Résumé:
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