Local structure of nitrogen-hydrogen complexes in dilute nitrides

We have investigated the structure of nitrogen-hydrogen complexes in GaAs1-yNy and InxGa1-xAs1-yNy dilute nitride alloys by performing x-ray absorption near-edge structure spectroscopy (XANES). We simulated the spectra based on first-principles calculations of the most recent defective structures proposed in the literature for hydrogenated materials. The comparison between the experimental data and simulations allows us to clarify that the core of the defect is a complex with C-2v structure in the neutral charge state, in agreement with the expansion of the lattice parameter measured by x-ray diffraction. Our results are compatible with the presence of H satellites bound to neighboring Ga atoms but not with complexes involving more than two H atoms bound to the same N. Nevertheless, we were not able to determine uniquely the number of H satellites, which may depend on growth conditions. Strain related to the epitaxial growth has a very little effect on the XANES spectra.