FORMATION OF THREADING DEFECTS IN GAN WURTZITE FILMS GROWN ON NONISOMORPHIC SUBSTRATES

Possible causes of a dense network of threading defects in epitaxial h exagonal GaN films grown on various substrates are discussed. We show that these defects originate at the substrate/film interface as the bo undaries between differently stacked hexagonal domains, and are create d by surface steps on substrates nonisomorphic with wurtzite GaN. We a rgue that these defects are inherent in the epitaxy of wurtzite films on nonisomorphic substrates. As a result, isomorphic substrates such a s ZnO and GaN should be explored for wurtzite nitride growth. Possible effects of these defects on the properties of wurtzite nitrides are b riefly discussed. (C) 1995 American Institute of Physics.