Monocrystalline silicon materials with the group IVA elements doped: A first-principles analysis

In this paper, the changes of lattice constant, stability and electronic structural properties of Si64-XMX (M=C, Ge, Sn, Pb; x=0, 1, 2, 3, 4) doped system under various doping types and concentrations were studied by using first principles calculation to determine the influence of doped IVA family elements on the properties of monocrystalline silicon materials. The results have shown that, the Ge, Sn and Pb doped systems will produce an expansion effect, and the lattice constant of the C doped system will decrease with the increasing of the number of doped atoms, and will have the greatest impact on the lattice constant of the system. The increase in defect formation energy is Pb>C>Sn>Ge, the Ge doped system is the easiest to synthesize; and as the doping concentration increases, the defect formation energy of each doping system also increases, indicating that high concentration doping systems are more difficult to synthesize. There are no virtual frequencies in the phonon spectra of all doped systems, and the systems are thermally stable. In addition, doping will gradually reduce the bandgap width as the doping concentration increases. The band gap characteristics will also change: when doped with C, the system will become Metalloid; when doped with Ge, the system remains unchanged; when doped with Sn and Pb, the system will become a direct band gap semiconductor. From the perspective of band gap and charge differential density, the effect of different doping elements on enhancing electronic transitions is C>Pb>Sn>Ge. This means that C doping system has the best improvement in conductivity.