Estimating the transit time of an AlyGa1−yAs HBT in the Gaussian doped base region for low to moderately high level of injection

For a Gaussian doped graded base AlGaAs Hetero-junction Bipolar Transistor (HBT), base transit time (BTT) has been determined using a suitable analytical model. Here the authors have investigated the dependency of base transit time on different physical and input parameters such as the collector current density, base emitter voltage etc. Electric field dependent carrier mobility also has been included into the analytic model and found that the base transit time worsens compared to the value found without taken the field dependent mobility into account.