High-Efficiency Photodetectors Based on Zinc Oxide Nanostructures on Porous Silicon Grown by Pulsed Laser Deposition

Abstract

In this study deposited zinc oxide (ZnO) nanostructures were prepared by pulsed laser deposition (PLD) technique on porous silicon (PS) substrates that were prepared via photoelectrochemical etching of silicon n-type (100). The study investigated the influence of laser energy on various characteristics of the fabricated devices, including their optical, morphological, structural, electrical, and photodetector features. The X-ray diffraction results indicate a dominant broad diffraction peak at 69.14°, and the ZnO phase aligns with the hexagonal wurtzite structure. The field emission scanning electron microscopy micrograph illustrates that porous silicon has a sponge-like fashion, while ZnO nanostructures have spherical grains distributed randomly and grow larger with laser energy. The optical characteristics of the manufactured samples were examined using techniques that include UV–vis absorption spectroscopy, UV–vis diffuse reflectance spectrometry, and photoluminescence spectroscopy. The findings indicated that decreased laser energy led to a blue shift in the energy gap. The reflectivity of the produced samples decreased after the deposition of a zinc oxide layer over porous silicon. The photoluminescence examination showed the presence of four distinct emission peaks, namely, UV, violet-blue, blue, and green, consequent to coating a ZnO layer onto the porous silicon substrate. Fourier transform infrared spectroscopy confirmed that ZnO thin films deposited on porous silicon cause surface oxidation and produced a new peak at 455.2 cm⁻¹ related to the Zn–O stretching band. The current density–voltage properties of the fabricated devices in the absence and presence of white light were investigated as a function of laser energy. The ZnO NPs/PS/n-Si photoreactors displayed rectifier features and had outstanding spectral responsivity from ultraviolet to near-infrared. Moreover, the fabricated photoreactor showed the most prominent external quantum efficiency (EQE) in the UV region. The results of this study are of great importance to the advancement of photodetectors and optoelectronic devices based on ZnO and porous silicon.