PURPOSE: To suppress an increase in a dark current and enable an operation at room temperature, with low noise, and at high sensitivity, by providing an avalanche multiplicating layer for amplifying photo-electrons by means of an avalanche multiplication due to a collision ionization on the way of transferring photo-electrons excited by incident photons to an emission surface through an internal electric field.

CONSTITUTION: An ohmic electrode 3 is formed on one side of a substrate 6 and a light absorption layer 1, an avalanche multiplication layer 7 made of multilayer thin film, a photoelectron emission surface 4, Cs2O layer 2, and a Schottky electrode 5 are formed on the other side. In the case when any vias voltage is not applied, photo-electrons excited by incident photons in a light absorption layer 1 cannot be transmitted through a conductive band barrier of the avalanche multiplication layer 7, thus they cannot arrive at the emission surface 4, resulting in generation of no photoelectron emission. In the case when a vias voltage is applied, photoelectrons are accelerated with an accelerating electric field, so that they arrive at the emission surface 4 by being transmitted through a conductive barrier of the avalanche multiplication layer 7. Photo-electrons produce the avalanche multiplication due to a collision ionization, when they cross the avalanche multiplication layer 7 and they arrive at the emission surface after being subjected to electronic multiplication, and as a result they are emissioned into vacuum via the Cs2O layer 2.