The role of oxygen in the sensitization of photoconductive PbSe films

Abstract Monocrystalline, textured and polycrystalline films of n-type PbSe were obtained by vacuum sublimation onto different types of substrates under otherwise identical experimental conditions. The effect of introducing oxygen to a certain partial pressure into the vacuum system during deposition and of the further sensitization of the films by a thermal treatment in air was studied by transmission electron microscopy and by mobility and carrier concentration measurements. A model for photoconductivity is advanced in which localized deep level centres are introduced into the grains by oxygen doping during the evaporation and become minority carrier traps when an air or selenium heat treatment lowers the Fermi level to achieve p-type conduction.