Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 15: Focussed Session: Geometry- and Topology-Controlled Nanoarchitectures I

HL 15.1: Talk

Tuesday, March 13, 2018, 09:30–09:45, EW 015

Field-induced quantum rings in cone-shell GaAs quantum dots — •Christian Heyn, Achim Küster, Michael Zocher, and Wolfgang Hansen — Center for Hybrid Nanostructures, University of Hamburg, D-22761 Hamburg, Germany

We study self-assembled GaAs quantum dots (QDs) and rings (QRs) in refilled AlGaAs nanoholes. The holes are fabricated using local droplet etching during molecular beam epitaxy. Controlled by the process conditions, QDs of varied shape can be generated in which the probability distributions of the carriers are concentrated, e.g., in the volume of a cone or on the cone shell. The optical emission of cone-shell QDs (CSQDs) is studied with single-dot photoluminescence (PL). Numerical simulations reproduce the experimental ground and excited-state emission energy of the CSQDs. Further simulations of the influence of a vertical electric field establish a field-dependent displacement of either the electron or the hole away from the tip of the cone. This displacement has several consequences. First, the Coulomb interaction is strongly reduced which compensates the single-particle Stark-shift. Accordingly, simulations as well as PL measurements indicate a non-parabolic Stark-shift with a regime of approximately constant emission energy. Second, the calculated exciton-recombination lifetime establishes a variability up to seven orders of magnitude. Third, regarding the shape of the wave-functions in CSQDs, we predict the controlled transformation of either the electron or the hole from a quasi zero-dimensional dot into a one-dimensional quantum ring by a gate-voltage. The respective other charge carrier remains as a dot.