Influence of 6H-SiC(0001) substrate surface morphology on the growth of AlN epitaxial layers

Epitaxial AlN films were grown on 6H-SiC(0001) substrates using an ammonia supersonic seeded beam. The films grown on substrates etched in hydrogen at high temperatures were shown by ion beam channeling to exhibit a higher de gree of order relative to those grown on the as-received substrates. Cross- sectional electron microscopy revealed sharper SiC-AlN interfaces with exte nded flat terraces. In particular, very few stacking mismatch boundaries we re observed to originate from the 1.5 nm steps which correspond to the 6H s tacking sequence of the substrate. (C) 1999 American Institute of Physics. [S0003-6951(99)01107-9].