Engineered ultra-wide bandgap Sm₂O₃/MWCNT nanocomposites for deep-ultra violet photodetectors

Abstract The current work focuses on the synthesis and control of cubic vs monoclinic phase structures of Sm₂O₃ via., cost-effective solution-based sol–gel technique. The structural analysis of the as-synthesized Sm₂O₃ powder reveals the phase-change from initial mixture of cubic and monoclinic phases (82:18) to almost cubic phase (96:4), with increase of polyethylene glycol 600 additive from 2% to 25% respectively. The dark-current of the films made from as-synthesized Sm₂O₃ powder revealed no measurable current, indicates its high defect tolerance against growth conditions. The multi-walled carbon nanotubes (MWCNT) are added as conducting scaffold into Sm₂O₃ insulating matrix, to facilitate carrier transport for light-generated carriers, upon UV exposure. The dark-current of the photodetectors increased from nano-ampere to milli-ampere range with increase in MWCNT weight concentration from 1% to 10% respectively. A nominal photo-to-dark current ratio (PDCR) of around 2 is observed for different MWCNT concentrations in Sm₂O₃ on glass substrates, upon UV light exposure. The PDCR is further increased to a maximum of 5.6 with the increase in grain-structure of Sm₂O₃ within the nanocomposite via., substrate-engineering. The observed PDCR of 5.6 is the first reported value (to the best of our knowledge) for Sm₂O₃-based nanocomposite material towards deep-UV photodetector applications. The experimental results suggest incorporation of conductive nanocomposites into ultra-wide bandgap oxide semiconductor materials seems to be a feasible and promising approach for the design of future cost-effective deep-UV photodetectors.