Analytical Modeling of Base Transit Time in SiGe ‐ HBTs Considering Recombination Effects Under Intermediate Injection Levels

ABSTRACT Analytical models of base transit time for SiGe‐HBTs usually neglected carrier recombination in the base under the assumption of very thin base. The validity of this assumption is questionable under intermediate injection level (IIL) condition, which is common for highly‐scaled devices operating in the high‐current regime. However, consideration of recombination in the base along with various nonideal physical models reported in the literature under IIL condition leads to the analytical intractability of the governing differential equation (GDE). Therefore, this work intends to develop an analytically tractable ‐ model of SiGe‐HBTs applicable under IIL conditions. The model also considers the effects of base width modulation (BWM) on to simulate the effects of the base pushout phenomena usually occurred at high‐current regime. Close match of the simulated model data and experimentally measured data for the collector current density, total transit time, unity gain‐bandwidth cutoff frequency and maximum frequency of oscillation validates the model quite well. It is noteworthy that significant deviation from the measured data has been observed for the model that does not consider recombination at high‐current regime. Therefore, the proposed model not only provides the justification of the consideration of the effects of carrier recombination in the base to develop analytical model but also shows the practical significance of the developed model to guide the device engineers to design modern highly‐scaled SiGe‐based HBT devices operating in the high current regime, thereby meeting the requirement of sustainable industrialization to facilitate sustainable development goal 9 (SDG 9).