Growth and Characterization of an a-Plane In_xGa_1?xN on a r-Plane Sapphire

The non-polar a-plane (1120) In_xGa_1?xN alloys with different indium compositions (0.074≤x≤0.555) were grown on r-plane (1012) sapphire substrates by metalorganic chemical vapor deposition, and the indium compositions x are estimated from x-ray diffraction measurements. The in-plane orientation of the In_xGa_1?xN with respect to the r-plane substrate is confirmed to be 1100_sapphire|| 1120_InxGa1?xN and 1101_sapphire|| 0001_InxGa1?xN. The effects of substrate temperature, reactor pressure and trimethylindium input flow on the indium incorporation and growth rate are investigated. The morphology of the a-plane In_xGa_1?xN is found to be significantly improved with the decreasing indium composition x and growth rate. Moreover, the in-plane anisotropic structural characteristics are revealed by high resolution x-ray diffraction employing azimuthal dependence, and the degree of anisotropy decreases with the increase of indium composition.