Use of high temperature hydrogen annealing to remove sub-surface damage in bulk GaN

Abstract The results of a study to use atmospheric pressure annealing in hydrogen for etching GaN to remove damage from mechanical polishing is reported. Annealing in hydrogen ambient can achieve high removal rates. However, the highest removal rates at a given temperature result in an unacceptably rough surface morphology, possibly related to surface accumulation of Ga during the etching. Lower GaN removal rates maintained smooth surfaces for unpolished GaN. Faster etch rates are always observed for damaged material, with results suggesting that such differential etching may be suppressed at higher temperatures. Both photoluminescence and optical microscopy indicate mechanical polishing damage can extend as far as 2 μm into the sample, and could be removed by hydrogen annealing.