Multiscale Modeling of Accumulation of Radiation Defects in Silicon Detectors Under Alpha Particle Irradiation

A multiscale approach to modeling of accumulation of radiation defects in silicon alpha detectors applied in the associated particle imaging systems is developed. The approach includes: calculation of primary knock-on atoms energy distribution, calculation of number of primary defects per one alpha particle, solution of system of kinetic equations for concentrations of all secondary defects, and calculation of leakage (dark) current of the detector. With this approach we have calculated the bulk generation current vs. alpha particle fluence for a detector irradiated with alpha particles with energy of 3.5 MeV. The results appeared to be in a good agreement with experimental data. Then we investigated how the bulk generation current of the irradiated device depends on concentrations of impurities (oxygen and carbon) and found a way to reduce the current by optimization of oxygen concentration in the semiconductor material.