Ultrathin broadband antireflection structure composed of multilayer hollow nanopillar arrays of c-Si and Ag shells embedded in a GaAs substrate

In this study, we investigated the spectral response and properties of compositional multilayer hollow nanopillars in the certain arrays that are embedded in a GaAs substrate to design a broadband antireflection subwavelength structure. Considering the arrays of multilayer hollow nanopillars (crystalline-Si/Ag/air) with the appropriate geometrical sizes, three kinds of optical modes at the absorption profile in the wide range of the spectrum are reported. Fabry–Perot (FP), hybrid, and plasmon resonance modes are the three appeared optical modes at the calculated absorption cross-sectional profile using numerical method. Quantifying the reflectance of the subwavelength structure, this parameter is measured as approximately 6.69% in the range of λ ∼ 400–2900 nm. We proved that proposed nanostructure is able to provide high ratio of optical energy absorption due to the existence of GaAs, c-Si and Ag substances that play fundamental role in this enhancement as the absorber materials.