Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 50: Poster II

HL 50.66: Poster

Donnerstag, 30. März 2006, 16:30–19:00, P3

FIR spectroscopy of single quantum dots fabricated by AFM — •Steffen Groth¹, Kevin Rachor¹, Carsten Graf von Westarp¹, Can-Ming Hu², and Detlef Heitmann¹ — ¹Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung, Universität Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany — ²Department of Physics and Astronomy University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2

We study charge excitations in single quantum dots fabricated on semiconductor heterostructures by atomic force microscope (AFM) nanolithography. For this purpose we have established the technique of anodical oxidation to pattern a split gate directly on a GaAs/AlGaAs heterostructure with a two-dimensional electron system confined 35 nm below the sample surface. This technique enables us to prepare barriers with a geometrical thickness of less than 200 nm. The dot geometry and size (down to a few 100 nm) are both tunable by changing the applied gate voltage. We monite the tunneling conductance of the single quantum dot which oscillates as a function of the gate voltage due to the Coulomb blockade. We perform the measurement at a temperature of 250 mK using a He3 cryostat with a 10 tesla magnet connected to a far-infrared (FIR) spectrometer. We expect that under the influence of FIR radiation, the Coulomb blockade peaks will be shifted due to the charge redistribution caused by collective excitations.

The authors are grateful to the DFG for support through SFB 508.