Fabrication of enhanced performance Visible-light photodetector based on Ag/ZnS/p-Si/Ag heterojunction grown by chemical bath deposition

In the present work, ZnS thin films were deposited onto Si-substrate using the chemical bath deposition technique, with a deposition time of 75 min and 100 min, and subsequently the deposited thin films were used to fabricate Ag/ZnS/p-Si/Ag heterojunction devices to study their visible light photodetection properties under illumination intensity of 30 mW/cm2 and 56 mW/cm2 under applied forward bias voltage of 0 V and 5 V. Glancing incidence X-ray diffraction analysis confirmed the cubic zinc-blende phase of the deposited thin films, and Scherrer analysis revealed a crystallite size of about 2.4 nm. Surface morphology was studied using scanning electron microscopy and scanning transmission electron microscopy. X-ray photoelectron spectroscopy confirmed the presence of desired Zn2+ and S2- chemical species in the deposited thin films. Optical transmittance spectra revealed the higher transmittance of the ZnS thin film deposited for 75 min, while Tauc analysis of the optical absorbance spectra revealed that the deposited thin films had an energy band gap of 3.9 eV. Photoluminescence emission spectra revealed the emission due to recombination transitions via defect-related energy sites. Analysis of the visible light photodetection parameters revealed that the fabricated devices exhibited high performance, especially in terms of response and recovery times, with stable, reproducible and rapid-switching on-off cycles, indicating the potential for application in optical sensing, detection, or communication.