The thermal and plasma‐assisted nitridation of GaAs(100) using NH3has been examined employing x‐ray diffraction, Auger electron spectroscopy, and atomic force microscopy to characterize the nitrided films. All thermally nitrided films were composed of a mixture of hexagonal and cubic GaN, whereas the addition of plasma excitation produced films purely of the cubic structure. Thicknesses of the thermally nitrided films, up to 7000 A˚, increased with both increasing temperature and nitridation time. The plasma‐assisted process holds promise for the formation of templates for homoepitaxial growth of cubic GaN. ©1995 American Institute of Physics.