Fabrication of ZnO thin film Schottky ultraviolet photodetector

Abstract

ZnO films, with C-axis preferred orientation, were deposited on SiO2/n- Si by radio frequency (RF) magnetron sputtering. The interdigital metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors were fabricated by using Ag as Schottky contact metal. For comparison, ZnO Schottky diodes were also fabricated by using Ag-ZnO-AI structures. Aluminum was used to form Ohmic contacts. Current voltage (I-V) characteristics of these devices have been analyzed. The Schottky diodes exhibit distinct rectifying I-V characteristics. The barrier height of the Ag/ZnO Schottky contacts is around 0.65 eV. The leakage current for MSM photodetector is less than 6 × 10 -7 A at a bias of 5V. The photoresponsivity of MSM photodetector is much higher in the ultraviolet range than in the visible range. The UV/visible (350nm/500nm) rejection ratio is more than one order of magnitude. The photoresponsivity of MSM detector exhibits a maximum value around 370 nm.