TUNNELING BETWEEN EDGE STATES IN THE QUANTUM HALL REGIME LIMITED BY AMESOSCOPIC ISLAND - A CURRENT-PLATEAU PHENOMENON

Well-developed current plateaus have been observed in the I-V characte ristics of Corbino devices in the quantum Hall regime, if a striplike island of mesoscopic dimensions is located between two trench fingers which are etched radially between the central and outer Ohmic contacts . The trenches are 100 nm wide and define, together with the island, t wo constrictions of 550-700-nm width. The current plateaus are due to a limitation of the tunneling rate by the filling of nonequilibrium st ates around the island. The evolution of the current plateaus with the filling factor is qualitatively explained by quasielastic inter-landa u-level tunneling. The latter mechanism determines the onset of the tu nneling-current plateau, which extends until the complete local breakd own of the quantum Hall regime around the island is reached. We invest igated this tunneling phenomenon as a function of the temperature in t he range from 23 mK to 2.1 K, and for various sizes of the island, ran ging from 100x250 nm(2) to 100 nmx8 mu m. The plateaus were better pro nounced, the lower the temperature and the smaller the island was. To explain the observed tunneling-current plateaus, we suggest a picture including the properties of the edge states (near the trenches and aro und the island) and the incompressible quantum Hall region in between them.