Performance Considerations for Photogate Based Active Pixel Sensors

Photogate based active pixel sensors (PG APS) are often used in CMOS imaging. In advanced applications (e.g. high-speed imaging or time-of-flight distance measurements) the pixel performance requirements are high, especially as far as the optical sensitivity of the PG and the transfer and readout speed of photogenerated charge carriers are concerned. In this contribution we investigate the electrical and optical performances of different PG based pixel configurations fabricated in the 0.35 mu m CMOS process available at the Fraunhofer IMS. Finally, we propose a high resistivity polysilicon gate based pixel structure to be applied in 3-D time-of-flight (ToF) measurements, that yields an enhanced charge transfer speed.