Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 58: Poster IIb
HL 58.4: Poster
Dienstag, 8. März 2005, 16:30–19:00, Poster TU F
Wave-function mixing in tunnel-coupled quantum point contacts — •G. Apetrii1, U. Kunze1, D. Schuh2, and G. Abstreiter2 — 1Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum, D-44780 Bochum — 2Walter Schottky Institut, Technische Universität München, D-85748 Garching
Closely spaced vertically stacked quantum point contacts (QPCs) were prepared on a GaAs/AlGaAs heterostructure comprising two 14.5 nm wide GaAs quantum wells (QWs) separated by a 1 nm wide Al0.32Ga0.68As barrier. The tunnel interaction of the two-dimensional electron systems contained in the two QWs is characterized at equilibrium by a symmetric-antisymmetric energy gap of 4 meV. The QPCs were processed by lithography with an atomic force microscope and subsequent wet-chemical etching. In two-terminal conductance and transconductance measurements at 4.2 K two series of signals originating in the two QPCs were identified. A top-gate/back-gate system together with a cooling bias technique were used for tuning the energy spectra of the tunnel-coupled QPCs in order to obtain degeneracies of 1D subbands. Clear anticrossings with mixing of the 1D wave functions are observed in grey-scale transconductance plots versus top-gate and back-gate voltage. Large anticrossing energy gaps amounting to 5 meV were determined experimentally by means of measurements under dc drain voltage.