Responsivity Enhanced NMOSFET Photodetector Fabricated by Standard CMOS Technology

Increasing the responsivity is one of the important issues for a photodetector. In this paper, we demonstrate an improved NMOSFET photodetector by using deep-n-well (DNW) structure which can improve the responsivity of the photodetector significantly. The experimental results show that the responsivity can be enhanced greatly by the DNW structure and is much larger than the previous work when DNW is biased with 0.5 V, while the dark current exhibits almost no increase. Further characterization indicates that the diode formed by the bulk and DNW can efficiently absorb photons and has a large gain factor of the photocurrent especially under low light condition, which gives a more promising application for the detector to detect the weak light.