Observations on surface morphologies and dislocations of a-plane GaN grown by metal organic chemical vapor deposition

In this study, we grew non-polar a-plane GaN thin films on r-plane sapphire using a series of growth conditions by metal-organic chemical vapor deposition. The results showed that high temperature and lowpressure conditions benefited two-dimension growth could lead to a fully coalesced a-plane GaN layer with a very smooth surface. The best surface morphology with an excellent mean roughness of 10.5 A was obtained. The different thickness AlN as a nucleation layer and the different δ/β ratio were also considered. The results revealed that the surface morphology would get worse when the thickness of nucleation layer and δ/β ratio were away from the values of optimal condition. The observation of transmission electronic microscopy shown the lowest density of threading dislocations was 1.85×10¹⁰ /cm ².