Antireflective characteristics of disordered GaAs subwavelength structures by thermally dewetted Au nanoparticles

We report the antireflective characteristics of disordered subwavelength structures (SWSs) fabricated on a GaAs substrate by thermal dewetting induced Au nanoparticle masks in a subsequent inductively coupled plasma etching process. The optical reflectance relies on the geometric profile of disordered GaAs SWSs. The average size of Au nanoparticles and the correlation distance between adjacent nanoparticles are determined by the Au film thickness and the thermal dewetting condition. It is found that the height and shape of the SWSs, which can be controlled by changing the etching parameters, affect the reflectance strongly. The tapered SWS with a height of ∼380 nm results in a relatively low reflectance spectra of <∼5% in the wavelength range of 350–900 nm. The angle-dependent reflectance is also investigated for the fabricated GaAs SWSs.