Electronic structure and chemical bonding anisotropy investigation of wurtzite AlN

TL;DR

This study investigates the electronic structure and chemical bonding anisotropy of wurtzite AlN using spectroscopic techniques and first-principles calculations, revealing hybridization regions and differences from metallic aluminum.

Contribution

It provides detailed insights into the hybridization regions and bonding anisotropy of wurtzite AlN through combined experimental and theoretical analysis.

Findings

Identification of N 2p - Al 3p hybridization regions at specific energies.

Observation of modified Al 3s spectral shape compared to Al metal.

Discussion of electronic structure differences between AlN and metallic Al.

Abstract

The electronic structure and the anisotropy of the Al - N {\pi} and {\sigma} chemical bonding of wurtzite AlN has been investigated by bulk-sensitive total fluorescence yield absorption and soft x-ray emission spectroscopies. The measured N K, Al L1, and Al L2,3 x-ray emission and N 1s x-ray absorption spectra are compared with calculated spectra using first principles density-functional theory including dipole transition matrix elements. The main N 2p - Al 3p hybridization regions are identified at -1.0 to -1.8 eV and -5.0 to -5.5 eV below the top of the valence band. In addition, N 2s - Al 3p and N 2s - Al 3s hybridization regions are found at the bottom of the valence band around -13.5 eV and -15 eV, respectively. A strongly modified spectral shape of Al 3s states in the Al L2,3 emission from AlN in comparison to Al metal is found, which is also reflected in the N 2p - Al 3p 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.