Visible-Blind Au/ZnO Quantum Dots-Based Highly Sensitive and Spectrum Selective Schottky Photodiode

The optical and electrical properties of Au/ZnO quantum dots (QDs)-based Schottky photodiode are analyzed in this paper. The thin film of ZnO QDs was deposited over the n-Si (111) substrate using the low-cost solution processing technique. The Schottky contact gold (Au) electrodes are deposited using thermal evaporation over the ZnO QDs thin films. The responsivity and contrast ratio of the photodiode are found to be 41.17 A/W and 2.289 × 10
⁴
, respectively, at -5 V applied bias. Furthermore, the spectral response of the photodiode has been analyzed for the spectrum of 250-900 nm. The photodiode shows the full width at half maxima of 90 nm with a central wavelength of 365 nm, which indicates the color selective nature of the photodiode. In further analysis, it is observed that the rectification ratio, ideality factor, and barrier height of this device are 2.21 × 10
³
, 2.57, and 0.80 eV, respectively. The obtained electrical and optical parameters are the best-reported values for the ZnO-based UV detectors. The transient response of the Schottky photodiode is found to be 73.1 ms (rise time) and 17.85 ms (falltime) under the illumination of UV LED for a square pulse of an ON-OFF period of 1 s.