Hexagonal growth spirals on GaN grown by molecular-beam epitaxy: Kinetics versus thermodynamics

GaN grown by molecular-beam epitaxy on Ga-polar GaN templates prepared by m etal organic chemical vapor deposition shows a variety of morphologies that depend on defects and growth conditions. We measured the mean terrace widt hs of hexagonal growth spirals or hillocks versus ammonia and Ga fluxes and substrate temperature. The measurements were compared to a near equilibriu m model of the growth. The results indicate that under excess Ga growth con ditions, Ga-polar GaN(0001) has a mean step-edge energy of 0.27 eV/Angstrom . (C) 2001 American Institute of Physics.