Characteristics and interactions of threading dislocations in GaN films grown on (0001) sapphire substrates with or without short-period superlattice insertion

Abstract

In this study, transmission electron microscopy was employed to investigate the characteristics of threading dislocations (TDs) in GaN films grown on the (0001) sapphire substrates with or without the insertion of Al0.3Ga0.7N (2 nm)/GaN (2 nm) short period superlattices (SPSLs). By using g (.) b = 0 invisibility criterion, it was found that most of the TDs were type a TDs in a GaN film either containing SPSL or having no SPSL insertion. Type a + c TDs were found to nucleate through the interactions between type a and type c TDs in GaN near the GaN/sapphire interface. Some of the type a TDs were observed to bend along GaN basal plane because of the influence of biaxial strain near the GaN/SPSL interface.