Interaction of Stacking Faults in Wurtzite a-Plane GaN on r-Plane Sapphire

The defect structure in a-plane GaN films grown on r-plane sapphire distinguishes itself significantly from the one found in c-plane GaN. Transmission electron microscopy studies oil a-plane GaN films grown by hydride vapour phase epitaxy reveal basal plane stacking faults, with a density in the range of 10(5) cm(-1) as a major planar defect in this type of growth. In addition, prismatic and pyramidal stacking faults were found lying in the {1 - 100} and {1 - 102) planes. The non-basal plane stacking faults are found in conjunction with nanopipe-like voids emerging at the film/substrate interface. It is suggested that the formation of the prismatic and pyramidal stacking faults is caused by interfacial strain during the early stage of growth.