@article{Next-Generation:5244,
      recid = {5244},
      author = {Melnychuk, Christopher},
      title = {Infrared Carrier Dynamics in Mercury Chalcogenide Quantum  Dots: from Fundamental Spectroscopy to Next-Generation  Optoelectronics},
      publisher = {University of Chicago},
      school = {Ph.D.},
      address = {2022-12},
      pages = {239},
      abstract = {The mercury chalcogenide quantum dots are an emerging  class of infrared nanomaterial being developed as  next-generation infrared photodetectors and light sources.  Although considerable progress has been made on the  development of near- and mid-infrared detectors and light  sources based on these systems, the basic material  photophysics remains relatively unexplored. In this thesis,  I describe time-resolved spectroscopy investigations of  HgTe and HgSe quantum dots in the near- and mid-infrared.  Transient absorption measurements on HgTe show that  biexciton Auger recombination is much slower than in bulk  materials of similar gaps, and comparable to that in  quantum dots with gaps an order of magnitude larger. This  suggests that the Auger mechanism is modified in quantum  dots compared to bulk semiconductors, and possibly  scattering-assisted. Using a simple detailed-balance model  of thermal carrier generation and recombination in an HgTe  quantum dot solid, I then show how the slow Auger  recombination leads to thermodynamic detector performance  limits which exceed those of commercial devices by an order  of magnitude. In HgSe, transient photoluminescence  upconversion measurements show near-total Auger suppression  in mid-infrared n-type particles and typical quantum dot  Auger behavior in near-infrared intrinsic particles. Auger  suppression is a fundamental benefit for mid-infrared  photodetection and lasing, and this phenomenon is ascribed  to the different densities of states in the two situations.  In the single-exciton regime, spectrally-resolved  photoluminescence dynamics reveal conduction fine structure  and direct phonon-mediated intersublevel relaxation at  early times. The mid-infrared nonradiative relaxation at  longer times is investigated through quantum yield and  lifetime measurements on n-type HgSe and HgSe/CdS  core/shell structures. Modeling indicates that near-field  energy transfer to infrared-absorbing species remains the  dominant nonradiative pathway out to the regime of several  nanoseconds, and the ~2% quantum yields measured in  thick-shell n-type HgSe/CdS are the largest reported to  date in mid-infrared colloidal nanomaterials. This thesis  highlights several unique aspects of carrier dynamics in  small-gap quantum dots, and it fundamentally justifies  continued work on devices made from these materials.},
      url = {http://knowledge.uchicago.edu/record/5244},
      doi = {https://doi.org/10.6082/uchicago.5244},
}