Capacitive effects in neutron-irradiated silicon diodes

The capacitance of two silicon diodes irradiated with 1 MeV neutrons has been measured. The capacitance–voltage characteristic demonstrates four effects (frequency dependence, negative capacitance, low-voltage peak, peak migration) that do not fit very well to what the lifetime theory predicts for p–n junction devices, but that are easily explained with relaxation theory. This suggests that the radiation damage has altered the semiconductor material from lifetime to relaxation. Possible mechanisms for the occurrence of the effects are suggested with an emphasis that relaxation theory be used for analysis. A defect introduction rate of 0.059 cm−1 has been evaluated.