EPITAXIAL SUBSTRATE AND METHOD FOR MANUFACTURING EPITAXIAL SUBSTRATE

摘要

Provided is a crack-free epitaxial substrate. An epitaxial substrate is provided in which a group of group-III nitride layers are formed on a base substrate made of (111)-oriented single crystal silicon such that a (0001) crystal plane of the group of group-III nitride layers is substantially in parallel with a substrate surface of the base substrate. The epitaxial substrate includes: a buffer layer formed of a first lamination unit and a second lamination unit being alternately laminated such that each of an uppermost portion and a lowermost portion of the buffer layer is formed of the first lamination unit; and a crystal layer formed on the buffer layer. The first lamination unit is formed of a first composition layer and a second composition layer having different compositions being alternately laminated so as to increase the thickness of the second composition layer in a portion more distant from the base substrate side, to thereby cause a compressive strain to exist in the first lamination unit such that the compressive strain increases in a portion more distant from the base substrate. The second lamination unit is formed as an intermediate layer that is substantially strain-free and formed with a thickness of 15 nm or more and 150 nm or less.