InGaAs quantum dots without wetting layer states for electrons
Julian Ritzmann, Ruhr-Universität Bochum, Bochum, GermanyMatthias Löbl, University of Basel, Basel, SwitzerlandSven Scholz, Ruhr-Universität Bochum, Bochum, GermanyImmo Söllner, University of Basel, Basel, GermanyThibaud Denneulin, Forschungszentrum Jülich, Jülich, GermanyAndras Kovacs, Forschungszentrum Jülich, Jülich, GermanyBeata E. Kardynal, Forschungszentrum Jülich, Jülich, GermanyAndreas D. Wieck, Ruhr-Universität Bochum, Bochum, GermanyRichard J. Warburton, University of Basel, Basel, SwitzerlandArne 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  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 . 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 , lead to damping of Rabi oscillations , and strongly influence the temperature dependence of the emission . 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.
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