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

Frequency-dependent capacitance-voltage (C-V) characteristics of neutron-irradiated high-resistivity silicon P/sup +/-n detectors have been observed up to a fluence of 8.0*10/sup 12/ n/cm/sup 2/. It has been found that the frequency dependence of the deviation of the C-V characteristic (from its normal V/sup -1/2/ dependence) is strongly dependent on the ratio of the defect density to the effective doping density N/sub t//N'/sub d/. As the defect density approaches the effective dopant density, or N/sub t//N'/sub d/ to 1, the junction capacitance eventually assumes the value of the detector geometry capacitance at high frequencies (f>or=10/sup 5/ 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.<
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