The atomic and electronic structure of the full-core threading screw dislocation in wurzite GaN was investigated using a self-consistent density-functional tight-binding calculation. It was shown that the atoms were severely strained in a hexagonal atomic core, and an extra charge transfer of 0.12e occurred at the core atoms from Ga to N, in addition to the typical charge transfer of 0.56e for bulk GaN. Filled and unfilled gap states were found to be spread over the entire band gap. The p states of the core N-atom mostly contribute to the tail states of valence and conduction bands, whereas the deep levels were heavily localized at the Ga and N core atoms. The coexistence of acceptor and donor gap states in the vicinity of the screw dislocations could be an origin of the leakage currents observed in GaN-based devices.

Local Electronic Structure of Threading Screw Dislocation in Wurtzite GaN. I.Belabbas, M.A.Belkhir, Y.H.Lee, J.Chen, A.Béré, P.Ruterana, G.Nouet: Computational Materials Science, 2006, 37[3], 410-6