Tip Avalanche Photodiode Claimed to Overcome SPAD Limitations

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Arxiv.org 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."

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