JPS63284827A - Manufacture of compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To form crystal in which a misfit dislocation is not created on a substrate by a method wherein, after a crystal layer of fluoride of calcium or barium and mixed crystal layers are formed so as to have thicknesses less than the critical thickness at which a misfit dislocation is not induced, a zinc telluride layer is formed and further a mercury-cadmium-tellurium compound semiconductor crystal layer is formed as an uppermost layer. CONSTITUTION:After a crystal layer 12 containing at least one of calcium fluoride, barium fluoride and strontium fluoride and mixed crystal layers 13 and 14 of the fluorides are formed so as to have thicknesses less than the critical thickness at which a misfit dislocation is not induced for the lower layer, a zinc telluride layer 15 is formed. After compound semiconductor crystal layers 16 and 17 containing at least one element among elements, i.e. zinc, mercury, cadmium and tellurium is formed on the substrate, a mercury-cadmium-tellurium compound semiconductor crystal layer 18 is formed as an uppermost layer. With this constitution, as a misfit dislocation is not created in the compound semiconductor crystal formed on the substrate, high quality compound semiconductor crystal can be obtained.

Description

[Detailed description of the invention] [Summary] Gallium arsenide (GaAs) substrate or silicon (St
) without causing misfit dislocations on a semiconductor substrate such as a mercury, cadmium, tellurium (HgCdTe) substrate.
) is a method of vapor-phase epitaxial growth of a heterogeneous crystal layer, the method comprising: growing a crystal layer of any one of calcium, strontium, and barium fluorides on a semiconductor substrate, or a mixed crystal of said fluorides on a lower crystal layer; A compound semiconductor containing at least one element among zinc, mercury, cadmium, and tellurium on which a zinc telluride layer is formed after formation at a thickness below a critical thickness at which misfit dislocations do not occur; After forming the crystal layer, a compound semiconductor crystal layer made of mercury, cadmium, and tellurium is further formed as the top layer, and the compound semiconductor crystal of a different type from the substrate is grown on the semiconductor substrate by vapor phase epitaxial growth while preventing misfit dislocations from occurring. How to form in a way.

[Industrial application field]

The present invention relates to a method for manufacturing compound semiconductor crystals, and in particular to a method for manufacturing compound semiconductor crystals, particularly
, relates to a method for manufacturing a compound semiconductor crystal of mercury, cadmium, and tellurium of a different type on a semiconductor substrate such as GaAs without causing lattice mismatch with the substrate.

A thin layer of compound semiconductor crystals of mercury, cadmium, and tellurium with a narrow energy band gap is used as a material for forming an infrared sensing element.

In particular, compound semiconductor crystals of mercury, cadmium, and tellurium, which have a narrow energy band gap and high photoelectric conversion efficiency for infrared rays, are formed in a thin layer on a semiconductor substrate such as 5tSGaAs, and this is used to achieve high-density integration. A semiconductor element such as an FET for operating this detection element is formed on the above-mentioned semiconductor substrate, and an element for detecting infrared rays and a semiconductor element for operating this detection element are packaged on the same substrate. There is a demand for high performance semiconductor devices.

[Conventional technology]

Conventionally, when forming mercury, cadmium, and tellurium crystals that are different from the crystal on a Si substrate, Applie
d Physics Letters 49(22),
19B6.1531, H8Zogg, S, Blun
As disclosed in IER, after a mixed crystal 2 of calcium fluoride, strontium fluoride, and barium fluoride is grown on a Si substrate 1 shown in FIG.
A crystal of mercury, cadmium, tellurium (Hgl-
, Cdx Te).

Also, on the GaAs substrate, mercury/
When forming cadmium/tellurium crystals, as previously filed by the applicant in Japanese Patent Application No. 62-028424, a crystal layer of zinc/selenium/tellurium is formed in advance, and then a CdTe crystal is formed on top of the crystal layer. A method was used to form crystals of mercury, cadmium, and tellurium.

[Problem that the invention seeks to solve]

However, mercury, cadmium,
When a tellurium crystal layer is formed, there is a lattice mismatch of 0.6% between Si and calcium fluoride (CaF2), and furthermore, there is a lattice mismatch of 0.6% between Si and calcium fluoride (CaF2), and furthermore, there is a lattice mismatch between Si and calcium fluoride (CaF2), which is formed on the mixed crystal with barium fluoride (BaFz). There is a lattice mismatch of 4.5% between the Si substrate and the fluoride mixed crystal, and between the mixed crystal and the CdTe.
There was a problem in that misfit dislocations (dislocations due to lattice mismatch, in which the lattices of different crystals do not match between different types of crystals) occur between the crystals of e.

In addition, in the method of forming a crystal layer of zinc, selenium, and tellurium on a GaAs substrate and forming a crystal of CdTe on top of the layer, between the GaAs substrate and the crystal of zinc, selenium, and tellurium,
Furthermore, it is difficult to solve the phenomenon of misfit dislocations occurring between zinc/selenium/tellurium and CdTe crystals.

Here, when a crystal of a different type is formed on a substrate with respect to the substrate, if the critical thickness of the crystal layer at which the crystal layer does not generate misfit dislocations with respect to the substrate is hc, the value of this hc is (United States Patent, Patent No. 3.7
No. 88.890 Patented Jan, 29.19
74), as shown in equation (1).

hc=b (1-v”)/4 f (1+ν)
cosλ, 21.1/f (people)...1 old...(1) Here, hc is the critical thickness, f is the number of misfit dislocations, ν is Poisson's ratio, and λ is the slip of the crystal formed on the substrate. The angle b between the direction of the surface and the normal to the line of intersection between the slip surface and the original substrate, b, indicates the size of the Burgers vector.

Furthermore, the hcO value in the case of Hg1-XCd and Te is given in Reference 2.
(Phys, 5tat, sol, (a) So, 663
(1983), 5object C1assifica
tion:1.5 andIO,2;22.4.4,
by J,)1. Ba5sonand H, Booye
ns: Introduction of Misf
It Disl.

cation in HgCdTe)
It is shown in Eq.

hc21.8/f (person) (2) When a crystal layer different from the substrate is formed on a substrate by combining equations (1) and (2), misfit dislocations occur. The critical thickness hc at which this does not occur is as shown in equation (2)°.

x, 1. ＃＜h c＜1.8/r −・−・・・・−・
(2) 'The misfit number f when a heterogeneous crystal having a lattice constant different from that of the substrate is formed on the substrate is shown in equation [3].

f=(lattice constant of different crystal layer/lattice constant of substrate)-1・
(3) Here, as in the conventional method, a barium fluoride (BaFz) crystal layer is formed on a Si substrate, and CdT is deposited on top of it.
When a crystal layer of e is formed, as shown in Table 1, the misfit number f = 4.5 Xl0-''.

Table 1 As a result, as in the conventional method, B
When a crystal layer of aF z is formed and a crystal layer of CdTe is formed on top of it, this crystal layer of CdTe forms the lower Ban.
The critical thickness h that does not generate misfit dislocations with the crystal layer g
When the value of c is calculated using equation (3), it becomes a thickness of 24 to 40 people.

This thickness is equivalent to the thickness of 5 to 9 overlapping lattice planes in the lattice spacing of the CdTe crystal, and it is difficult to form such a thin crystal layer in terms of manufacturing.

Therefore, in the conventional method of forming a CdTe crystal layer on a BaF2 crystal layer, it is difficult to form a CdTe crystal without generating misfit dislocations. If mercury, cadmium, and tellurium are further formed on top of the mercury, cadmium, and tellurium, the crystallinity of the mercury, cadmium, and tellurium crystal layer deteriorates.

The present invention solves the above-mentioned problems, and as shown in Table 2, after forming a crystal layer with a lattice spacing close to the Si or GaAs substrate, that is, with a small misfit number f, A method for manufacturing a mercury/cadmium/tellurium crystal layer that does not cause misfit dislocations on an St or GaAs substrate as the final layer after forming a multilayer structure of crystal layers with close lattice spacing that does not cause misfit dislocations. For the purpose of providing.

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

Table 1 [Means for solving the problems] The method for manufacturing a compound semiconductor crystal of the present invention includes a crystal layer containing any one of calcium, strontium, and barium fluorides on a semiconductor substrate, or a crystal layer containing any one of calcium, strontium, and barium fluorides. After forming a fluoride mixed crystal to a thickness below the critical thickness at which misfit dislocations do not occur with respect to the lower crystal layer, a zinc telluride layer is formed, and zinc, mercury, cadmium, and tellurium elements are deposited on the substrate. After forming a compound semiconductor crystal layer containing one or more elements, a compound semiconductor crystal layer containing mercury, cadmium, and tellurium is further formed as the uppermost layer.

[Effect]

The method for manufacturing a compound semiconductor crystal of the present invention includes Si, GaA
Ca, a mixed crystal of fluorides of Ca, Sr, and Ba, on a semiconductor substrate of s without generating misfit dislocations with the substrate;
Srv Ba1-av F! (0≦U≦1.0≦V≦
1) Form a crystal layer. If the values of u and v are appropriately selected, this crystal layer can have the same lattice constant as the ZnTe crystal layer, so that a ZnTe crystal can be formed without generating misfit dislocations with respect to the substrate. Furthermore, Zn
A compound semiconductor crystal consisting of zinc element and at least one element selected from mercury, cadmium, and tellurium is laminated in a multilayer structure in a state where no misfit dislocation occurs in the Te crystal layer, and then By forming a crystal of mercury, cadmium, and tellurium, a crystal of mercury, cadmium, and tellurium that does not cause misfit dislocation to the substrate can be formed.

〔Example〕

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

FIG. 1 shows a first embodiment in which a crystal layer of mercury, cadmium, and tellurium is formed on a Si substrate 1. As shown in the figure, a crystal layer 12 of CaF is formed on a Si substrate 11, and CaFz is used as the source material. , formed to a thickness of 200 mm by molecular beam epitaxial growth.

When a crystal layer 12 of CaF2 is formed on this Si substrate 11, the lattice constant of Si is 5.431 and CaF2 is 5.431 as shown in Table 2.
Since the lattice constant of Fz is 5.46, from equation (3), f -5,4615,431-1=5.3 Xl0-'
Therefore, from equation (1), hc = 1.1/f = 206 people, and this thickness is less than the critical thickness.

Considering the critical thickness of 2, the thickness of CaF is 50~200
It is good to have the thickness of a person. Next, on the CaF crystal layer 12, a CauS layer is formed using a molecular beam epitaxial growth method.
A crystal layer 13 of rv Ba1-uv pg is formed.

In this case, the lattice constant of CaF2 is 5.46, Cau
The lattice constant of Srv Bat-a-vF2 is 6.20-
0.74u -0.4v, so change U from 1 to 0.1
, ■ from 0 to 0.06, respectively 0.01.0.006
Grow each layer by 100 people while making changes.

Then, on the crystal layer 13 of Ca, Srv Ba1-u-v Fz, Cau+Srv+ aal-ul-vI Fg
crystal layer 14 (however, 0.74u, +0.4v1=0.
98.0≦u1≦1.0≦v1≦1) using the molecular beam epitaxial growth method, ul””0.1 s V+=0
．． It is formed to a thickness of 200 people under the conditions of 06.

This critical thickness hc can be determined from equation (4).

h c (Ca u+srv+Ba+-ul-v+Fz
/Cau Srv Bat-u-vFz) -(6,2
00,74ut O,4vI)/(6,200,74
u-0,4v) -1・・・・・・・・・・・・・・・
-(4) Next, a ZnTe crystal layer 15 is formed on the crystal layer 14.
is formed using a molecular beam epitaxial growth method or a vapor phase epitaxial growth method. This ZnTe crystal layer 15 is made of the above-mentioned Caul Sr vI Ba 1-u
l-Vlp! Since the lattice constant is the same as that of the crystal layer 14, no misfit dislocation occurs.

Next, on this ZnTe crystal layer 15, Zny cd,
-, Te crystal layer 16 and ZnTe crystal layer 15 below it.
It is formed by molecular beam epitaxial growth or vapor phase epitaxial growth to a thickness that does not cause misfit dislocations.

When this thickness is calculated using equation (5) derived from equation (2), for example, Zny Cd of y = 0.9, -,
Te layer with 290 people, Zn with y = 0.5, cd, -,
There will be 58 people in the Te layer.

h c = (Zn, CdI-, Te/ZnTe) =
29/(1y)(person)・・・・・・・・・・(5
) Further, on this Zn, cd, -, Te crystal layer 16, Z
Using a molecular beam epitaxial growth method or a vapor phase epitaxial growth method, the CdI-5-t Hgt Te crystal layer 17 is grown to a thickness that does not cause misfit dislocations to the underlying Zn, Cd, -, Te crystal layer 16. Form.

When this thickness is calculated using equation (6) calculated from equation (2), for example, Zn y CdI- with y = 0.5
When forming a crystal layer of Zn@Cd1-Cd1-5-tH with s = 0.1 and t = 0.3 following yTe, its thickness was determined by 77 people. h c = (Zn s CdI-5-z Hgz Te
/Zn, cd, -, Te) = (583-34z
)/ (19(2-s)-t) (person)...
・(6) Further, on this Zn, Cdl-5-c Hgz Te crystal layer 17, fig, -XCd, Te crystal layer 18,
It is formed using a molecular beam epitaxial growth method or a vapor phase epitaxial growth method to a thickness that does not cause misfit dislocation with the Znm CdI-Cdl-5-tH crystal layer 7 below.

This thickness is calculated using equation (7) derived from equation (2). For example, when s = 0.1 and t = 0.3, Zn
, If a crystalline layer of HgI-zCdgTe with x = 0.3 is subsequently formed on a crystalline layer of CCdl-5-tHcTe, the thickness will be 398 people.

h c = (Hg, -XCd X Te/Zn*C
dI-5-t Hg t Te) = (58334s
1.8t)/(19s+t +x -1) (person)・
・・・・・・・・・(7) In this way, Hgt-8C formed in the top layer
d. Since the Te crystal layer 18 does not generate misfit dislocations with respect to the Si substrate 11, a good semiconductor crystal can be obtained.

FIG. 2 shows a second embodiment of the invention.

As shown in the figure, CauzSrvJa+-uz is grown on a GaAs substrate 21 using a molecular beam epitaxial growth method.
-vzFz (however, 0.74uz + 0.4vz =
0.547) is formed. In this case, for example, under the conditions of u z =0.3 and v-=0.8125, the lattice constant is equal to that of GaAs, and no misfit dislocation occurs.

In this case, the thickness is increased by, for example, 200 people.

Next, Cau3Srv3Bal-us- is deposited on the crystal layer 22.
wJz crystal layer 23, u3 from 0.3 to 0.1, v3 from 0.8215 to 0.06, respectively, 0.01.0.00
While changing the thickness by 6, the thickness of each layer is grown by 100 people.

Next, Cau4SrvJat-an-v is placed on the crystal layer 23.
A crystal layer 24 of Jz (0.74ua + 0.4V4 = 0.98) is formed to a thickness of 200 mm under the conditions of u = 0.1 and V4 = 0.06. The critical thickness in this case is hc
can be obtained from equation (8).

h e ”'(Ca u4srvJa+-un-v4F
z/Cau3SrvJa+-u3-v3Fri=(6,20-0,74u4-0.4V4)/(6,2
0-0,74u+ -0,4v+) 1...
(8) Next, a ZnTe crystal layer 25 is formed on the crystal layer 24 using a molecular beam epitaxial growth method or a vapor phase epitaxial growth method. This ZnTe
The crystal layer 25 of the above-mentioned Caut Sr vl Ba
I-ul-Vlp! Since the lattice constant is the same as that of the crystal layer 24, no misfit dislocation occurs.

Next, on this ZnTe crystal layer 25, Zn, cd,
-, Te crystal layer 26 and ZnTe crystal layer 25 below it.
It is formed by molecular beam epitaxial growth or vapor phase epitaxial growth to a thickness that does not cause misfit dislocations. When this thickness is calculated using equation (5) derived from equation (2), for example, Z of y = 0.9
ny cd, -, 290 Te layer, Z of y = 0.5
ny Cd, -.

There will be 58 people in the Te layer.

Further, on this Zn, cct, -, Te crystal layer 26, a Zn, Cdt-5-t Hgt Te crystal layer 27 is formed to a thickness that does not cause misfit dislocation with the Zn y Cd1-y Te crystal layer 26 below. It is formed using a molecular beam epitaxial growth method or a vapor phase epitaxial growth method.

When this thickness is calculated using equation (6) calculated from equation (2), for example, zn of y=0.5, Cd1-,
Te followed by Z with s = 0.1 and t = 0.3
When forming a crystal layer of n@Cdt-t-tugsTe, its thickness is 77 nm.

Further, on this Zns Cdt-5-t Hgz Te crystal layer 27, a Hgt-x Cd, Te crystal layer 28 is formed.
Zn, CdCdl-5-1HTe crystal layer 27 below
It is formed using a molecular beam epitaxial growth method or a vapor phase epitaxial growth method to a thickness that does not cause misfit dislocations. When this thickness is calculated using equation (7) derived from equation (2), for example, s = 0.1
, t = 0.3 Zn@Cd1-s-t Hg L
Hgt with x = 0.3 on top of the crystalline layer of Te
-x When forming a Cd, Te crystal layer, the thickness is 398 layers.

〔Effect of the invention〕

As described above, according to the method of the present invention, no misfit dislocation occurs in the compound semiconductor crystal formed on the substrate, so that a high-quality compound semiconductor crystal can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a semiconductor crystal formed in a first embodiment of the invention, and FIG. 2 is a sectional view showing the structure of a semiconductor crystal formed in a second embodiment of the invention. FIG. 3 is a cross-sectional view showing the structure of a semiconductor crystal formed by a conventional method. In the figure, 11 is an St substrate, 12 is a CaF crystal layer, 13 is a Ca,
Srv Ba1-u-v Ft crystal layer, 14 is Cau
+Srv+Ba+-ul-v+Fz crystal layer (however, 0.7
4ut + 0.4V+ = 0.98), 15.2
5 is a ZnTe crystal layer, 16.26 is Zny Cdl-,
Te crystal layer, 17.27 is Zns Cdl-5-z H
gc Te crystal layer, 18.28 is HgI-x CdxT
e crystal layer, 21 is a GaAs substrate, 22 is CautSrw
tBar-uz-w2Fg crystal layer (however, 0.74L1.
+0.4VZ =0.547), 23 is Cag3Srv
Ja+-u3-vzFz crystal layer, 24 is Ca uaSr
vJal-a4-v4P! Crystal layer (however, 0.14u
a + 0.4va ”0.98) Outside of Figure 2 / l + ne fr / J to J Crystal d Figure 3

Claims (1)

[Claims] A crystal layer (12) containing any one of calcium, barium or strontium fluoride, or a mixed crystal of the fluoride (13, 1) on the semiconductor substrate (11, 21).
4, 22, 23, 24) to a thickness below the critical thickness at which misfit dislocations do not occur with respect to the lower crystal layer, a zinc telluride layer (15, 25) is formed, and a zinc telluride layer (15, 25) is formed on the substrate. , mercury, cadmium, tellurium, a compound semiconductor crystal layer (16, 17
, 26, 27), a compound semiconductor crystal layer (18, 28) made of mercury, cadmium, and tellurium is further formed on the top layer.
1. A method for manufacturing a compound semiconductor crystal, characterized in that a compound semiconductor crystal is formed.