A technique based upon wet chemical etching was demonstrated that permitted the quick and accurate evaluation of edge- and screw/mixed-type threading dislocations in GaN. Large and small etch pits were formed by phosphoric acid on the etched surfaces. The large etch pits were attributed to screw/mixed threading dislocations and the small ones to edge threading dislocations, according to their locations on the surface and Burgers vectors of threading dislocations. Additionally, the origin of small etch pits was confirmed by a transmission electron microscopy. The difference in the size of etch pits was discussed in view of their origin and merging. Over-etching at elevated temperatures or for a long time may result in merging of individual etch pits and underestimating of the density of threading dislocations. Wet chemical etching has also been proved efficient in revealing the distribution of threading dislocations in epitaxial lateral overgrowth GaN.

Measurement of Threading Dislocation Densities in GaN by Wet Chemical Etching. J.Chen, J.F.Wang, H.Wang, J.J.Zhu, S.M.Zhang, D.G.Zhao, D.S.Jiang, H.Yang, U.Jahn, K.H.Ploog: Semiconductor Science and Technology, 2006, 21[9], 1229-35