Suppressing Colloidal Quantum Dot Multimer Fusion Leads to High-Performance InSb Infrared Photodetectors

Environmentally friendly InSb colloidal quantum dots (CQDs) short-wave infrared (SWIR) photodetectors feature characteristics of low-cost, high-volume scalability, CMOS integrability, and compliance with RoHS regulations, and hold great commercial potential. Yet, their performance falls short of commercially relevant specifications. In this work, it is posited that CQD fusion observed in these dots leads to the formation of band-tail trap states and it is further demonstrated that avoidance of such band-tail trap states is crucial for device performance. By doing so, InSb CQDs SWIR photodetectors are reported with compelling performance metrics, including a dark current of 4 µA cm^-2, EQE of ≈20% (at -1 V), a linear dynamic range over 140 dB and a response time of 90 ns. This represents a more than ten-fold reduction in dark current compared to previously report InSb CQD photodetectors in the SWIR range. The record high PLQY of 10% for InSb/InP CQDs taken together with the high EQE of the device at zero bias confirm the achievement of high-quality InSb CQDs through the suppression of band-tail trap states and passivation of surface defects.