Abstract
A threshold vanishing of the Hall emf with decreasing gate voltage is observed at ≈ 77 K in semiconductor systems which are disordered as a result of a high built-in charge density near the plane of the 2D-electron channel. The effect is observed at a channel conductivity σ ≈e2/h and is due to a transition to nondegenerate-electron transport via a 2D percolation cluster having a quasi-1D character of the conduction. We have established that the conductance of “short” structures, having a length of the order of the correlation length of a percolation cluster, equals ≈e2/h per electron and is determined by isolated percolation paths having a lowered percolation threshold. These phenomena are a general property of disordered 2D systems.
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