The growth of single-phase SiCAIN epitaxial films from mutually insoluble components SiC and AlN is accomplished by molecular beam epitaxy via the use of a specially designed unimolecular precursor H3SiCN. The film growth takes place on 6H-SiC(0 0 0 1) and Si(1 1 1) substrates at 750 degreesC. The growth on Si(1 1 1) does not require prior removal of the native oxide layer. In situ reaction of the oxide layer with fluxes of Al atoms and the H3SiCN precursor transforms the amorphous oxide into a Si-Al-O-N crystalline interface on which heteroepitaxy of SiCAlN proceeds. Theoretical structural models of the hexagonal SiCAlN agree well with the experimental microstructure observed in cross-sectional electron microscopy images. Calculations show a fundamental band gap at 3.2 eV for the stoichiometric SiCAlN, in agreement with photoluminescence data. (C) 2003 Elsevier Science B.V. All rights reserved.