GAN GROWN ON HYDROGEN PLASMA CLEANED 6H-SIC SUBSTRATES

We report epitaxial GaN layers grown on 6H-SiC (0001) substrates. A two stage substrate preparation procedure is described which effectively removes oxygen from the SiC substrate surface without the need of elaborate high temperature processing. In the first step, dangling Si bonds on the substrate surface are hydrogen passivated using a HF dip before introduction into vacuum. Second, the substrate is treated with a hydrogen plasma reducing the amount of oxygen-carbon bonding to below the x-ray photoemission detection limit. Upon heating in the molecular beam epitaxy (MBE) growth chamber, the SiC substrates are observed to have a sharp (1 X 1) reconstruction with Kikuchi lines readily visible. GaN epilayers deposited on AlN buffer layers by plasma enhanced MBE show sharp x-ray diffraction and photoluminescence peaks.