JPH03141191A - Production of compound semiconductor crystal substrate - Google Patents

Abstract

PURPOSE:To reduce linear defects caused by slips in a substrate by growing an epitaxial layer at a temperature lower than the growth temperature of a mixed crystal layer when the epitaxial layer is grown on the mixed crystal layer formed by a gaseous phase epitaxial method, etc. CONSTITUTION:A mixed crystal layer is grown by a gaseous phase epitaxial method or liquid phase epitaxial method to form a mixed crystal substrate. When an epitaxial layer is grown on the substrate, the epitaxial layer is grown at a growth temperature lower than the growth temperature (Ta) of the mixed crystal layer, thereby permitting to grow the epitaxial layer in a state that thermal strains existing in the substrate are closed, prevent slips in the substrate and reduce linear defects caused by the slips.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a compound semiconductor substrate, for example, I
[[-Relates to a technique that is effective when growing a mixed crystal layer on a V group mixed crystal epitaxial substrate by vapor phase epitaxial method.

[Prior Art] Conventionally, as a semiconductor substrate for a light emitting diode, Ga
It has been proposed to grow a mixed crystal epitaxial layer such as As P or Qa I nP, and further epitaxially grow the mixed crystal layer on this mixed crystal substrate.

Conventionally, in order to reduce defects on the surface of a mixed crystal epitaxial substrate, a method has been implemented in which the mixed crystal substrate is baked in a reaction tube before epitaxial growth to remove impurities on the surface and clean it before epitaxial growth. Ta.

However, if mixed crystal epitaxial growth is performed after baking, pyramid-shaped point defects on the substrate surface can be reduced, but there is a problem in that the number of linear defects increases. When such defects appear, the light emitting efficiency of a light emitting diode fabricated using this mixed crystal substrate decreases.

The present invention has been made in view of the above problems, and its purpose is to reduce defects on the surface of an epitaxial layer grown on a mixed crystal substrate.

[Means for Solving the Problems] The present inventors believe that the cause of increase in linear defects due to epitaxial growth on a mixed crystal substrate and baking treatment prior to the epitaxial growth is as follows.
Thermal strain inherent in the mixed crystal substrate is released all at once during epitaxial growth and baking, causing slip within the crystal, and linear defects appear on the surface of the mixed crystal substrate.If the epitaxial layer is grown in this state, linear defects will occur. We thought that this might be due to the propagation of the mixed crystal layer to the epitaxial layer, so we grew and baked the mixed crystal layer and the epitaxial layer thereon under various temperature conditions.

As a result, it has been found that linear defects can be reduced by epitaxial growth at a temperature lower than that during growth of the mixed crystal layer, and by performing baking at a lower temperature than the temperature during epitaxial growth.

The present invention has been made based on the above knowledge, and when growing an epitaxial layer on a mixed crystal substrate formed by growing a mixed crystal layer by a vapor phase epitaxial method or a liquid phase epitaxial method, The epitaxial layer is grown at a growth temperature (TC) lower than the temperature (Ta). Furthermore, preferably, before starting the growth of the epitaxial layer, the mixed crystal substrate is placed in a growth apparatus at a temperature (Tc) higher than the growth temperature (Tc) of the epitaxial layer and lower than the growth temperature (Ta) of the mixed crystal layer It is proposed to perform baking treatment with Tb). Further, since the higher the baking treatment temperature Tb is, the better the cleaning effect is, the mixed crystal growth temperature Ta is preferably set as high as possible.

[Function] According to the above-described means, if the growth temperature of the mixed crystal layer is Ta1 and the growth temperature of the epitaxial layer thereon is Tc, then T
c (Since the epitaxial layer is grown under the temperature condition T a, the epitaxial layer is grown while the thermal strain inherent in the mixed crystal substrate is confined, reducing linear defects caused by slip within the substrate. can do.

Furthermore, assuming that the baking temperature is Tb, baking is performed under the temperature condition T c < T b < Ta before growing the epitaxial layer, so the surface can be cleaned without causing any slip within the substrate. I can do it,
This makes it possible to reduce not only linear defects but also point defects caused by impurities.

[Example 1] On a GaAs substrate, one GaAs, ,@lP*0me mixed crystal layer was grown using the chloride CVD method, which is one of the vapor phase epitaxial growth methods, at a growth temperature Ta of 740°C.
A mixed crystal substrate grown to a thickness of 00 μm and GaAs*+@@P grown at Ta=790°C using the same chloride CVD method.
A mixed crystal substrate was prepared by growing an 11+44 mixed crystal layer to a thickness of 100 μm.

Then, on these mixed crystal substrates, Ga is lattice-matched to the mixed crystal substrates.
The InP mixed crystal epitaxial layer was grown at a growth temperature Tc of 7.
The film was grown to 2 μm at 60° C. by MOCVD. The results are shown in Table 1.

Table 1 From this, it can be seen that when the temperature condition is Tb (Ta), the number of linear defects is reduced and the number of dislocations can be reduced.

[Example 2] QaAso on a GaAs substrate. A mixed crystal was grown using a chloride CVD method to prepare a mixed crystal substrate.

The growth temperature Ta of the GaAsP mixed crystal is 790°C.

This Ga A s P mixed crystal substrate was heated to a temperature Tb=700
℃.

After baking at 750°C and 800°C for 7 minutes, GaI was deposited on the GaAsP mixed crystal substrate using MOCVD.
An nP layer was grown to a thickness of 2 μm. GaInP growth temperature Tc
The temperature was 700°C. The results are shown in Table 2.

Table 2 Table 3 From this table, it can be seen that defects are reduced under temperature conditions that satisfy T c < T b (T a ).

[Example 3] A substrate was prepared in which a Ga,..., In,..., P mixed crystal was grown on a GaP substrate by an LPE method (liquid phase epitaxial method) using a step Guhring method. The mixed crystal growth temperature is 7
The temperature is 50°C. This Q a I n P mixed crystal substrate was baked at a temperature Tb of 680°C and 730'C.

Baked at 780°C for 15 minutes, this Ga
The same type of mixed crystal Ga is deposited on the I nP mixed crystal substrate using the MOCVD method.
,,, I n, , P layer was grown. MOCVD
The growth temperature Tc is 680°C. The results are shown in Table 3.

[Effects of the Invention] As explained above, the present invention provides a method for growing an epitaxial layer on a mixed crystal substrate formed by growing a mixed crystal layer by a vapor phase epitaxial method or a liquid phase epitaxial method. Since the epitaxial layer is grown at a growth temperature (Tc) lower than the growth temperature (Ta), the epitaxial layer is grown while the thermal strain inherent in the mixed crystal substrate is confined. It is possible to prevent slippage within the wafer and reduce linear defects caused by this.

Furthermore, before starting the growth of the epitaxial layer, the mixed crystal substrate is placed in the growth apparatus, and the epitaxial layer growth temperature (T
Since the baking treatment is performed at a temperature (Tb) which is higher than c) and lower than the growth temperature (Ta) of the mixed crystal layer, the surface can be cleaned without causing any slip within the substrate, and as a result, the linear This has the effect of reducing not only defects but also point defects caused by impurities.

March 30, 1990

Claims (2)

[Claims] (1) When growing an epitaxial layer on a mixed crystal substrate formed by growing a mixed crystal layer by a vapor phase epitaxial method or a liquid phase epitaxial method, the growth temperature (Ta) is lower than the growth temperature (Ta) of the above mixed crystal layer. 1. A method for manufacturing a compound semiconductor crystal substrate, characterized in that an epitaxial layer is grown using Tc). (2) Before starting the growth of the epitaxial layer, place the mixed crystal substrate in a growth apparatus at a temperature (Tb) higher than the growth temperature (Tc) of the epitaxial layer and lower than the growth temperature (Ta) of the mixed crystal layer. 2. The method for manufacturing a compound semiconductor crystal substrate according to claim 1, wherein the baking treatment is carried out in step 2.