The growth of GaN nanowires by controlling the surface diffusion of Ga species on sapphire in a plasma-enhanced chemical vapour deposition system was investigated. Under nitrogen-rich growth conditions, Ga had a tendency to adsorb on the substrate surface; diffusing to nanowires and contributing to their growth. The significance of surface diffusion in the growth of nanowires was dependent upon the environment of the nanowire at the substrate surface, as well as the gas phase species and compositions. Under nitrogen-rich growth conditions, the growth rate was strongly dependent upon the surface diffusion of gallium, but the addition of 5% hydrogen to the nitrogen plasma instantly attenuated the surface diffusion effect. The gallium desorbed easily from the surface, by reaction with hydrogen. On the other hand, under gallium-rich growth conditions, nanowire growth was shown to be dominated by gas-phase deposition, with a negligible contribution arising from surface diffusion.

Controlled Surface Diffusion in Plasma-Enhanced Chemical Vapor Deposition of GaN Nanowires. W.C.Hou, F.C.N.Hong: Nanotechnology, 2009, 20[5], 055606