Berlin 2008 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 30: Quantum dots and wires: Transport properties II

HL 30.4: Vortrag

Dienstag, 26. Februar 2008, 15:00–15:15, ER 164

Coulomb blockade energies in the shape-modified InAs quantum dots — •Razvan Roescu, Dirk Reuter, and Andreas D. Wieck — Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany

Rapid thermal annealing (RTA) and an Indium flush technique are methods commonly used to blue-shift the emission wavelengths for self-assembled InAs quantum dots (QDs). These methods induce modifications in the shape and the composition of the QDs. By employing capacitance-voltage spectroscopy we show that carrier-carrier interactions in such modified QDs are also affected. The Coulomb blockade energy in the ground state - the energy paid by the second electron (or hole) to enter the dot when there is already one carrier inside - is found to decrease significantly with decreasing emission wavelength if the RTA process was used, whereas it stays almost constant if the In flush technique was employed to shift the emission wavelength. These findings can be correlated to the differences in the resulting QD shape for the two different processes used. The decrease in Coulomb blockade energy for the RTA process is consistent with the results of wave function mapping, pointing to an increase in the wave function extension with decreasing emission wavelength.