A microstructural comparison of the initial growth of AlN and GaN layers on basal plane sapphire and sic substrates by low pressure metalorganic chemical vapor deposition

Abstract

The initial growth by low pressure metalorganic chemical vapor deposition and subsequent thermal annealing of A1N and GaN epitaxial layers on SiC and sapphire substrates is examined using high resolution transmission electron microscopy and atomic force microscopy. Growth under low pressure conditions on sapphire substrates is significantly different from that reported for conventional (atmospheric pressure) conditions. Smooth, single crystal A1N and GaN layers were deposited on sapphire in the initial low temperature (600°C) growth step. Interfacial bonding and not lattice mismatch was found to be the determin ing factor for obtaining good crystallinity for the epitaxial layers as indicated by the growth results on SiC substrates.