Temperature dependent common emitter current gain and collector-emitter offset voltage study in AlGaN/GaN heterojunction bipolar transistors

We have demonstrated state-of-the-art performance of AlGaN/GaN heterojunction bipolar transistors (HBTs) with a common emitter (CE) current gain of 31 at 175 K and 11.3 at 295 K. The increase in collector current and CE current gain at lower temperature can be attributed to the reduced base-emitter interface recombination current. We also observed an increase of collector-emitter offset voltage with decrease of temperature. The increase of V/sub CEOFF/ at lower temperature is related to an increase of V/sub BE/ as the base bulk current is increased, or to the reduction of the ideality factor n/sub BE/.