Photoresponse Performance Evaluation of ZnO UV Photodetector Based on Noise Analysis

The ZnO film photosensitive chips prepared by sputtering method were post-treated by air-anneal at different temperatures and Ar or air-plasma treatments for different time. Then, photosensitive chips were packaged into UV photodetectors with a standard TO-5 package to meet the sensitivity, selectivity, and stability standards. Noise analysis was used as an efficient tool to evaluate the quality and reliability of ZnO UV photodetectors, and the overall performance evaluation based on 1/f noise physical model is made to build the relationship between photoresponse and surface defect state density. The 1/f noise comes from defect-related carriers' number fluctuation, which are trap and detrap processes of free electrons from oxygen vacancies at the surface of ZnO. This can be analyzed semi-quantitatively by the surface trap energy density obtained by voltage power spectral density. For the photosensitive chip treated by 300° air-anneal, we can obtain the largest responsivity 6.7 A/W, the smallest noise equivalent power 2.7 × 10
^-9
W, and the largest specific detectivity 9*10
¹⁰
Jones at 300 nm under the bias of 5 V. The excellent photoresponse performance is also indicated by large linear dynamic range and fast response and recovery speeds.