Photosensitivity in Epitaxial PbS Films

A study has been made of the photosensitivity in epitaxial PbS films which were sensitized by heat treatments in air or sulfur vapor. The sensitizing process results in the formation of narrow lines of material which are more p type than the host film. The resultant junctions are responsible for the photosensitivity. The junctions are associated with crystal defects which are faintly visible under a microscope and appear as lines running in (100) directions. Introduction of these lines can be sufficiently controlled so that only a few are introduced into a sample. This enables individual junctions to be studied. Various properties of the epitaxial films were determined and compared to the corresponding properties of the well-known polycrystalline PbS detectors.