Novel defect complexes and their role in the p-type doping of GaN

Hydrogen is known to play a key role in p-type doping of GaN. It is believed that H passivates Mg dopants and then is removed by annealing. We present first principles calculations in terms of which we show that the doping process is significantly more complex. Several substitutional-interstitial complexes form and can bind H, with vibrational frequencies that correlate well with hitherto unidentified observed lines. We predict that these defects, which limit doping efficiency, can be eliminated by annealing in an atmosphere of H and N prior to the final anneal that removes H.