Strained Si-based technology has imposed a new challenge for understanding dopant implantation and diffusion in SiGe that is often used as the buffer layer for a strained Si cap layer. In this work, we describe our latest modeling effort investigating the difference in dopant implantation and diffusion between Si and SiGe. A lattice expansion theory was developed to account for the volume change due to Ge in Si and its effect on defect formation enthalpy. The theory predicts that As diffusion in SiGe is enhanced by a factor of ∼10, P diffusion by a factor of ∼2, and B diffusion is retarded by a factor of ∼6, when compared to bulk Si. These predictions are consistent with experiment. Dopant profiles for As, P, and B were simulated using process simulators FLOOPS and DIOS. The simulated profiles are in good agreement with experiment.