Comparisons of the proton-induced dark current and charge transfer efficiency responses of n- and p-channel CCDs

The proton-induced charge transfer efficiency (CTE) behavior for the Lawrence Berkeley National Laboratory (LBNL) p-channel CCD [being developed for the Supernovae Acceleration Probe (SNAP)] is compared with the Hubble Space Telescope’s (HST) Wide Field Camera 3 (WFC3) n-channel CCDs CTE using 55Fe x-rays, first pixel edge response (FPR), and extended pixel edge response (EPER) techniques. The pre- and post-proton radiation performance parameters of p-channel CCDs designed by LBNL and fabricated at Dalsa Semiconductor, Inc. are compared with n-channel CCDs from E2V, Inc. LBNL p-channel CCDs both with and without notched parallel registers are compared with the E2V CCD43 [a notched, multi-phase pinned (MPP) device] and the E2V CCD44 (an un-notched, non-MPP device), using the same readout timing and measured over the same range of temperatures. The CTE performance of the p-channel CCD is about an order of magnitude better than similar n-channel CCDs for the conditions measured here after a 63 MeV proton fluence of 2.5 x 109 cm-2, which is equivalent to 2.5 years in the HST orbit behind shielding comparable to about 2.5 cm Al. Our measurements are compared with previous CTE measurements at 12 MeV by Bebek et al. The ~ 10 x CTE improvements relative to n-channel CCDs is seen at -83°C, a temperature which is optimized for n-channel CCD performance. Advantages from p-channel CCDs should be greater at other temperatures. Dark current measurements and hot pixel issues are also discussed.