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Proceedings Paper

High-sensitivity NIR photodiodes using black silicon
Author(s): Juha Heinonen; Antti Haarahiltunen; Michael Dov Serue; Ville Vähänissi; Toni P. Pasanen; Hele Savin; Lutz Werner; Mikko A. Juntunen
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Paper Abstract

There is an increasing demand for highly sensitive near infrared (NIR) detectors due to many rapidly growing application areas, such as LiDAR and optical communications. Despite the limited NIR absorption, silicon is a common substrate material in NIR detectors due to low cost and maturity of the technology. To boost the NIR performance of silicon devices, one option is texturizing the front and/or back surface to reduce reflectance and extend the optical path by scattering. Here we demonstrate silicon photodiodes with nanostructured front surface (i.e. black silicon fabricated with reactive ion etching (RIE) that exhibit significantly enhanced external quantum efficiency (EQE) at NIR wavelengths compared to typical state-of-the-art silicon photodiodes. The detectors exhibit over 90% EQE with wavelengths up to 1040 nm and above 60% at 1100 nm. Identical detectors with a planar surface are also investigated revealing that the enhancement from black silicon effectively corresponds to increasing the substrate thickness up to 43% at 1100 nm depending on the thickness of the active layer and back surface structure. This confirms that in addition to reduced reflectance, scattering of transmitted light induced by black silicon plays a key role in the EQE enhancement which benefits especially devices such as backside illuminated photodetectors where very thin substrates are required. We also demonstrate that the high EQE of the black silicon detectors is maintained at incidence angles up to 60 degrees allowing excellent performance in applications where the light is not always perpendicular.

Paper Details

Date Published: 3 March 2020
PDF: 7 pages
Proc. SPIE 11276, Optical Components and Materials XVII, 112760G (3 March 2020); doi: 10.1117/12.2544756
Show Author Affiliations
Juha Heinonen, ElFys, Inc. (Finland)
Antti Haarahiltunen, ElFys, Inc. (Finland)
Michael Dov Serue, ElFys, Inc. (Finland)
Ville Vähänissi, Aalto Univ. (Finland)
Toni P. Pasanen, Aalto Univ. (Finland)
Hele Savin, Aalto Univ. (Finland)
Lutz Werner, Physikalisch-Technische Bundesanstalt (Germany)
Mikko A. Juntunen, ElFys, Inc. (Finland)


Published in SPIE Proceedings Vol. 11276:
Optical Components and Materials XVII
Shibin Jiang; Michel J. F. Digonnet, Editor(s)

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