Characterization and device applications of p-type ZnO films prepared by thermal oxidation of sputter-deposited zinc oxynitride

• Published in: Journal of alloys and compounds 2017-02, Vol.695, p.124-132
• Main Author: Rakhshani, A.E.
• Format: Article
• Language: English
• Subjects: Electroluminescence; Homojunction diode; p-type ZnO; Photoluminescence; Schottky diode; Sputtering; Thermal oxidation
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2016.10.187

Formation of nitrogen-doped p-type ZnO (p-ZnO) and related homojunction devices has been reported extensively using a variety of techniques with the exception of thermal oxidation of ZnON that is a simple and less explored method. We converted sputter-deposited ZnON films to p-ZnO at relatively low oxidation temperatures (400–500 °C) as compared with other reports. Chemical bonding states of nitrogen in p-ZnO films were examined by XPS analysis and the mechanism of p-type doping was discussed. Films were characterized by XRD, SEM, photocurrent spectroscopy, and photoluminescence (PL) measurement. Films were composed from nano-size crystallites with (100) preferential orientation. A shallow acceptor level with a 70–90 meV binding energy and a 1.72-eV deep level were measured and identified. PL thermal quenching of the films had activation energy of 34 meV. Schottky barrier (SB) and homojunction diodes, with two different types of n-ZnO, were fabricated on films and their parameters were compared with the reported data. The SB and both types of homojunction diodes had high rectification factors (104-105) and good device parameters. The conductance of homojunction diode based on sputter-deposited n-ZnO showed thermal activation energies of 0.08–0.12 eV, 0.16–0.20 eV, and 0.40–0.50 eV. The homojunction diode based on n-ZnO nano-rods exhibited strong electroluminescence in the visible region from which two defect-related transition energies of 2.21 eV and 2.66 eV were obtained. In conclusion, good quality p-ZnO films and related devices can be prepared by thermal oxidation of ZnON films. •p-ZnO films are prepared by thermal oxidation of sputter-deposited zinc oxynitride.•Mechanism of nitrogen doping is described based on experimental evidences.•An acceptor level 70–90 meV above the valence band edge is detected in p-ZnO films.•A deep level located 1.72 eV above the valence band edge is present in p-ZnO films.•Schottky and homojunction diodes with excellent device parameters are prepared.