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Self-assembled quantum dots in a nanowire system for quantum photonics


Quantum dots embedded within nanowires represent one of the most promising technologies for applications in quantum photonics. Whereas the top-down fabrication of such structures remains a technological challenge, their bottom-up fabrication through self-assembly is a potentially more powerful strategy. However, present approaches often yield quantum dots with large optical linewidths, making reproducibility of their physical properties difficult. We present a versatile quantum-dot-in-nanowire system that reproducibly self-assembles in core–shell GaAs/AlGaAs nanowires. The quantum dots form at the apex of a GaAs/AlGaAs interface, are highly stable, and can be positioned with nanometre precision relative to the nanowire centre. Unusually, their emission is blue-shifted relative to the lowest energy continuum states of the GaAs core. Large-scale electronic structure calculations show that the origin of the optical transitions lies in quantum confinement due to Al-rich barriers. By emitting in the red and self-assembling on silicon substrates, these quantum dots could therefore become building blocks for solid-state lighting devices and third-generation solar cells.

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Figure 1: Schematics of the quantum-dot-in-nanowire system.
Figure 2: Structure of quantum-dots-in-a-nanowire.
Figure 3: Cathodoluminescence of a single nanowire.
Figure 4: Photoluminescence of a quantum-dot-in-nanowire system.
Figure 5: Atomistic calculations of electronic states in a quantum-dot- in-nanowire system.


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A.F.i.M. acknowledges funding from ERC through the UpCon grant and SNF through Grant No. 134506. Both A.F.i.M. and R.J.W. acknowledge support from NCCR QSIT. The Phantoms Foundation is acknowledged for sponsoring B.K.’s visit to Lund University. This work was supported by the Spanish MICINN Projects MAT2010-15138, CSD2009-00013 and CSD2009-00050. J.A. and J.R.M. acknowledge Generalitat de Catalunya 2009-SGR-770, NanoAraCat and XaRMAE and European RDF support. The authors acknowledge F. J. Belarre for the making of the TEM cross-sections; A.G. thanks L. Samuelson and the Swedish Research Council for support. D.D.O. acknowledges N. D. M. Hine and the ONETEP developers’ group for discussions and software support, and the EPFL HPC service for generous provision of computing resources. The work carried out by J.W.L. and A.Z. was funded by the US Department of Energy, Office of Science, Basic Energy Science, Materials Sciences and Engineering under contract number DE-AC36-08GO28308 to NREL and CU Boulder.

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M.H., E.R-A. and A.F.i.M. grew the samples. J.A., J.R.M. and C.M. performed HAADF STEM and EELS analysis. S.C-B. and M.C. mapped the composition of the quantum dots by EDX. J.A. and S.C-B. worked on the atomic modelling of the quantum dots. A.G. and B.K. measured the cathodoluminescence. M.H., Y.F., G.W., A.V.K., J.H. and R.J.W. participated in the optical spectroscopy studies. D.D.O. and N.M. performed density functional theory calculations. J.W.L. and A.Z. performed the empirical pseudopotential calculations. A.F.i.M. conceived and designed the experiments, and together with R.J.W., A.Z. and N.M. supervised the project. Y.F. made the figures and artwork. A.F.i.M., R.J.W., Y.F., A.Z., D.D.O., N.M. and J.A. wrote and edited the manuscript. All authors discussed the results and commented on the manuscript.

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Correspondence to M. Heiss or Y. Fontana or A. Fontcuberta i Morral.

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The authors declare no competing financial interests.

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Heiss, M., Fontana, Y., Gustafsson, A. et al. Self-assembled quantum dots in a nanowire system for quantum photonics. Nature Mater 12, 439–444 (2013).

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