Electrical and Ultraviolet-A Detection Properties of E-Beam Evaporated n-TiO2 Capped p-Si Nanowires Heterojunction Photodiodes

Abstract

Fabrication and Ultraviolet (UV) detection properties of p-Si Nanowires (NWs)/n-TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin film-based heterojunction photodiodes have been reported in this paper. The highly oriented, uniform and vertically aligned p-type single crystalline silicon nanowire (SiNW) arrays have been synthesized by the two-step process of electroless metal deposition and etching technique. A thin layer (~120 nm) of anatase phase titanium dioxide (TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) is then deposited on the top of p-SiNWs using electron-beam evaporation technique. The surface morphology and crystallinity of p-SiNWs and n-TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> capped SiNWs have been characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction techniques. The optical properties of the as-deposited n-TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin film grown on p-SiNWs were analyzed using the photoluminescence measurements. The UV detection properties of the p-SiNWs/n-TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> heterojunction was studied by measuring the room temperature current-voltage (I - V ) characteristics under dark and UV illumination conditions with incident optical power(P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sub> ) ≈ 650 μW at wavelength (λ) ≈ 365 nm. The as-fabricated p-SiNWs/n-TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin film heterojunction photodiode showed an excellent value of Detectivity ~ 8.66 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> mHz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> W <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> with the external quantum efficiency (EQE) ~ 79.33%, responsivity~ 0.234 A/W, and contrast ratio ~ 113.82 at -11 V bias. Other parameters such as rectification ratio (~ 519.82), Turn-on voltage (~0.732 V) and effective barrier height (~0.7924 eV) under dark condition were also calculated. The proposed p-SiNWs/n-TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) thin film hetrojunction can thus be explored for UV-A detection.detection.