Electron Mobility Model for Strained-Si Devices

Strained-Si material has emerged as a strong contender for developing transistors for next-generation electronics, because this material system offers superior transport properties. We suggest a model describing the low-field bulk mobility tensor for electrons in strained-Si layers as a function of strain. Our analytical model includes the effect of strain-induced splitting of the conduction band valleys in Si, intervalley scattering, and doping dependence. Intervalley scattering has been modeled on the equilibrium electron distribution and the valley splitting for a given strain tensor. The effect of different substrate orientations is considered by performing coordinate transformations for the strain tensor and effective masses. Monte Carlo simulations accounting for various scattering mechanisms and the splitting of the anisotropic conduction band valleys due to strain in combination with an accurate ionized impurity scattering model were carried out to verify the results for the complete range of Ge contents and for a general orientation of the SiGe buffer layer. Our mobility model is suitable for implementation into a conventional technology CAD simulation tool.