文档介绍：Raman Spectroscopy of Quantum Dots
Christian Schf311er
Institut f0r Angewandte Physik und Zentrum for Mikrostrukturforschung,
Universit&t Hamburg, Jungiusstral3e 11, D-20355 Hamburg, Germany
Abstract: We review recent resonant Raman experiments on GaAs-AIGaAs quan-
tum dots. We were able to observe simultaneously single-particle-likeelectronic ex-
citations (SPE) and collective spin-density and charge-density excitations (SDE and
CDE). This allows us to determine the influence of many-particle interactions in the
quantum dots. Moreover, by a detailed analysis of wave-vector and ic-field
dependent measurements, we can identify transitions between different electronic
shells of the quasiatomic systems which predominantly contribute to the observed
low-energy SDE's and resemble an atomic fine structure.
1 Introduction
The first experiments of inelastic light scattering by collective plasma oscillations (plas-
mons) of free electrons, coupled to LO phonons, in n-type bulk GaAs were performed
by Mooradian and Wright in 1968 [1]. Later Mooradian also observed under resonant
excitation, ., the laser frequency is in the vicinity of the optical E0 + A energy gap of
the semiconductor, excitations which - at that time - were interpreted as single-particle
excitations [2]. According to the experimental findings, Hamilton and McWhorter de-
duced in their theoretical work that this single-particle scattering, which results from so
called spin-density fluctuations, can be observed in zincblende-type semiconductors in
depolarized scattering geometry, ., the polarization directions of ing and scat-
tered light are perpendicular to each other. Scattering by plasmons due to charge-density
fluctuations is visible in parallel polarization configuration (polarized geometry) [3]. In
contrast to light scattering by optical phonons, the electronic Raman signals are strongly
dependent on resonance enhancement effects at optical