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

Abstract

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.