Critical thickness of AlN thin film grown on Al2O3(0001)

High-quality thin aluminum nitride films of different thicknesses between 1 7 A and 1000 Angstrom, were grown on sapphire (0001) by DC-faced target spu ttering at 500 degreesC. A change in lattice constants of films due to a la ttice mismatch between films and substrates was observed. The growth mechan ism of epitaxial AIN film in the early stage was found to be consistent wit h the extended atomic distance mismatch (EADM) model. From the fitting resu lt of the lattice constant as a function of thickness based on the equilibr ium theory, the critical thickness at which dislocations are introduced int o AIN films grown on Al2O3(0001) was estimated as similar to 4.5 Angstrom.