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

摘要

Zinc nitride thin films were deposited by magnetron sputtering using ZnN target in plasma containing either N_2 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 ℃ in N_2 and O_2 environments. Films deposited in Ar plasma were opaque and conductive (ρ～10~1 to 10~2 Ω cm, N_D～10~(18) to 10~(20) cm~(-3)) due to excess of Zn in the structure. After annealing at 400 ℃, the films became more stoichiometric, Zn_3N_2, and transparent, but further annealing up to 550 ℃ deteriorated the electrical properties. Films deposited in N_2 plasma were transparent but very resistive even after annealing. Both types of films were converted into p-type ZnO upon oxidation at 400 ℃. 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.