Self-powered and improved photoresponsive broadband photodetecting sensors using Au/NiFe2O4/p-Si heterojunction architecture

Abstract

Recently, heterojunctions-based photodetectors (PDs) with outstanding photosensitivity and fast switching time received substantial attention due to their broadband (BB) photoresponse in various regimes of the electromagnetic spectrum. Still, there is an increasing demand to accomplish BB PDs operating at photovoltaic (self-driven) mode for serving the today's societal energy efficient needs. In this work, Au and NiFe2O4 thin films were deposited onto p-Si substrates to accomplish interdigitated Au/NiFe2O4/p-Si heterojunction type BB PDs operated in self-powered mode. The structural, optical, morphological and magnetic parameters of the prepared NiFe2O4 thin films as a function of annealing process were studied using XRD, UV–Vis, AFM and XAS/XMCD techniques. Tauc's plot fitted from the UV–Vis absorption data for the as-deposited, 700 °C and 800 °C NiFe2O4 thin films were 4.85, 3.42 and 2.85 eV, respectively. The photodetection parameters of the fabricated interdigitated Au/NiFe2O4/p-Si BB PDs were analyzed with I–V, photoresponsivity and response (rise/fall) times as a function of annealing process. All the fabricated Au/NiFe2O4/p-Si BB PD devices with/without annealing process operated in photovoltaic mode (at 0 V). The PD device annealed at 800 °C unveiled better photoresponsivity (12.35 A/W @1060 nm), detectivity (5.9 × 1014 Jones @1060 nm) and rise/fall times (89 ms/185 ms @900 nm) compared to the as-prepared/700 °C annealed PD devices. The reason for this was attributable to the accomplished improvement in crystallinity (XRD), surface morphology (AFM), reduction of bandgap (UV–Vis) and variation of spin/orbital magnetic moments (XAS/XMCD). In this work, we suggest one of the alternative and cost-effective electron beam evaporation method to grow the desired epitaxial NiFe2O4 thin films compared to the other physical vapor deposition approaches such as PLD and ALD to fit the future necessities of optoelectronic field.