An ultra-black silicon absorber

An ultra-black (A > 99%) broadband absorber concept on the basis of a needle-like silicon nanostructure called Black Silicon is proposed. The absorber comprises Black Silicon established by inductively coupled plasma reactive ion etching (ICP-RIE) on a highly doped, degenerated silicon substrate. Improved absorbers also incorporate an additional oxide capping layer on the nanostructures and reach an absorptance of A > 99.5% in the range of 350 to 2000nm and A approximate to 99.8% between 1000 and 1250nm. Fabrication of the absorbers is consistent with CMOS standards and requires no lithography. (Picture: Kasper, Friedrich-Schiller-University Jena)