Synergy Effect of Xenon Plasma Ions and Ultraviolet Lights on GaN Etch Surface Damage and Modification

Surface damage/modification of n-GaN by Xe plasma etching has been investigated for a variety of gas pressures and etching times, using an experiment and a simulation. The result has been compared with that for the Kr plasma etching. The surface morphology etched by the Xe plasma is dependent on gas pressure and etching time. At a low gas pressure (10 mTorr), where there is no UV light emission from the plasma, the surface morphology is observed to be as smooth as that of the as-grown surface, and is independent of etching time. At a high gas pressure (50 mTorr), where there is the UV radiation emission resulting from XeII, there are defects on the etched surface when the etching time increases (200 min), which would probably result from synergy effect of the Xe plasma ions and UV radiations. This result is significantly different from that etched by the Kr plasma which does not change from that of the as-grown surface. The simulation also shows that the Ga/N ratio at the surface etched by the Xe plasma is lower than that by the Kr plasma, which would be related to the difference between the surface morphologies by these two plasmas.