Interfacial structure of a-plane GaN grown on r-plane sapphire

The interface between a-plane GaN, grown by metal organic vapor phase epitaxy and hydride vapor phase epitaxy, and r-plane sapphire was investigated by transmission electron microscopy in [1−100] and [0001] zone axis orientations. The interfacial structure was well defined allowing a direct observation of the misfit dislocations in both orientations. An analysis of these dislocations revealed for the respective Burgers vectors a 1/32−1−10 component in the {0002} planes and a 1/20001 component in the {1−100} planes. In addition, the relative atomic column configurations in the GaN and sapphire were determined based on Bloch-wave simulations in comparison with the experimental images.