title: Crystal Phase Quantum Dots in the Ultrathin Core of GaAs-AlGaAs Core-Shell Nanowires.
abstract: Semiconductor quantum dots embedded in nanowires (NW-QDs) can be used as efficient sources of nonclassical light with ultrahigh brightness and indistinguishability, needed for photonic quantum information technologies. Although most NW-QDs studied so far focus on heterostructure-type QDs that provide an effective electronic confinement potential using chemically distinct regions with dissimilar electronic structure, homostructure NWs can localize excitons at crystal phase defects in leading to NW-QDs. Here, we optically investigate QD emitters embedded in GaAs-AlGaAs core-shell NWs, where the excitons are confined in an ultrathin-diameter NW core and localized along the axis of the NW core at wurtzite (WZ)/zincblende (ZB) crystal phase defects. Photoluminescence (PL)-excitation measurements performed on the QD-emission reveal sharp resonances arising from excited electronic states of the axial confinement potential. The QD-like nature of the emissive centers are suggested by the observation of a narrow PL line width, as low as ~300 μeV, and confirmed by the observation of clear photon antibunching in autocorrelation measurements. Most interestingly, time-resolved PL measurements reveal a very short radiative lifetime <1 ns, indicative of a transition from a type-II to type-I band alignment of the WZ/ZB crystal interface in GaAs due to the strong quantum confinement in the ultrathin NW core.
authors.affiliation: Walter Schottky Institut, Physik Department, and Nanosystems Initiative Munich, Technische Universität München , Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Loitsch
authors.affiliation: Walter Schottky Institut, Physik Department, and Nanosystems Initiative Munich, Technische Universität München , Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Winnerl
authors.affiliation: Walter Schottky Institut, Physik Department, and Nanosystems Initiative Munich, Technische Universität München , Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Grimaldi
authors.affiliation: Walter Schottky Institut, Physik Department, and Nanosystems Initiative Munich, Technische Universität München , Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Jakob
authors.initials: J
authors.lastname: Wierzbowski
authors.affiliation: Walter Schottky Institut, Physik Department, and Nanosystems Initiative Munich, Technische Universität München , Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rudolph
authors.affiliation: Walter Schottky Institut, Physik Department, and Nanosystems Initiative Munich, Technische Universität München , Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Morkötter
authors.affiliation: Department of Chemistry, Ludwig-Maximilians-Universität Munich , Butenandtstraße 5-13, 81377 München, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Döblinger
authors.affiliation: Walter Schottky Institut, Physik Department, and Nanosystems Initiative Munich, Technische Universität München , Am Coulombwall 4, 85748 Garching, Germany.|Institute for Advanced Study, Technische Universität München , Lichtenbergstraße 2a, 85748 Garching, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Abstreiter
authors.affiliation: Walter Schottky Institut, Physik Department, and Nanosystems Initiative Munich, Technische Universität München , Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Koblmüller
authors.affiliation: Walter Schottky Institut, Physik Department, and Nanosystems Initiative Munich, Technische Universität München , Am Coulombwall 4, 85748 Garching, Germany.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Finley
keywords: III−V; nanowire; photoluminescence; polytypism; quantum dot