Influence of La3+ doping on nebulizer spray pyrolysed In2S3 thin film for enhanced photodetector performance

Abstract

In recent years, the photodetectors gained much attention due to their wide range of applications and fabrication of high-performance, cost-effective devices using environmentally friendly material is always challenging. In this work we report the fabrication of Lanthanum -doped indium sulfide thin films (In2S3:La) using a low-cost nebulizer spray pyrolysis method. La-doping concentration is varied from 0 to 5 wt% and the effect of doping on the properties of In2S3 thin films are investigated using X-ray diffraction (XRD), energy dispersive x-ray analysis (EDX), field emission scanning electron microscope (FESEM), UV–Vis spectroscopy, photoluminescence spectra. Incorporation of 3 wt% of La3+ in In2S3 lattice has substantially improved the crystallinity, surface morphology and optical properties of the thin films suitable for the device fabrication. Moderate doping of La3+ in the crystal lattice of β-In2S3 led to a red-shift in the absorption edge, which benefited utilization of wider light spectrum. Photodetectors are fabricated using In2S3:La (0–5 wt%) films and photodetector performance parameters are evaluated using I-V characteristics and current–time characterization. The In2S3 film with 3% La dopant concentration showed high photodetector performance with estimated detectivity (D*), photoresponsivity (R), and external quantum efficiency (EQE) of 1.11 × 1011 Jones, 5.05 × 10-1 AW−1, 118% respectively. For the same sample, the rise and fall time calculated from transient photo-response analysis is found to be 0.4 s and 0.3 s respectively. These optimally doped In2S3:La 3wt% thin film samples could be useful for the fabrication of photosensor based optoelectronic devices.