Enhancing responsivity and detectivity in broadband UV-VIS photodetector by ex-situ UV-ozone annealing technique

In the present study, we fabricated an Ultraviolet-visible (UV-Vis) photodetector by radio frequency (RF)-sputtering ZnMgO thin films on an n-type <001> Si substrate and studied the effect of UV-Ozone annealing, which has been proposed as a simple and low-cost post-growth strategy to improve its optical detection capability. The crystalline quality of the ZnMgO thin films was studied through high-resolution X-ray diffraction measurements, which revealed the dominant ZnMgO <002> peak at around 34.64 degrees and 34.66 degrees for the as-deposited and UV-Ozone annealed samples, respectively. The detector fabricated using the as-deposited ZnMgO thin film exhibited a photoresponsivity of 98 A/W, peak detectivity of 2.82 x 10(13) Jones and noise-equivalent power of 7.6 x 10(-13) W/root Hz for 370 nm incident light. Moreover, a high photoresponsivity of 24.4 A/W was obtained in the visible region up to 600 nm. After UV-Ozone annealing for 70 min, responsivity and detectivity improved remarkably to 199 A/W and 3.69 x 10(13) Jones, respectively, and noise-equivalent power reduced to 5.4x10(-13) WA/root Hz. Furthermore, the UV-Ozone annealed photodetector exhibited good switching behavior with rise and fall times of 45.5 and 76.0 ms, respectively.