Thermal oxidation of n-type ZnN films made by rfrf-sputtering from a zinc nitride target, and their conversion into p-type films

Transparent p-type thin films, containing zinc oxide phases, have been fabricated from the oxidation of n-type zinc nitride films. The zinc nitride thin films were deposited by rfrf-magnetron sputtering from a zinc nitride target in pure N2 and pure Ar plasma. Films deposited in Ar plasma were conductive (resistivity 4.7×10−2 Ω cm and carrier concentrations around 1020 cm−3) Zn-rich ZnxNy films of low transmittance, whereas ZnxNy films deposited in N2 plasma showed high transmittance (>80%), but five orders of magnitude lower conductivity. Thermal oxidation up to 550 ∘C converted all films into p-type materials, exhibiting high resistivity, 102–103 Ω cm, and carrier concentration around 1013 cm−3. However, upon oxidation, the ZnxNy films did not show the zinc oxide phase, whereas Zn-rich ZnxNy films were converted into films containing ZnO and ZnO2 phases. All films exhibited transmittance >85% with a characteristic excitonic dip in the transmittance curve at 365 nm. Low temperature photoluminescence revealed the existence of exciton emissions at 3.36 and 3.305 eV for the p-type zinc oxide film.