Effects of indium selenide substrates on the performance of niobium pentoxide optoelectronic devices

To widen the photo-responsivity range of niobium pentoxide photodetectors, InSe thin films were deposited by thermal evaporation technique under high vacuum pressure and used as substrates for growing Nb₂O₅ thin films. The resulting InSe/Nb₂O₅ (ISNO) stacked layers formed amorphous/amorphous structure. Optical analyses showed that the niobium pentoxide layers successfully suppressed the free carrier absorption observed in InSe substrates. A new direct allowed transitions energy band gap of 0.85 eV was formed at the interface between InSe and Nb₂O₅. The ISNO interfaces exhibited conduction and valence band offsets in the ranges of 0.25–0.65 eV and \(1.85-1.47\) eV, respectively. Depositing Nb₂O₅ onto InSe extended the light responsivity range of Nb₂O₅ from the ultraviolet to the near infrared range. Notably, ISNO photodetectors displayed impressive features, with large current responsivities and large external quantum efficiencies of 4.7 A/W and 9.7 A/W and 1000% and 3000%, under visible-infrared and ultraviolet radiations, respectively.These characteristics make the ISNO heterojunction devices promising candidates for broadband photodetectors and other optoelectronic applications.