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 <; 110 > 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, <; 100 > Si devices with a tensile strain are interestingly found to be more competitive than their <; 110 >-compressive counterparts.