文档介绍：Near-field Scanning Optical Spectroscopy
of Semiconductor Nanostructures
Christoph Lienau
Max-Born-lnstitut f0r Nichtlineare Optik und Kurzzeitspektroskopie,
Rudower Chaussee 6, D-12489 Berlin, Germany
Abstract: The nanoscopic optical properties of a novel quantum-well-embedded
GaAs quantum wire structure grown on patterned (311)A GaAs surfaces are mapped
using near-field scanning optical microscopy at temperatures between I0 and 300 K.
The local confinement potential of a single quantum wire and the embedding 2D
quantum well continuum is directly extracted using near-field photoluminescence ex-
citation spectroscopy with subwavelength resolution. Shallow asymmetric potential
barriers separating quantum wire and embedding quantum well are identified and
their strong influence on carrier transport and trapping into the quantum wire is ana-
lyzed in steady state and time-resolved near-field photoluminescence experiments at
variable temperatures.
1 Introduction
There is currently a tremendous worldwide research effort towards the fabrication of
low-dimensional semiconductor nanostructures such as one-dimensional quantum wires
(QWR) or zero-dimensional quantum dots (QD). This effort arises partly from the desire
to design laser devices with improved optical characteristics such as higher optical gain,
ultra-low threshold current and narrow spectral linewidths [1,2]. Moreover, unique new
physical properties such as narrowed densities of states, increased excitonic effects [3,4],
strongly enhanced carder mobilities [5] and modified phonon scattering rates [6] are pre-
dicted for such low-dimensional systems. The low-dimensional confinement of carriers in
semiconductor nanostructures is based on spatial variations of the bandstructure, . the
bandgap, on a nanometer scale. The study of such confinement potentials and their influ-
ence on the carrier dynamics in nanostructures requires sophisticated experimenta