FORMATION OF NARROW CHANNELS USING SPLIT BACK-GATES DEFINED BY IN-SITU FOCUSED ION-BEAM LITHOGRAPHY

We have fabricated high electron mobility transistors incorporating sp lit back-gates using the technique of in situ focused ion beam lithogr aphy and molecular beam epitaxial regrowth. We show that it is possibl e to form quasi-ballistic channels by biasing the split back-gate and have succeeded in defining wires of 400 nm width. Application of a sma ll perpendicular magnetic field has allowed us to demonstrate that bou ndary scattering in these devices is mostly specular, as for conventio nal structures fabricated with Schottky gates.