Silicon Photonic Crystal Architecture for Ultra-Thin, High-Efficiency Single Photon Detectors

A trade-off between counting rate and absorption efficiency is unavoidable in the traditional single photon avalanche detectors (SPAD). We numerically demonstrate that this trade-off can be circumvented using silicon photonic crystal based ultra-thin SPAD architecture that is capable of achieving high photon counting rate and high absorption efficiency simultaneously. We optimize the photon trapping capability over a broad spectral range of 400–1100nm in a 5 μm-thick crystalline silicon photonic crystal with inverted conical pore unit cells. The optimized photonic crystal SPAD, with 2.01 μm lattice constant, 20nm front antireflection coating and 55nm back passivation coating (both SiO
2
), yields an integrated absorption efficiency of 87.16% over the 400–1100nm spectral range. This ultra-thin architecture holds a strong potential to pave the way for silicon SPADs with > 80% broadband detection efficiency while maintaining a low timing jitter, in contrast to the typical 60–70% peak efficiency over a narrow spectral range in thick SPADs with high timing jitter.