Radiation Damage Coefficients for Silicon Depletion Regions

An experimental and analytical study of radiation effects on silicon depletion regions has been performed. Data are presented which yield damage coefficients appropriate for describing the effects of fission neutrons and Co60 gamma rays on depleted regions and on the SiO2-Si interface. A model incorporating these coefficients is described and used to perform calculations of radiation-induced increases in dark (or leakage) current in CCDs, diodes, and JFETs. The model calculations performed involve no adjustable parameters. Agreement between calculations and experimental results is within a factor of < 2 in most cases. Model calculations for these devices are based on the assumption that dark current is primarily attributable to carriers thermally generated at centers in the depletion region bulk. Results of short-term annnealing measurements on CCDs are presented which provide information regarding damage in depletion regions at early times following pulsed neutron bombardment. Evidence of the production of interface states in an MOS device by neutron bombardment is also presented.