Analysis of deep level parameters in irradiated silicon detectors

Both the collected charge and the capacitance of a silicon detector are proportional to the depleted depth of the space charge region. The presence of deep levels introduces frequency dependence in the measured capacitance, and this frequency dependence can be corrected for by analyzing the data using admittance spectroscopy. An equivalent circuit for a PN junction containing deep levels is used to accurately model deep level response. Activation energy, majority carrier cross-section and the concentration of active deep levels at the edge of the space charge region is determined. Space charge region depth as a function of the applied voltage is extracted for various detectors irradiated with neutrons and pions. When possible, depleted depths are compared to charge collection measurements.