Ultralow broadband optical reflection of silicon nanostructured surfaces coupled with antireflection coating

Abstract

The impact of antireflection-coating (ARC) thickness, and the dimensions of the nanostructures, was systematically investigated by numerical simulation performed by Lumerical finite-different time-domain software. SiNW and SiNC array, coupled with a conformal ARC layer, consist of the square lattices of SiNWand SiNC. SiNW and SiNC arrays with a a-ZnO ARC layer are found to have much lower reflectance. The refractive index of the α-ZnO thin film is between 1.65 and 1.95 in the photon energy spectrum from 1.0 to 4.0 eV, which is close to the square root of the indices of silicon and air. It is also found that at 1.8 eV, with the weak internal resonance, light energy density reaches the same peak of reflectance for both the SiNC arrays with and without the ARC layer. The SiNC arrays with a α-ZnO ARC layer is found to moderate the effect of abrupt interface, which show a better antireflection performance than the SiNC arrays without an ARC layer.