EXPERIMENTAL STUDIES OF ELECTRONIC TRANSPORT IN SEMICONDUCTOR QUANTUM-DOT STRUCTURES

We have studied the low temperature electrical properties of semiconductor quantum dot structures at high magnetic fields. The devices consisted of lithographically defined aluminium gates deposited on to the surface of a GaAs/AlGaAs heterojunction substrate and the dot structures were formed on the application of a suitable negative bias to the gates. At high magnetic fields electronic transport occurred via edge states and we were able to use the well known properties of these states to study transmission through the dot structures. In particular we observed large resistance resonances superimposed on the quantised magnetoresistance plateaux of the dot. These resonances were found to persist with reduced amplitude to above a degree Kelvin and showed a sensitive dependence on the applied gate voltage. We associate them with the increased edge state interaction introduced by the dot and discuss our results in terms of the various scattering mechanisms inherent to quantum dot structures.