Imaging random telegraph signal sites near a quasi 1D electron system

Conductance of a quasi 1D electron system (Q1DES) is a sensitive detector of the local electric potential. Electrons hopping between defect states can generate a random telegraph signal in conductance measurements made against time. Such a detector, defined in a GaAs/A1GaAs heterostructure, was used to generate images of the electric potential of a scanning charged tip and structure seen in the Q1DES conductance images is consistent with an electron hopping between two defect states separated by slightly more than the Bohr orbit. The occupation probability being mediated by the position of the scanning tip over the defect near the Q1DES. Images suggest that a puddle of mobile charge in the donor layer can screen the tip from the defect system.