Impact of step height of silicon carbide (SiC) substrates on heteroepitaxial growth of aluminum nitride (AlN) was investigated. Step-and-terrace structures with various step heights, 6 monolayer (ML), 3ML and 1ML, were formed on 6H-SiC (0 0 0 1) vicinal substrates by high-temperature gas etching. 2H-AlN layers were grown on the substrate by plasma-assisted molecular-beam epitaxy (MBE) and then these layers were characterized by atomic-force microscopy (AFM) and X-ray diffraction (XRD). High-quality AlN can be grown on SiC substrates with 6ML- and 3ML-height step, while AlN grown on SiC substrates with 1ML-height step exhibited inferior crystalline quality. A model for high-quality AlN growth on SiC substrates with 3ML-height step is proposed. (C) 2008 Elsevier B. V. All rights reserved.