Scaling and strain dependence of nanoscale strained-Si p-MOSFET performance

Self-consistent fullband Monte Carlo simulations based on nonlocal empirical pseudopotential band structures including spin-orbit splitting are employed to estimate the on-current in nanoscale strained-Si p-MOSFETs. Effective gate lengths from L_eff = 75 nm down to L_eff = 25 nm and strain levels corresponding to germanium contents of up to x = 0.4 in the relaxed Si_1-xGe_x substrate are considered. It is found that the on-current continuously increases for growing substrate germanium contents. The strain-induced performance enhancement moderately decreases with scaling, but the improvement at L_eff = 25 nm still attains 20% for x = 0.4. In contrast to strained-Si n-MOSFETs, increasing the substrate germanium content beyond x = 0.2 is essential for p-MOSFET performance improvement by strain in the sub 0.1 μm regime. However, even for x = 0.4 the on-current in a strained-Si p-MOSFET is still smaller than in a corresponding unstrained-Si n-MOSFET.