Ga self-interstitials in GaN investigated by ab-initio calculations of the electronic g-tensor

In GaN, an exceptionally important role is played by Ga-interstitials being mobile at room temperature: Despite rather large formation energy, they have been observed in irradiated uurtzite-GaN: at least two similar, but clearly distict ODEPR-signals L5 and L6/L6* have been identified (via exceptionally large, nearly isotropic hyperfine splittings of about 4 GHz) as interstitial Ga-i(2+) in two diffent lattice configurations. However, judging from experimental data and total energy calculations alone, the exact microscopic configuration remains unclear. In this theoretical work, the situation is elucidated by ab-initio calculating the complete set of EPR 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 (GI-PAW) approach. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.