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° and 34.66° 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 × 1013 Jones and noise-equivalent power of 7.6 × 10−13 W/√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 × 1013 Jones, respectively, and noise-equivalent power reduced to 5.4×10−13 W/√Hz. Furthermore, the UV-Ozone annealed photodetector exhibited good switching behavior with rise and fall times of 45.5 and 76.0 ms, respectively.