Nitrogen-hydrogen complex in GaAs{sub x}N{sub 1-x} revealed by x-ray absorption spectroscopy

GaAsN alloys belong to a class of semiconductors with fascinating physical properties. Indeed, a small amount of nitrogen incorporation in GaAs leads to a counterintuitive and large band-gap reduction, and to an unexpected sudden increase in the effective mass of electrons. Even more surprisingly, both electronic and structural changes can be reversed fully and in a tunable manner by hydrogen incorporation. In this paper, we combine x-ray absorption spectroscopy at the nitrogen edge with ab initio simulations to investigate the atomic geometry of N-H complexes in hydrogenated GaAsN. In this way, we provide experimental evidence that dihydrogen-nitrogen complexes with C{sub 2v} symmetry are the most abundant species in hydrogenated GaAsN. This finding contradicts previous predictions of 'in-line' N-H{sub 2}* complexes as the predominant species, and accounts for recent infrared absorption experiments.