Effect of bias voltage on the space charge in irradiated silicon detectors

Full depletion voltage of irradiated silicon pad detectors was observed to increase with time after applied bias voltage. The increase of VfdVfd, obtained from C–V   measurements, is proportional to the fluence and is independent of the irradiation particle type, space charge sign, silicon material, and thickness. Upon switching off the bias voltage, the VfdVfd returns to those expected values for an unbiased sample. However, the leakage current is not affected. The same behavior is observed in the measurements of the charge collection efficiency for the minimum ionizing particles. As the time constants of the increase and decrease of VfdVfd are of the order of 10 h at −8∘C, the effect can play an important role in the future high-energy physics experiments.