Effects of Gamma Radiations on the I-V Electrical Parameters of a n-MOSFET

Hostile environments usually contain different types of ionizing radiations. In Si-based MOSFETs, radiation-induced defects can lead to drastical degradations in the relevant current-voltage characteristics. At the micro-scale, the capacitance reveals degeneration due to an accumulation of trapped holes within the oxide layer and at the oxide-channel interface. As a peculiar feature of this degeneration, several electrical parameters of the transistor are directly impacted by the variation in the gate-oxide capacitance. It has been found from experimental measurements that the threshold potential exhibits a negative shift as the absorbed gamma ray dose increases. As it is already suggested, the negative shift in the threshold potential results from a trapping of positive charges into the gate capacitance. In the present work, the trapping of holes is rather assumed to behave as a compensating donor center. Which leads to relate them into the acceptor doping concentration. In the paper, we have also investigated the electron transport under exposure to gamma radiations. For this purpose, we have developed a direct and a small-signal current models. From I-V measurements, a set of fitting laws has been derived for the static and dynamic parameters as a function of the total ionizing dose. An attempt to explain the physical origin of the induced-dysfunction will be made for the n-MOSFET investigated