GAS-SOURCE MOLECULAR-BEAM EPITAXY OF CUBIC GAN GAAS(001) USING HYDRAZINE/

Growth nucleation and evolution of morphology of GaN on (0 0 1) GaAs i s investigated as a function of the N2H4/Ga flux ratio. The use of hyd razine allows us to reach high flux ratios without causing any damage to the epitaxial layer. Epitaxial GaN is purely cubic but shows growth anisotropy dependent on the flux ratio. GaN layers grown at low flux ratios shows three-dimensional nucleation and no preferential island o rientation. With higher flux ratios the nucleation rate increases, the surface becomes smoother, and the growth anisotropy markedly increase s. The growth morphology reflects the surface anisotropy of the underl ying GaAs substrate. Cathodoluminescence measurements show that the ex citon recombination is the dominant light emission mechanism at 300 an d 77 K.