Determination of Effective Trapping Times for Electrons and Holes in Irradiated Silicon

A set of standard and oxygenated silicon diodes with different resistivities (1 kOhm cm and 15 kOhm cm) was irradiated with neutrons to fluences up to 2*10^{14} cm^{-2} 1 MeV neutron NIEL equivalent. After beneficial annealing the signal response from the diodes was studied using TCT (transient current technique). Red laser (lambda=670 nm) illumination was used for creation of electrons and holes. Assuming exponential decrease of the drifting charge in time, the effective trapping probability of electrons and holes was deduced from the evolution of the induced current at voltages above the full depletion voltage. The effective trapping probabilities of holes were found to be larger than for electrons. The trapping probability is shown to scale linearly with fluence. No significant difference between effective trapping probabilities for different materials was measured.