Formation of p-n Junction in a-Se Thin Film and Its Application to High Sensitivity Photodetector Driven by Diamond Cold Cathode

In this study, photoconductor made of amorphous selenium (a-Se) is studied to improve a sensitivity of vacuum-tube type photodetectors. An electrochemical process was applied to a-Se films to form a p-n structure within the film. The formation of p-n structure was confirmed by time-of-flight secondary ion mass spectroscopy as well as its electronic property. The a-Se film was then combined into a prototype photodetector, and enhancement of sensitivity was evaluated in terms of nominal quantum efficiency and signal-to-noise ratio. The results showed that the formation of a p-n junction within a-Se film increased the sensitivity of the photodetector, especially at relatively low operation voltages.