Excess Base Current Model for Gamma-Irradiated SiGe Bipolar Transistors

The radiation hardness of advanced SiGe BiCMOS technologies is being evaluated in order to check their applicability for the front-end readout electronics of the ATLAS Upgrade in the framework of the Super-LHC at CERN. A model that describes the effect of ionizing radiation on bipolar transistors as an exponential term is widely accepted. Nevertheless, this model is not very precise in the bias ranges of interest for these applications. We propose a new empirical model that, by the addition of one extra parameter to the classical exponential model, describes more accurately the ionization radiation effects on SiGe bipolar transistors in the range of interest.