Engineering Doping Profiles in SiN Waveguide-Coupled Horizontal Silicon SPADs for Enhanced Single-Photon Detection and Low Dark Noise

Abstract

Single-photon detection using superconducting nanowire detectors has become a benchmark technology for quantum photonic applications, offering exceptional performance across a wide spectral range. However, their operation at cryogenic temperatures (typically 1–4 K) substantially increases system cost and complexity, limiting their integration into compact and scalable on-chip quantum systems where photon generation, manipulation, and detection must coexist. As a promising alternative, thin horizontal silicon p–n junctions enable room-temperature operation and are fully compatible with photonic integrated circuits (PICs), offering a viable route toward large-scale quantum photonic integration. Nevertheless, current silicon-based SPAD platforms exhibit high dark count rates (DCR), typically around 100 kHz/ μ m, primarily due to non-optimized doping concentrations. In this work, we present a systematic optimization of the doping profile using coupled process and device simulations to establish a direct correlation between ion implantation parameters and SPAD performance. By identifying optimal doping conditions, the DCR is suppressed by 98.18% for planar SPADs and 95.01% for rib-SPADs. We further analyze the trade-off between photon detection efficiency and dark noise, and investigate the influence of excess bias and device length on overall performance. The avalanche buildup time is also evaluated to characterize the temporal response of the optimized SPAD structures. The resulting design framework provides CMOS-compatible guidelines for engineering scalable, cost-effective, and room-temperature single-photon detectors suitable for monolithic integration within quantum PICs.