Quantum ballistic transport in semiconductor nanostructures; effect of smooth features in confining potentials

Abstract

Using a mode-matching method, we investigate the ballistic transport properties of noninteracting electrons in two types of semiconductor nanostructures in which the confining potential has smooth, rounded corners. The rounded corners are simulated by dividing the structures into narrow strips and varying the width of each strip. The two structures we have investigated are a straight channel connecting two reservoirs of two-dimensional electrons and a cross-bar structure consisting of two perpendicular channels, one of which connects to the reservoirs. In the case of the straight channel we find that the rounded corners decreases oscillations in the conductance. For the cross-bar structure we have compared with results from Berggren et al. (K.-F. Berggren, C. Besev and Z.-L. Ji, Physica Scripta T 42 (1992) 141) who used a model with sharp corners. For low values of the Fermi energy our results are in good agreement with theirs, which validates the simplication of using sharp corners. As the energy increases differences appear, and at certain energies, the rounded corners drastically changes the conductance, transforming a resonance peak to an anti-resonance dip.