Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 39: Quantum dots: Optical and transport properties

HL 39.9: Vortrag

Donnerstag, 26. März 2009, 12:00–12:15, BEY 81

Time-resolved observation of electron tunneling from self-assembled QD using a 2DEG — •Bastian Marquardt¹, Martin Geller¹, Axel Lorke¹, and Dirk Reuter² — ¹Experimental Physics & CeNIDE, Universität Duisburg-Essen, Duisburg — ²Angewandte Festkörperphysik, Ruhr-Universität Bochum, Bochum

We developed a novel technique to probe the tunneling dynamics of quantum dot carriers (QD) into a nearby two-dimensional electron gas (2DEG). This method employs the 2DEG as a detector for the tunneling charge into and out of the InAs-QD-layer. A time-resolved two-terminal resistance measurement allows us to investigate the tunneling times of the emission processes. Furthermore, this new technique allows us to probe samples with very slow tunneling times, in contrast to the commonly used frequency-dependent capacitance-voltage (CV) spectroscopy. The CV-spectroscopy has been proven to be a valuable tool to investigate coupled electron systems with fast tunneling times (τ<<100ms). In the case of weakly coupled QD-2DEG electron systems with extremly slow tunneling times τ>1s, the CV-spectroscopy is not able to probe the tunneling dynamics because of the insufficient s/n-ratio for low frequencies. Additionally, in contrast to CV-spectroscopy the resistance of a 2DEG is given by its aspect ratio and not its size. This enables us to scale down the sample dimensions to few or even single QDs in the future. On the basis of the measured transients the tunneling times for different applied electrical fields are evaluated. Our technique makes it possible to study non-equilibrium tunneling into excited dot-states.