Compositional and morphological analysis of In_xGa_1-xN/GaN epilayers

The compositional and surface morphological properties of In_xGa_1-xN epilayers with different indium content grown on GaN sublayers have been studied by x-ray diffraction (XRD), RBS, XPS and atomic force microscopy (AFM). The In_xGa_1-xN epilayers were grown on GaN by metal-organic chemical vapour deposition. Reliable x values, ranging from 0.10±0.01 to 0.22±0.01, were determined by complementary XRD and RBS investigations, and no bulk phase segregation was found by XRD. The thickness of In_xGa_1-xN epilayers was determined by RBS to be between 70 and 260 nm. In contrast to the lack of phase segregation of In_xGa_1-xN in the bulk, surface In-Ga alloy species were detected by XPS even at low indium content (x to approximately 10%), and the amount of this species increases with indium content. Indium content was also found by AFM to have a significant influence on the surface morphologies of In_xGa_1-xN. The surface root-mean-square roughness increased from 0.82 nm at x = 0.10 to 9.0 nm at x = 0.23.