Wednesday, October 21, 2020

Tip Avalanche Photodiode Claimed to Overcome SPAD Limitations paper "Tip Avalanche Photodiode -- A new generation Silicon Photomultiplier based on non-planar technology" by Eugen Engelmann, Wolfgang Schmailzl, Peter Iskra, Florian Wiest, Elena Popova, and Sergey Vinogradov from KETEK, Germany, and MEPhI, Russia, promises to revolutionize SPAD design:

"The Silicon Photomultiplier (SiPM) is a mature photodetector concept that is applied in a variety of applications ranging from medical imaging to automotive LiDAR systems. Over the last few years, improvements of the sensor performance are gradually approaching to a saturation. In this work we present our new concept to overcome the intrinsic limitations of planar configurations of electrodes. Our non-planar technology is based on focusing and enhancing the electric fields by tip-like electrodes. The shape of the electric field and the lack of typical micro-cell edges, allows us to exclude cell separation boundaries and eliminate dead space around active cell areas. Our design provides a high-density micro-cell layout with a high geometric efficiency. It resolves the well-known trade-off between the detection efficiency and the dynamic range. The first "Tip Avalanche Photodiode" (TAPD) prototypes show a remarkable geometric efficiency above 80% for a micro-cell pitch of 15μm. This directly translates into a photon detection efficiency (PDE) record peak value of 73% at 600nm with respect to the state-of-the-art SiPMs. Moreover, the PDE remains above a value of 45% up to a wavelength of 800nm with another record value of 22% at 905nm. The reduced micro-cell capacity allows for a fast recovery time below 4ns, which improves the operation at high photon rates. Overall, the TAPD is anticipated to be a very promising SiPM generation for various wide-spectral and high-dynamic-range applications in health science, biophysics, particle physics and LiDARs."


  1. Really good to find values ​​above 80% for a micro cell range of 15μm

  2. Great results but not exactly new - see EPFL/Canon (IISW'20) and imec (single photon workshop'19 and IISW'20).

    1. Correction - not IISW but ISSW - international SPAD sensor workshop

    2. It differs from those papers in that the avalanche region is away from the silicon interface. If achieved, it would be superior to conventional structures in many ways.

  3. The first use of this structure is quite old, Sigmund 1968. However the authors correctly cite this paper as the likely first use of a spherical junction in photon counting Geiger-mode. Its nice to see the older papers being used as a basis for newer innovations.

    H. Sigmund, “Photoelectrical properties of spherical avalanche diodes in silicon,” Infrared Physics, vol. 8, no. 4, pp. 259 – 264, 1968. [Online]. Available:


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