The effect of rare-earth element (Gd, Nd, La) doping of NiO films on UV photodetector

Abstract

Abstract The semiconductor-based UV photodetectors are the most essential devices in the field of space observations, military, DNA sequencing, analysis of protein, medical imaging, checking of atmospheric pollution, optical communications radiation, etc. With such a wide range of possible applications, the nanostructured pristine and rare-earth (RE) doped NiO ((NiO: Gd(1%), NiO:Nd(1%), NiO:La(1%)) thin films were prepared and investigated for their suitability as UV photodetectors. The films were prepared by nebulized spray pyrolysis (NSP) at a substrate temperature of 450 °C. The x-ray diffraction studies confirm the cubic single phase with the polycrystalline nature of the prepared films. The spectroscopic studies such as absorbance and photoluminescence confirm that increase in the optical bandgap and 391 nm PL emission is attributed to the near band edge emission of the NiO. The x-ray photoelectron spectroscopy reveals the presence of nickel and the doped elements with their oxidation states. The UV photodetector performance of the prepared NiO films was carried out under the irradiation of 365 nm light. The NiO:Gd exhibits the best responsivity (0.353 AW−1), external quantum efficiency (120%), detectivity (1.72 × 1010 Jones) and rise time (2.0 s), and fall time (2.2 s). Importantly, strategies such as limited doping (1 at.%) and larger ionic radii of Gd incorporation into the host NiO cause a moderate increase in the lattice distortion and inhibit the recombination rate instead of behaving as a recombination center. In addition, the conduction band (CB) electrons are trapped by a greater number of oxygen vacancies residing at the Gd3+ 4f state and cause a good separation of charge carriers. Overall, these modifications enhance the mean lifetime of electrons, consequently reducing the recombination rate and enhancing the photoresponse.