Fabrication and characterization of nitrogen doped p-ZnO on n-Si heterojunctions

Metal oxide semiconductors are promising materials for fabricating p-n heterojunctions which are technologically important for many electronic devices. The reason is their unique characteristics of tuneable electrical properties that can be controlled by doping. In the present work, a p-n heterojunction was fabricated by depositing nitrogen doped zinc oxide (ZnO:N) thin films on an n-type Si substrate using the radio frequency (RF) sputtering method. X-ray diffraction patterns shows the preferred orientation (002) peak of ZnO, which deteriorated with increasing N concentration. The crystallite size varied from 35 to 20 nm for different N concentration. The morphology of the ZnO:N thin films were highly dense and smooth. The optical band gap of the heterojunctions increased from 3.2 to 3.3 eV as the flow rate increased from 5 to 9 SCCM N2. The current-voltage (I-V) characteristics confirm the p-n junction behaviour of the ZnO:N/Si heterojunctions. The I-V characteristics were also measured at different temperatures in the dark. The photoelectric response on the I-V characteristics of the heterojunctions was also measured. The stability of the ZnO:N/Si heterojunction with respect to time duration was assessed. The results demonstrate that such physical processed novel thin films are promising for potential applications in electro-optic devices.