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 increasingx. 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. ©1995 American Institute of Physics.