EDGE CHANNELS AND THE QUANTUM-HALL-EFFECT BREAKDOWN

Quantum Hall devices have been investigated in the regime of the break down of dissipationless current flow by means of a photoresistance ima ging technique. It is possible to distinguish three stages in developm ent of the breakdown: (i) the initial rise of the longitudinal resista nce due to a change with the Hall electric field of the percolation th reshold leading to electron backscattering between the edges; (ii) at higher bias currents a strong response from the edges is observed in t wo-dimensional images, in agreement with the edge-state model; (iii) o n increasing the bias current further, electron heating effects are se en to prevail.