Thermal stability of WSix and W Schottky contacts on n-GaN

WSix Schottky contacts on GaN are found to exhibit improved thermal stability compared to pure W contacts. While the W contacts degrade for anneal temperatures greater than or equal to500 degreesC through reaction with the GaN to form beta- W2N, the WSix contacts show a stable Schottky barrier height of similar to0.5 eV as obtained from I-V measurements up to temperatures >600 degreesC. The reverse leakage current in both types of diodes is considerably higher than predicted from thermionic emission and image-force-induced barrier height lowering. The reverse current density was found to vary approximately as V-B(0.5) (V-B is the reverse bias) and suggests the presence of additional current transport mechanism in both types of diodes. (C) 2003 American Institute of Physics.