Improving charge mobility in quantum dot (QD) films is important for the performance of photodetectors, solar cells and light-emitting diodes. However, these applications also require preservation of well defined QD electronic states and optical transitions. Here, we present HgTe QD films that show high mobility for charges transported through discrete QD states. A hybrid surface passivation process efficiently eliminates surface states, provides tunable air-stable n and p doping and enables hysteresis-free filling of QD states evidenced by strong conductance modulation. QD films dried at room temperature without any post-treatments exhibit mobility up to μ ~ 8 cm2 V−1 s−1 at a low carrier density of less than one electron per QD, band-like behaviour down to 77 K, and similar drift and Hall mobilities at all temperatures. This unprecedented set of electronic properties raises important questions about the delocalization and hopping mechanisms for transport in QD solids, and introduces opportunities for improving QD technologies.
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The data sets generated and analysed during the current study are available from the corresponding author on reasonable request. Source data for Figs. 1–4 are provided with the paper.
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This work was supported by the University of Chicago Materials Research Science and Engineering Center, which is funded by the NSF under award number DMR-1420709, by the Defense Advanced Research Projects Agency (DARPA) as a subcontract to Voxtel, Inc. for the Wired program, by the Department of Defense (DOD) Air Force Office of Scientific Research under grant number FA9550-18-1-0099 and by the National Science Foundation under grant DMR-1708378.
The authors declare no competing interests.
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Unprocessed Fourier-transform infrared absorption spectra of undoped and n-type doped 12.5 ± 1.0 nm HgTe QDs and fitting. SAXS data and fitting.
Unprocessed FET transport data of HgTe and intraband spectra.
Mobility as a function of temperature.
Hall voltage, Seebeck coefficient, Hall mobility and FET mobility at different temperatures. Photoresponse data.
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Lan, X., Chen, M., Hudson, M.H. et al. Quantum dot solids showing state-resolved band-like transport. Nat. Mater. (2020). https://doi.org/10.1038/s41563-019-0582-2