PURPOSE: To reduce a dark current due to applying bias voltage by providing an i-type intermediate layer of high resistance between a light absorbing layer and electron emitting layer of a photoelectron emitting surface, so that a photoelectron can be emitted by the low bias voltage.
CONSTITUTION: When near infrared light hν is incident from an exposed surface of a p+ type InP semiconductor substrate 1 upon a photoelectron emitting surface applied with suitable bias voltage, the near infrared light hν, permeating the substrate 1, is absorbed by a p-InGaAsP light absorbing layer 2, to excite a photoelectron (e). The photoelectron (e) is accelerated by an electric field formed by applying bias voltage, to traverse an interface of the light absorbing layer 2, i-type InP intermediate layer 3 of high resistance and a p-InP electron emitting layer 4, and after transition to a conduction band, the photoelectron leads to a surface of the electron emitting surface 4. The photoelectron (e) passes through the interface of the light absorbing layer 2 and the intermediate layer 3 by a tunnel effect even at low bias voltage. By applying suitable Cs to a surface of the electron emitting layer 4, the arriving photoelectron (e) is easily emitted to the outside from an exposed surface of the layer 4.
MIZUSHIMA YOSHIHIKO
HIROHATA TORU
