Gallium nitride thin films on sapphire substrates were produced from a gallium dimethylamide-based liquid precursor by chemical solution deposition. After pyrolysis in ammonia atmosphere, films obtained from precursors with low polymer content consisted of an irregular and facetted epitaxial GaN interface layer covered by a thin layer of polycrystalline grains, whereas precursors of higher polymer concentration lead to entirely polycrystalline GaN films. At an intermediate growth stage, the formation of a gallium oxide nitride phase was observed. Epitaxial GaN growth is discussed with respect to possible material transport paths, including vapor phase transport. (C) 2002 Elsevier Science B.V. All rights reserved.