SELECTIVE-POPULATION OF EDGE STATES IN SI-MOSFETS IN THE QUANTUM HALL REGIME

We have performed electron transport studies in the quantum Hall regime on high-mobility Si-MOSFETS with an adjustable discontinuity in the density of the two-dimensional electron gas. To achieve this we etch a gap with submicron width in the gate electrode and bias the two parts independently. For equal and integer filling factors on both sides of the gap there is negligible reflection of electrons in edge states meaning that the barrier is low compared with the Landau-level separation. For unequal but integer filling factors the longitudinal resistance across the gap is quantized, indicating that in this case the transmission coefficient of the edge states is either zero or one, depending on the gate voltages.