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 heterojuction bipolar transistors (HBTs) with a common emitter (CE) current gain of 31 at 175K and 11.3 at 295K. 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 the decrease of temperature. The increase of V-CEOFF at lower temperature is related to an increase of V-BE as the base bulk current is increased, or to the reduction of the ideality factor n(BE).