The etching of a-plane GaN epilayers grown by metal–organic chemical vapour deposition

Morphology of nonpolar (1120) a-plane GaN epilayers on r-plane (1102) sapphire substrate grown by low-pressure metal–organic vapour deposition was investigated after KOH solution etching. Many micron- and nano-meter columns on the a-plane GaN surface were observed by scanning electron microscopy. An etching mechanism model is proposed to interpret the origin of the peculiar etching morphology. The basal stacking fault in the a-plane GaN plays a very important role in the etching process.