Four-transistor pinned photodiodes in standard CMOS technologies for time-of-flight sensors

Abstract

This paper studies pinned photodiodes with transmission gates and floating diffusions (FD) as a possible pixel structure for time-of flight sensors fabricated in standard CMOS technologies. Although the doping profiles cannot be modified in standard technologies, it is possible to adjust the geometrical parameters that have an important influence on the performance of the devices. The study is made in terms of the uncertainty introduced in the distance measurement due to the dark current, the noise introduced by the reset transistor and the transmission speed of the photogenerated charges to the FD.