A model for shifts in the gate turn-on voltage of insulated-gate field-effect devices induced by ionizing radiation

Insulated gate field-effect devices with thermally grown silicon dioxide and deposited nitride insulation were subjected to electron irradiation up to a total dose of sufficient magnitude to establish dynamic equilibrium. The resultant linear shift of the gate turn-on voltage with applied gate bias over a wide range of biasing conditions has been interpreted by a model postulating a positive space charge region bounded by the insulator-semiconductor interface and a negative space charge region bounded by the insulator-metal interface. It is shown that the linearity holds for an arbitrary space charge distribution within these two regions whose widths are independent of the gate voltage during irradiation. The conditions for obtaining completely radiation-resistant devices have also been derived.