Regensburg 2004 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 44: Poster II
HL 44.17: Poster
Donnerstag, 11. März 2004, 16:30–19:00, Poster A
Low temperature transport in a two-dimensional superlattice — •T. Feil1, M. Reinwald1, H.-P. Tranitz1, W. Wegscheider1, D. Schuh 2, M. Bichler2, and G. Abstreiter2 — 1Institut für Experimentalphysik, Universität Regensburg, 93040 Regensburg, Germany — 2Walter Schottky Institut, TU München, Am Coulombwall, 85748 Garching, Germany
We study negative differential conductance in atomically precise, short-period modulated two dimensional electron systems realized with the Cleaved-Edge-Overgrowth method. The device allows the density-dependent study of electron transport in cosine-like minibands. For low densities we find stable NDC in the current-voltage-characteristics which is in agreement with numerical simulations that describe the time evolution of density fluctuations in the system. Microwave absorption experiments show a shift and suppression of the NDC peak which is expected when the NDC is based on Bloch oscillations. The Bloch oscillation picture is further confirmed by studying the density dependence of the low field conductance. When we increase the density and therefore subsequently fill the miniband we reach a point where the overall transport is quenched as expected theoretically due to the fact that a filled miniband cannot carry any current. This density dependence of the transport also leads to a relation between the electron density and the gate voltage of the system, which in turn gives a density value for the transition from stable to unstable NDC. This transition point quantitatively agrees well with our simulations. Supported by DFG via SFB348 and by BMBF 01BM918.