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

Abstract

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 ∼1.0 eV, allowing C–N dissociation and growth of GaN single crystals.