The electronic structure of GaN and Ga investigated by soft x-ray spectroscopy and first-principles methods

TL;DR

This study combines soft x-ray spectroscopy and first-principles calculations to analyze the electronic structure and bonding in GaN and Ga, revealing hybridization regions and spectral features specific to GaN.

Contribution

It provides a detailed comparison of GaN and Ga electronic structures using experimental spectroscopy and advanced DFT calculations, including hybridization and spectral features.

Findings

Identification of specific hybridization regions in GaN's valence band.

Discovery of a satellite feature at -10 eV in GaN emission spectra.

Differences in spectroscopic features between GaN and Ga explained by band-structure calculations.

Abstract

The electronic structure and chemical bonding of wurtzite-GaN investigated by N 1s soft x-ray absorption spectroscopy and N K, Ga M1, and Ga M2,3 emission spectroscopy is compared to that of pure Ga. The measurements are interpreted by calculated spectra using first-principles density-functional theory (DFT) including dipole transition matrix elements and additional on-site Coulomb interaction (WC-GGA+U). The Ga 4p - N 2p and Ga 4s - N 2p hybridization and chemical bond regions are identified at the top of the valence band between -1.0 and -2.0 and further down between -5.5 and -6.5 eV, respectively. In addition, N 2s - N 2p - Ga 4s and N 2s - N 2p - Ga 3d hybridization regions occur at the bottom of the valence band between -13 and -15 eV, and between -17.0 and -18.0 eV, respectively. A band-like satellite feature is also found around -10 eV in the Ga M1 and Ga M2,3 emission from GaN, but is absent in pure Ga and the calculated ground state spectra. The difference between the identified spectroscopic features of GaN and Ga are discussed in relation to the various hybridization regions calculated within band-structure methods.