Highly Sensitive PMOSFET Photodetector and Its Application to CMOS Active Pixel Sensor

摘要

In this paper, a highly sensitive p-channel metal oxide field effect transistor (PMOSFET) photodetector fabricated using a standard complementary metal oxide semiconductor (CMOS) process is described. The photodetector is configured by the floating gate-well tied PMOSFET. The device has similar I_(DS)-V_(DS) characteristics to a general PMOSFET when the incident light power instead of the gate voltage is supplied and has a transient response fast enough that there is no image lag in its application to an imager with television resolution. A 1 * 16 CMOS active pixel sensor using the PMOSFET photodetector was also designed and fabricated using 1-poly and 2-metal 1.5 μm CMOS technology. The unit pixel of this sensor consists of a PMOSFET photodetector and four n-channel metal oxide field effect transistors (NMOSFET). Its area is 86 μM * 90.5 μm and fill factor is 12%. Even though the pixel has a relatively small its fill factor, a sufficient photocurrent can be obtained. A highly sensitive pixel is feasible with the use of the photodetector with current amplification and the pixel circuit with voltage gain.