Pseudo-planar Ge-on-Si single-photon avalanche diode detector with record low noise-equivalent power

Ross W. Millar, Jarosław Kirdoda, Fiona Thorburn, Xin Yi, Zoë M. Greener, Laura Huddleston, Bhavana Benakaprasad, Scott Watson, Conor Coughlan, Gerald S. Buller, Douglas J. Paul

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)
36 Downloads (Pure)


Single-photon avalanche diode (SPAD) detectors are of significant interest for numerous applications, including light detection and ranging (LIDAR), and quantum technologies such as quantum-key distribution and quantum information processing. Here we present a record low noise-equivalent-power (NEP) for Ge-on-Si SPADs using a pseudo-planar design, showing high detection efficiency in the short-wave infrared; a spectral region which is key for quantum technologies and hugely beneficial for LIDAR. These devices can leverage the benefits of Si avalanche layers, with lower afterpulsing compared to InGaAs/InP, and reduced cost due to Si foundry compatibility. By scaling the SPAD pixels down to 26μm diameter, a step change in performance has been demonstrated, with significantly reduced dark count rates (DCRs), and low jitter (134ps). Ge-on-Si SPADs were fabricated using photolithography techniques and characterised using time-correlated single-photon counting. The DCR reaches as low as kilocount/s at 100K for excess bias up to ∼5%. This reduction in DCR enables higher temperature operation; e.g. the DCR of a 26μm diameter pixel at 150 K is approximately equivalent to a 100 μm diameter pixel at 77 K (100s of kilocounts/s). These low values of DCR, coupled with the relatively temperature independent single photon detection efficiencies (SPDE) of ∼29% (at 1310nm wavelength) leads to a record low NEP of 7.7×10-17WHz-1/2. This is approximately 2 orders of magnitude lower than previous similarly sized mesa-geometry Ge-on-Si SPADs. This technology can potentially offer a lowcost, Si foundry compatible SPAD operating at short-wave infrared wavelengths, with potential applications in quantum technologies and autonomous vehicle LIDAR.

Original languageEnglish
Title of host publicationQuantum Technology
Subtitle of host publicationDriving Commercialisation of an Enabling Science II
EditorsMiles J. Padgett, Kai Bongs, Alessandro Fedrizzi, Alberto Politi
ISBN (Electronic)9781510646070
ISBN (Print)9781510646063
Publication statusPublished - 6 Oct 2021
EventSPIE Photonex 2021 - Glasgow, United Kingdom
Duration: 28 Sept 202130 Sept 2021

Publication series

NameProceedings of SPIE
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceSPIE Photonex 2021
Country/TerritoryUnited Kingdom
Internet address


  • Detector
  • Germanium
  • lidar
  • quantum
  • quantum technology
  • Silicon photonics
  • Single photon detector
  • SPAD

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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