Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 39: Quantenpunkte und -dr
ähte: Transporteigenschaften I
HL 39.7: Vortrag
Montag, 7. März 2005, 11:30–11:45, TU P-N202
Electrostatically defined single gate quantum dots — •C. Rössler1, A. K. Hüttel1, S. Ludwig1, J. P. Kotthaus1, and W. Wegscheider2 — 1CeNS und Department für Physik der LMU, 80539 München — 2Institut für Angewandte und Experimentelle Physik, Universität Regensburg, 93040 Regensburg
We perform transport measurements on quantum dots (QD) defined by means of negatively biased gate electrodes on top of a AlGaAs/GaAs heterostructure. The two–dimensional electron gas (2DEG) is only 37 nm below the surface of our δ–doped sample. Conductance measurements in the Coulomb blockade regime, for example on a QD defined by three gates, are strongly affected by temporal charge fluctuations. Our layout contains one complex shaped gate. If biased sufficiently, it divides the 2DEG into two electrically isolated areas. At lower bias voltage, the geometry of this gate results in a QD beneath it, even if all other gates are grounded. This has been reproduced on three different samples. Strikingly, the transport properties of the single gate dot are undisturbed by the fluctuations. We investigate this QD in its few electron limit. The coupling to the leads depends strongly on the gate voltage which is the only control parameter. In the regime of strong coupling, we observe Kondo signatures and investigate its temperature and magnetic field dependencies.