JPS62186524A - Epitaxial wafer - Google Patents

Abstract

PURPOSE:To obtain an epitaxial wafer having an epitaxy layer with few defects, by adding a minute amount of gallium in an indium phosphite layer on an indium phosphide substrate. CONSTITUTION:On an indium phosphide substrate, one or more epitaxial layers including at least one indium phosphide layer are grown, and an epitaxial wafer is formed. At this time, a minute amount of gallium is added in the one or more indium phosphide layers. Thus, the epitaxial wafer having the epitaxy layer with few defects is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an epitaxial wafer in which a single layer or multiple layers containing indium phosphide are epitaxially grown on an indium phosphide substrate.

[Technical background of the invention and its problems]

Ni-V compound semiconductors are used in optical devices such as semiconductor lasers, photodiodes, and field effect transistors;
It is used as a material for electronic devices. In order to fabricate a device using a compound semiconductor, a compound microscopic conductor thin film is generally grown -F- or multilayer epitaxially on a single crystal substrate of indium phosphide (hereinafter referred to as "Ero-P"), gallium arsenide, or the like. Known methods for epitaxial growth include liquid phase growth, vapor phase growth, and organometallic pyrolysis vapor growth.

The characteristics of the fabricated device greatly depend on the quality of the epitaxial layer, and if there are dislocations in the epitaxial layer,
Characteristics, yield, etc. deteriorate.

Although the dislocations in the epitaxial layer do not necessarily have a one-to-one correspondence with the dislocations in the substrate, it is generally recognized that if there are fewer dislocations in the substrate, there will be fewer dislocations in the epitaxial layer.

This reduces dislocations in the epitaxial layer and improves device performance.
In order to improve yield, it is common practice to use a substrate with fewer dislocations.

In the case of InP, substrates with few dislocations can only be obtained by doping them with high concentrations of sulfur or sacrificial lead. However, when epitaxial growth is performed on a highly doped substrate, undesirable phenomena such as impurity diffusion from the substrate and autodoping may occur. On the other hand, 'I
In semi-insulating substrates used for manufacturing It field effect transistors, etc., the etch bit density, which is an index of dislocation density, is in the tens of thousands/cIIl! In order to improve device characteristics, yield, etc.

It is desirable to reduce dislocations in epitaxial layers.

[Purpose of the invention]

The present invention has been made in view of the above, and an object of the present invention is to provide an epitaxial wafer having an epitaxially grown layer with few defects even when epitaxial growth is performed on a substrate with many defects.

[Summary of the invention]

In the present invention, a trace amount of gallium (hereinafter referred to as Ga) is added when epitaxially growing InP. The present invention relates to an epitaxial wafer including one or more I'nP epitaxial layers having a low dislocation density.

In the present invention, as the concentration of Ga added is increased, I
nP epitaxial layer and I nP! ! It is expected that the lattice constant of the i-plate will shift, the strain will increase, and eventually mismatched dislocations will occur. In the experiment.

If Ga exceeds 3% of Group III members in the same phase, Ga
Since the etch pit density was 1ffi, which is the same as that in the case where no etchant is used, the amount of Ga to be added should be within a range not exceeding 3 of the group (3) in the solid phase. Furthermore, when the amount of Ga added was less than 0.08 inch, the average etch pit density became comparable to that of the substrate.

In order to obtain reliable effects, it is desirable to increase the amount of Oa added to more than 0.08% of the group (2) in the solid phase.

〔Effect of the invention〕

InP epitaxial structure 1 to which the present invention is applied.

A comparison of the density of etch bits corresponding to crystal dislocations for the conventional InP epitaxial layer revealed that when the etch pit density of the substrate was approximately 40,000 jVcm, the etch pit density of the InP epitaxial layer to which the present invention was applied was higher than that of the conventional method. The etch pit density was 1/2 to 1/4 of the etch pit density of the ERO-P epitaxial layer.

In addition, we epitaxially grew a GaInAsP layer using the conventional method on the InP epitaxial layer to which the present invention was applied, and compared the etch pit density of the top layer with a similar structure using only the conventional method. In contrast, the wafer containing the InP layer according to the invention is l/2
The etch pit density is below -) Friend.

[Embodiments of the invention]

In order to directly observe the effects of the present invention, samples with different amounts of Ga added were etched using an etching solution mixed in a ratio of 2 parts phosphoric acid to 1 part hydrobromic acid, and the etch pit densities were compared. Since etch bits generally appear in correspondence with dislocations, their density serves as a quantitative indicator of dislocations. Figure 1 shows a comparison of the etch pit densities obtained by epitaxially growing an InP single layer of several microns by varying the amount of Ga added on an InP iron-doped semi-insulating substrate with an etch pit density of approximately 400,007 cm. (By adding a small amount of Ga, the etch pit density becomes thicker (reduced), and the amount of Ga added is 2
There was not much change until it reached 91+.

However, the etch pit density rapidly increased around 3 inches and became comparable to the case where no GR was added.

Figures 2 and 3 show that the amount of Ga added is 0 and 0, respectively.
7%, and samples with olfactory thicknesses of 3.5 μm and 4 μm were etched at room temperature for 40 seconds.

Figures 4 and 5M compare the etch pit densities of the substrates after removing the grown layers of the samples in Figures 2 and 3 by etching, respectively. No difference in etch pit density was seen between FIGS. 4 and 5.

FIG. 6 shows a Ga-added I layer according to the present invention on an etch pit doped n-type substrate with an etch pit density of approximately 300,007 cm.
This is a plot of the etch pit density of the upper InP layer with respect to Ga addition of 1'' in the lower InP layer when nPii is grown to several microns and then a normal InP layer is grown to several microns. It can be seen that even in a multilayer wafer, by adding the Ga-added 102 layer to the lower layer, the etch bits in the upper layer are also reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the amount of Ga added and the etch bit density in the embodiments of the present invention, and FIG.
1. Crystal structure of ROP epitaxial rH (
Figure @3 is a microscopic photograph of the etch bit).
Figure 4 is a micrograph showing the crystal structure (etch bit) of the substrate from which the epitaxial layer of Figure 2 has been removed, and Figure 5 is a micrograph showing the crystal structure (etch bit) of the substrate. Figure 3 is a micrograph showing the crystal structure (etch bit) of the substrate from which the epitaxial layer has been peeled off, and Figure 6 is a micrograph showing the crystal structure (etched bits) of the substrate from which the epitaxial layer has been peeled off.
FIG. 3 is a diagram showing the relationship between the amount of Ga added to the lower layer at 9 o'clock and the etch bit density of the upper layer after growing normal InP on the upper layer. Agent Patent attorney Nori Chika Ken Kikuo Takehana 0.1 1.0 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) In an epitaxial wafer in which one or more epitaxial layers containing at least one indium phosphide layer are grown on an indium phosphide substrate, a trace amount of gallium is added to one or more indium phosphide layers. An epitaxial wafer featuring: (2) The epitaxial wafer according to claim 1, wherein the amount of gallium added is 0.08% to 3% relative to indium in solid phase ratio.