Field‐Controlled Quantum Dot to Ring Transformation in Wave‐Function Tunable Cone‐Shell Quantum Structures

Abstract

A new type of quantum structure is discussed where the probability distributions of the charge carriers are concentrated on the shell of a cone. These GaAs cone‐shell quantum structures (CSQSs) are filled into nanoholes in AlGaAs that are fabricated in a self‐assembled fashion using local droplet etching during molecular beam epitaxy. The structural properties of the CSQSs are studied with atomic force microscopy (AFM) and the optical emission with single‐dot photoluminescence (PL). Numerical simulations of the influence of a vertical electric field predict a strong field‐dependent displacement of either the electron or the hole away from the tip of the cone shell. This displacement has several consequences. First, the Coulomb interaction is strongly reduced. Accordingly, simulations as well as PL measurements indicate a non‐parabolic Stark‐shift for CSQSs with a regime of approximately constant emission energy. Second, the calculated exciton‐recombination lifetimes establish a variability from nanoseconds up to milliseconds. Third, regarding the shape of the electron or hole probability distributions, we predict a gate‐voltage controlled transformation from a dot into a ring shape. The respective other charge carrier remains as a dot.

Topology and Geometry Controlled Properties of Nanoarchitectures

“…Christian Heyn et al [12] proposed field-controlled quantum dot to ring transformation in wave-function tunable cone-shell quantum structures. The GaAs cone-shell quantum structures were filled into nanoholes in AlGaAs that were fabricated in a self-assembled fashion using local droplet etching during molecular beam epitaxy.…”

Wave‐Function Topology Effects on Charged Excitons in Type‐II InAs/GaAsSb Quantum Dots and Rings

“…Beyond a Sb concentration , the band alignment between the QD and overlayer material changes, turning into type‐II for the valence band, and further correcting the emission wavelength and radiative lifetime . In this situation, the electron and the hole get localized in different spatial regions building up a vertical and an in‐plane dipole moment . InAs/GaAsSb QDs are thus a good candidate for the observation of optical Aharonov–Bohm effects (OABE), as studied in other systems for neutral and charged exciton complexes .…”

“…[7] In this situation, the electron and the hole get localized in different spatial regions building up a vertical and an in-plane dipole moment. [8,9] InAs/GaAsSb QDs are thus a good candidate for the observation of optical Aharonov-Bohm effects (OABE), as studied in other systems for neutral [10][11][12][13] and charged exciton complexes. [14,15] Indeed, we have recently reported the dynamic control of the OABE via an external voltage monitoring the ensemble photoluminescence in a magnetic field, and thus with no actual information about the charge state.…”

Electronic structure of vertically coupled quantum dot-ring heterostructures under applied electromagnetic probes. A finite-element approach

“…The semiconductor quantum dot-quantum ring (QDR) complex, in which charge carriers undergo the combined influence of -coupled- QD- and QR-type quantum confinement, has also been a subject of study 45 – 58 . Among these examples, there are several works devoted to fabricating QDR systems 46 , 47 , 50 , 54 , 56 , 58 .…”

“…The semiconductor quantum dot-quantum ring (QDR) complex, in which charge carriers undergo the combined influence of -coupled- QD- and QR-type quantum confinement, has also been a subject of study 45 – 58 . Among these examples, there are several works devoted to fabricating QDR systems 46 , 47 , 50 , 54 , 56 , 58 . It is worth to highlight as well the very recent investigation by Heyn et al in which a new kind of nanostructure related with the phenomenon of field-induced quantum dot to ring transformation in GaAs cone-shell quantum structures has been put forward 58 .…”