Ionizing Radiation Effects on GaAsP MIS Capacitor Structures

This paper reports the effects of ionizing radiation on GaAsP MIS capacitor structures fabricated using a thermally grown dielectric and a chromium gate. The devices were irradiated with both Co60 gamma rays and high-energy (0.5 < E < 2.2 MeV) electrons at doses ranging from 104 to 108 rads(GaAsP). Results of studies of charge buildup show that a net negative charge is trapped in the dielectric during irradiation; this contrasts with the positive radiation-induced charge trapping observed in silicon dioxide. Flatband voltage shifts were less than 2 volts up to a dose of 108 rads(GaAsP). This compares favorably with shifts of greater than 10 volts which are noted in typical unhardened silicon structures under similar irradiation conditions.