[Paper] Analysis of Using Holes as Carriers in the Film in an 8K Stacked CMOS Image Sensor Overlaid with a Crystalline-Selenium Multiplication Layer

Abstract

A prototyped 8K stacked CMOS image sensor overlaid with a crystalline-selenium-based avalanche-multiplication layer, in which holes are used as traveling carriers in the film, was fabricated. Analysis of energy-band diagrams through the film to the n-type floating-diffusion region revealed that (i) large spot noise in the captured image could be suppressed and (ii) the high voltage required for avalanche multiplication could be applied to the film by using holes as carriers even when defects existed in the film. According to the results of experiments, no large spot noise occurred when the voltage applied to the film was +5 V. Additionally, the photoelectric-conversion current was increased by 1.4 times compared to the saturation-signal level when the applied voltage was +21.6 V. These results confirm charge multiplication in a crystalline-selenium-based stacked CMOS image sensor.