Fabrication of hybrid nanostructured Bi2S3/Si heterojunction photodetector by laser ablation in thiourea

Abstract

This work reports on the fabrication of a high-performance Bi₂S₃/Si visible photodetector by laser ablation of Bi target in thiourea without using a catalyst. The structural, morphological, optical, and electrical properties of Bi₂S₃ colloids are studied. The X-ray diffraction pattern reveals that the synthesized Bi₂S₃ is crystalline with an orthorhombic structure. An increase in laser energy density leads to improved crystallinity. Scanning electron microscopy investigation of the Bi₂S₃ confirms the formation of several morphologies: porous fibrous (PFs), nanoparticles (NPs), and nanorods (NRs), depending on the laser energy density. The optical energy gap of Bi₂S₃ nanostructures was found to decrease from 1.85 to 1.74 eV as the laser energy density increased from 9.55 to 15.92 J/cm². Hall measurements show that the electrical conductivity and electron mobility of Bi₂S₃ decreases with an increase in laser energy density. The fabricated Bi₂S₃/Si photodetectors exhibit figures of merit that depend on the laser energy density. The optimum photodetector, fabricated at a laser energy density of 15.92 J/cm², was found to have a responsivity of 1.32 A/W and an external quantum efficiency of 480 % at 350 nm. The rise/fall time ratio for the photodetector fabricated at 15.92 J/cm² was 0.34/0.34 s.