Thermal annealing effect on zinc nitride thin films deposited by reactive rf-magnetron sputtering process

Zinc nitride films were deposited by reactive radio-frequency magnetron sputtering using a zinc target in a nitrogen and argon plasma. The deposited films were annealed in either air or O2 at 300 °C to investigate the annealing effect on the microstructure, optical properties, and electronic characteristics of zinc nitride films. It was found that the annealing process decreased the crystallinity of zinc nitride films. It was also found that the optical band gap decreased from 1.33 eV to 1.14 eV after annealing. The analysis of film composition suggested that the concentration of oxygen increased slightly after annealing. Although the conduction type of both as-deposited and annealed films were n-type, the annealed films exhibited a higher resistivity, lower carrier concentration and lower mobility than the as-deposited films. Also, it was found that the as-deposited films did not exhibit any photoconducting behavior whereas the annealed films exhibited a pronounced photoconducting behavior.