Etching of n-GaN - Important step in device processing

Photo-assisted electrochemical (PEC) and photo-assisted electrodeless (ELPEC) etching of n-doped GaN layers grown on sapphire in a KOH based solution under illumination of Hg arc lamp is demonstrated. Smooth surfaces were obtained for a narrow range of etching conditions. It was found out that this window could be extended by using etching conditions which produced “whiskers”. For ELPEC etching final etched surfaces were much smoother with stirring but showed distinct bar objects. Such objects could be eliminated by chopped irradiation when also the etching rate decreased and smoothing of pyramidal and bar objects in the etched surfaces was observed. This effect is most probably caused by the electron-hole pair recombination suppressed at semiconductor dislocation locations.