Influence of mechanical strain in Si and Ge p-type double gate MOSFETs

We theoretically investigate the impact of uniaxial strain in extremely thin Si and Ge p-type double gate transistors. Quantum transport modeling is treated using a 6-band k.p Hamiltonian and the non-equilibrium Green's function formalism including hole-phonon scattering. Based on this framework we analyze the influence of strain on current characteristics considering different transport directions and gate length's. The results first confirm the dominance of Ge in long devices (15 nm gate length) for which best electrical performances are obtained for channels along < 1 1 0 > with a uniaxial compressive strain. Situation is reversed for shorter devices (7 nm gate length) where the small effective masses of Ge deteriorate the off-regime of transistors regardless the considered strain. Due to weaker hole-phonon scattering, < 1 0 0 > Si devices with a tensile strain are interestingly found to be more competitive than their < 1 1 0 >-compressive counterparts.