Asymmetry of charge relaxation times in quantum dots: The influence of degeneracy
1 Faculty of Physics and CENIDE, University of Duisburg- Essen - Lotharstr. 1, 47057 Duisburg, Germany
2 Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum - Universitätstr. 150, 44780 Bochum, Germany
Received: 5 March 2014
Accepted: 24 April 2014
Using time-resolved transconductance spectroscopy, we study the tunneling dynamics between a two-dimensional electron gas (2DEG) and self-assembled quantum dots (QDs), embedded in a field-effect transistor structure. We find that the tunneling of electrons from the 2DEG into the QDs is governed by a different time constant than the reverse process, i.e., tunneling from the QDs to the 2DEG. This asymmetry is a clear signature of Coulomb interaction and makes it possible to determine the degeneracy of the quantum-dot orbitals even when the individual states cannot be resolved energetically because of inhomogeneous broadening. Our experimental data can be qualitatively explained within a master-equation approach.
PACS: 73.63.Kv – Quantum dots / 73.23.Hk – Coulomb blockade; single-electron tunneling / 73.40.Gk – Tunneling
© EPLA, 2014