Heterojunction HgCdTe photovoltaic detector and its production process

A photovoltaic detector with a planar structure having a first Hg.sub.1-x.sbsb.1 Cd.sub.x.sbsb.1 Te monocrystalline semiconductor layer with a first conductivity type, x.sub.1 being a number between 0 and 1, said first semiconductor layer containing a first region of a second conductivity type, an electrical insulant located above the first semiconductor layer and an electric contact element located on the insulant serving to collect the electric signal produced in said first region, wherein a second Hg.sub.1-x.sbsb.2 Cd.sub.x.sbsb.2 Te monocrystalline semiconductor layer of the first conductivity type is interposed between the first semiconductor layer and the insulant, x.sub.2 being a number exceeding x.sub.1, between 0 and 1, said second semiconductor layer containing a second region of the second conductivity type facing and in contact with said first region and wherein the contact element comprises a part traversing said second region and partly penetrating said first region, and a means for processing a signal produced in the first region being provided in the second semiconductor layer, said means comprise a NMOS transistor coupled to a charge transfer device.