We have investigated the electrical properties of V (20 nm)/Ti (60 nm)/Au (20 nm) contacts to Ga- and N-polar n-GaN. Regardless of the crystal polarities, all the samples exhibit similar electrical characteristics. The as-deposited samples are ohmic. However, they become nonohmic when annealed at 300-500 degrees C. The samples are ohmic again at 700 degrees C. Based on the X-ray photoemission spectroscopy and Auger electron spectroscopy results, the ohmic and degradation behaviors are explained in terms of the formation of donorlike surface defects and Ga vacancies, which are generated by dry etching, the out-diffusion of Ga, and the formation of nitride phases. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3294501] All rights reserved.