Suppression of plasma-induced damage on GaN etched by a Cl2 plasma at high temperatures

Plasma-induced damage (PID) during plasma-etching processes was suppressed by the application of Cl2 plasma etching at an optimal temperature of 400 °C, based on results of evaluations of photoluminescence (PL), stoichiometric composition, and surface roughness. The effects of ions, photons, and radicals on damage formation were separated from the effects of plasma using the pallet for plasma evaluation (PAPE) method. The PID was induced primarily by energetic ion bombardments at temperatures lower than 400 °C and decreased with increasing temperature. Irradiations by photons and radicals were enhanced to form the PID and to develop surface roughness at temperatures higher than 400 °C. Consequently, Cl2 plasma etching at 400 °C resulted optimally in low damage and a stoichiometric and smooth GaN surface.