Effects of indium surfactant and MgN intermediate layers on surface morphology and crystalline quality of nonpolar a-plane AlGaN epi-layers

High quality non-polar a-plane AlGaN epi-layers with dual MgN interlayers were successfully grown on semi-polar r-plane sapphire substrates with the indium-surfactant-assisted metal organic chemical vapor disposition (MOCVD) technology, and characterized with atomic force microscopy, cathode luminescence (CL), and high-resolution X-ray diffraction rocking curve. It was found that both surface morphology and crystalline quality of the non-polar AlGaN films were strongly dependent on the mass flow of indium surfactant in the MOCVD growth process. In fact, the great suppression of the deep energy level impurity-related transitions in the CL spectra indicates a significant enhancement in crystalline quality for the non-polar AlGaN films. Moreover, with the optimization of the indium surfactant mass flow, a root mean square value as small as 10.9 nm was achieved, demonstrating a remarkable improvement in surface morphology for the a-plane AlGaN epi-layer.