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

Abstract

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 low-pressure 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 angstrom was obtained. The different thickness AlN as a nucleation layer and the different delta/beta ratio were also considered. The results revealed that the surface morphology would get worse when the thickness of nucleation layer and delta/beta ratio were away from the values of optimal condition. The observation of transmission electronic microscopy shown the lowest density of threading dislocations was 1.85x10(10) /cm(2). (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.