Mobility enhancement in thin silicon films: Strain and thickness dependences of the effective masses and non-parabolicity parameter

A two-band kmiddotp model is used to describe the subband structure in strained thin silicon films. The model provides the dependence of the conductivity effective mass on both strain and film thickness simultaneously. The shear strain induced decrease of the conductivity effective mass is more pronounced in stressed thin silicon films. This conductivity mass decrease ensures the mobility enhancement in MOSFETs even with extremely thin silicon films. The two-band kmiddotp model also describes the non-parabolicity dependence on film thickness and on strain. The dependence of the non-parabolicity parameter on both film thickness and strain reduces the mobility enhancement due to the conductivity mass modification in advanced MOSFETs with strained ultra-thin silicon body.