Magnetoresistance effects in laterally confined n-GaAs/(AlGa)As heterostructures

The authors have investigated the magnetoresistance of laterally confined n-GaAs/(AlGa)As heterostructures in the temperature range from 2 K to 300 K and at magnetic fields up to 11 T. The 2DEG at the interface is confined to narrow channels which are 10 mu m long and with lithographic widths between 0.16 mu m and 0.54 mu m. They assess the effectiveness of the confinement in terms of carrier depletion, the nature of the side-wall scattering and the stability of the conductivity as a function of time. They also compare the conduction channel width with the lithographic width. The low field magnetoresistance is analysed in terms of electron interaction effects, weak localisation, universal conductance fluctuations (UCF) and a side-wall skipping orbit effect. In particular, at high temperatures (T>20 K) the skipping effect develops a temperature dependence which is explained by the variation of the phase-breaking rate obtained from the UCF analysis.