Momentum selectivity and anisotropy effects in the nitrogen K-edge resonant inelastic X-ray scattering from GaN

High-resolution soft X-ray emission and absorption spectra near the N K-edge of wurtzite GaN are presented. The experimental data are interpreted in terms of band structure based full-potential electronic structure calculations. The absorption spectra, compared with calculations including core hole screening, indicate partial core hole screening in the absorption process. The resonant emission spectra demonstrate pronounced dispersions of the spectral structures, identifying effects of momentum conservation due to resonant inelastic X-ray scattering (RIXS) with anisotropic electronic structure of GaN. In view of a wide range of optoelectronic applications of GaN, our findings on the momentum selectivity in RIXS can be utilized in development of GaN based nanoelectronics devices by controlling direct vs indirect band gap character of GaN nanostructures.