Density-functional theory was used to investigate N-vacancy (VN) diffusion in wurtzite GaN and VN complexes with a substitutional Mg acceptor (MgGaVN). Two VN diffusion paths were identified: a perpendicular path producing movement perpendicular to the c axis and a diagonal path producing movement both perpendicular and parallel to the c axis. The VN charge state was found to affect strongly the diffusion activation energies; which ranged from 2.49eV for VN+3 to 3.55eV for VN+1 along the perpendicular path and from 2.65eV for VN+3 to 3.96eV for VN+1 along the diagonal path. Two bound MgGaVN configurations were identified: a parallel configuration with VN located next to MgGa and along the c axis from it, and a perpendicular configuration with VN located next to MgGa and transverse to the c axis from it. The binding energies ranged from 0.29 to 0.58eV; depending upon the MgGaVN configuration and charge state. The results were used to evaluate a proposed process which involved MgGaVN dissociation and VN diffusion.

N Vacancy Diffusion and Trapping in Mg-Doped Wurtzite GaN. A.F.Wright, T.R.Mattsson: Journal of Applied Physics, 2004, 96[4], 2015-22