Omnidirectional reflectance and vanishing Brewster angle of disordered semiconductor nanopillar surface with gradually changed refractive index

Abstract

The geometrical-factor dependent Brewster angle shift in angular reflection spectra of the subwavelength nanopillar roughened semiconductor antireflective surface is investigated. Modeling of the nanopillar roughened surface evidently accounts for the shift and vanishing of the high-contrast transverse magnetic (TM) TM-mode angular reflectance spectrum with enlarging nanopillar height. The Brewster angle down-shifts by 20° with corresponding reflectance minimum increasing from <0.01% to 5.3% as the height of nanopillar increases from 0 to 240 nm, and the Brewster angle vanishing phenomenon is persistently observed until its disappearance with the nanopillar height enlarging up to 240 nm, leaving a slightly increased reflectance at larger incident angles.