Back‐gated split‐gate transistor: A one‐dimensional ballistic channel with variable Fermi energy

We have studied the quantized conductance of a one‐dimensional ballistic channel in the two‐dimensional electron gas of a back‐gated GaAs/AlGaAs heterostructure. A standard Schottky split‐gate fabricated with electron‐beam lithography techniques is used to define the one‐dimensional channel, but we incorporate an epitaxially grownin situ back‐gate, situated ∼1 μm below the electron gas, to provide additional control of the carrier density. Quantized conductance steps can be induced by changing the bias on either gate, highlighting the self‐consistent nature of the electrostatics involved. We show that we can, in principle, achieve independent control of the one‐dimensional carrier density and channel width.