Transient response in PPD CMOS image sensors irradiated by gamma rays: variation of dose rates and integration times

The transient responses in CMOS image sensors (CISs) during radiation are one of the most important key issues to the detector design, reliability and applicability. The radiation experiments of transient responses in CISs are presented. The CISs have 4 Megapixels and pinned photodiode (PPD) pixel architecture with a standard 0.18 lm CMOS technology. The transient responses induced by gamma radiation at the dose rates of 0.01, 0.02, 0.05, 0.1, 0.2, 0.3 rad(Si)/s are compared to analyze the influence of dose rates. The transient responses of the PPD CISs at different integration times ranged from 1.02 to 20.51ms during radiation are also analyzed. The transient response characteristics of the PPD CISs induced by gamma radiation present a transient disturbance and a random signal distribution. The experimental results show that the mean signal levels increase linearly with increasing dose rates or integration times during radiation, which indicates a method to improve the CIS detector precision. The mechanisms of the transient responses in PPD CISs are also demonstrated.