Comparative study of UV-ZnO NRs photodetectors based on seeded porous silicon by RF-sputtering and drop-casting methods

Photodetectors (PDs) play a fundamental role in the advancement of modern optical communication technologies. Utilising the simple methodology to develop metal–semiconductor-metal (MSM) PDs based on zinc oxide nanorods (ZnO NRs) will be beneficial for this purpose. In this work, a comparative analysis of fabrication approaches of seed layer onto porous silicon (PSi) via radio frequency (RF) magnetron sputtering and drop-casting (dc) methods have been performed. In addition, the influence of these methodologies on the morphological, structural, and optical properties of ZnO NRs along with the performance of the fabricated UV-PDs was investigated. The optical, structural, and morphological characteristics of the samples have been examined by using atomic force microscopy (AFM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), UV–VIS spectroscopy, Photoluminescence (PL), and Energy-dispersive X-ray analysis (EDX). Moreover, the performance of the fabricated Metal–Semiconductor-Metal (MSM) devices is calculated from the Current–Voltage (I–V) and Current–Time (I–T) measurements. Due to the high number of nano-junctions between the rods and the higher aspect ratio of ZnO NRs, the photodetector based on ZnO seeded via the drop-casting method gave the best electrical performance. The device (Pd/ZnO NRs/Pd)/seeded PSi via drop-casting technique showed a responsivity value of 1.12 A/W, a high gain of 7.4, high sensitivity value of 645.5%, and external quantum efficiency (EQE) of 372% at 3 V bias voltage under UV light with a wavelength of 375 nm. The device also shows a sensitivity of 17,553.8% at 0 V bias voltage, therefore, it can be considered a self-powered photodetector.