Abstract

Integrated photodetectors are key building blocks of scalable photonics platforms. Many recent improvements have been made for integrated avalanche photodetectors (APDs) operating at infrared telecommunications wavelengths, but their visible-spectrum counterparts remain relatively unexplored. Here, we demonstrate PIN-doped silicon APDs for visible light detection, monolithically integrated with a silicon nitride photonics circuit via end-fire coupling. An in-depth study of multiple PIN doping profiles reveals different optimal designs based on the desired operating regimes. At −49 dBm input power, they show 0.25 A/W (0.8 A/W) responsivity at reverse bias as low as 0.5 V (5.5 V), with corresponding dark current of $< $ 3 pA (50 pA). We also report fast RF response with an optimal 3 dB bandwidth of 11 GHz and gain-bandwidth product of 142 GHz, with all devices yielding open eye diagrams at 25 Gbps or above. Coupled with CMOS-compatible fabrication, our APDs will enable scalable photonics applications in sensing, communications, and quantum technologies at visible wavelengths.

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