Nitrogen passivation by hydrogen in GaAsyN1_y and InxGa1_xAsyN1_y alloys

Previous theoretical studies on N-H complexes in GaAsN have been extended here to new di-hydrogen complex configurations and to N-H complexes in the In0.25Ga0.75As0.97N0.03 alloy. Moreover, a deeper analysis has been performed on the structure, formation energies, chemical bonding and electronic properties of old and new N-H complexes in the above alloys. On the ground of the achieved results, the existence of a novel di-hydrogen complex is predicted that is characterized by a C2v symmetry and peculiar vibrational properties. Complexes with this symmetry are not stable in N-free GaAs. Further, we propose a sound model for the N passivation founded on the characteristics of the electronic states and the local atomic relaxations induced by the N-H complexes. This model explains why the N passivation is not achieved in the case of monohydrogen complexes and realized through the formation of the N-H dihydrogen complexes. Finally, it is suggested that different N-H complexes (and different vibrational spectra) should be observed in hydrogenated p-type and n-type N-containing alloys.