A CRYSTALLOGRAPHIC MODEL OF (00.1) ALUMINUM NITRIDE EPITAXIAL THIN-FILM GROWTH ON (00.1) SAPPHIRE SUBSTRATE

High-quality thin aluminum nitride films were grown on different orientations of sapphire substrates by metalorganic chemical vapor deposition. (00.1) AlN thin film grown on (00.1) Al2O3 has better crystallinity than (11.0) AlN on (01.2) sapphire. Full width at half maximum of a rocking curve is 97.2 arcsec, which is the narrowest value to our knowledge. A crystallographic model between AlN thin films and sapphire substrates was proposed to explain the process of crystal growth. ''Extended atomic distance mismatch'' which is the mismatch of atomic distance for a longer period was introduced. It is shown that the mismatch is relaxed by edge-type dislocations. Extended atomic distance mismatch was used to interpret the results that (00.1) AlN has better crystallinity than (11.0) AlN, but (11.0) GaN has better crystallinity than (00.1) GaN.