Annealing temperature effect on structural and optoelectronic properties of γ-In2Se3 thin films towards highly stable photodetector applications

Abstract

Metal chalcogenide-based photodetectors have been studied extensively in recent years. However, the dark current, detective spectral ranges, responsivities, and response time are still unsatisfactory. Also, the major challenge for photodetector material is the deposition of large-scale material, a high-quality film with high reliability and low variability. In this work, we have synthesized Indium selenide (γ-In2Se3) thin films using the RF magnetron sputtering technique. We have thoroughly investigated the effect of annealing temperature on structural, optical, morphological, and photo-sensing properties of the synthesized thin films. Low angle XRD confirms the formation of hexagonal γ-In2Se3 films. The crystallite size increases from 56 nm to 64 nm with an increase in annealing temperature. Raman spectroscopy and XPS techniques confirm the γ phase of indium selenide. FE-SEM analysis revealed that the synthesized films are compact and uniform. Also, they are free from holes and cracks, which is necessary for semiconductor applications. The agglomeration of particles is observed with an increase in annealing temperature. The EDS spectra revealed that synthesized γ-In2Se3 films have ideal stoichiometry with In:Se ratio of 2:3. The UV–visible spectroscopy analysis showed a slight decrease in bandgap from 2.0 eV to 1.93 eV with an increase in annealing temperature. Other optical properties, such as absorption coefficient (α), extinction coefficient (k), the real and imaginary part of dielectric constant, optical conductivity, etc., of synthesized γ-In2Se3 films critically depend on the annealing temperature. Finally, the synthesized γ-In2Se3 thin films were used to fabricate photodetectors on ITO-coated interdigital electrodes. All γ-In2Se3 photodetector shows good stability and repeatability under dark and illumination conditions. The rise and decay time decrease with increase in annealing temperature. Photodetector with γ-In2Se3 thin film annealed at 300 °C exhibited excellent photoresponsivity (1.12 mA/ W) and stable photoswitching behavior. A fast rise (0.22 s) and decay time (2.85 s) were observed for the prepared photodetector. Our work demonstrates that γ-In2Se3 photodetector can be a promising material for photodetection applications.