Highly sensitive active pixel sensor using a PMOSFET photodetector

An active pixel CMOS image sensor in which a PMOSFET is used as a photodetector is described. The photodetector is configured by using a floating gate/n-well tied PMOSFET. The designed photodetector has I-DS-V-DS characteristics similar to those of a general PMOSFET when the incident light power, instead of the gate voltage, is supplied. A I x 16 image sensor array was designed and fabricated using I-poly and 2-metal 1.5 mum CMOS technology. The unit pixel of this sensor consists of a PMOSFET photodetector and 4 NMOSFETs, its area is 86 X 90.5 mum, and the fill factor is 12%. A highly sensitive pixel is feasible owing to the relatively small area of the photodetector and the pixel circuit with voltage gain.