Impact of n+/p+-doped Polysilicon Gate in Lateral Overflow Transistor on Organic Photoconductive Film CMOS Image Sensor Dark Currents

In this study, we developed an organic photoconductive film complementary metal–oxide–semiconductor (CMOS) image sensor incorporating a lateral overflow (OF) MOS field-effect transistor. This configuration effectively prevents excessive potential buildup in the charge storage region. By using a p-type gate electrode for the n-channel OF transistor, we attained the threshold voltage necessary for voltage clamp operation and successfully minimized the p–n junction leakage current (dark current) in the charge storage area. Both experimental and simulation results show that the dark current is notably influenced by the depletion region beneath the OF transistor’s gate electrode.