Optimizing the optoelectronic properties of broadband FeS2/Si photodetectors via deposition temperature tuning in chemical bath deposition

Abstract

This study investigates the fabrication and characterization of n-FeS₂/p-Si heterojunction photodetectors using chemical bath deposition (CBD) at deposition temperatures ranging from 50 °C to 80 °C. The impact of temperature on the structural, morphological, and optical properties of FeS₂ thin films was evaluated. X-ray diffraction (XRD) revealed polycrystalline cubic FeS₂ with improved crystallinity as the deposition temperature increased. The optical energy gaps of the films ranged from 2.41 eV to 1.6 eV, decreasing with higher temperatures. Scanning electron microscopy (FE-SEM) showed that grain size increased from 30 nm to 180 nm as the temperature rose. Hall effect measurements confirmed the n-type conductivity of the film, with mobility decreasing from 5 to 3.17 cm² V⁻¹ s⁻¹ at higher temperatures. The heterojunctions exhibited rectifying behavior, with the best ideality factor of 1.7 observed at 60 °C. The photodetector fabricated at 60 °C showed superior performance, with a responsivity of 0.37 A W⁻¹ at 520 nm and 0.7 A W⁻¹ at 770 nm, an external quantum efficiency of 52%, and a detectivity of 8 × 10¹¹ Jones at 520 nm, making it the optimal configuration for efficient broadband photodetection.