Group III-V nitride-based semiconductor substrate and method of making same

Abstract

A method of making a group III-V nitride-based semiconductor substrate has the steps of: providing a first crystal substrate; placing the first crystal substrate on a susceptor; holding down the first crystal substrate on the susceptor; and growing a first group III-V nitride-based semiconductor crystal on the first crystal substrate.

Description

[0001] The present application is based on Japanese patent application No. 2005-113416, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to a group III-V nitride-based semiconductor substrate and a method of making the same. [0004] 2. Description of the Related Art [0005] GaN-based compound semiconductors such as gallium nitride (GaN), indium gallium nitride (InGaN) and aluminum gallium nitride (AlGaN) attract attention for a material of blue light emitting diode (LED) or laser diode (LD). Further, since the GaN-based compound semiconductors have a good heat resistance and environment resistance, they have begun to be applied to other electronic devices. [0006] At present, a substrate used widely to grow GaN is sapphire. In general, a method is used in which GaN is epitaxially grown on a sapphire single crystal substrate by MOVPE (metalorganic vapor phase epitaxy) etc. [0007]...

AI Technical Summary

Benefits of technology

[0015] It is an object of the invention to provide a group III-V nitride-based semiconductor substrate and a method of the same that can offer an improved uniformity in in-plane property.

[0059] The invention is featured in that, in the growth of nitride semiconductor by HVPE (hydride vapor phase epitaxy), temperature of crystal during the growth is kept uniform to make the growth speed and impurity concentration uniform. Thereby, various properties such as dislocation density to be varied therewith can be significantly enhanced.

[0062] Second, the non-uniformity in growth temperature causes a warp in crystal. Thereby, the in-plane dispersion of crystal axes may be increased.

[0068] (C) The underlying substrate is to have an increased thickness. Thereby, its rigidity can be enhanced to prevent the deformation by a stress.

[0069] (d) An opaque body is to be disposed under the underlying substrate For example, a carbon thin layer is coated on the bottom face of the underlying substrate. Thereby, even when the underlying substrate locally gets away from the susceptor, the reduction of temperature can be prevented at that portion

[0075] Using a substrate of the invention, a device epitaxial layer with a large surface area can be fabricated in a high uniformity. Therefore, it is very advantageous in economical aspect. Thus, in the invention, the in-plane non-uniformity of the substrate properties caused by the non-uniformity of the growth temperature can be eliminated. Thereby, a group III-V nitride semiconductor substrate can be obtained with a high quality and a high uniformity.

Problems solved by technology

First, the non-uniformity in growth temperature causes non-uniformity in growth speed.

Furthermore, if the growth speed is varied, a dopant introduction density is also varied, which causes non-uniformity in carrier concentration and electrical resistivity.

In addition, although a GaN crystal after growth is generally polished at both faces thereof to be used for a wafer, the in-plane polishing speed may be non-uniform due to a difference in dislocation density or carrier concentration and, thereby, the final thickness may be non-uniform.

Second, the non-uniformity in growth temperature causes a warp in crystal.

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