External electric field induced band dispersion engineering in Si1−xGex nanowires

Abstract

Abstract The effects of external electric field F on the structures and the electronic and optical properties of (1 1 1)-oriented Si 1− x Ge x alloy nanowires (NWs) are quantitatively investigated using density functional theory. We demonstrate that F has little effect on structural composition, but can induce robust modulation of energy band dispersions by redistributing charge density and orbital levels of the NWs. The significant variations of conduction band minimum (CBM) of the alloy NWs play a key role in band engineering at lower F , while changes of valence band maximum (VBM) also become important at higher F . The incorporation of Ge atoms in the alloy NWs enhances the sensitivity of CBM and VBM to the applied F . Finally, nonlinear variation of optical properties of the alloy NWs under F is predicted and understood based on F induced band engineering. Our results suggest an effective way to externally tune band dispersion features of Si 1− x Ge x alloy NWs and may be important for potential applications in SiGe based devices at nanoscale.