A GUMMEL-POON MODEL FOR ABRUPT AND GRADED HETEROJUNCTION BIPOLAR-TRANSISTORS (HBTS)

A Gummel-Poon model for abrupt and graded GaAlAs/GaAs/GaAs heterojunction bipolar transistors (HBTs) is developed. The effect of carrier recombination at the emitter-base heterojunction, space charge region (SCR) width modulation effect, and base-widening effect at large collector currents have been considered. Results from this model are compared with numerical results, experimental results, and results from the most recent analytical models. The results show that the common-emitter current gain behavior in the low collector current region can be predicted more accurately by this model, and that interface and surface recombination affect the current gain more dominantly than the other recombination processes. Dependence of cutoff frequency on collector current obtained from the present model agrees well with the experimental results. This model can also predict both current gain and cutoff frequency falloffs at large collector current. This model can be easily implemented in the SPICE program. © 1990.