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Abstract

HgTe colloidal quantum dots (CQDs) are an emerging technology important for the development of low-cost, next-generation infrared technologies. However, photodetectors based on HgTe CQDs must also be capable of delivering performances equivalent to or better than the epitaxial technologies to compete commercially. Here, concepts and methods are described for designing emerging HgTe CQD photodiodes with detection in the shortwave and mid-wave infrared spectral regions and figures-of-merit rapidly approaching the commercial epitaxial technologies. The concepts investigated for the design of HgTe CQD photodiodes included heterojunction diodes with charge-selective transport layers and homojunction diodes with thin films of doped HgTe CQDs. The former likely suffer from unfavorable heterojunction band alignment that is detrimental to device operation and challenging to control in narrow-gap CQDs. Doping thin films of HgTe CQDs, however, is successful, following the introduction of a solid-state cation exchange process. Heterojunctions of HgTe CQDs and doped semiconductor nanoparticles were also essential to the concept and design of inverted-polarity HgTe CQD photodiodes. Finally, the designs developed within this work culminate in the demonstration of a SWIR/MWIR dual-band infrared photodetector. Further developments of the HgTe CQD photodiodes will follow from addressing design and material challenges for enhancing the charge collection efficiency, absorption, and operating temperature of these photodiodes. Today, the shortwave infrared HgTe CQD photodiodes demonstrate the most promise, and mid-wave HgTe CQD detectors with high temperature operation are under development. The designs here may also extend to the HgTe CQDs with absorption in the long-wave infrared and position HgTe CQDs as an emerging technology for the future of infrared detectors.

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