Avalanche multiplication and ionization coefficient in AlGaAs/InGaAs p-n-p heterojunction bipolar transistors

The hole-initiated impact ionization multiplication factor M-p-1 and the ionization coefficient alpha (p) in AlGaAs/InGaAs p-n-p heterojunction bipolar transistors (HBTs) are presented. A large discrepancy is observed at low electric field when the measured data from the p-n-p HBTs are compared with those given from avalanche photodiode. The results show that the conventional impact ionization models, based on local electric field, substantially overestimate the hole impact ionization multiplication factor M-p-1. We believe that the hole ionization coefficient in p-n-p HBTs where significant dead space effects occur in the collector space charge region. (C) 2000 American Institute of Physics. [S0003- 6951(01)04001-3].