Thin layers of cubic GaN were grown on GaAs(1 0 0) by atmospheric pressure metalorganic vapor phase epitaxy using dimethylhydrazine (DMHy) as the nitrogen precursor. Samples fabricated at various growth conditions were characterized using atomic force microscopy. The surface morphology of the samples was clearly affected by both the growth temperature and the V/III molar ratio. Two distinct growth modes of GaN, two-dimensional (2D) and island growth (3D), were observed. k critical temperature was discovered, below which the growth was 2D, and above which 3D growth took place. This critical temperature was found to increase with increasing V/III ratio. In this work, a smooth 8 nm thick GaN layer was grown at 600 degreesC v h a V/III ratio of 100. Such layers have potential applications in GaAs heterostructure electronics. (C) 2003 Elsevier B.V. All rights reserved.