Noise Properties of Mg-Doped ZnO Nanorods Visible-Blind Photosensors

In this investigation, Mg-doped ZnO nanorods were synthesized successfully on a glass substrate at 80 °C by hydrothermal method. The average length and diameter of the Mg-ZnO nanorods were 609 nm and approximately 50 nm, respectively. The X-ray diffraction spectrum showed the Mg-ZnO nanorods had a wurtzite hexagonal phase. The Mg-doped ZnO nanorods are found to be single crystals grown along the c-axis. The photosensors showed good stability properties in ultraviolet (UV) illumination. The resulting Mg-doped ZnO nanorods have excellent potential for application in a UV photodetector (PD) because of the Mg-doped ZnO nanorods UV PD has a high UV-to-visible ratio, fast rise/fall time. Furthermore, the dynamic response of the Mg-doped ZnO nanorods PD with Au electrodes was stable and reproducible with an on/off current contrast ratio of approximately 4 × 10³. The ultraviolet-to-visible rejection ratio of the sample is approximately 400 when biased at 1 V, and the fabricated UV PD is visible-blind with a sharp cutoff at 350 nm. The low-frequency noise spectra obtained from the UV PD were caused purely by the 1/f noise. The noise-equivalent power and normalized detectivity (D^*) of the Mg-ZnO nanorod PD were 0.335 × 10^-9 W and 1.49 × 10⁸cm · Hz^0.5 · W^-1, respectively.