Patent ID: 8017977

Claim:
A field effect transistor, comprising: a buffer layer composed of a semiconductor formed on a substrate; a channel layer composed of a GaN formed on the buffer layer; a compositionally graded layer formed on the channel layer, the compositionally graded layer consisting of: a first graded layer formed directly on the channel layer and composed of Al x Ga 1-x N whose Al mole fraction x decreases with increasing distance from the channel layer, and a second graded layer formed on the first graded layer and composed of Al y Ga 1-y N whose Al mole fraction y increases with increasing distance from the first graded layer; a recess formed in the compositionally graded layer such that a surface of the first graded layer appears within the recess, a source ohmic electrode formed on the first graded layer; a drain ohmic electrode formed on the first or second graded layer; and a gate Schottky electrode formed on the surface of the first graded layer appearing within the recess.