Electronic structure and chemical bonding anisotropy investigation of wurtzite AlN

Abstract

The electronic structure and the anisotropy of the AlN π and σ chemical bonding of wurtzite AlN has been investigated by bulk-sensitive total fluorescence yield absorption and soft x-ray emission spectroscopies. The measured NK, Al L1, and Al L2,3 x-ray emission and N1s x-ray absorption spectra are compared with calculated spectra using first-principles density-functional theory including dipole transition matrix elements. The main N2p-Al3p-Al 3d and N2p-Al3s hyridization regions are identified at -1.0 to -1.8eV and -5.0 to -5.5eV below the top of the valence band, respectively. In addition, N2s-Al3p and N2s-Al3s hybridization regions are found at the bottom of the valence band around -13.5 and -15eV, respectively. A strongly modified spectral shape of Al3s states in the Al L2,3 emission from AlN in comparison to Al metal is found, which is also reflected in the N2p-Al3p hybridization observed in the Al L1 emission. The differences between the electronic structure and chemical bonding of AlN and Al metal are discussed in relation to the position of the hybridization regions and the valence-band edge influencing the magnitude of the large band gap. © 2009 The American Physical Society.