Enhancing detectivity in mid-infrared photodetectors through structural parameter engineering in HgSe-HgTe colloidal quantum dots

The escalating demand for cost-effective, flexible, and solution-processed materials in infrared (IR) photodetection presents a compelling alternative to current epitaxially grown optoelectronic technology. Colloidal quantum dots (CQDs) have emerged as a versatile platform for optoelectronic device fabrication, offering affordability, low-temperature synthesis, and scalability. Specifically, mercury chalcogenide CQDs exhibit notable intraband absorption in the mid-IR region. In this study, we explore an intraband HgSe-HgTe CQD photodetector structure tailored for mid-IR light detection. Through numerical optimization, we engineer detectivity by varying key design parameters - the film doping density, CQD diameter, and number of periods in the active layer - under different temperatures and biases. Results indicate that, at 60 K and 1 V bias, our optimally designed HgSe-HgTe CQD IR photodetector attains a peak detectivity of 8.14×1010 Jones for a film doping density of 1019 cm-3 of HgSe CQDs, 9.34×1010 Jones for HgSe CQDs with a 4.8 nm diameter, and 8.72×1010 Jones for 9 periods of HgSe-HgTe CQDs.