Deposition and properties of zinc phosphide films

Thin films of zinc phosphide have been deposited on tungsten-coated steel substrates at 400–600 °C by the reaction of zinc and phosphine in a hydrogen atmosphere; tungsten was used as a barrier against the diffusion of iron from the substrate into zinc phosphide. By using a proper PH3/Zn molar ratio, the deposited films have been identified by electron microprobe and x-ray diffraction techniques to be Zn3P2. The electrical resistivity and photovoltage of unintentionally doped zinc phosphide films were measured as a function of the composition of the reaction mixture. The effective intragrain minority carrier diffusion length in nearly stoichiometric films was measured by the scanned beam method using a Schottky barrier structure. The incorporation of dopants into zinc phosphide films was also explored.