The effects of annealing on the performance of Schottky devices on a-plane GaN/r-plane sapphire were investigated. The results show that the post-anneal Schottky barrier height (SBH) increased with increasing annealing temperature, reaching a peak increase of 43% at 500 degrees C. A further increase in the anneal temperature above 500 degrees C degraded the SBH. The ideality factor displayed a weak dependence on post-annealing temperature until rising dramatically at a post-annealing temperature of 600 degrees C. The degradation at 600 degrees C post-annealing temperature can be attributed to the formation of Nickel-Gallides. In-situ current-voltage characteristics obtained between 15 degrees C and 165 degrees C revealed that both the ideality factor and SBH were stable up to 165 degrees C with increasing in-situ measurement temperature. (C) 2010 Elsevier B.V. All rights reserved.