Preparation of high-responsivity strontium–doped CuO/Si heterojunction photodetector by spray pyrolysis

In this work, the fabrication and characterization of a strontium-doped CuO/Si photodetector by chemical spray pyrolysis are demonstrated. The structural, electrical, and optical properties of CuO film and strontium-doped CuO film doped at doping concentrations of 3% and 6% are studied. The X-ray diffraction studies reveal that the deposited CuO film is crystalline with a monoclinic structure, and a new Cu₄O₃ phase was observed when the film was doped with strontium. The optical energy gap decreases from 2.5 to 2.25 eV after doping with Sr at 6%. The scanning electron microscopy investigation shows that the grain size decreases from 150 to 75 nm after doping with 6% strontium. The DC electrical conductivity of the film decreased after doping, and the activation energy was determined and found to be 0.52 and 0.75 eV for Sr dopant at 3% and 6%, respectively. The current–voltage characteristics of CuO/Si and CuO:Sr/Si heterojunction photodetectors under dark and light conditions are studied as a function of doping concentration. The photodetectors show rectification characteristics. The figures of merit of the photodetectors are measured. The responsivity (R_λ) of the photodetectors increases from 0.9 to 1.7 and 2.85 A/W at 650 nm after doping with strontium at doping concentrations of 3 and 6%, respectively. The maximum external quantum efficiency (EQE) and specific detectivity (D*) were 2.79 × 10²% and 2.66 × 10¹² Jones, respectively, for a CuO:Sr/Si photodetector doped with 3%.