STUDY OF ELECTRONIC AND OPTICAL PROPERTIES OF SILICON NITRIDE IN CRYSTALLOGRAPHIC PHASES α AND β

Abstract

We have performed a systematic study based on density functional theory (DFT) using linearized augmented plane wave method (FP-LAPW) for the calculation of the electronic and optical properties of silicon nitride (Si 3 N 4 ) in both α and β crystallographic phases. But before we do that, structural optimization has been treated calling the Birch-Murnaghan equation of state and the Hellmann-Feynman forces minimization has been done calling the PerdewBurke-Ernzerhof

potential within the generalized gradient approximation (PBE-GGA). The results have shown that electronic behavior can be affected by the variation in lattice parameters, which is viewing in bands structure and density of states spectra, knowing that all electronic properties have been evaluated using the modified Tran-Blaha potential with the local density approximation (LDA). The optimization of electronic properties has indicated that in pure silicon nitride the orbital hybridization can give the appropriate optical properties for photovoltaic application. So, in pure silicon nitride, the strong orbital hybridization leads to the large bandgap and weedy optical properties in the visible range. But after doping with Al or P as required, the calculation exhibits hoping results leading to the increase of the absorption coefficient and, in general, the optical properties. Keywords: silicon nitride, ab-initio calculation, band gap, and dielectric tensor