Local environment of Nitrogen in GaN{y}As{1-y} epilayers on GaAs (001)   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 GaN{y}As{1-y} epilayers on GaAs (001), 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 N-pairs may point to a role for molecular N_2 in epitaxial growth kinetics. 
J. A. Gupta, M. W. C. Dharma-wardana (NRC Canada), A. J\"urgensen,   E.D. Crozier, J.J. Rehr, M.Prange