Carrier mobilities in irradiated silicon

Using laser pulses with <1 ns duration and a 500 MHz digital oscilloscope the current pulses were investigated for p–i–n Si diodes irradiated by neutrons up to 1 MeV equivalent fluences of 2.4×1014 n/cm2. Fitting the current pulse duration as a function of bias voltage allowed measurement of mobility and saturation velocity for both electrons and holes. No significant changes in these parameters were observed up to the maximum fluence. There are indications of a non-uniform space charge distribution in heavily irradiated diodes.