Origin and suppression of dark current for high-performance colloidal quantum dot short-wave infrared photodetectors

The development of cost-effective and highly sensitive short-wave infrared (SWIR) photodetectors is crucial for the expanding applications of SWIR imaging in civilian applications such as machine vision, autonomous driving, and augmented reality. Colloidal quantum dots (CQDs) have emerged as promising candidates for this purpose, offering distinct advantages over traditional III-V binary and ternary semiconductors. These advantages include the ability to precisely tune the bandgap through size modulation of CQDs and the ease of monolithic integration with Si readout integrated circuits (ROICs) via solution processing. Achieving a minimal reverse bias dark current density (J_d) while maintaining high external quantum efficiency is essential for enhancing the light detection sensitivity of CQDs-based SWIR photodiodes to a level competitive with III-V semiconductors. This challenge has garnered increasing research attention in recent years. Herein, the latest advancements in understanding and mitigating J_d in CQDs SWIR photodiodes are summarized. Starting with a brief overview of the material fundamentals of CQDs, the origins of J_d in CQDs photodiodes, including reverse injection from electrode, diffusion/drift currents, Shockley-Read-Hall generation/recombination currents, trap-assisted tunneling, and shunt/leakage currents, are discussed together with their latest research progresses about strategies adopted to suppress J_d. Finally, a brief conclusion and outlook on future research directions aimed at minimizing J_d and retaining high photoresponse of CQDs SWIR photodiodes are provided.