Photocathode with improved quantum yield

An electromagnetic radiation detector comprising a glass inlet window having an upstream face intended to receive a flux of incident photons as well as a downstream face opposite to the upstream face, a photocathode in the form of a semiconductor layer, intended to generate photoelectrons from the incident photons and to emit said photoelectrons thus generated, an electron multiplier device configured to receive the photoelectrons emitted by the photocathode and to generate for each received photoelectron a plurality of secondary electrons and an output device configured to generate an output signal from said secondary electrons, wherein a transparent conductive layer is deposited over the downstream face of the inlet window and that a thin insulating layer is disposed between said conductive layer and the semiconductor layer, the conductive layer being electrically connected to a first electrode and the semiconductor layer being electrically connected to a second electrode, the first electrode being intended to be set at a potential lower than that applied at the second electrode.