Real and reciprocal space mapping of the mosaic dispersion in self-nucleated AlxGa1−xN thin films on (00.1) sapphire

Abstract

Measures of the mosaic dispersion of a series of self-nucleated AlxGa1−xN thin films, grown by low-pressure metalorganic chemical vapor deposition in a nitrogen carrier gas, have been accumulated by a combination of reciprocal space x-ray scattering patterns and real space images from scanning tunneling and atomic force microscopies. The films are shown to be dense mosaics of highly oriented islands whose in-plane and out-of-plane orientational coherence and in-plane island size decrease with increasing x. The highly correlated reductions in island size and orientational coherence are believed to be attributable to a decrease in surface mobility of reactants, which is independent of nucleation layer or carrier gas.