Gary Evans, Mani Sundaram Axel Reisinger, Jason Bundas, Robin Dawson, Juha-Pekka Laine
In-situ exposure of InAs/InAsSb strained layer superlattice focal plane arrays to gamma-rays revealed the possibility of a detector capable of imaging through a total ionizing dose event. Two long wave infrared focal plane arrays were exposed to a Co60 source at dose rates of 60 Rads/s and 70 Rads/s in incremental steps up to a total accumulated dose of 30 kRads. The first device showed no degradation in dark current density with accumulated dose while the second device tested showed a small increase up to 1 kRad and minimal increases with subsequent dose steps. The primary imaging defect in the focal plane arrays with exposure to high energy photons was the appearance of bright pixels. A correlation was made between the number and magnitude of ionization events seen in the material and detector bias. The silicon read-out integrated circuit used with the detector material tested in these experiments began to show significant deterioration near 30 kRads.
Two long wave infrared InAs/InAsSb strained layer superlattice focal plane arrays were subjected to several exposures from the fast burst reactor at White Sands Missile Range in NM, with a max fluence of 1 x 1012 neutrons/cm2. The primary effect from a neutron event contributing to a degradation in image quality was an increase in the distribution of dark current density values, which blurs the features of an image. Standard deviation of dark current density measurements for the array increased by 6 x 10-5 A/cm2 which constitutes a 406 % increase in pixel-to-pixel variation. Following an accumulated fluence of 1.6 x 1012 neutrons/cm2 there was an absolute decrease in quantum efficiency of 2 % and a relative increase in noise equivalent differential temperature of 64 plus-minus 225 %.
A single long wave infrared focal plane array was operated in a 200 MeV proton beam with dark current density measurements performed at incremental steps for a total accumulated fluence of 2.5 x 1011 protons/cm2. The degradation seen in the focal plane array when exposed to protons confirmed the effects seen with gamma-rays and fast neutrons.
Electrical and Computer Engineering
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Fumo, Patrick, "Investigation of the effects of harmful radiation on type-II strained layer superlattice focal plane arrays operated in the long wave infrared" (2018). Electrical Engineering Theses and Dissertations. 63.