GaN crystal substrate

Abstract

A GaN crystal substrate has a crystal growth surface on which a crystal is grown, and a rear surface opposite to the crystal growth surface. The crystal growth surface has a roughness Ra(C)of at most 10 nm, and the rear surface has a roughness Ra(R) of at least 0.5 μand at most 10 μm. A ratio Ra(R)/Ra(C) of the surface roughness Ra(R) to the surface roughness Ra(C) is at least 50. Thus, a GaN crystal substrate of which front and rear surfaces are distinguishable from each other is provided, without impairing the morphology of a semiconductor layer grown on the GaN crystal substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic top view showing one embodiment of a GaN crystal substrate according to the present invention.

FIG. 1B is a schematic side view corresponding to FIG. 1A.

FIG. 1C is a schematic bottom view corresponding to FIG. 1A.

FIG. 2A is a schematic top view showing another embodiment of a GaN crystal substrate according to the present invention.

FIG. 2B is a schematic cross-sectional view along IIB in FIGS. 2A and 2C.

FIG. 2C is a schematic bottom view corresponding to FIG. 2A.

FIG. 3A is a schematic top view showing still another embodiment of a GaN crystal substrate according to the present invention.

FIG. 3B is a schematic cross-sectional view along IIIB in FIGS. 3A and 3C.

FIG. 3C is a schematic bottom view corresponding to FIG. 3A.

FIG. 4A is a schematic top view showing still another embodiment of a GaN crystal substrate according to the present invention.

FIG. 4B is a schematic cross-sectional view along IVB in FIGS. 4A and 4C.

FIG. 4C is a schematic bottom view corresponding to FIG. 4A.

FIG. 5A is a schematic top view showing still another embodiment of a GaN crystal substrate according to the present invention.

FIG. 5B is a schematic cross-sectional view along VB in FIGS. 5A and 5C.

FIG. 5C is a schematic bottom view corresponding to FIG. 5A.

FIG. 6A is a schematic top view showing still another embodiment of a GaN crystal substrate according to the present invention.

FIG. 6B is a schematic cross-sectional view along VIB in FIGS. 6A and 6C.

FIG. 6C is a schematic bottom view corresponding to FIG. 6A.

FIG. 7A is a schematic top view showing still another embodiment of a GaN crystal substrate according to the present invention.

FIG. 7B is a schematic cross-sectional view along VIIB in FIGS. 7A and 7D.

FIG. 7C is a schematic cross-sectional view along VIIC in FIGS. 7A and 7D.

FIG. 7D is a schematic bottom view corresponding to FIG. 7A.

FIG. 8A is a schematic top view showing still another embodiment of a GaN crystal substrate according to the present invention.

FIG. 8B is a schematic cross-sectional view along VIIIB in FIGS. 8A and 8D.

FIG. 8C is a schematic cross-sectional view along VIIIC in FIGS. 8A and 8D.

FIG. 8D is a schematic bottom view corresponding to FIG. 8A.

FIG. 9A is a schematic enlarged cross-sectional view where a differently oriented crystal region is a c-axis reversed crystal region.

FIG. 9B is a schematic enlarged cross-sectional view where a differently oriented crystal region is a polycrystal region.

FIG. 10 is a schematic cross-sectional view showing one embodiment of a manufacturing method of a GaN crystal substrate including as a part thereof a c-axis reversed crystal region as a differently oriented crystal region.

FIG. 11 is a schematic cross-sectional view showing one embodiment of a manufacturing method of a GaN crystal substrate including as a part thereof a polycrystal region as a differently oriented crystal region.

Claims

1. A GaN crystal substrate, having: a crystal growth surface on which a crystal is grown; anda rear surface opposite to said crystal growth surface, whereinsaid crystal growth surface has a roughness Ra(C) of at most 10 nm, andsaid rear surface has a roughness Ra(R) of at least 0.5 μm and at most 10 μm, anda ratio Ra(R)/Ra(C) of said surface roughness RaR) to said surface roughness Ra(C) is at least 50.

2. The GaN crystal substrate according to claim 1, further comprising a laser mark formed at said rear surface, whereinsaid laser mark is formed to be indicative of an arbitrarily specified crystal orientation.

3. A GaN crystal substrate, comprising: a matrix crystal region; anda differently oriented crystal region including a crystal that is different in at least one crystal axis from a crystal of said matrix crystal region, whereinsaid differently oriented crystal region is formed to have a shape indicative of an arbitrarily specified crystal orientation.

4. The GaN crystal substrate according to claim 3, wherein said differently oriented crystal region penetrates said substrate in thickness direction,said substrate has a crystal growth surface on which a crystal is grown, and a rear surface opposite to said crystal growth surface, andfirst and second patterns of said differently oriented crystal region appearing on said crystal growth surface and said rear surface of said substrate, respectively, are different from each other in relation to an outer shape of said substrate.

5. The GaN crystal substrate according to claim 3, wherein said differently oriented crystal region is a c-axis reversed crystal region formed by a crystal that is identical to a crystal of said matrix crystal region in a-axis orientation and that is reverse to the crystal of said matrix crystal region in c-axis orientation.

6. The GaN crystal substrate according to claim 3, wherein said differently oriented crystal region is a polycrystal region including a plurality of crystals that are different from a crystal of said matrix crystal region in a-axis orientation and that are identical to the crystal of said matrix crystal region in c-axis orientation.