Highly and Variably Sensitive Complementary Metal Oxide Semiconductor Active Pixel Sensor Using P-Channel Metal Oxide Semiconductor Field Effect Transistor-Type Photodetector with Transfer Gate

Abstract

In this paper, a new sensor using a p-channel metal oxide semiconductor field effect transistor (PMOSFET)-type photodetector with a transfer gate has been designed and fabricated by a 0.35 µm standard complementary metal oxide semiconductor (CMOS) process. The photodetector is composed of a floating gate connected to an n-well and a transfer gate. The transfer gate controls photocurrent flow by controlling the barrier for holes in the PMOSFET-type photodetector. The designed photodetector has similar IDS–VDS characteristics to a conventional PMOSFET when the incident light power instead of the gate voltage is varied. A unit pixel that uses this photodetector consists of a PMOSFET-type photodetector with a transfer gate and four n-channel metal oxide semiconductor field effect transistors (NMOSFETs). Its area is 7.2 ×8.1 µm2. It is confirmed that this photodetector, with a high and variable level of sensitivity, could be applied to an image acquisition system at a low illumination level.