Etching process of narrow wire and application to tunable-barrier electron pump

Single electron sources have been studied as a device to establish an electric current standard for 30 years and recently as an on-demand coherent source for fermion quantum optics. In order to construct the single electron source on a GaAs/AlGaAs two-dimensional electron gas (2DEG), it is often necessary to fabricate a sub-micrometer wire by etching. We have established techniques to fabricate the wire made of the fragile 2DEG by combining photolithography and electron beam lithography with one-step photoresist coating, which enables us to etch fine and coarse structures simultaneously. It has been demonstrated that the fabricated single electron source pumps a fixed number of electrons per cycle with radio frequency. The fabrication technique improves the lithography process with lower risk of damage to the 2DEG.