We have investigated the growth of GaN on silicon by low-pressure metal organic chemical vapor deposition. Good quality GaN layers are grown on silicon(111) using an AlAs nucleation layer. AlAs is thermally stable even at 1050 °C and, unlike GaN and AlN buffer layers, the formation of SiNx on the Si surface is prevented. Single crystalline GaN films are obtained by introducing a thin low-temperature GaN buffer layer grown on the AlAs nucleation layer. The GaN layers are characterized by x-ray diffraction, atomic force microscopy, secondary ion mass spectroscopy, photoluminescence, and cathodoluminescence. © 1999 American Institute of Physics.