| Abstract: | Heterojunction Bipolar Transistors with SiGe base and Si emitter and collector have increasingly become important in high speed applications in electronics due to better performance of these devices with a modest increase in complexity of fabrication process.Speed of these devices is mainly determined by transit time of minority carriers across the device.Base transit time is the most important component of the total transit time.An analytical model is developed here to predict the variation of base transit time with Ge content,base doping concentration,temperature,and other device parameters.Studies have been made for both uniform and exponential doping distributions with different Ge profiles in the base region.Band gap narrowing effect due to high doping concentration is also taken into account in the model. |
