Modeling and simulation of high-level injection behavior in double heterojunction bipolar transistors

The combination of velocity saturation, and a valence band offset at the base-collector junction reduces the performance of double heterojunction bipolar transistors at high injection levels because of the formation of a retarding potential barrier. This barrier causes saturation of the transconductance, early onset of high level injection in the base, and a rapid decrease of f_T for J _C>J_K. An analytical model is developed for computation of the barrier height and the I-V characteristics. The results are in good agreement with computer simulation