The microstructure of GaN nucleation layers grown by MOCVD on (11(2)over-bar0) sapphire versus pressure

For the last decade, GaN and related compounds have been of great interest due to the development of applications such as high brightness light-emitting diodes and laser diodes operating in the blue/green to ultraviolet range. Thin GaN films are mostly grown by metal-organic chemical vapour deposition on c-plane sapphire. However, relatively less information has been reported about the growth mechanisms of GaN on (112 0) sapphire. In this research, the evolution of morphology and defect structure in GaN thin films on the a-plane of sapphire is investigated using transmission electron microscopy. The nucleation is carried out at high temperature (1028degreesC) with variation of the pressure (20-600 torr).