Geometry-related optical properties in vertically aligned GaAs nanowires arrays: A study of sizes and embedding medium effects Articles uri icon

published in

publication date

  • October 2023

start page

  • 1

end page

  • 13

issue

  • 171187

volume

  • 288

International Standard Serial Number (ISSN)

  • 0030-4026

abstract

  • We investigate the effects of the geometrical sizes and surrounding media on the optical
    properties of a periodic square array of GaAs nanowires (NWs) as candidates for applications on
    photovoltaic solar cells as well as sensors. As filling media, different insulator materials such
    as PMMA, Polycarbonate, Polystyrene and PVP are considered in this study. The simulated
    system is made of three stacked layers along with two semi-infinite air spaces. The stacked
    layer system is defined by a transparent layer of Indium Tin Oxide (ITO), the active region
    of GaAs nanowires array embedded into the filling medium and a substrate of Silicon (Si).
    The multilayer absorbance is simulated by transfer matrix method (TMM); while the GaAs
    nanowires surrounded by filling medium is treated as an homogeneous layer whose effective
    dielectric function is described by Bruggeman effective medium theory. For both s- and ppolarizations at normal and oblique incidences, we observe a typical oscillating behavior
    in the absorbance/reflectance spectra, regardless the type of embedding medium and sizes
    investigated. For all investigated sizes, we obtain that the absorbance values decrease for longer
    wavelength. Greater D/P ratio for longer NWs benefit the light trapping with absorbance values
    up to 80 per cent in the VIS range. For small variations of the refractive index (dielectric
    constant) of the filling media surrounding GaAs NWs, we observed a perceptible change in
    their reflectance spectral values at specific wavelengths. On the other hand, the Brewster
    angle, calculated at the interface of the ITO layer and the effective embedded nanowires
    composite, is seen to be sensitive to the D/P ratio size, as far as the wavelength is varied.
    The above numerical results are in good agreement with those reported in the literature by
    experimental research and sophisticated FDTD simulations in III¿V semiconductor nanowires,
    which demonstrates that our TMM simulations are adequate approximations to account on
    optical properties in multilayered structures when homogenization of multilayers is required.

subjects

  • Physics