Abstract: Disclosed is a photodetector adapted to be used with a voltage source for replacing the conventional CCD. The photodetector includes a substrate electrically connected with an electrode of the voltage source for generating electron-hole pairs in response to a light, a conducting layer electrically connected with the other electrode of the voltage source, and an ultra thin (˜nm) insulating layer formed between the conducting layer and the substrate, wherein one of electrons and holes, excited by the light, in the substrate will move to the conducting layer through the insulating layer so as to form a photo current when the voltage source provides a bias voltage.