Morphology and microstructure of dislocation etch pits in GaN epilayers etched by

molten KOH were investigated by atomic force microscopy, scanning electron

microscopy, and transmission electron microscopy. Three types of etch pits (α, β

and γ) were observed. The α-type etch pit exhibited an inverted trapezoidal shape,

the β one has a triangular shape, and the γ-type one has a combination of triangular

and trapezoidal shapes. TEM observation showed that α, β and γ type etch pits

originated from screw, edge and mixed-type threading dislocations, respectively.

For the screw-type threading dislocation, it was easily etched along the steps that

the dislocation terminates, and consequently, a small Ga-polar plane was formed to

prevent further vertical etching. For the edge-type threading dislocation, it was

easily etched along the dislocation line. Since the mixed-type threading

dislocations have both screw and edge components, the γ-type etch pit has a

combination of α- and β-type shapes. It was also found that the chemical

stabilization of Ga-polar surface played an important role in the formation of

various types of dislocation etch pits

Microstructure and Origin of Dislocation Etch Pits in GaN Epilayers Grown by

Metal Organic Chemical Vapor Deposition. L.Lu, Z.Y.Gao, B.Shen, F.J.Xu,

S.Huang, Z.L.Miao, Y.Hao, Z.J.Yang, G.Y.Zhang, X.P.Zhang, J.Xu, D.P.Yu:

Journal of Applied Physics, 2008, 104[12], 123525