NUCLEATION OF CUBIC GAN GAAS(001) GROWN BY GAS-SOURCE MOLECULAR-BEAM EPITAXY WITH HYDRAZINE/

Growth nucleation and evolution of morphology of GaN on (001) GaAs is investigated as a function of the N2H4/Ga flux ratio. The use of hydra zine allows us to reach high flux ratios without causing any damage to the epitaxial layer. Epitaxial GaN is purely cubic but shows growth a nisotropy dependent on the flux ratio. GaN layers grown at low flux ra tios show three-dimensional nucleation and no preferential island orie ntation. With higher flux ratios, the nucleation rate increases, the s urface becomes smoother, and the growth anisotropy markedly increases. The growth morphology reflects the surface anisotropy of the underlyi ng GaAs substrate. (C) 1996 American Institute of Physics.