Abstract
Micrometer-sized loops of two-dimensional electron gas have been made on GaAs-AlGaAs heterostructures by electrostatic confinement. A split gate is used to define the loop, allowing the width of the conducting channels to be varied by changing the gate voltage. The magnetoresistance has been measured at low temperatures (T<100 mK) and shows strong Aharonov-Bohm oscillations with amplitudes of up to 7% of the total resistance in the narrowest devices. The oscillations are strong out to B approximately=0.5 T and then die out as B increases to approximately=1 T, with a possible dependence on the channel width. Magnetic depopulation of the ID-sub-bands is also seen.