Capacitance Voltage Characteristics of Neutron Irradiated n+ pp+ and p+ nn+ Junctions

The small signal capacitance-voltage characteristics of neutron irradiated p+ nn+ and n+ pp+ diodes are described. The capacitance characteristics were measured at frequencies of 1 kHz, 10 kHz, 100 kHz and 1 MHz for five neutron fluences. A qualitative difference in the effect of neutron fluence on the capacitance characteristics of p+ nn+ and n+ pp+ diodes is described. A computer aided device model which is based on an equivalent circuit representation of two deep defect levels is described. The capacitance characteristics of neutron irradiated pR+ nn+ diodes with three different pre-radiation resistivities were computed using the device model representation of two deep acceptor levels. The computed curves are in good agreement with the measured characteristics.