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Ultralow Gain-Normalized Dark Current Density in a Colloidal Quantum Dot Avalanche Photodiode with a SACM
Junrui Yang1, Xing Yang2, Jing Liu1,3,4
1Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, 430074 Wuhan, China.
None:
Short-wave infrared (SWIR) avalanche photodiodes (APDs) are important for LiDAR, free-space optical communication, and low-light imaging. Colloidal quantum dots (CQDs) offer a solution-processable, silicon-compatible SWIR platform, but conventional CQD p-i-n APDs couple photon absorption and avalanche multiplication in the same narrow-bandgap layer, causing severe dark-current growth under high reverse bias. Here, we demonstrate a CQD/i-ZnO APD based on a separate-absorption-charge-multiplication (SACM) architecture. By relocating the high-field multiplication region from the narrow-bandgap CQD absorber to wide-bandgap i-ZnO, this design suppresses tunneling-induced dark current while retaining avalanche multiplication. The optimized device achieves a gain-normalized dark current density of 4.86 × 10-7 A cm-2, the lowest reported among CQD photodetectors with internal gain, and a specific detectivity of 1.15 × 1012 Jones. These results establish SACM field engineering as an effective route toward low-dark-current CQD-based SWIR APDs.
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