A Physically-Based Electron Mobility Model for Strained Si Devices

A model describing the mobility tensor for electrons in strained Si layers as a function of strain is presented. It includes the effect of strain-induced splitting of the conduction band valleys in Si, inter-valley scattering, and doping dependence. The dependence of the electron mobility components on the orientation of the underlying SiGe layer is taken into account by performing a transformation of the strain tensor from the interface coordinate system to the principal coordinate system. In order to validate the model, Monte Carlo simulations were performed and the results obtained have been fit to experimental data which are available mainly in the form of piezo-resistance coefficients. Results obtained from the model exhibit very good agreement with the Monte Carlo results for all strain levels and substrate orientations. The model is suitable for implementation into any conventional TCAD simulation tool.