JPH02241039A - Growth method of epitaxial crystal - Google Patents

Abstract

PURPOSE:To prevent the generation of mutual diffusion between atom constituting a substrate and atom constituting an epitaxial layer by a method wherein, after a crystal layer formed of atom constituting the epitaxial layer of compound semiconductor crystal to be formed is previously formed on the substrate, the epitaxial layer of compound semiconductor crystal is grown on said crystal layer. CONSTITUTION:On a substrate 1, crystal layers 12, 13 are formed of atom constituting an epitaxial layer 14 of compound semiconductor crystal to be formed. Said layers 12, 13 are previously formed on the substrate 11 in the manner in which, as the result of heating at the time of epitaxial growth of the substrate 11, said layers 12, 13 mutually diffuse and turn to the same composition. Then the epitaxial layer 14 of the above-mentioned compound semiconductor crystal is grown on the crystal layers 12, 13. For example, on a sapphire substrate 11, the crystal layer 12 of CdTe is formed to be about 100 and several Angstrom thick by MOCVD method, and thereon the crystal layer 13 of HgTe is formed to be about 400Angstrom thick by MOCVD method. On the crystal layers 12, 13, the epitaxial layer 14 of Hg1-xCdxTe is grown by liquid epitaxial growth.

Description

[Detailed Description of the Invention] [Summary] A method for growing an epitaxial crystal in which atoms constituting a substrate and atoms constituting an epitaxial crystal formed on the substrate do not interdiffuse with each other, regarding a method for epitaxial growth of a compound semiconductor crystal. A crystal layer formed of atoms constituting an epitaxial layer of a compound semiconductor crystal to be formed on a substrate is formed on the crystal layer by interdiffusing the crystal layer by heating during epitaxial growth of the substrate. It is constructed by forming the epitaxial layer of the compound semiconductor crystal in advance on the substrate so as to have the same composition as the intended epitaxial layer, and then growing the epitaxial layer of the compound semiconductor crystal on the crystal layer.

[Industrial application field]

The present invention relates to a method for liquid phase epitaxial growth of compound semiconductor crystals.

Mercury, cadmium, tellurium (Hg+
A compound semiconductor crystal consisting of CdXTe) is used.

In order to obtain such a compound semiconductor crystal in a large area and in a thin layer state convenient for manufacturing a sensing element, a liquid phase epitaxial growth method or the like is used on a compound semiconductor substrate such as CdTe. Hgt-x Cd, lT
An epitaxial crystal of e is formed.

[Conventional technology]

When forming an epitaxial crystal of Hg, XCdx Te on such a CdTe substrate by a liquid phase epitaxial growth method, as shown in FIG. A melt 3 of Hg, Cd, and Te alloyed by mixing predetermined amounts of each is inserted into a heating furnace (not shown), and the temperature of the heating furnace is raised to melt the above melt. After the substrate 2 is brought into contact with the molten melt 3, the temperature of the molten melt 3 is lowered by lowering the temperature of the heating furnace, and epitaxial crystals of HgI-xCd and Te are formed on the substrate.

[Problem to be solved by the invention]

By the way, since the CdTe substrate is heated in the above epitaxial growth process, the Cd atoms constituting the substrate and the mercury (of HgI-x Cdx Te formed on the substrate)
A problem arises in that Hg and Cd atoms are interdiffused and a mutually diffused layer of Hg and Cd is formed at the interface between the substrate and the epitaxial layer as shown in FIG.

Within this interdiffusion layer, the concentration of Cd atoms and Hg atoms is diffused with a predetermined concentration gradient, and if such an interdiffusion layer exists, the interdiffusion layer will contain the desired HgI-1C
d, Te, and there are many problems such as a decrease in the detection sensitivity of the infrared detection element for a predetermined wavelength to be detected.

In the epitaxial crystal forming the above-mentioned infrared sensing element, the concentration of mercury atoms or the concentration of Cd atoms changes sharply at the interface between the substrate and the epitaxial layer, and the epitaxial layer has a predetermined composition and a predetermined thickness. It is desirable that the

In other words, in FIG. 3 above, the desired HgI-x Cdx Te
It is desirable that there is no interdiffusion layer that does not have a composition of .

The present invention solves the above-mentioned problems, and provides an epitaxial growth method that prevents mutual diffusion between atoms constituting the substrate and atoms constituting the epitaxial layer at the boundary between the substrate and the epitaxial layer. purpose.

[Means to solve the problem]

In the epitaxial growth method of the present invention that achieves the above object, a crystal layer formed of atoms constituting an epitaxial layer of a compound semiconductor crystal to be formed on a substrate is interdiffused by heating during epitaxial growth of the substrate. The compound semiconductor crystal is formed in advance on the substrate so as to have the same composition as the epitaxial layer to be formed thereon, and then the epitaxial layer of the compound semiconductor crystal is grown on the crystal layer.

By using a sapphire substrate whose main component is alumina (Al2O2), which has different constituent atoms for the epitaxial layer and the epitaxial layer, the conventional problem of diffusion of the constituent atoms of the substrate from the substrate to the epitaxial layer is prevented. do.

Furthermore, a plurality of crystal layers having different compositions, that is, CdTe and H, constituting the mixed crystal epitaxial layer to be formed on the substrate
A crystal layer of gTe is formed in advance before the growth of an epitaxial layer of g+-x Cdx Te. Then, mutual diffusion occurs between the crystal layers of CdTe and HgTe, and when these crystal layers interdifuse, HgI, lCd
Since the composition is similar to that of the epitaxially grown layer of Te, an epitaxial layer is formed in which the composition changes rapidly at the interface between the substrate and the epitaxial layer.

[For production]

The method of the present invention applies to a mixed crystal compound semiconductor crystal to be formed on a substrate for epitaxial growth, such as HgTe and CdT.
Epitaxial of Hg1-, Cd, and Te mixed crystals of e [Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

As shown in FIG.
The crystal layer 12 of dTe is MOCVD (Metal
Organic Chemical Vapor De
It is formed to a thickness of about 100 layers using the position method.

The reason for forming the CdTe crystal layer on the sapphire substrate in this way is that the Hg1-X crystal layer is formed directly on the sapphire substrate.
When an epitaxial layer of ca, Te (x""0.2) is formed, Hg+-x Cdx Te
Since the crystallinity of CdT is poor, CdT is coated on the sapphire substrate
After forming the crystal layer i12 of e, a HgTe crystal layer 13 for preventing diffusion of Cd atoms from the CdTe crystal N12 into the epitaxial layer is formed to a thickness of about 400 nm by the MOCVD method described above. When forming a mixed crystal of IgTe and CdTe, 11@Te and CdTe
If the composition ratio of each component is 8:2, HgTe and C
The mixed crystal of dTe is Hg+-x Cdx Te (x=0.2
).

Next, the substrate 11 on which the CdTe crystal layer 12 and the HgTe crystal layer 13 are laminated is placed in the epitaxial growth jig 1 shown in FIG. 2, and epitaxial growth is performed.

Then, by heating the substrate during liquid phase epitaxial growth, Cd atoms in the CdTe crystal layer 12 and Hg in the HgTe13
Even if interdiffusion of atoms occurs, the mixed crystal of CdTe and HgTe formed by the interdiffusion of these respective compound semiconductor crystals will contain the H to be epitaxially grown on the substrate.
Since the crystal is g+-x CdXTe (x=0.2), an epitaxial layer in which the boundary composition between the substrate and the epitaxial layer changes rapidly can be obtained.

In addition, since the substrate is a sapphire substrate whose main component is alumina, the l1g+-x C
The composition is different from that of dXTe crystals, and since alumina does not easily decompose even when the substrate is heated during liquid phase epitaxial growth, the atoms constituting the substrate cannot be transferred from the substrate to the epitaxial layer in the conventional method. An epitaxial layer is obtained in which diffusion is prevented and the composition of the substrate and epitaxial layer changes abruptly at the epitaxial layer growth interface.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, the atoms constituting the substrate are prevented from diffusing into the epitaxial layer formed on the substrate, so that there is no sudden diffusion of the atoms forming the substrate into the epitaxial layer formed on the substrate. The effect is that an epitaxial layer with compositional variations is formed.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a substrate for epitaxial growth used in the method of the present invention, FIG. 2 is an explanatory diagram of the liquid phase epitaxial growth method, and FIG. 3 is a diagram of an inconvenient state in the conventional method. In the figure, 11 is a sapphire substrate, 12 is a CdTe crystal layer, 13 is an ngTe crystal layer, 14 is a Hg+-x Cd, ITe epitaxial layer, and 15 is an interdiffusion layer. Figure 1: Explanation of L-phase epidaxy ψL4 power consumption Figure 2

Claims (1)

[Claims] The crystal layers (12, 13) formed of atoms constituting the epitaxial layer (14) of a compound semiconductor crystal to be formed on the substrate (11) are heated during the epitaxial growth of the substrate. ) is formed in advance on the substrate (11) so that it interdiffuses to have the same composition as the epitaxial layer to be formed thereon, and then the compound semiconductor crystal is deposited on the crystal layer (12, 13). A method for growing an epitaxial crystal, the method comprising growing an epitaxial layer (14).