Mid-Infrared Intraband Photodetector via High Carrier Mobility HgSe Colloidal Quantum Dots

In this work, a room-temperature mixed-phase ligand exchange method is developed to obtain a relatively high carrier mobility (∼1 cm²/(V s)) on HgSe intraband colloidal quantum dot solids without any observable trap state. What is more, the doping from 1S_e to 1P_e state in the conduction band could be precisely controlled by additional salts during this method, proved by optical and transport experiments. The high mobility and controllable doping benefit the mid-infrared photodetector utilizing the 1S_e to 1P_e transition, with a 1000-fold improvement in response speed, which is several μs, a 55-fold increase in responsivity, which is 77 mA/W, and a 10-fold increase in specific detectivity, which is above 1.7 × 10⁹ Jones at 80 K. The high-performance photodetector could serve as an intraband infrared camera for thermal imaging, as well as a CO₂ gas sensor with a range from 0.25 to 2000 ppm.