Initial nitridation of gallium arsenide to promote the nucleation and epitaxy of gallium nitride (GaN) is prone to interface roughening and defect generation. This paper reports the deposition of gallium nitride (GaN) onto GaAs(100) substrates using two alternative approaches: either a low temperature aluminium nitride (AIN) buffer layer or a graded transition from gallium arsenide to gallium nitride growth. The interaction of nitrogen atoms with the GaAs(100) - c(4 x 4)As stabilized surface and the recrystallization of ALN buffer layers deposited at 400 degrees C were observed by reflection anisotropy spectroscopy and dynamic optical reflectivity. Raman spectra of the resulting films suggest the presence of mixed cubic and hexagonal GaN phases.