Superior photoresponse MIS Schottky barrier diodes with nanoporous:Sn–WO3 films for ultraviolet photodetector application

Abstract

A highly ordered nanoporous structure based MIS type photo-detector is a promising device for next-generation optoelectronic applications due to its excellent light absorption, better mechanical strength, low density with a larger diffusion coefficient and charge accommodation ability. Herein, we have fabricated a highly sensitive MIS Schottky barrier diode by sandwiching nanoporous:Sn–WO₃ films as the interfacial layer prepared by a jet nebulizer spray pyrolysis technique. XRD patterns confirmed the polycrystalline nature with monoclinic and orthorhombic phases of Sn–WO₃ films, whose crystallite size gradually increased with the Sn concentration. The FE-SEM images confirmed that the Sn–WO₃ composite films with 12 wt% of Sn exhibited unique surface morphology of nanoplates, nanowires and nanoporous-like structures. The optical band gap energy improved from 3.2 to 3.6 eV with increased Sn concentration. By establishing the nanoporous structure of Sn–WO₃, we are the first to report on the photo-diode properties of Cu/nanoporous:Sn–WO₃/p-Si diodes which recorded a positive photo-response with a higher reverse saturation current under illumination. This is supported by the enhanced detectivity of the interface layer with an increased Sn concentration. We have achieved an ultra-high responsivity of 5083.5 mA W⁻¹ for the diode fabricated with 12 wt% of Sn, which is 154 times higher than that of pure WO₃. The presence of a nanoporous:Sn–WO₃ layer in the MIS diode helped in recording ∼60% quantum efficiency thereby making it ideal for ultra-violet photo-detector applications.