Thermal stability of W ohmic contacts to <i>n</i>-type GaN

Abstract

W was found to produce low specific contact resistance (ρc∼8.0×10−5 Ω cm2) ohmic contacts to n+-GaN (n=1.5×1019 cm−3) with limited reaction between the metal and semiconductor up to 1000 °C. The formation of the β–W2N and W–N interfacial phases were deemed responsible for the electrical integrity observed at these annealing temperatures. No Ga out-diffusion was observed on the surface of thin (500 Å) W contacts even after 1000 °C, 1 min anneals. Thus, W appears to be a stable contact to n+-GaN for high temperature applications.