ZnO Nanoneedle Based Efficient UV-Photodetector

Abstract

This article reports the fabrication and characterization of nano-structured ITO/ZnO ultraviolet photodetector. A ZnO thin film was deposited by spray pyrolysis technique followed by interdigitated ITO as electrode deposition by RF sputter. Grazing angle x-ray diffraction (GIXRD) study indicates preferential growth along c-axis (002) of thin-film leading nanoneedle formation which was further confirmed by scanning electron microscopy (SEM) imaging. X-ray photoelectron spectroscopy (XPS) analysis of Oxygen 1s (O 1s) was carried out. A peak was observed at 531.8 eV indicating the presence of oxygen vacancy, 530 eV peak relates to the ZnO phase. The bandgap was determined by the Tauc plot; which was found to be 3.22eV. The donor carrier concentration is found to be 8.85x10¹⁸ cm^-3 based on room temperature Hall measurement. A near ohmic behaviour was observed which can be interpreted by the existence of high carrier concentration in ZnO. This results in a very thin depletion width of the order of 5nm; therefore, charge transport through the junction is dominated by tunnelling of electrons through depletion width.