High current effects in double heterojunction bipolar transistors
At high current densities, the onset of the Kirk effect is often the main frequency and power constraint in bipolar transistors. In this paper, we present an analytical model that accurately describes the physics behind the parasitic electron barrier formation in double heterojunction bipolar transistors in the Si/SiGe, GaInP/GaAs and InP/GaAsSb material systems at the onset of the Kirk effect. The model is tested by comparison with observations on GaInP/GaAs-based devices. A new lateral current spreading effect due to the electron barrier dependence on collector current density is also discussed.