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

Abstract

The electronic structure and chemical bonding of wurtzite-GaN investigated by N1s soft x-ray absorption spectroscopy and NK, 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 Ga4p-N2p and Ga4s-N2p 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 -6.5eV, respectively. In addition, N2s-N2p-Ga4s and N2s-N2p-Ga3d hybridization regions occur at the bottom of the valence band between -13 and -15eV, and between -17.0 and -18.0eV, respectively. A bandlike satellite feature is also found around -10eV 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. © 2010 The American Physical Society.