The effect of nitrogen on the properties of zinc nitride thin films and their conversion into p-ZnO:N films

Zinc nitride thin films were deposited by magnetron sputtering using ZnN target in plasma containing either N2 or Ar gases. The rf-power was 100 W and the pressure was 5 mTorr. The properties of the films were examined with thermal treatments up to 550 °C in N2 and O2 environments. Films deposited in Ar plasma were opaque and conductive (ρ ∼ 10− 1 to 10− 2 Ω cm, ND ∼ 1018 to 1020 cm− 3) due to excess of Zn in the structure. After annealing at 400 °C, the films became more stoichiometric, Zn3N2, and transparent, but further annealing up to 550 °C deteriorated the electrical properties. Films deposited in N2 plasma were transparent but very resistive even after annealing. Both types of films were converted into p-type ZnO upon oxidation at 400 °C. All thermally treated zinc nitride films exhibited a shoulder in transmittance at around 345 nm which was more profound for the Ar-deposited films and particularly for the oxidized films. Zinc nitride has been found to be a wide band gap material which makes it a potential candidate for transparent optoelectronic devices.