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Black Germanium fabricated by reactive ion etching

 
: Steglich, M.; Käsebier, T.; Kley, E.-B.; Tünnermann, A.

:

Applied physics. A 122 (2016), No.9, Art. 836, 5 pp.
ISSN: 0340-3793
ISSN: 0721-7250
ISSN: 0947-8396 (Print)
ISSN: 1432-0630 (Online)
English
Journal Article
Fraunhofer IOF ()

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.

: http://publica.fraunhofer.de/documents/N-421739.html