Preparation and Characteristics Study of High-Quantum Efficiency Ni/PSi/c-Si and cd/PSi/c-Si Double-Junction Photodetectors

In this work, nanocrystalline porous silicon (PSi) was prepared by the photo-electrochemical etching (PECE) technique. A comparison study between the optoelectronic properties of double junctions Ni/PSi/c-Si and Cd/PSi/c-Si photodetectors is reported. The Ni and Cd thin films were deposited on the porous silicon layers by the thermal evaporation technique. The structural, electrical, and optoelectronic properties of Cd/PSi/n-Si and Ni/PSi/c-Si devices were examined at room temperature. The XRD analysis confirmed the formation of the nanocrystalline structure of the PSi layer. Scanning electron microscope (SEM) studies reveal the formation of circular pores with an average diameter of 250 nm. The dark and illuminated I-V characteristics of the photodetectors are investigated at room temperature, and the junction characteristics of the Cd/PSi/c-Si junction are better than those of the Ni/PSi/c-Si junction. The maximum responsivity of the Cd/PSi/c-Si photodetector is 1.47AW−1 at 400 nm, while the maximum responsivity of Ni/PSi/c-Si was about 1.45AW−1 at 540 nm. The external quantum efficiency (EQE) of Cd/PSi/c-Si and Ni/PSi/c-Si photodetectors was 450% and 330% at 400 nm, respectively.