Characterization of Bi2O3/ZnS heterojunctions designed for visible light communications

In the current work, the structural, morphological and optical properties of the Bi2O3/ZnS heterojunctions as visible light communication (VLC) technology element are explored. Bismuth oxide layers of thicknesses of 200 nm are used as substrate to evaporate ZnS films of thicknesses of 500 nm by the thermal evaporation technique under vacuum pressure of 10−5 mbar. The heterojunction devices are studied by the x-ray diffraction, scanning electron microscopy, optical spectrophotometry and microwave spectroscopy techniques. The Bi2O3/ZnS heterojunctions are found to form a highly strained structure with extremely large lattice mismatches. By the strained structure and with the valence and conduction band offsets that exhibit values of 1.04 and 0.41 eV, respectively, it was possible to enhance the light absorbability of ZnS by 459 times at 3.10 eV. In addition, the dielectric constant spectra of the device display a linear and nonlinear optical properties below and above 1.94 eV, respectively. Moreover, the optical conductivity parameters including the drift mobility and plasmon frequency and the cutoff frequency spectra of an area of 0.50 cm2 of Bi2O3/ZnS interfaces have shown the ability of using these heterojunction devices as light signal receivers that attenuate signals at terahertz frequencies in the range of 0.27–1.00 THz. As an additional demonstration, the Bi2O3/ZnS heterojunction devices were subjected to a microwave signal propagation in the frequency domain of 0.01–2.90 GHz. The device performed as band filters at gigahertz frequencies.