Patent ID: 7132703

Claim:
A field-effect transistor comprising: a carrier supply layer supplying carriers; a Schottky contact layer forming a Schottky barrier; and an intermediate layer formed between the carrier supply layer and the Schottky contact layer, the intermediate layer having an electron affinity which is higher than an electron affinity of the carrier supply layer but lower than an electron affinity of the Schottky contact layer, wherein the Schottky contact layer is made of InGaP, the carrier supply layer is made of Al 0.25 Ga 0.75 As, the intermediate layer is made of Al x Ga 1-x As, where 0 ≦x ≦0.25, x denoting a composition ratio, and the composition ratio x gradually increases from the interface between the intermediate layer and the Schottky contact layer to the interface between the intermediate layer and the carrier supply layer.