Layers of GaN were grown, by means of molecular-beam epitaxy, onto Ga-polar GaN templates which had been prepared by metal-organic chemical vapour deposition. They exhibited various morphologies which depended upon the defects and growth conditions. The mean terrace widths of hexagonal growth spirals and hillocks were measured as a function of the NH3 and Ga fluxes and the substrate temperature. The results indicated that, under excess-Ga growth conditions, Ga-polar GaN(00•1) had a mean step-edge energy of 0.27eV/Ǻ.

Hexagonal Growth Spirals on GaN Grown by Molecular-Beam Epitaxy: Kinetics versus Thermodynamics. A.Parkhomovsky, A.M.Dabiran, B.Benjaminsson, P.I.Cohen: Applied Physics Letters, 2001, 78[16], 2315-7