METHOD FOR PRESERVING A GALLIUM NITRIDE SUBSTRATE, PRESERVED GALLIUM NITRIDE SUBSTRATE, SEMICONDUCTOR DEVICE, AND MANUFACTURING METHOD THEREFOR

摘要

Provided is a method for preserving a gallium nitride substrate (1) that has a principal surface with a plane orientation other than (0001) or (000-1) and can be used to manufacture a semiconductor device having good characteristics. Said gallium nitride substrate has a flat first principal surface (1m), and the plane orientation at an arbitrary point P on the first principal surface (1m), said point P being at least 3 mm away from the outer edge of the first principal surface, is tilted at an angle ?a, between -10° and 10°, with respect to the plane orientation of an arbitrary crystal plane (1a) tilted at an angle between 50° and 90° with respect to either a (0001) surface or a (000-1) surface (1c) at point P. In the provided method, the aforementioned gallium nitride substrate is preserved in an atmosphere having an oxygen concentration of no more than 15% by volume and a water vapor concentration of no more than 20 g/m³.