Experimental study of saddle point conductance in strongly disordered Si-metal nitride oxide semiconductor structure at high magnetic fields

We have experimentally shown that percolating 2D electron systems based on Si-metal-nitride-oxide semiconductor structures with strong fluctuation pot ential reveal conductance quantization signatures up to room temperature, d espite the sample sizes being in the micrometer range. The gate length of t he structure was chosen to be comparable with the percolation correlation l ength, while its width is much bigger. Under high magnetic field action the structure shows positive magnetoresistance at gate voltages where the cond uctance G is lower than e(2)/h and negative at higher values. We have inter preted these effects in terms of a self-organized disordered structure in w hich the resistance is controlled by the conductance of a single fluctuatio n potential saddle point constriction having quantized values. (C) 2001 Pub lished by Elsevier Science B.V.