9 research outputs found
Dynamic Acoustic Control of Individual Optically Active Quantum Dot-like Emission Centers in Heterostructure Nanowires
We probe and control the optical properties of emission centers forming in
radial het- erostructure GaAs-Al0.3Ga0.7As nanowires and show that these
emitters, located in Al0.3Ga0.7As layers, can exhibit quantum-dot like
characteristics. We employ a radio frequency surface acoustic wave to
dynamically control their emission energy and occupancy state on a nanosec- ond
timescale. In the spectral oscillations we identify unambiguous signatures
arising from both the mechanical and electrical component of the surface
acoustic wave. In addition, differ- ent emission lines of a single quantum dot
exhibit pronounced anti-correlated intensity oscilla- tions during the acoustic
cycle. These arise from a dynamically triggered carrier extraction out of the
quantum dot to a continuum in the radial heterostructure. Using finite element
modeling and Wentzel-Kramers-Brillouin theory we identify quantum tunneling as
the underlying mech- anism. These simulation results quantitatively reproduce
the observed switching and show that in our systems these quantum dots are
spatially separated from the continuum by > 10.5 nm.Comment: This document is the unedited Author's version of a Submitted Work
that was subsequently accepted for publication in Nano Letters, copyright
\c{copyright} American Chemical Society after peer review. To access the
final edited and published work see
http://pubs.acs.org/doi/abs/10.1021/nl404043
High Mobility One- and Two-Dimensional Electron Systems in Nanowire-Based Quantum Heterostructures
Free-standing semiconductor nanowires in
combination with advanced gate-architectures hold an exceptional
promise as miniaturized building blocks in future
integrated circuits. However, semiconductor nanowires are
often corrupted by an increased number of close-by surface
states, which are detrimental with respect to their optical and
electronic properties. This conceptual challenge hampers their
potentials in high-speed electronics and therefore new
concepts are needed in order to enhance carrier mobilities.
We have introduced a novel type of core−shell nanowire
heterostructures that incorporate modulation or remote doping and hence may lead to high-mobility electrons. We demonstrate
the validity of such concepts using inelastic light scattering to study single modulation-doped GaAs/Al0.16Ga0.84As core-multishell
nanowires grown on silicon. We conclude from a detailed experimental study and theoretical analysis of the observed spin and
charge density fluctuations that one- and two-dimensional electron channels are formed in a GaAs coaxial quantum well spatially
separated from the donor ions. A total carrier density of about 3 × 107 cm−1 and an electron mobility in the order of 50 000 cm2/
(V s) are estimated. Spatial mappings of individual GaAs/Al0.16Ga0.84As core−multishell nanowires show inhomogeneous
properties along the wires probably related to structural defects. The first demonstration of such unambiguous 1D- and 2Delectron
channels and the respective charge carrier properties in these advanced nanowire-based quantum heterostructures is the
basis for various novel nanoelectronic and photonic devices