In GaN, an exceptionally important role was played by Ga-interstitials being mobile at room temperature. Despite rather large formation energy, they were observed in irradiated wurtzite-GaN: at least 2 similar, but clearly distinct ODEPR-signals L5 and L6/L6* were identified (via exceptionally large, nearly isotropic hyperfine splittings of about 4GHz) as interstitial Gai2+ in 2 different lattice configurations. However, judging from experimental data and total energy calculations alone, the exact microscopic configuration remains unclear. Here, the situation was elucidated by ab initio calculation of the complete set of electron paramagnetic resonance parameters, hyperfine splittings as well as g-tensors, for the stable structural configurations of the Ga-interstitial using a gauge-including projector augmented plane wave approach.

Ga Self-Interstitials in GaN Investigated by ab initio Calculations of the Electronic g-Tensor. U.Gerstmann, A.P.Seitsonen, F.Mauri: Physica Status Solidi B, 2008, 245[5], 924-6