Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 39: Quantenpunkte und -dr
ähte: Transporteigenschaften I
HL 39.4: Vortrag
Montag, 7. März 2005, 10:45–11:00, TU P-N202
Investigation of tunneling rates in quantum dots using a quantum point contact — •M. C. Rogge1, C. Fricke1, B. Harke1, R. J. Haug1, and W. Wegscheider2 — 1Institut für Festkörperphysik, Universität Hannover, D-30167 Hannover — 2Angewandte und Experimentelle Physik, Universität Regensburg, D-93040 Regensburg
We present transport measurements on a coupled system including a quantum dot and a quantum point contact. We use a GaAs/AlGaAs heterostructure containing a two-dimensional electron system (2DES) 34 nm below the surface. The device is built using an atomic force microscope (AFM) for lithography. The lateral quantum dot and the quantum point contact are defined using local anodic oxidation (LAO). We investigate our device in a 3He/4He dilution refrigerator. We measure the transport through the quantum dot and at the same time use the quantum point contact as a charge detector. Thus we can still observe charge fluctuations on the dot in a regime, where the current through the dot is too low for transport measurements. In this regime we were able to investigate and compare the tunneling rates to source and drain leads. Thus we were able to find a symmetry line, on which the tunneling rates to both leads are equal. Keeping the tunneling rates symmetric, we were able to detect the change in charge induced by exited dot states in nonlinear measurements.