Structure, electronic properties, and formation mechanisms of hydrogen-nitrogen complexes in GaPyN1-y alloys,

The structure, formation energies, chemical bonding, and electronic properties of N-H complexes in the GaP0.97N0.03 alloy have been investigated by density functional theory and local density approximation theoretical methods. The achieved results closely parallel those previously found in the case of the GaAs0.97N0.03 alloy. In particular, they show that a same H-2(*)-like complex can neutralize the N effects on the GaP band structure as it does in the case of GaAsN. These results can account for the H passivation of the N effects observed in GaPN; however, they do not explain some differences in the optical behavior of hydrogenated GaPN and GaAsN. We have investigated therefore the formation mechanism of the H-2(*)-like complex. The resulting model suggests that H+ ions diffusing in the GaP (GaAs) lattice form an intermediate dihydrogen complex which then transforms into the H-2(*)-like one. Thus, the existence of the complex responsible of the N passivation is related to the presence and motion of H+ in the GaP and GaAs lattices. In this concern, we have estimated that the bonds formed by H+ in GaP are stronger than those formed in GaAs, thus inducing a slower motion of these ions in GaP. This can result in different efficiencies of the hydrogenation procedure in GaPN and GaAsN, which may account for the different behavior of the two alloys upon hydrogenation.