Mg Doping Affects Dislocation Core Structures in GaN

Aberration-corrected scanning transmission electron microscopy was used to investigate the core structures of threading dislocations in undoped GaN films with both high and low dislocation densities, and in a comparable high dislocation density Mg-doped GaN film. All a-type dislocations in all samples have a 5/7-atom core structure. In contrast, most (a + c)-type dislocations in undoped GaN dissociate due to local strain variations from nearby dislocations. In contrast, Mg doping prevents (a + c)-type dislocation dissociation. Our data indicate that Mg affects dislocation cores in GaN significantly.