The effects of B and P impurities on the electronic and optical properties of Si1 − x Ge x nanowires
The effects of B and P single doping and co-doping on the substitutional impurities energies, electronic and optical properties of Si1 − x Ge x nanowires (NWs) are investigated using first-principles calculations. We demonstrated that B-P co-doping is energetically favored with respect to single B or P doping. The shifts of band edges are found: compared with undoped wires, B-doped Si1 − x Ge x NWs have the valence band edge (VBE) moving significantly towards higher energy, while in P-doped Si1 − x Ge x NWs, the conduction band edge (CBE) is downward shifted. Further analysis confirms that conduction band minimum (CBM) of doped wires is strongly localized on P atom, and valence band maximum (VBM) on B atom. Finally, optical properties of Si1 − x Ge x NWs with different dopants and various Ge concentrations are understood. Our results imply the possibility of impurity based engineering of electronic and optical properties of Si1 − x Ge x NWs.