Thermal and reverse base current effects on heterojunction bipolar transistors and circuits

Device modeling of the heterojunction bipolar transistor (HBT) has been examined. The Gummel-Poon model derived from silicon bipolar transistor is able to predict the base and collector currents of the HBT with good accuracy for negligible self- heating. The present model extends the Gummel-Poon model equations to account for self-heating using a nonlinear thermal resistance. The present model also accounts for base current reversal due to impact ionization in the collector-base depletion region. Effects of self-heating on the performance of analog circuits such as current mirrors and small-signal amplifiers are evaluated.