Anisotropic spectroscopy of nitrogen K-edge in group-III nitrides

Ab initio calculation of nitrogen K-edges for use in the core-level spectroscopy of industrially important group-III nitrides (AlN, GaN, InN) has been carried out systematically including the core-hole effect. The theoretical spectra for transition into final states with px,y and pz symmetries are in good agreement with the available anisotropic electron energy-loss measurements. Our spectra can be used as "fingerprints" to characterize the group-III nitrides, for example, not only to distinguish between different polymorphs of group-III nitrides, but also to identify the presence of surface oxidation. We have also presented our simulated results in terms of an orientation-average spectrum and a sample orientation-dependent dichroic spectrum for future reference.