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

WSi x Schottky contacts on GaN are found to exhibit improved thermal stability compared to pure W contacts. While the W contacts degrade for anneal temperatures ⩾500 °C through reaction with the GaN to form β-W2N, the WSix contacts show a stable Schottky barrier height of ∼0.5 eV as obtained from I–V measurements up to temperatures >600 °C. 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 VB0.5 (VB is the reverse bias) and suggests the presence of additional current transport mechanism in both types of diodes.