JPS62145736A - Liquid phase epitaxial growth - Google Patents

Abstract

PURPOSE:To prevent a GaAs substrate from being eluted into fused HgCdTe by covering the exposed part of the GaAs substrate with a protective film. CONSTITUTION:A silicon oxide or silicon nitride protective film 2 is formed on the surface of a GaAs substrate 1 selectively except the region where an epitaxial layer is made to grow by CVD. A CdTe layer 3 is formed on the exposed surface of the GaAs substrate 1 by MOCVD or MBE. A HgCdTe layer 4 is formed on the CdTe layer 3 by an LPE method, which is a dipping method. In this case, the silicon oxide or silicon nitride is hardly eluted into fused HgCdTe and protects the surface of the GaAs substrate 1 with a precise surface. Therefore, as the GaAs substrate has no exposed part, contamination of the fused HgCdTe caused by the elution of the GaAs substrate can be avoided.

Description

[Detailed Description of the Invention] [Summary] In the LPE growth method that uses a crystal substrate whose constituent elements are different from those of the epitaxially grown crystal, the substrate is coated with a protective film to prevent the substrate components from dissolving into the growth melt. Do it like this.

[Industrial application field]

The present invention relates to an LPE growth method using a crystal substrate having a different constituent element from that of the epitaxially grown crystal.

The so-called heterogeneous substrate LPE growth method, which uses a crystal substrate having a different constituent element from the epitaxially grown crystal, is used for producing HgCdTe crystals used in infrared detectors and the like. The HgCdTe LPE crystal is first produced by MOCVD on the (111) plane of a GaAs substrate, which can be produced relatively easily.
A several pm layer of CdTe@ is formed by a method or an MBE method, and then an HgCdTe layer is formed at a temperature of about 500° C. by an LPE growth method using a dipping method.

At this time, when the back surface of the GaAs substrate comes into contact with the melt, a portion of the substrate melts into the melt and is incorporated as unnecessary impurities into the epitaxial layer, making it impossible to obtain a highly pure crystal. In the HgCdTe crystal, Ga acts as an n-type impurity and As acts as an n-type impurity, making it impossible to accurately control the carrier concentration.

As described above, dissolution of the substrate into the melt is harmful, and therefore countermeasures are desired.

[Conventional technology]

FIG. 2 is a cross-sectional view illustrating the conventional LPE growth method on different substrates.
It is dipped into a melt 5 consisting of: The melt 5 is placed in a quartz reaction tube 6, maintained at about 500°C by a heater 8, and the surface of the melt 5 is covered with hydrogen or Ar gas.

When the GaAs substrate 1 is immersed at a temperature higher than the liquidus temperature of the melt, Ga and As penetrate into the l1gCdTe melt 5 and contaminate the melt 5.

[Problem that the invention seeks to solve]

The exposed portion of the GaAs substrate surface where the CdTe layer is not formed and is dipped in the melt is covered with a protective film.
Prevents elution of Ga and As into the melt.

[Means for solving the problem] The solution to the above problem is that in a liquid phase epitaxial growth method using a crystal substrate having different constituent elements from the crystal to be epitaxially grown, a region on the surface of the crystal substrate that does not require crystal growth, This is achieved by the liquid phase epitaxial growth method according to the present invention, which includes the step of coating at least the area that comes into contact with the melt with a protective film that does not react with the melt and immersing it in the melt.

[Effect]

The present invention uses a protective film such as silicon oxide or silicon nitride to
By coating the exposed parts of the substrate, Ga,
Prevents elution of As.

〔Example〕

FIGS. 1(a) to 1(d) are cross-sectional views illustrating the steps of the LPE growth method with a protective film of the present invention.

In FIG. 1(a), reference numeral 1 indicates a GaAs-based membrane having a thickness of several hundred μm.

In FIG. 1(b), a protective film 2 made of silicon oxide or silicon nitride is selectively formed on the surface of the GaAs substrate 1 in areas other than those where the lobular growth is to be performed by the CVD method.

In FIG. 1(c), a CdTe layer 3 is grown on the exposed surface of the GaAs substrate 1 by MOCVD or MBE.

In FIG. 1(d), a HgCdTe layer 4 is grown on the CdTe layer 3 by the dipping LPE growth method shown in FIG.

In this case, silicon oxide or silicon nitride is mostly ngCdT.
It does not dissolve into the melt of e and protects the GaAs substrate surface with a dense surface. Therefore, since there is no exposed portion of the GaAs substrate, no contamination of the melt due to elution of the GaAs substrate occurs.

In this embodiment, the substrate is a GaAs substrate, but a similar protective film can be used for an intermediate CdTe layer and a shrimp HgCdTe layer using an 'S+ substrate.

In addition, HgCdTe was mentioned as the melt for the epitaxial growth layer, but it is not suitable for dipping method LP where substrate elution is a problem.
The present invention can be applied to the B growth method.

〔Effect of the invention〕

The exposed part of the GaAs substrate is covered with a protective film, and the l1gCdT
Since the growth is performed while preventing the GaAs substrate from dissolving into the melt, a highly pure HgCdTe crystal can be obtained.

[Brief explanation of drawings]

FIGS. 1(a) to 1(d) are cross-sectional views illustrating the steps of the LPE growth method with a protective film according to the present invention, and FIG. 2 is a sectional view illustrating the conventional LPE growth method with a heterogeneous substrate. In the figure, 1 is the substrate, which is a GaAs substrate, 2 is a protective film, 3 is a CdTe layer, and 4 is a HgCdTe layer. ．． f)#,! Ear version LPE box table method Σ theory Moe f3'r #
Floor plan figure 2

Claims (1)

[Claims] In a liquid phase epitaxial growth method using a crystal substrate having different constituent elements from the crystal to be epitaxially grown, at least the area in contact with the melt of the area on the surface of the crystal substrate that does not require crystal growth is A liquid phase epitaxial growth method comprising the step of coating with a protective film (2) that does not react with the liquid and immersing it in the melt.