上海科技大学知识管理系统

Traditional CMOS image sensors generally use PN photodiodes or PPDs as the photosensitive element, which are formed based on N-well/P-type substrates using the LV-CMOS (process). The PIN photosensitive element has small junction capacitance and high quantum efficiency. By using High-Voltage CMOS( HV-CMOS ) , monolithic integration of CMOS circuits with PIN photodiodes can be achieved. In this paper, the relationship between the photo-response characteristics, NEP of CMOS detectors and pixel size and reset voltage are studied. The results show that the pixel charge gain can be increased by about one order of magnitude when the photosensitive element is changed from PN to PIN and the transient charge gain of the pixel is larger than 1/C-pd. This is closely related to the size of the diode and reset voltage. It is found that small pixels are more suitable for fast detection of short integration time under weak signals because of their higher charge gain and lower equivalent noise. If combined with microlenses , small pixels can be further advantageous in low light detection.