Abstract
A reactive ion etching technique for the preparation of statistical “Black Germanium” antireflection surfaces, relying on self-organization in a Cl2 etch chemistry, is presented. The morphology of the fabricated Black Germanium surfaces is the result of a random lateral distribution of pyramidal etch pits with heights around (1450 ± 150) nm and sidewall angles between 80° and 85°. The pyramids’ base edges are oriented along the <110> crystal directions of Germanium, indicating a crystal anisotropy of the etching process. In the Vis–NIR, the tapered Black Germanium surface structure suppresses interface reflection to <2.5 % for normal incidence and still to <6 % at an angle of incidence of 70°. The presented Black Germanium might find applications as low-cost AR structure in optoelectronics and IR optics.
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The authors gratefully acknowledge the financial support by the fo+ (Contract No. 03WKCK1D) funding program of the German Federal Ministry of Education and Research.
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Steglich, M., Käsebier, T., Kley, EB. et al. Black Germanium fabricated by reactive ion etching. Appl. Phys. A 122, 836 (2016). https://doi.org/10.1007/s00339-016-0318-y
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DOI: https://doi.org/10.1007/s00339-016-0318-y