INSTABILITIES IN QUANTUM POINT-CONTACT STRUCTURES

We discuss the appearance of strong nonlinearities including S-type ne gative differential conductance in the I-V characteristics of quantum point contact (QPC) structures. Time-dependent measurements demonstrat e that the highly nonlinear d.c. I-V features are associated with a te mporal average of random telegraph switching (RTS) between different c urrent levels. The RTS is only observed when the voltage across the de vice is such that the chemical potential on one side of the QPC is ali gned with the bottom of a one-dimensional subband in the QPC. As the c hemical potential is moved further into the subband, the switching beh avior disappears until the next subband minimum is reached. (C) 1996 A cademic Press Limited