SINGLE-ELECTRON TRANSISTOR FABRICATED BY FOCUSED LASER BEAM-INDUCED DOPING OF A GAAS ALGAAS HETEROSTRUCTURE/

A single-electron transistor has been fabricated by an optical fabrica tion method. A small dot, a source and drain reservoir, and in-plane g ates are all built from the two-dimensional electron gas of an n-type GaAs/AlGaAs heterostructure. Laser-written p-doped lines are used to d efine this dot with a diameter of about 70 nm and to insulate it from the in-plane gates. Tunnel junctions connect the dot with source and d rain. The in-plane gates are used to tune the tunnel junctions and to change the electrostatic potential of the dot. A large charging energy of 5 meV and clear Coulomb-blockade oscillations are observed at heli um temperature, due to a small dot capacitance of about 3 x 10-(17) F. (C) 1997 American Institute of Physics.