The effect of plasma exposure to n-type GaN surfaces was examined. Etch pits were formed as a result of preferential sputtering at the sites of threading dislocations. Dark spots which were visible before plasma exposure could be attributed to screw dislocations, while those that emerge after plasma exposure were edge dislocations. The optimum condition for revealing defects clearly was derived, and was adopted for the study of dislocations in a series of GaN epilayers grown under different conditions. A distinct trend in the dislocation density could be observed as the dopant concentration of the film varied.

Exposure of Defects in GaN by Plasma Etching. H.W.Choi, C.Liu, M.G.Cheong, J.Zhang, S.J.Chua: Applied Physics A, 2005, 80[2], 405-7