Local density-functional methods were used to investigate the behavior of O and O-related defect complexes at {10•0}-type surfaces. It was found that O had a tendency to segregate to the (10•0) surface. A Ga-vacancy, surrounded by three O impurities, VGa-(ON)3, was identified as being a particularly stable and electrically inert complex. It was suggested that such complexes impeded growth at the walls of nanopipes and prevented them from growing inwards. Other donor-related defect complexes; in particular, Ga vacancies surrounded by three Si atoms as second-nearest neighbors, were expected to have the same effect.

The formation of nanopipes caused by donor impurities in GaN R.Gutiérrez, M.Haugk, T.Frauenheim, J.Elsner, R.Jones, M.I.Heggie, S.Oberg, P.R.Briddon: Philosophical Magazine Letters, 1999, 79[3], 147-52