Accurate Mobility and Energy Relaxation Time Models for SiGe HBTs Numerical Simulation

Applications in the emerging high-frequency markets more and more use SiGe hetero-junction bipolar transistors (HBTs). TCADs accurately predicting device characteristics are indispensable for HBTs development, thus efficient device simulation demands for well-calibrated models. Although commercial tools enable to simulate HBTs, reliable transport parameters are not available, as generally parameters dependence on variable germanium content are not modeled accurately. Critical issues enclose suitable modeling for mobility and energy relaxation time. Since literature is deficient in proper models, this work focuses on the development of calibrated analytical models for mobility and energy relaxation time for strained SiGe HBTs including, but not restricted to, dependence upon germanium mole fraction. Reliable experimental data, especially for strained SiGe, are hardly available, and besides, energy relaxation time requires Monte-Carlo (MC) simulations, therefore a comprehensive and experimentally verified MC transport model was applied to generate transport parameters for the hydrodynamic (HD) device simulations.