Evolution of proton-induced defects in a cryogenically irradiated p-channel CCD

P-channel CCDs have been shown to display improved tolerance to radiation-induced charge transfer inefficiency (CTI) when compared to n-channel CCDs. This is attributed to the properties of the dominant charge-trapping defect species in p-channel silicon relative to the operating conditions of the CCD. However, precise knowledge of defect parameters is required in order to correct for any induced CTI. The method of single trap-pumping allows us to analyse the defect parameters to a degree of accuracy that cannot be achieved with other common defect analysis techniques such as deep-level transient spectroscopy (DLTS). We have analysed using this method the defect distribution in an e2v p-channel CCD204 irradiated with protons at cryogenic temperature (153K). The dominant charge trapping defects at these conditions have been identified as the donor level of the silicon divacancy and the carbon interstitial defect. The defect parameters are analysed both immediately post irradiation and following several subsequent room-temperature anneal phases. The evolution of the defect distribution over time and through each anneal phase provides insight into defect interactions and mobility post-irradiation. The results demonstrate the importance of cryogenic irradiation and annealing studies, with large variations seen in the defect distribution when compared to a device irradiated at room-temperature, which is the current standard procedure for radiation testing.