First-principle study of energy-band control by cross-sectional morphology in [110]-Si nanowires

We report first-principle electronic-structure calculations that clarify roles of cross-sectional morphology in electronic structures of Si nanowires (SiNWs) with the dimension ranging from 3 nm to 6 nm. We find that quantum confinement effects cause substantial dependence of the position of the conduction-band minima on the cross-sectional shapes of NWs. It is found that the SiNW along [110] direction with the elliptic cross-section extending [001] direction has the largest number of channels within 50 meV from the conduction-band bottom, thus being a good candidate for the field effect transistor. Our LDA results are analyzed in terms of a simple model that provides an approach to design suitable cross-sectional shapes of SiNWs for the FET application.