The structural properties of Be substitutional acceptors and interstitial donors were investigated by using first-principles calculations which were based upon pseudopotentials and density functional theory. In p-type material, the Be interstitials acted as donors and had formation energies which were comparable to that of substitutional Be on Ga sites; which was an acceptor. Under thermodynamic equilibrium conditions, the incorporation of Be interstitials therefore resulted in severe compensation. The total-energy surface was explored in order to investigate the kinetics of Be interstitial incorporation and out-diffusion. The diffusivity of Be interstitials was highly anisotropic; with a migration barrier, in planes perpendicular to the c-axis, of 1.2eV. The barrier for motion along the c-axis was 2.9eV. Complex formation between interstitial donors and substitutional acceptors, and between H and substitutional Be, was also studied.

First-Principles Studies of Beryllium Doping of GaN. C.G.Van de Walle, S.Limpijumnong, J.Neugebauer: Physical Review B, 2001, 63[24], 245205