Short-period superlattices of AlN/Al0.08Ga0.92N grown on AlN substrates

High-quality short-period superlattices of AlN/Al0.08Ga0.92N have been grown by gas-source molecular-beam epitaxy with ammonia on Al face of AlN (0001) substrates. A significant reduction was achieved in the dislocation density, down to 3x10(8) cm(-2). Complete removal of residual Al2O3 surface oxide is needed in order to obtain low dislocation density in homoepitaxy on AlN. We show that the presence of Al2O3 islands with the surface coverage as low as 0.2% results in increased dislocation density. (C) 2004 American Institute of Physics.