Antireflective Subwavelength Structures on 4H-SiC for UV Photodetectors

Abstract

We report on the fabrication of moth-eye antireflection gratings on silicon carbide substrates using a silica mask inverted from hydrogen silsesquioxane (HSQ) technique. We demonstrate optical properties of subwavelength structure on 4H-SiC. The micro-cone array is fabricated by an ECR-reactive ion etching using Cl 2 -O 2 plasma. A nano-pillar array of silica, formed by an electron-beam lithography using HSQ negative-tone resist and annealing process, is used as the etching mask. The fabricated cone array has a period of 140 nm and a height of 177 nm. Measured reflectivity of the antireflection structured surface is below 2% at 330 nm and 10% at 500 nm for incident angle of 20 degree. The specular reflection is slightly affected by varying the angle of incidence up to 80 o of sand p-polarized light at 350 nm.

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