Highly sensitive self-powered solar-blind ultraviolet photodetectors based on n-Zn1-xFexO/p-Si heterojunctions

Abstract

The pristine and iron-doped ZnO thin films were fabricated on p-type silicon and glass substrates using the radio-frequency magnetron sputter deposition technique. The structural, morphological, and electrical properties of the deposited thin films were analyzed using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), and I-V characteristics. XRD analysis revealed the preferential growth of ZnO along the c-axis, with lattice parameter (c) values of 5.216, 5.234, and 5.241 Å for the pristine ZnO, Zn0.97Fe0.03O, and Zn0.95Fe0.05O thin films, respectively. The crystallite sizes were measured to be 13.2 nm, 16.2 nm, and 18.3 nm for the respective films. The elemental analysis of the deposited films was done under X-ray photoelectron spectroscopy (XPS), which revealed the concentrations of iron Zn0.97Fe0.03O, and Zn0.95Fe0.05O thin films were 2.93 at% and 5.14 at%, respectively. Raman spectroscopy confirmed the presence of the hexagonal wurtzite structural form in the deposited films. The I-V characteristics of the deposited films confirmed the formation of a heterojunction between the film and the silicon substrate. Furthermore, the constructed heterojunction devices were evaluated for their ability to detect ultraviolet (UV) radiations of wavelengths 365 nm and 254 nm. The devices exhibited response and recovery times of less than 1 s. The detectivity values were found to be 0.321 ×1011, 1.051 ×1011, and 2.992 ×1011 Jones for the ZnO/p-Si, Zn0.97Fe0.03O/p-Si, and Zn0.95Fe0.05O/p-Si devices, respectively, under a fixed illumination intensity of 0.812 mW/cm2 for a UVA source with a wavelength of 365 nm. These results confirm the excellent photodetection ability of the constructed devices. The mechanism of UV radiation detection by the devices has also been extensively discussed.