Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 25: Quantum dots and wires: Optical properties II
HL 25.8: Talk
Tuesday, March 27, 2007, 16:00–16:15, H17
Optical Investigations of Single Pairs of Vertically Stacked Asymmetric InP Quantum Dots — •Matthias Reischle1, Gareth Beirne1, Robert Roßbach1, Michael Jetter1, Heinz Schweizer2, and Peter Michler1 — 1Institut für Strahlenphysik, Allmandring 3, 70569 Stuttgart, Germany — 24. Physikalisches Institut, Pfaffenwaldring 57, 70569 Stuttgart, Germany
Coupled quantum dots (QD) are interesting candidates for future devices, such as, quantum gates for quantum computers. While most of the previous studies concentrated on double dot systems with similar dot sizes relatively few studies have concentrated on asymmetric quantum dot pairs. Nevertheless, this system is easier to realize, as QDs naturally exhibit size inhomogenities.
Single vertically stacked pairs of InP QDs that are separated by different barrier widths have been investigated. We could, on average, produce smaller upper dots that emit at higher energies than the bottom layer of dots. This arrangement allows for the tunneling of carriers from the small dots to the large dots. We have found that coupling is clearly present for a small barrier width, while for a large barrier width the dots are found to act independently. A transition from primarily electron tunneling to exciton tunneling with decreasing barrier width has also been found by comparing the photoluminescence spectra. In addition, from time-resolved measurements we could estimate the tunneling times which are in accordance with those presented previously in the literature. Finally we simulate our results using a simple rate equation model which supports the proposed tunneling mechanism.