Time-Resolved Intrinsic and Extrinsic Photoresponse of Colloidal SWIR-Active Indium Antimonide Quantum Dot Photodetectors

Colloidal indium antimonide (InSb) quantum dots (QDs) are highly promising nanomaterials for SWIR photodetectors due to their optical properties, solution processability, and low toxicity. Here, we present surface engineering of colloidal InSb QDs and an investigation of the intrinsic and extrinsic photoresponse time (τIn and tEx) of InSb QD photodetectors. Chloride (Cl-) ligands are chosen for surface engineering and their effects are studied by X-ray photoelectron spectroscopy. Using a pump-probe technique based on asynchronous optical sampling (ASOPS), we find that τIn of Cl-capped InSb QDs can be described by two components of 1.5 ns and 200 ps. By studying the dependence of these components on the voltage, the excitation power, and the temperature, we assign them to trap-assisted Auger recombination and carrier trapping. For tEx, we obtain much faster rise times (9.77 µs) than fall times (635 μs), indicating prolonged recovery due to slow release of trapped carriers. We devise measures to partially mitigate this drawback, enabling sub-microsecond photo switching and a 3 dB bandwidth of 5 MHz. Our findings highlight the potential of colloidal InSb QDs for environmentally benign and high-speed SWIR photodetectors.