Damage Separation in Proton-Irradiated Bipolar Junction Transistors as a Function of Energy

Damage separation analysis was performed for two types of bipolar junction transistors (BJTs) following proton irradiation over the energy range of 1.6 - 650 MeV. The functional dependence of excess base current on fluence for each device type is consistent with base polarity as it relates to the effect of oxide-trapped charge on surface recombination. For a given fluence, the excess base current decreases with proton energy due to reductions in non-ionizing energy loss (NIEL) and stopping power. Relative damage coefficients, computed from normalized Delta I-B versus fluence curves, imply a mix of ionization and displacement damage. The relative amounts of ionization damage and displacement damage as a function of proton energy are consistent with charge yield (CY), stopping power and NIEL. A simple model for the energy dependence of damage contributions, based on CY and the relative amounts of deposited ionizing and non-ionizing energy, is described. The model calculations as a function of proton energy are in good agreement with the relative damage contributions estimated from the damage separation analysis.