Limit of validity of the thermionic-field-emission treatment of electron injection across emitter-base junctions in abrupt heterojunction bipolar transistors

A hybrid model is developed to simulate electron transport through the emitter-base heterojunction and the base region of abrupt heterojunction bipolar transistors. The energy distribution of the injected electron flux through the emitter-base junction is calculated using a rigorous quantum-mechanical treatment of electron tunneling and thermionic emission across the spike at the emitter-base junction. The results are compared with those predicted by the conventional thermionic-field-emission model. For both models, the electron fluxes injected across the emitter-base junction are used as initial energy distributions in a regional Monte Carlo calculation to model electron transport through the base. The average base transit times are calculated using the impulse response technique as a function of the emitter-base voltage. The differences between the thermionic-field-emission model and the rigorous quantum-mechanical approaches to model electron transport through abrupt heterojunction bipolar transistors are pointed out.