InF3 Surface Passivation on InAs Quantum Dots Enhances Photoluminescence and Reduces Trap-Induced Dark Current in Shortwave Infrared Photodetectors.

Shortwave infrared (SWIR) photodetectors are crucial for emerging technologies such as autonomous driving, smart agriculture, industrial inspection, and eye-safe LiDAR. Colloidal indium arsenide (InAs) quantum dots (QDs) offer a low-cost, RoHS-compliant alternative to epitaxial III-V semiconductors. But their performance is limited by a high density of surface trap states that induce nonradiative recombination and potentially give rise to a high dark current in photodiodes. Here, we demonstrate that InF3 can effectively passivate these surface traps, significantly improving both optical and electronic properties. In nonpolar solvents, a simple InF3 treatment on oleylamine/chloride-capped In(As,P) and oleate-capped InAs QDs increases the photoluminescence quantum yield to 13% and 4%, respectively─the highest reported for core-only InAs QDs. In polar media, the InF3 treatment remains effective but reduces colloidal stability. To overcome this limitation, a solid-state in situ InF3 treatment of QD films was used. The treatment doubles the carrier lifetime and lowers the dark carrier density, confirmed by ultrafast transient absorption spectroscopy, microwave conductivity, and electrochemically gated transistor measurements. In SWIR photodetectors, this leads to an order-of-magnitude reduction in dark current density and a 3-fold increase in the calculated specific detectivity, assuming it is shot-noise-limited. Temperature-dependent dark current density and thermal admittance spectroscopy measurements reveal that deep trap states dominate the dark current in InAs QDs photodetectors. The InF3 treatment strongly suppresses these traps. These findings establish InF3 passivation as a powerful, promising strategy for mitigating surface-trap-induced dark current and advancing high-performance, RoHS-compliant SWIR photodetectors.