HRXRD Study of Epitaxial GaN Films Grown on ZnO Buffer Layers by Magnetron Sputtering

摘要

GaN films were deposited on ZnO buffer layers of different thicknesses over sapphire substrates by reactive sputtering of a GaAs target in 100 percent nitrogen at 700 deg C. HRXRD measurements and the corresponding micro-structural analysis show that with increase in buffer layer thickness from 25 to 200 nm, the coherence length along the growth direction remains unaffected. In contrast, along lateral direction, it decreases drastically with increase in buffer layer thickness. Over a narrow range of buffer layer thickness (50-100 nm), high quality epitaxial GaN films were grown with crystallite tilt of 0.6 - 0.7 deg and microstrain of 6 -7 X 10~(-4).