Studies of frequency dependent C-V characteristics of neutron irradiated p+-n silicon detectors

Frequency-dependent capacitance-voltage (C-V) characteristics of neutron-irradiated high-resistivity silicon P⁺ -n detectors have been observed up to a fluence of 8.0×10 ¹² n/cm². It has been found that the frequency dependence of the deviation of the C-V characteristic (from its normal V^-1/2 dependence) is strongly dependent on the ratio of the defect density to the effective doping density N_t/N´_d. As the defect density approaches the effective dopant density, or N_t /N´_d→1, the junction capacitance eventually assumes the value of the detector geometry capacitance at high frequencies (f⩾10⁵ Hz), independent of voltage. A two-trap-level model that uses the concept of quasi-Fermi levels and predicts the effects of C-V frequency dependence and dopant compensation observed has been developed