BASE AND COLLECTOR LEAKAGE CURRENTS OF ALGAAS GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS/

Base and collector leakage currents are extremely important to AlGaAs/ GaAs heterojunction bipolar transistor (HBT) dc characteristics, and a simple model to describe such currents is presented. This study sugge sts that these currents are originated from the electron and hole leak age through the dielectric-layer (e.g., polyimide, nitride, etc.) inte rface at the emitter-base and base-collector peripheries, as well as t hrough the n+-subcollector/semi-insulating substrate interface. Five H BTs having similar intrinsic make-ups (i.e., doping concentration and layer thickness) but different extrinsic make-ups (i.e., finger patter n, perimeter, dielectric layer, etc.) are investigated, and with the a id of the model, the possible mechanisms contributing to their leakage behavior identified.