A detector of radiation uses a composite material, and process manufactures the detector. The detector includes layers (6) of a semiconducting composite material including a host matrix made of a polymer and semiconducting-type guest particles dispersed through the host matrix, means (22 26) for creating an electric field in the layers, and a stack of sheets (4) of a first material emitting particles by interaction with the radiation, the layers alternating with the sheets, each of the layers being associated with one of the sheets, the stack having opposite faces, each containing the edges of the sheets and layers. The means for creating includes, for each layer, a group of parallel and conductive tracks (22) which extend from one face to the other, parallel to this layer, and which are in contact with it.