Non-polar a-plane GaN thin films were grown onto r-plane sapphire using a series of growth conditions by metal-organic chemical vapor deposition. The results showed that high temperature and low-pressure conditions benefited 2-dimensional 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 10.5Å 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 1.85x1010/cm2.

Observations on Surface Morphologies and Dislocations of a-Plane GaN Grown by Metal Organic Chemical Vapor Deposition. T.S.Ko, T.C.Wang, H.G.Chen, R.C.Gao, G.S.Huang, T.C.Lu, H.C.Kuo, S.C.Wang: Physica Status Solidi C, 2007, 4[7], 2510-4