A floating gate MOSFET dosimeter requiring no external bias supply

MOSFET dosimeters incorporating an electrically floating polysilicon gate have been fabricated in a commercial CMOS technology. Charge is placed on the floating gate by tunnelling from a small overlapping injector gate. Subsequent irradiation partially discharges the floating gate, producing a change in threshold voltage which can be used to infer the absorbed dose. No external power source is required during this sensing period. Sensitivities up to 70mVGy(-1) (0.7 mV/rad) have been obtained for temperature-compensated matched-pair dosimeters under Co-60 gamma irradiation.