Photoresponses of MOS transistor

Illumination effects on the drain current were studied for a p-channel enhancement-type MOS transistor, and the results show that the photoresponses are mainly due to electron excitation in the conduction band from surface states lying near the top of the valence band. It also appears that the hole density of the channel decresses in the vicinity of the drain region but is almost constant over the entire channel when more than 200 µm away from the drain edge.