Microstructural and light emission properties of ZnSnP 2 thin film absorber: Study of native defects
Abstract Thin films of ZnSnP 2 were successfully grown on p-type silicon (001), sapphire and glass substrate by e-beam evaporation method. The as-deposited films were characterized using scanning and high resolution transmission electron microscopes, reflectance and transmittance spectroscopy and photoluminescence measurement at low temperature. Polycrystalline nature of the films was verified by high resolution transmission electron microscopy. An optical band gap of 1.71 eV was estimated at room temperature. Two broad luminescence bands at 1.529 eV and at 1.634 eV were observed at 15 K. The light emission characteristics of the ZnSnP 2 were explained in terms of donor-acceptor pair recombination mechanism. Tin-on-zinc sites and zinc vacancies/zinc-on-tin sites were considered as donor and acceptor due to presence of native defects in the films. A schematic band model based on the experimental finding was suggested to account for the DA pair recombination.