Transmission electron microscopy was used to investigate the characteristics of threading dislocations in GaN films grown on the (00▪1) sapphire substrates with or without the insertion of Al0.3Ga0.7N (2nm)/GaN (2nm) short-period superlattices. By using the g·b = 0 invisibility criterion, it was found that most of the threading dislocations were type-a threading dislocations in a GaN film either containing short-period superlattices or having no short-period superlattice insertion. Type a + c threading dislocations were found to nucleate through the interactions between type-a and type-c threading dislocations in GaN near to the GaN/sapphire interface. Some of the type-a threading dislocations were observed to bend along GaN basal plane because of the influence of biaxial strain near the GaN/short-period superlattice interface.

Characteristics and Interactions of Threading Dislocations in GaN Films Grown on (00▪1) Sapphire Substrates with or without Short-Period Superlattice Insertion. W.L.Wang, J.R.Gong, C.L.Wang, W.T.Liao, J.L.He, Y.C.Chi, J.B.Shi: Japanese Journal of Applied Physics, 2006, 45[9A], 6888-92