Aluminum nitride (AlN) has been proposed as an alternative to oxide-based dielectrics for use in metal-insulator-semiconductor devices. In this study AlN deposition was performed on Si substrates using metallorganic molecular beam epitaxy at 325-425degreesC. The interfacial and electrical characteristics both as deposited and after rapid thermal annealing at 400 and 840degreesC were investigated. The lowest growth temperature, 325degreesC, produced partially amorphous films which did not appear to suffer from carbon or oxygen contamination. All the films deposited in this study were smooth, with root-mean-square roughnesses of typically similar to1 Angstrom. While the as-grown surface morphology and roughness were independent of growth temperature, annealing in forming gas at 400degreesC did produce slightly more surface roughening in the films grown at the higher temperatures. The lowest growth temperature produced films with significantly better capacitance-voltage (C-V) behavior than films which were completely polycrystalline. Annealing generally improved the C-V behavior but degraded the breakdown field strength values.