HgTe colloidal quantum dots (QDs) are of interest because quantum confinement of semimetallic bulk HgTe allows one to synthetically control the bandgap throughout the infrared. Here, we synthesize high quality HgTe QDs and tune the doping both chemically and electrochemically. Electron-doped HgTe QDs display an intraband absorbance and bleaching of the first two excitonic features. Unlike previous studies of doped QDs, we see splitting of the intraband peaks corresponding to electronic transitions from the doped 1Se state to a series of non-degenerate 1Pe states. Spectroelectrochemical studies reveal that the degree of splitting and relative oscillator strength of the intraband absorabance features remain constant across doping levels up to two electrons per QD. Moreover, we find that in QDs of different sizes the energy and degree of splitting of the intraband peaks vary linearly with confinement energy. Theoretical modeling suggests that the splitting of the 1Pe level arises from a combination of spin-orbit coupling and structural asymmetry. We postulate that split intraband features are first observed here due to the size uniformity of the as-synthesized QDs and strong spin-orbit coupling inherent to HgTe. The monodispersity of the QDs was evaluated using absorption, SAXS, and self-assembly and suggests a diameter distribution of ~10% across multiple synthesized batches of different sizes.

Spectroscopic evidence of conduction band fine structure in colloidal HgTe quantum dots with well-defined intraband transitions

256th National Meeting (2018)

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