Long-term base current instability in AlGaAs/GaAs HBTs: physical mechanisms, modeling, and SPICE simulation

This paper provides an overview of the long-term base current instability in the AlGaAs/GaAs heterojunction bipolar transistor (HBT), which is a main mechanism governing the HBT long-term current gain drift and thus a major concern for the HBT reliability. Topics covered include: (1) types of base current instability and their underlying physical mechanisms; (2) leakage currents in the HBT and their relevance to the reliability; (3) electrothermal interaction and their impact on the HBT reliability; (4) analytic model for predicting the HBTs mean time to failure (MTTF); and (5) SPICE implementation and simulation of HBT circuit reliability. Measurements and device simulation results are also included in support of the modeling and analysis. (C) 1998 Elsevier Science Ltd. All rights reserved.