The possible cause of a dense network of threading defects in epitaxial hexagonal films which had been grown onto various substrates was considered. It was shown that these defects originated at the substrate/film interface, as boundaries between differently stacked hexagonal domains, and were created by surface steps on substrates that were non-isomorphic with wurtzite GaN. It was proposed that these defects were inherent to the epitaxy of wurtzite films on non-isomorphic substrates. It was therefore suggested that isomorphic substrates, such as ZnO and GaN, should be considered for wurtzite nitride growth.

B.N.Sverdlov, G.A.Martin, H.Morkoç, D.J.Smith: Applied Physics Letters, 1995, 67[14], 2063-5