C2v nitrogen-hydrogen complexes in GaAsN revealed by X-ray absorption near-edge spectroscopy and ab initio simulations

Hydrogenation of GaAsN alloys has recently attracted great interest thanks to the possibility of passivating in a tunable way the large band gap reduction induced by N incorporation. Even if, nowadays, it is well established that the formation of N-H complexes is at the origin of N passivation, uncovering the structure of the complex responsible for the experimental observations represents a more difficult task. In this work, we combine X-ray Absorption Near Edge Spectroscopy (XANES) at the nitrogen K-edge with ab-initio simulations to investigate the atomic geometry of N-H complexes in hydrogenated GaAsN; simulations are performed in a Real Space-Full Multiple Scattering approach. We provide evidence that a dihydrogen-nitrogen complex with C2v symmetry is the most abundant species in hydrogenated GaAsN. We show that the use of very large atomic clusters and of broadening terms in the potential are necessary in order to reproduce the experimental data. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.