Direction dependent homoepitaxial growth and bandgap of GaN nanowires

Abstract

ABSTRACT Here, we report a direct synthe sis approach for obtaining GaN nanowires with control on growth directions: or c-direction, and or a-direction, on amorphous substrates. The direct nitridation of Ga droplets using either dissociated ammonia or N 2 /H 2 plasma resulted in GaN nanowires with growth direction; and the vapor transport of controlled (low) amounts of Ga flux in the presence of dissociated ammonia resulted in GaN nanowires with growth direction. In both cases, the resulting GaN nanowires have diameters as small as 20 nm and lengths exceeding one hundred microns. Photoluminescence measurements showed that the bandgap of wires blue-shifted by 50 meV from the wires with direction. Homo-epitaxial growth studies onto the pre-synthesized a-direction GaN nanowires led to belt or ribbon shaped morphologies. Homo-epitaxial growth onto c-direction wires developed micro hexagonal prism morphologies. The island growth morphologies observed on the hundred micron long, sub 30 nm size nanowires suggest that the surface transport of adatoms on c-direction wires exhibit ballistic transport or “one-dimensional” transport with mean di stances over several tens of microns. Keywords: Gallium nitride, nanowires, homo-epitaxy, surface diffusion