X-ray absorption spectra of In x Ga1-x N alloys with insight from atom-specific simulations

We report N-K-edge x-ray absorption near-edge spectra of a set of InxGa1-xN alloy epilayers with 0.36<=x<=0.87, including linear dichroism effects. Careful experimental and data treatment procedures lead to consistent variations of spectral features with In concentration and sample orientation with respect to the direction of linear polarization of the x-ray beam. Insight into the origin of spectral features is provided by a combination of ab initio simulations of the equilibrium structure and atom-by-atom spectral simulations. The relation between the spectral lineshape and the variations in the composition of the first coordination shell and the corresponding local structural distortions is discussed.