Time-Resolved Intrinsic and Extrinsic Photoresponse of Colloidal Short-Wavelength Infrared-Active Indium Antimonide Quantum Dot Photodetectors.

Colloidal indium antimonide (InSb) quantum dots (QDs) are highly promising nanomaterials for short-wavelength infrared (SWIR) photodetectors due to their optical properties, solution processability, and low toxicity. Here, surface engineering of colloidal InSb QDs and an investigation of the intrinsic and extrinsic photoresponse time (τ _In and t _Ex) of InSb QD photodetectors is presented. Chloride (Cl^-) ligands are chosen for surface engineering and their effect is studied by X-ray photoelectron spectroscopy. Using a pump-probe technique based on asynchronous optical sampling (ASOPS), we find that τ _In of Cl-capped InSb QDs (InSb-Cl 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 t _Ex, much faster rise times (9.77 μs) than fall times (635 μs) indicate prolonged recovery due to slow release of trapped carriers is obtained. We devise measures to partially mitigate this drawback, enabling submicrosecond photo switching and a 3 dB bandwidth of 5 MHz. These findings highlight the potential of environmentally benign and high-speed SWIR photodetectors based on colloidal III-V semiconductor nanomaterials.