Effects of pseudo-disordered sizes distributions on the optical and electrical properties of GaAs nanowires arrays

We investigate the optical and electrical properties of GaAs nanowires (NWs) arrays constituted by unit cells with several NWs diameter and length sizes. The mix of geometrical sizes in each unit cell is to optimize the light absorption and the consequent improvement of the electrical performance parameters of these photovoltaic cells. The simulated system is a multilayer structure defined by a transparent layer of Indium Tin Oxide (ITO), the active region of GaAs NWs arrays embedded into the filling medium PMMA 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. We observe a typical oscillating behavior in the absorbance spectra, regardless the type of geometrical sizes investigated. 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. For all investigated sizes, we obtain that the absorbance values decrease for longer wavelength. Greater NWs diameter and longer NWs length in the unit cells entail a better light absorption of the arrays. This feature favor an enhancement of the short circuit density, the open circuit voltage, the fill factor and the efficiency of these photovoltaic cells. With p-polarization at oblique incidence, the degree of diameter-disorder in unit cells that constitute the GaAs NWs array slightly improve their optical and electrical transport properties.