Mourad Boujnah

In this study, density functional theory has been used to investigate the structural and electronic properties of lead selenide (PbSe) and lead sulfide (PbS) semiconductors and their alloys PbSe1-xSx using the virtual crystal approximation (VCA) and random structure (RS) generations. The generalized gradient approximation (GGA) has been used to obtain lattice parameters which are compared with theory and experimental results. The generalized gradient approximation (MGGA) of TB09LDA has been used to calculate the electronic bands, for different sulfur compositions (0≤x≤1, ∆x=0.1). It has been observed that the transition from the valence band to the conduction band takes place at the L point, which agrees with previous theoretical investigations. It has been observed that both the bandgap and lattice parameters of the alloys obey Vegard's law. Effective band diagrams obtained from the unfolding of supercell band diagrams, reported for the first time for this system, show that the impacts of alloy disorder are low in the vicinity of the L point, indicating that the alloy composition do not appear to influence the transport phenomena. This work shows the suitability of the VCA approximation and the band unfolding method, to deal and describe the composition-dependent properties of the PbSe1-xSx pseudo binary alloys.