TECHNICAL FIELD

The technical field relates to a Group III nitride substrate and a method for producing a Group III nitride crystal.

BACKGROUND

In recent years, a crystal of a Group III nitride, such as GaN, is receiving attention as a material of a light emitting diode and the like. As one of the production methods of the crystal of a Group III nitride, a flux method has been known, in which a Group III element and nitrogen are reacted in a flux of Na or the like, and a crystal is grown on a substrate. The substrate used herein is generally a sapphire substrate or the like. As another production method, a vapor phase epitaxial method has been known, such as an HVPE method (hydride vapor phase epitaxial method), in which a halide gas of a Group III element and ammonia are reacted, and a crystal is grown on a substrate, and an OVPE method (oxide vapor phase epitaxial method), in which an oxide gas of a Group III element and ammonia are reacted. In the HVPE method and the OVPE method, the substrate used is also generally a sapphire substrate or the like. However, a sapphire substrate has a lattice mismatch ratio of 13.8% to GaN, and when a Group III nitride crystal is grown on a sapphire substrate, there is a problem that crystal defects are liable to occur.

As a substrate for producing a Group III nitride, an ScAlMgO4substrate has been proposed (see, for example, Patent Literature 1). Patent Literature 1: JP-A-2015-178448

The lattice constant of the ScAlMgO4substrate has a smaller mismatch ratio than sapphire, but does not completely agree with the lattice constant of a Group III nitride. Accordingly, there is a problem that a Group III nitride crystal undergoes warpage, cracks, and crystal defects when the crystal is grown on a substrate formed of a single crystal represented by the general formula RAMgO4(wherein R represents one or a plurality of trivalent elements selected from the group consisting of Sc, In, Y, and a lanthanoid element, and A represents one or a plurality of trivalent elements selected from the group consisting of Fe (III), Ga, and Al), examples of which include an ScAlMgO4substrate.

SUMMARY

An object herein is to provide a Group III nitride crystal with high quality.

For achieving the aforementioned and other objects, there is provided, as one aspect, a Group III nitride substrate containing a base material part of a Group III nitride having a front surface and a back surface, the front surface of the base material part and the back surface of the base material part having different Mg concentrations from each other.

According to the aforementioned and other aspects, a Group III nitride substrate with high quality can be produced.

