Varying load resistances of zinc oxide ultraviolet photodetectors: A simple method to change responsivity

Abstract

The metal–semiconductor–metal structured ultraviolet photodetector has been fabricated based on Zinc oxide thin films grown by a radio frequency magnetron sputtering technique, and Au is used as the contact metal. The dark current of the photodetector is as low as 1.17nA at 3V bias in the current–voltage measurements. The photoresponse properties are characterized by varying the load resistors (1kΩ, 10kΩ, 100kΩ, 1MΩ and 22MΩ), and the corresponding responsivities are 2.69, 1.27, 0.25, 0.02 and 7.20×10−4A/W. It can be found that the responsivity of the photodetector is enhanced with the load resistors decreasing; however, the signal-to-noise ratio decreases. It is demonstrated that the best method to make the ZnO-based photodetector suitable for different application environments is with the appropriate load resistance.