Abstract: An infrared sensitive photodiode which is made of an epitaxial layer of a miconductor alloy which is a lead chalcogenide, a lead-tin chalcogenide, or a lead-cadmium chalcogenide grown on a single crystal substrate of an infrared transparent, electrically insulating material, an Ohmic contact deposited on the epitaxial layer, and a non-Ohmic Pb metal contact deposited on the epitaxial layer to form a Schottky barrier, the improvement comprising the inclusion of halide ions in the interface region between the non-Ohmic lead metal contact and the epitaxial layer of semiconductor material.

Abstract: A process for preparing an infrared sensitive photodiode comprising the ss of(1) forming by vacuum deposition an epitaxial layer of a semiconductor alloy material which is PbS, PbSe, PbTe, PbS.sub.x Se.sub.1-x, PbS.sub.x Te.sub.1-x, PbSe.sub.x Te.sub.1-x, Pb.sub.y Sn.sub.1-y S, Pb.sub.y Sn.sub.1-y Se, Pb.sub.y Sn.sub.1-y Te, Pb.sub.y Sn.sub.1-y S.sub.x Se.sub.1-x, Pb.sub.y Sn.sub.1-y S.sub.x Te.sub.1-x, Pb.sub.y Sn.sub.1-y Se.sub.x Te.sub.1-x, Pb.sub.z Cd.sub.1-z S, Pb.sub.z Cd.sub.1-z Se, Pb.sub.z Cd.sub.1-z Te, Pb.sub.z Cd.sub.1-z S.sub.x Se.sub.1-x, Pb.sub.z Cd.sub.1-z S.sub.x Te.sub.1-x, or Pb.sub.z Cd.sub.1-z Se.sub.x Te.sub.1-x, wherein 0<x<1, 0<y<1, and 0<z<1, to cover at least a portion of the surface of a substrate composed of an infrared transparent single crystal material which is an alkali halide or an alkaline earth halide;(2) forming a layer of a lead halide which is PbCl.sub.2, PbBr.sub.2, PbF.sub.