Visible-Light Integrated PIN Avalanche Photodetectors With High Responsivity and Bandwidth

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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&lt; $</tex-math></inline-formula> 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.