Arsenic impurities in GaN

We present a comprehensive first-principles investigation of arsenic incorporation in GaN. Incorporation of As on the N site, which has previously been implicitly assumed, is favorable only under n-type conditions in a Ga-rich environment. Less Ga-rich conditions, and particularly p-type doping, strongly favor incorporation of As on the Ga site, where it behaves as a deep double donor. Arsenic thus acts as a compensating center, forming a real threat to acceptor doping of GaN and making p-type doping of GaAsN alloys impossible. The calculated donor levels for AsGa are consistent with luminescence lines around 2.6–2.7 eV in GaN intentionally doped with As.