Modeling and analysis of ZnSe-Ge HBTs

A Gummel-Poon model is developed for ZnSe-Ge-GaAs heterojunction bipolar transistors (HBTs). In this structure, undoped Ge spacers are placed at the emitter-base and collector-base junctions. Injected current components as well as bulk, spacer, and space charge recombination current components are modeled. Early voltage and bandgap narrowing effects are included in the model. The device performance was simulated and compared with the experimental results. The paper shows a good agreement between our model and the experimental results. The paper shows also that using spacers would improve the device performance. The advantages of this model is that it is analytical, compact, and can be easily implemented in CAD tool programs to simulate single or double HBTs with similar or dissimilar materials structure for the emitter and collector.