GaN etching damage by capacitively-coupled RF Ar plasma exposure is significantly dependent on gas pressure and exposure time. At a low gas pressure (10 mTorr), the N/Ga ratio decreases by the physical etching effect with increasing exposure time, while the GaN surface morphology is smooth. At a high gas pressure (50 mTorr), there are other effects such as UV radiation, by which the GaN surface morphology becomes rough as the exposure time increases from similar to 60 min. (C) 2007 Elsevier B.V. All rights reserved.