The influence of dislocations upon the conductivity of a 2-dimensional electron gas, at liquid He temperatures and in a high magnetic field, was considered. Two types of dislocation sub-structure were studied experimentally. These corresponded either to a family of parallel dislocation segments that were introduced by plastic bending, or to a family of parallel and long misfit dislocations which were created during epitaxial growth by controlling the epilayer thickness. It was shown that both types of dislocation sub-structure led to a strongly anisotropic behavior of the longitudinal conductivity, whereas the quantum Hall effect was not significantly affected by the presence of dislocations. A theoretical treatment of the case of anisotropic potentials was proposed as a generalization of the simpler case of isotropic (short-range) potentials. With the aid of this analysis it was possible to explain, in the case of dislocation segments, why - although they were anisotropic - the normalized conductivity curves which were obtained for the principal axis were identical. It was shown that normal Dingle plots could be used to check the extra broadening of the Landau levels which was due to dislocations. The second type of dislocation sub-structure was shown to be equivalent to quasi 1-dimensional systems which arose from a truncation of the 2-dimensional electron gas into parallel ribbons that were localized between the dislocation potential barriers. No ballistic effects were observed.

Z.Bougrioua, J.L.Farvacque, D.Ferré: Journal of Applied Physics, 1996, 79[3], 1546-55