2 MeV Electron Irradiation Effects in (HG,CD) TE CCDS

The effects of 2 MeV electrons, up to a dose of 105 rad(ZnS), on DC biased and continuously operating (Hg, Cd)Te charge-coupled devices (CCDs) at 77 K are discussed. Radiation induced flatband shifts were observed to be proportional to the electric field in the gate insulator. Typical flatband voltage shifts for thick insulator areas of the device were 3 volts for a dose of l×104 rad (ZnS). Degradation in CCD performance characteristics was observed in devices which were irradiated during operation. This degradation is attributed to flatband shifts. No increase in interface state density was observed. After 104 rad(ZnS), charge transfer efficiency and ´effective´ full well capacity had degraded from pre-irradiation values of .996 and 8×1011/cm2 to .992 and 4×1011/cm2, respectively. Charge collected during a 1 msec integration of the dark current had increased by a factor of three from a pre-irradiation value of 1.2x1011/cm2 to 3.8×1011/cm2.