pMOSFET Performance Enhancement With Strained $\hbox {Si}_{1 - x}\hbox {Ge}_{x}$ Channels

The inversion-layer hole mobility in MOSFETs with thin silicon-germanium (Si_1-xGe_x) channels grown pseudomorphically on Si is calculated using a self-consistent 6 × 6 k ·p Poisson-Schrödinger mobility simulator calibrated to experimental and simulation data. The addition of uniaxial compressive stress to the inherent biaxial compressive strain of the pseudomorphic Si_1-xGe_x layer is found to further enhance hole mobility by up to 2.5×. Two-dimensional device simulations are used to assess the benefit of the Si_1-xGe_x heterostructure channel for boosting the ON-state current (I_on) of p-channel MOSFETs with a gate length (L_g) of 18 nm; the results show a moderate (10%-40%) improvement over a bulk-Si MOSFET.