Well-developed current plateaus have been observed in the $I-V$ characteristics 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, two constrictions of 550–700-nm width. The current plateaus are due to a limitation of the tunneling rate by the filling of nonequilibrium states around the island. The evolution of the current plateaus with the filling factor is qualitatively explained by quasielastic inter-Landau-level tunneling. The latter mechanism determines the onset of the tunneling-current plateau, which extends until the complete local breakdown of the quantum Hall regime around the island is reached. We investigated this tunneling phenomenon as a function of the temperature in the range from 23 mK to 2.1 K, and for various sizes of the island, ranging from $100\times 250{\mathrm{nm}}^2$ to 100 nm×8 μm. The plateaus were better pronounced, 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 around the island) and the incompressible quantum Hall region in between them.

• Received 23 March 1998

DOI:https://doi.org/10.1103/PhysRevB.58.4028