Modeling of Transient Ionizing Radiation Effects in Bipolar Devices at High Dose-Rates

We have developed a dynamic model for photo-electric effect in bipolar devices exposed to a wide range of ionizing radiation intensities. We represent the stationary and dynamic photocurrents by current sources in parallel with each p-n-junction. These sources include the prompt photocurrent of the depletion regions, and the delayed response associated with the build-up and discharge of excess charge carriers in the quasi-neutral (q-n) regions adjacent to the junctions. The latter are described in terms of dynamic delay times for each q-n region, which can be represented by RC equivalent delay circuits. The model has been implemented in the circuit simulator AIM-Spice, and has been verified by numerical simulations.