Optical properties of zinc nitride thin films fabricated by rf-sputtering from ZnN target

RF-magnetron sputtering was employed to deposit zinc nitride films, from zinc nitride target, in plasma containing a mixture of Ar–N2 gases. The effect of ambient atmosphere as well as thermal treatments (annealing in nitrogen and oxidation) on the optical properties of the films were examined. The transparency and conductivity of the films just after deposition were dependent on the amount of Zn in the structure. The films exhibited n-type conductivity and wide optical band gap. Annealing improved their transparency but they became more resistive. Oxygen was detected in films remained in the ambient atmosphere for a long period of time just after deposition, affecting transmissivity. Annealing promoted adsorption of oxygen in their structure, and the optical properties of high temperature annealed films resembled those of zinc oxide films having nitrogen as acceptor dopant. Band-edge emission peaks arising from acceptor exciton as well as nitrogen-related defect centers were revealed by low temperature photoluminescence.