Barium Oxide‑Based Photodetectors Engineered for Visible Light and Near‑Infrared Communication Applications

Abstract

Thermally deposited p-type barium oxide (BaO) thin films, coated with a 50-nm-thick silicon oxide (p-SiO₂) protective layer, are employed as photodetectors. In a vacuum environment with a pressure of 10⁻5 mbar, stacked layers of p− BaO and p− SiO₂ are grown onto n-type Si substrates. Structural investigations revealed the preferred growth of the tetragonal phase of BaO. Temperature-dependent electrical resistivity and optical absorption measurements determined a work function of 4.29 eV for p− BaO. Additionally, the design of the energy band diagram indicated an almost negligible built-in potential at the –Si/p-BaO interface. The resulting n-Si/p− BaO/p− SiO₂ photodetectors demonstrated high current responsivities of 0.24 A/W, 0.17 A/W, and 4.5 A/W under illumination with blue, red, and near-infrared (NIR) light, respectively. Corresponding external quantum efficiency percentages exceeded 69%, 34%, and 580%. Furthermore, the calculated photodetector parameters, including specific detectivity, noise equivalent power, linear dynamic range, and time-dependent current growth/decay cycles, confirmed the suitability of the proposed devices for visible light and NIR communication technologies.