Se-Woong Baek1
Korea University1
The detection of infrared (IR) light is crucial for realizing various future applications, including recognition, bio-imaging, spectroscopy, and object inspection. In particular, utilizing photons beyond the silicon absorption band-edge (i.e., 1550 nm) becomes important to demonstrate long-range communications and quantum technologies. Colloidal quantum dots (CQDs), semiconducting nanocrystals, are promising alternative materials due to their quantum-confined bandgap tunability across visible to shortwave-infrared (SWIR) wavelengths. However, CQD-based IR optoelectronics currently face two challenges: the use of toxic elements such as Pb, Cd, and Hg, and lower performance compared to epitaxial semiconductors.<br/>This talk showcases how to build IR devices using non-toxic CQD materials, including III-V, I-VI, and beyond. Various short-ligand passivation strategies enable stable CQD ink, thereby rendering high-quality conductive solids. We reveal that the extent of ligand passivation yields a surface-mediated photomultiplication effect, boosting the responsivity of devices. Furthermore, we have demonstrated an efficient avalanche breakdown in the CQD multiplication layer, achieving a fast response time below the nanosecond level with a notable gain of up to ~10<sup>4</sup>. This represents a record gain x bandwidth product among all prior solution-processed IR photodetectors operated at 1550 nm.