Al L-2,L-3 edge x-ray absorption spectra in III-V semiconductors: Many-body perturbation theory in comparison with experiment

We investigate core excitations of the Al 2p edge in the III-V semiconductors AlP, AlAs, AlSb, and AlN. For the latter, we consider the wurtzite, zinc-blende, and rock-salt polymorphs. First-principles calculations are performed utilizing two different approaches, which are the solution of the Bethe-Salpeter equation (BSE) as well as the supercell technique employing the core-hole approximation. In addition, measurements of the electron energy-loss near-edge structure of the metastable AlN phase are presented. We find that the relative intensities of the spectral features are better described by the BSE than by the supercell method. We analyze the character of the near-edge peaks and trace back their origin to strongly bound core excitons in the case of AlSb and rock-salt AlN.