Mechanism for enhanced single-crystal GaN growth in the C-assisted Na-flux method

First-principles molecular dynamics simulations are used to examine the effect of C addition in Na-flux growth of GaN. The mechanism for suppression of polycrystalline growth and the enhancement of single-crystal growth was identified by systematically calculating activation free energies for the formation and dissociation of C-N bonds. The energy barrier for C-N dissociation in a Ga-Na melt is >= 3 eV; thus, dissociation is inhibited and the growth of polycrystals is suppressed. However, at kink sites at a Na/GaN interface with excess Ga atoms, the barrier is only similar to 1.0 eV, allowing C-N dissociation and growth of GaN single crystals. (C) 2016 The Japan Society of Applied Physics