InGaAs quantum dots without wetting layer states for electrons

Julian Ritzmann, Ruhr-Universität Bochum, Bochum, Germany
Matthias Löbl, University of Basel, Basel, Switzerland
Sven Scholz, Ruhr-Universität Bochum, Bochum, Germany
Immo Söllner, University of Basel, Basel, Germany
Thibaud Denneulin, Forschungszentrum Jülich, Jülich, Germany
Andras Kovacs, Forschungszentrum Jülich, Jülich, Germany
Beata E. Kardynal, Forschungszentrum Jülich, Jülich, Germany
Andreas D. Wieck, Ruhr-Universität Bochum, Bochum, Germany
Richard J. Warburton, University of Basel, Basel, Switzerland
Arne Ludwig, Ruhr-Universität Bochum, Bochum, Germany

InGaAs quantum dots are a widely used solid-state platform for quantum optics. Benefiting from its large optical dipole moment, the quantum dot can be employed as a single photon source [1] or it can act as host for a single spin [2-3]. Thus, it is often referred to as an artificial atom. However, this analogy is often too simplistic. A quantum dot is inevitably embedded in, and coupled to, a solid-state environment. In particular, hybridization between quantum dot states and the so-called wetting layer has been observed [4]. The wetting layer is inherent to standard Stranski-Krastanov quantum dots and results in a continuum of electronic states relatively close in energy to the confined quantum dot states. The wetting layer continuum can influence the interaction between a quantum dot and a cavity [5], lead to damping of Rabi oscillations [6], and strongly influence the temperature dependence of the emission [7]. In all these experiments, the quantum dot does not behave like a purely atom-like system. Here, we present a novel growth method that eliminates wetting layer states for electrons.

We present spectroscopy on highly charged excitons, observing striking features which could not be measured in the presence of a wetting layer. We demonstrate that the modified growth procedure results in a much deeper quantum dot confinement potential and model the magnetic field dispersion. These new quantum dots retain close to transform-limited linewidths in resonance fluorescence and thus are promising for a variety of applications such as cavity QED.

References
[1] A. V. Kuhlmann et al., Nat. Commun. 6, 8204 (2014).
[2] J. H. Prechtel et al., Nat. Mater. 15, 981 (2016).
[3] M. Atatüre et al., Science 312, 551 (2006).
[4] K. Karrai et al., Nature 427, 135 (2004).
[5] M. Settnes et al., Phys. Rev. Lett. 111, 067403 (2013).
[6] J. M. Villas-Bôas et al., Phys. Rev. Lett. 94, 057404 (2005).
[7] B. Urbaszek et al., Phys. Rev. B 69, 035304 (2004).

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