During edge-TCT studies on irradiated p-type sensors, a significant change on signal amplitude and shape from subsequent laser pulses has been observed, even with pulse repetition time of several microseconds.
We observed in particular a strong reduction of the collected signal, which can be due to a recombination with the previously trapped charge or to a significant change of the electric configuration due to the trapped charge.
By means of edge- and top- TCT measurements, we investigated the dependence on generation depth, temperature, pulse repetition time, intensity and voltage. Results indicate that the latter phenomena, also known as polarization, gives main contribution to the signal change. This is well known in larger band-gap materials like diamond, but usually negligible in silicon at the relative high measurement temperature of about -25°C.
A mathematical analysis of the results and simulations performed with kDetSim confirm the formulated description on the trapping effect