Electrical characteristics and thermal stability of W, WSiN, and Nb contacts to p-and n- type GaN

A comprehensive annealing study of W, WSiN, and Nb refractory contacts to both p- and n-GaN was performed. Samples were examined by current-voltage (I-V) measurements. Both W and Nb contacts to n-GaN showed rectifying characteristics with Schottky barrier heights (qoB) of 0.63 eV. For p-GaN, the I-V curves showed very leaky behavior. In contrast, I-V curves of WSiN/n-GaN were very leaky while those of WSiN/p-GaN were rectifying with qoB of 0.8 eV. The degradation temperature of both W and WSiN contacts was 700°C and that of Nb contacts was 300°C.