Patent ID: 7411226

Claim:
An indium phosphide (InP) high electron mobility transistor (HEMT) structure having improved long-term performance, the HEMT structure comprising: a semi-insulating substrate; an epitaxial structure formed on the substrate and comprising a semiconductor channel layer and an overlying semiconductor barrier layer; a metal gate structure extending into the barrier layer and forming a Schottky junction with the barrier layer, wherein an electrical voltage applied to the metal gate structure controls current flow in the channel layer, and wherein the metal gate structure comprises: a first layer in contact with the barrier layer, the first layer of the metal gate structure being molybdenum (Mo); and three additional layers of metal overlying the first layer; and wherein the first layer of the metal gate structure mitigates long-term degradation of the Schottky junction and improves long-term reliability of the HEMT structure.