SiO2 insulating layers were first deposited onto GaN by photochemical vapor deposition (photo-CVD) technology using a deuterium (D-2) lamp as the excitation source. Physical, chemical, and electrical characteristics of the Al/SiO2/GaN metal-insulator-semiconductor (MIS) capacitors are reported for the first time. It was also found that the limiting factor of SiO2 growth rate was the number of SiH4 and O-2 molecules available to provide excited Si and O atoms. Furthermore, it was found from high-frequency capacitance-voltage measurements that the photo-CVD SiO2/n-GaN interface state density, D-it, was estimated to be 8.4x10(11) cm(-2) eV(-1) for the photo-CVD SiO2 layers prepared at 300degreesC. With an applied field of 4 MV/cm, the oxide leakage current density was found to be only 6.6x10(-7) A/cm(2). (C) 2003 The Electrochemical Society.