EVIDENCE FOR NONEQUILIBRIUM BASE TRANSPORT IN SI AND SIGE BIPOLAR-TRANSISTORS AT CRYOGENIC TEMPERATURES

In this paper we observe discrepancies between measured and simulated values for collector current and transconductance in advanced Si and S iGe bipolar devices at cryogenic temperatures. The deviation of these quantities from values predicted by standard drift-diffusion theory is shown to be consistent with the expected effects of non-equilibrium c arrier transport across the neutral base region. A simple model based on non-equilibrium transport theory is used to account for the observe d discrepancies in both parameters, resulting in excellent quantitativ e agreement with measured data over the temperature range 50-300 K.