Radiation effects on electrical conduction properties in MIS capacitor

Effects of radiation on MOS structure were investigated by measurements of current vs. bias voltage (I-V) characteristics. It is shown that the I-V characteristics are dependent on the total irradiation doses. When the gate is negatively biased, the current through the oxide is found to be ohmic current at a lower field and space-charge-limiting current at a higher field. The dose dependence of the ohmic current can be explained by the effect of positive space charge induced in the oxide layer irradiation. When the gate is positively biased, the current is found to be ohmic current at a lower field and Schottky current at a higher field. The voltage at which the transition from the ohmic current to the Schottky current occurs is found to decrease with increasing irradiation doses. This tendency can be explained in terms of the effective potential barrier lowering due to the trap charges at the Si-SiO₂ interface