Event Details

Light detection at extreme (single-photon) sensitivity lies at the heart of various applications, including low-light imaging, sensing, quantum information technologies, LiDAR, biomedicine, free space communication, and DoD applications. Conventional CMOS single-photon avalanche diodes (SPADs) either rely on passive quenching, leading to extended RC-based recovery times, or employ external quenching circuitry that limits fill factor and spatial resolution. Self-quenched SPADs hold promise for the above limitations, but the long self-recovery time has limited the device performance. Here, we present a high dynamic range detector with an active self-recovery mechanism that can accelerate the self-recovery process by 100 times, making it a Self-QUenched, Actively REcovered (SQUARE) SPAD to detect single photons without post amplifiers. To facilitate adoption of the device using CMOS process, we developed a theoretical framework and a Verilog-A circuit model that capture avalanche dynamics and practical foundry constraints. To extend the operation wavelength to NIR and SWIR regimes, colloidal quantum dots (CQD) are incorporated into the design, making possible quantum dot (Q-SQUARE) detectors on CMOS. Since both the a-Si gain medium and colloidal quantum dots are platform-agnostic, the devices can also be fabricated on display, wearable, and flexible platforms for ubiquitous, multi-spectral optical sensing and imaging.

August 1, 2025

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Host: Steve Crago
POC: Amy Kasmir

Speaker Bio

Yuhwa Lo is the William SC Chang Distinguished Professor of the ECE Department at UCSD. His research interests include semiconductor materials and devices, microfluidics, lab-on-chip, bioimaging, and biomedical systems. He has been active in lab-to-fab and lab-to-market translational research, and has successfully commercialized his research to semiconductor, biotech, and healthcare industries over the past decades. He is a fellow of the IEEE, Optica, and National Academy of Inventors.