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

Conductance of a quasi 1D electron system (Q1DES) is a sensitive detector o f the local electric potential. Electrons hopping between defect states can generate a random telegraph signal in conductance measurements made agains t 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 elect ron hopping between two defect states separated by slightly more than the B ohr 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 syst em.