Local environment of nitrogen in GaNyAs1−y epilayers on GaAs (0 0 1) studied using X-ray absorption near edge spectroscopy

X-ray absorption near-edge spectroscopy (XANES) is used to study the N environment in bulk GaN and in GaNyAs1−y epilayers on GaAs (0 0 1), for y∼5%. Density-functional optimized structures were used to predict XANES via multiple-scattering theory. We obtain striking agreement for pure GaN. An alloy model with nitrogen pairs on Ga accurately predicts the threshold energy, the width of the XANES 'white line', and features above threshold, for the given X-ray polarization. The presence of large quantitities of N-pairs may point to a role for molecular N2 in epitaxial growth kinetics.