. 3, when a crystal layer 3 of mercury, cadmium, tellurium (Hg _1-X Cd _X Te) is formed on a compound semiconductor substrate 1 such as GaAs, the ternary compound semiconductor is directly formed. Since it is difficult to form, a compound semiconductor such as binary CdTe is formed as the buffer layer 2, and the crystal 3 of Hg _1-X Cd _X Te is formed thereon.

[Problems to be solved by the invention]

However, since the CdTe crystal 2 formed on the GaAs substrate 1 has a different lattice constant with respect to the substrate, misfit dislocations (the lattices of different crystals do not match between different crystals, that is, lattice mismatch). Dislocation) occurs and the crystallinity of the Hg _1-X Cd _X Te crystal layer formed on the CdTe deteriorates.

When the critical thickness of the crystal layer becomes a state of not generating misfit dislocations and h _c, the value of the h _c literature 1 (United States Patent, Patent No. 3,788,890 Patented Jan.29,197
It becomes as shown in the formula (1) by 4).

h _c = b (1-ν) / 4f (1 + ν) cosλ 1.1 / f (Å) (1) where h _c is the critical thickness, f is the number of misfit dislocations, ν is the Poisson's ratio, and λ is the substrate. The angle between the direction of the slip surface of the crystal formed above and the normal line standing on the line of intersection between the slip surface and the original substrate, and b indicates the magnitude of the Burgers vector.

Furthermore, the value of h _c in the case of Hg _1-X Cd _X Te is given in Reference 2 (Phys.stat.
sol. (a) So, 663 (1983), Subject Classification:
1.5and10.2; 22.4,4, by JHBasson and H. Booyens: Int
roduction of Misfit Dislocation in HgCdTe) is shown by the equation (2).

h _c 1.8 / f (Å) (2) When a crystal layer different from the substrate is formed on the substrate by combining the equations (1) and (2), the critical thickness h _c at which misfit dislocations do not occur Becomes as shown in the equation (2) ′.

1.1 / f <h _c <1.8 / f (2) ′ The misfit number f when a dissimilar crystal having a different lattice constant from the substrate is formed on the substrate is shown in the equation (3).

f = | (lattice constant of different crystal layer / lattice constant of substrate) −1 | (3) As a result, as in the conventional method, Cd is formed on the GaAs substrate.
When a Te crystal layer is formed, the misfit number f = 1.47 ×
10 ^-1, and the value of the critical thickness h _c the crystal layer of the CdTe generates no misfit dislocation, a thickness of as calculated using the first (2) 'equation 7.5A～12.2A. This thickness is equal to the thickness of one or two layers of lattice planes of the CdTe crystal, and it is difficult to form such a thin crystal layer in manufacturing.

The present invention solves the above-mentioned problems and, as shown in Table 1, after forming a crystal layer having a lattice spacing close to that of a GaAs substrate, that is, having a small misfit number f, the crystal layer is Provided is a method for producing a mercury-cadmium-tellurium crystal layer that does not generate misfit dislocations, that is, does not generate misfit dislocations on a GaAs substrate as a final layer after forming a crystal layer having a close lattice spacing into a multilayer structure. With the goal.

Table 1 shows the lattice constants of the crystals used in the method of the present invention.

[Means for Solving Problems] A method for producing a compound semiconductor crystal according to the present invention is such that zinc-selenium-tellurium [Zn Se _1-y Te
_y (0 ≦ y <0.43)] of the crystal layer is formed by laminating a plurality of layers while varying the composition, and then zinc element, selenium, mercury.
Multiple layers of compound semiconductor crystal layers containing at least one element of cadmium / tellurium are formed by varying the composition, and then a compound semiconductor crystal layer of mercury / cadmium / tellurium is further laminated on the uppermost layer. To

The thickness of the crystal layer of zinc selenium tellurium [Zn Se _1-y Te _y (0 ≦ y <0.43)] previously formed on the gallium arsenide substrate is in the range of 50Å to [680 / (1 + 29y)] Å And

[Action]

The method for producing a compound semiconductor crystal of the present invention, a GaAs substrate,
ZnSe _1-y Te _y with few misfits to the substrate
First, a crystal layer of (0 ≦ y <0.43) is formed. Where ZnSe
The crystal layer of _1-y Te _y has a lattice constant of 5.668 + 0.434y (Å), which is 9 layers when the lattice spacing is ZnSe, that is, 5.668.
When a crystal layer of about Å × 9 = 50Å is formed, this crystal layer is a number that can be technically grown, and this value is the lower limit.

Further, the critical thickness when forming a different crystal on the substrate is h _c = 1.8 / f as shown in the equation (2), and f is a misfit number, so f = (ZnSe _1-y Te _y lattice constant / GaAs lattice constant) -1 ... (4) The lattice constant of ZnSe _1-y Te _y is determined by the Vegard law.
Since it is 5.668 + 0.434yÅ, the value of h _c when the ZnSe _1-y Te _y crystal layer is formed on the GaAs substrate by using the formulas (2) and (4) is (5) ) As shown in the equation.

h _c = 1.8 / f = (1.8) / [(5.668 + 0.434y) /5.653] -1 = 10.176 / (0.015 + 0.434y) = 680 / (1 + 29y) ...... (5) With the above lower limit value , If a crystal layer of ZnSe _1-y Te _y (0 ≦ y <0.43) is formed within the range of the critical thickness value shown in equation (5), ZnSe will be generated in the state where misfit dislocations do not occur in the GaAs substrate. A crystal layer of _1-y Te _y (0 ≦ y <0.43) can be formed.

In this way, if a crystal of mercury, cadmium, tellurium is further formed on the uppermost layer of this crystal layer on the GaAs substrate without causing misfit dislocations with the substrate, the crystal becomes Ga
A high-quality crystal that does not generate misfit dislocations with respect to the As substrate.

〔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-organic film is formed on the GaAs substrate 11.
-Chemical-Vapor-Deposition (hereinafter referred to as MOCVD)
According to the method, a ZnSe (ZnSe _1-y Te _y , y = 0) crystal layer 12
Form A to a thickness of about 400Å.

In this way, ZnSe (ZnSe _1-y
Since the critical thickness of the crystal crystal layer of Te _y , y = 0, that is, 0 ≦ y <0.43) is 680 Å, the ZnSe crystal layer does not generate misfit dislocations with respect to the GaAs substrate.

Then formed to a thickness of an extent that Zn Se _1-y Te _y crystal layer 12A and the misfit dislocations ZnSe thereunder crystal layer 12B does not occur on the crystal layer 12A of the ZnSe.

In formula (6) derived from formula (2), this thickness is, for example, a Zn Se _1-y Te _y crystal with y = 0.05.
The thickness will be Å.

h _c (ZnSe _1-y Te _y /ZnSe)=4.15/y (6) Next, ZnSe _1-w Te is formed on the ZnSe _1-y Te _y crystal layer 12B.
The crystal layer 12C of _w is formed to a thickness such that misfit dislocations do not occur with the crystal layer 12B of Zn Se _1-y Te _y thereunder.

This thickness is, for example, ZnS of y = 0.05 in the formula (7).
When the crystal layer 12C with w = 0.1 is formed on the crystal 1B of e _1-y Te _y , its thickness is 83Å as shown in the equation (7).

h _c (Zn Se _1-w Te _w / ZnSe _1-y Te _y ) = 4.15 / (wy) (Å) (7) In this way, ZnSe _{1-ui with} more Te than the lower layer Te _ui
The layer 12D is formed to a thickness such that misfit dislocations do not occur, and then the ZnTe crystal layer 13 is formed on the ZnSe _1-un Te _un layer 12E and the ZnSe _1-un Te _un crystal layer 12E thereunder. It is formed to a thickness such that misfit dislocations do not occur.

When this thickness is calculated using the formula (8) derived from the formula (2), for example, when ZnTe _1-u Te _u with u = 0.95 is formed and then ZnTe is formed, the thickness is 280 Å.

h _c (Zn Te / ZnSe _1-u Te _u ) ＝ 14 / (1-u) (Å) ……
(8) Next, on this ZnTe crystal layer 13, a Zn _z Cd _1-z Te crystal layer
Forming 14

When this thickness is calculated using the equation (9) derived from the equation (2), for example, the z layer is continuously formed on the ZnTe crystal layer 13.
In the case of forming the crystal layer 14 of Zn _z Cd _1-z Te of = 0.9, its thickness is 290Å.

h _c = (Zn _z Cd _1-z Te / ZnTe) = 29 / (1-y) (Å) (9) Further, Zn _s Cd _1- on the crystal layer 14 of Zn _z Cd _1-z Te. _st Hg _t
The Te crystal layer 15 and the Zn _z Cd _1-z Te crystal layer 14 thereunder are formed to a thickness such that misfit dislocations do not occur.

When this thickness is calculated using the equation (10) calculated from the equation (2), for example, Zn _z Cd _1-z Te with z = 0.5, followed by Zn _s Cd ₁ with s = 0.1 and t = 0.3. _When forming a _-st Hg _t Te crystal layer, its thickness is 77Å.

h _c = (Zn _s Cd _1-st Hg _t Te / Zn _z Cd _1-z Te) = (583−34z) / [19 (z−s) −t] (Å) …… (10) Furthermore, this Zn _s Cd _1-st Hg _t Te On the crystal layer 15, Hg _1-x Cd _x
The Te crystal layer 16 is replaced by the Zn _s Cd _1-st Hg _t Te crystal layer 15 below.
And the thickness is such that misfit dislocations do not occur.

When this thickness is calculated using the equation (11) derived from the equation (2), for example, Zn _s Cd _1-st H with s = 0.1 and t = 0.3.
Hg _1-x Cd _x Te with x = 0.3 on top of the crystalline layer of g _t Te
When forming the crystal layer of, the thickness is 398Å.

h _c = (Hg _1-x Cd _x Te / Zn _s Cd _1-st Hg _t Te) = (583−34s−1.8t) / (19s + t + x−1) (Å) …… (11) Hg _1-x Cd _x Te formed on the top layer
Since the crystal layer 16 does not generate misfit dislocations with respect to the GaAs substrate 11, a good semiconductor crystal can be obtained.

In order to obtain a crystal layer of Hg _1-x Cd _x Te having a desired thickness, the parameters w, u _i , u _n , z may be considered according to the equations (7) to (11).

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

Next, a hydrogen gas supply valve 23, a valve 25 communicating with a dimethylzinc storage container 24, and a dimethylselenium storage container 26.
Open the valve 27 leading to the dimethyl tellurium container 29 and the flow controller (mass flow meter) 23A, 25A, 27A, 30A connected to each supply valve 23, 25, 27, 30
Is operated to introduce hydrogen gas into the reaction tube 21 and hydrogen gas carrying dimethyl zinc, dimethyl selenium and dimethyl tellurium, and heat the substrate by energizing the high frequency coil 28 provided in the reaction tube 21. A crystal layer 12A of ZnSe _1-y Te _y (y = 0, ZnSe) is formed on the substrate 11.

Then, by changing the flow rate of the line leading to the container 29 of dimethyl tellurium, hydrogen gas carrying dimethyl tellurium by changing the concentration of dimethyl tellurium, hydrogen gas carrying dimethyl selenium, hydrogen gas carrying dimethyl zinc, Introduced into the reaction tube 21, ZnSe _1-y Te _y crystal layer 12B, Zn
A crystal layer 12C of Se _1-w Te _w is formed on the substrate.

Thus sequentially, u _i, u _n, and to change the coefficients ZnSe _1-y
A crystal layer of Te _y is formed on the substrate.

Then, the valve 27 leading to the dimethylselenium container 26 is closed, and hydrogen gas carrying dimethyl tellurium and dimethyl zinc is introduced into the reaction tube to form a ZnTe crystal layer 13 on the substrate.

Next, a valve 32 connected to the dimethyl cadmium container 31
Mass flow meter 32A connected to valve 32 by opening
Is operated, hydrogen gas carrying dimethyl cadmium,
By introducing hydrogen gas supporting dimethylzinc and hydrogen gas supporting dimethylcadmium into the reaction tube 21, Zn _z Cd _1-z
A Te crystal layer 14 is formed on the substrate.

Next, the valve 34 connected to the container 33 containing mercury is opened, the mass flow meter 34A connected to the valve 34 is operated, and hydrogen gas carrying mercury in the reaction tube, hydrogen gas carrying dimethylcadmium, hydrogen carrying dimethylzinc. A gas is introduced into the reaction tube to form a Zn _s Cd _1-st Hg _t Te crystal layer.
Forming fifteen.

Then, the valve connected to the dimethylzinc container 24 is closed, and hydrogen gas supporting mercury in the reaction tube, hydrogen gas supporting dimethylcadmium, and hydrogen gas supporting dimethyltellurium are introduced and Hg _1-x on the substrate. A crystal layer 16 of Cd _x Te is formed.

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

〔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 GaAs substrate, 12A is a ZnSe crystal layer, 12B is a ZnSe _1-y Te _y crystal layer, 12C is a ZnSe _1-w Te _w crystal layer, 12D is a ZnSe _1-ui Te _ui crystal layer, and 12E. Is ZnSe _1-un Te _un crystal layer, 13 is ZnCd crystal layer, 14 is Z
n _z Cd _1-z Te crystal layer, 15 is Zn _s Cd _1-st Hg _t Te crystal layer, 16
Is Hg _1-x Cd _x Te crystal layer, 21 is a reaction tube, 22 is a substrate mount, 2
3,25,27,30,32,34 are valves, 23A, 25A, 27A, 30A, 32A, 34A
Is a mass flow meter, 24 is a dimethyl zinc container, 26 is a dimethyl selenium container, 28 is a high frequency coil, 29 is a dimethyl tellurium container, 31 is a dimethyl cadmium container, and 33 is a mercury container.

Claims (2)

[Claims] 1. A plurality of crystal layers (12A to 12F) of zinc selenium tellurium [Zn Se _1-y Te _y (0 ≦ y <0.43)] are preliminarily formed on a gallium arsenide substrate (11) by varying the composition. After forming a layer stack, a plurality of compound semiconductor crystal layers (13, 14, 15) containing zinc element and at least one element of selenium, cadmium, tellurium, and mercury are formed on the substrate, and then the uppermost layer. A method for producing a compound semiconductor crystal, characterized in that a compound semiconductor crystal layer made of mercury, cadmium, tellurium (16) is formed on the substrate. 2. Zinc selenium tellurium [Zn Se _1-y Te _y (0 ≦ y <0.4
3)] the crystal layer thickness is 50Å ~ [680 / (1 + 29y)] Å
The method for producing a compound semiconductor crystal according to claim 1, wherein