Physics-based single-piece charge model for strained-Si MOSFETs

A physics-based single-piece charge model for strained-silicon (s-Si) MOSFETs from accumulation to strong-inversion regions is presented. The model is formulated from regional solutions of the well-known Pao-Sah equation and unified with interpolation functions while keeping the physics in the derived flat-band voltages that depend on the device material and structural parameters, such as band gaps, conduction and valence band offsets, Ge mole fraction, layer thickness, and doping. The model is validated by comparison with numerical devices for a wide range of Ge mole fractions and s-Si layer thicknesses. It is shown that the model accurately describes the physical behavior of the surface potentials, terminal charges and capacitances, especially charge accumulation/depletion at the s-Si/SiGe interface that gives rise to the observed "plateau" in the capacitance-voltage characteristics.