Surface morphology and optical characterization of GaN grown on α-Al2O3 (0001) by radio-frequency-assisted molecular beam epitaxy

Abstract
Wurtzitic GaN epilayers have been grown on sapphire (0001) substrates by radio-frequency atomic nitrogen plasma-assisted molecular beam epitaxy.Atomic force microscopy,reflectivity, and photoluminescence measurements have been performed in order to investigate the influence of in situ and ex situannealing on the surface morphology and optical properties. We demonstrate a significant improvement in both the structural and optical quality of our GaN epilayers using in situannealed low-temperature-deposited GaN buffer layers.