Etch‐induced damage characteristics of n‐GaN surfaces by capacitively coupled radio frequency He and Ar plasmas

Abstract

AbstractThe surface morphology of n‐GaN etched by the He plasma is independent of gas pressure and etch time: it is observed to be as smooth as that of the as‐grown. This result is significantly different from that by the Ar plasma etch which causes surface defects at a high gas pressure (50∼100 mTorr) and long etch time (> 60 min) due to synergy effect of plasma ions and UV lights emitted. This difference would result from a difference between UV light spectra emitted: for the He plasma there is no UV light less than 380 nm in wavelength, whereas for the Ar plasma there is the UV light emission. The simulation shows that the N/Ga ratio at the surface etched by the He plasma at each gas pressure (Ga‐rich) is much lower than that by the Ar plasma. The results simulated for the He plasma are in disagreement with those measured by XPS, which would probably indicate additional removal of Ga from the Ga‐rich surface by volatilisation/evaporation due to thermal effect. For the Ar plasma, the experimental N/Ga ratio at a low gas pressure (10 mTorr) is reproduced by physical effect, whereas at the high gas pressure it is not reproduced, which would be closely related to occurrence of the surface defects. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)