Temperature dependence of liquid-gallium ordering on the surface of epitaxially grown GaN

The three-dimensional ordering of the gallium (Ga) adlayers on GaN(0001) and (000 ) surfaces was probed using in situ X-ray scattering under MBE conditions. An ordered bilayer of Ga forms on GaN(0001) but the ordering decreases at substrate temperatures of <450 °C, consistent with the mechanism of non-equilibrium epitaxial growth. Monolayer Ga that forms on GaN(000 ) is laterally disordered and has no temperature dependence, along with droplets of excess Ga. The vertical and lateral B-factors for each Ga layer were confirmed using first-principles molecular dynamics calculations.