Enhancing the performance of single-photon avalanche diodes using semiconductor metasurfaces

Single-photon detection is a rapidly growing field, with applications spanning from biomedical imaging to quantum communication. The use of single-photon avalanche diodes (SPADs) for detection over the near-infrared (NIR) spectral region is gaining significant interest due to their potential for achieving high performance alongside portability. Here, we cover SPAD design choices specific to the NIR region and discuss how these choices relate to trade-offs in photon detection efficiency (PDE), dark count rate (DCR), and timing jitter. In particular, we discuss the effects of adjusting the material layer stack, temperature, and operating bias. We then present our perspective on incorporating optical metasurfaces into the SPAD active area to boost the detector performance. We propose that the collective interaction between the nanostructures that make up the metasurface will increase PDE through enhanced absorption compared to that of planar devices. Our metasurface-based SPAD shows a 2.5-fold enhancement in the calculated PDE compared to a planar mesa SPAD using an InGaAs/InAlAs material system. Furthermore, we propose that the smaller device volume will translate to reductions in DCR and timing jitter. We believe that the culmination of these performance benefits from the integration of metasurfaces will lead to next-generation SPADs. Finally, an outlook on the experimental challenges of realizing this technology is given.