Electronic structures of the Si(001) thin film under 〈110〉- and 〈010〉-direction uniaxial tensile strains

The electronic structures of the Si(001) ultra-thin film under various 〈110〉- and 〈010〉-direction uniaxial tensile strains have been calculated using the first-principles modified pseudofunction calculation method and a 20-layer single slab model. It can be inferred from calculated effective masses of electrons near the absolute conduction band minimum (CBM) that the 〈110〉-direction tensile strain induces enhancement and reduction of the mobility in parallel and perpendicular conduction channels, respectively. As for the 〈010〉-direction tensile strain, the effective mass results suggest that tensile strain induces reduction of the mobility in both parallel and perpendicular conduction channels. Under both 〈110〉- and 〈010〉-direction strains, the band gap decreases and near-CBM density of states increases with strain, which suggests strain induced enhancement of thermally excited electron carrier density.