High-sensitivity NIR photodiodes using black silicon

Juha Heinonen, Antti Haarahiltunen, Michael Serue, Ville Vähänissi, Toni Pasanen, Hele Savin, Lutz Werner, Mikko Juntunen

Research output: Contribution to journalConference articleScientificpeer-review

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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
Original languageEnglish
Article number112760G
Number of pages7
JournalSPIE CONFERENCE PROCEEDINGS
Volume11276
DOIs
Publication statusPublished - 2020
MoE publication typeA4 Article in a conference publication
EventSPIE Photonics West - Moscone Center, San Francisco, United States
Duration: 1 Feb 20206 Feb 2020

Keywords

  • Black Silicon
  • near infrared
  • responsivity
  • silicon
  • photodiode

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