Thin layers (300 Angstrom) of plasma enhanced chemical vapor deposited SiO2 were grown on p-GaN Schottky rectifiers at different pressures (600-900 mTorr), rf applied powers (50-400 W, 13.56 MHz) and SiH4/N2O gas flow ratios (1-12.5). Relatively small (10%) changes in reverse breakdown voltage (V-B) and ideality factor (n) were observed under all of these conditions. The main degradation mechanism appears to be creation of additional leakage paths around the periphery of the rectifying contact. Competing mechanisms involving hydrogen passivation of Mg acceptors or creation of nitrogen vacancies are less important under our conditions. (C) 2002 Elsevier Science Ltd. All rights reserved.