Structural Stability of Vicinal AlN(0001) and GaN(0001) Surfaces with Steps and Kinks under Metal–Organic Vapor-Phase Epitaxy Condition: A First-Principles Study

The structural stability of vicinal AlN(0001) and GaN(0001) surfaces with steps and kinks under metal-organic vapor-phase epitaxy (MOVPE) conditions is investigated on the basis of density functional calculations. The calculated surface energies and kink formation energies demonstrate that the step edges without kinks, in which N dangling bonds and N–H bonds appear, are stable compared to those with kinks over the wide range of Al and Ga chemicals for AlN and GaN surfaces, respectively. The stabilization of the surface with kinks is understood by considering the numbers of dangling bonds and N–H bonds that are generated/eliminated by the kinks. The analysis of electronic states caused by the steps and kinks is also carried out for their identification in future experiments. The results shed some insights for understanding the relationship between surface morphology and growth conditions during MOVPE of nitride semiconductors.