SINGLE-ELECTRON TRANSISTOR AS AN ELECTROMETER MEASURING CHEMICAL-POTENTIAL VARIATIONS

The magnetic field dependence of the chemical potential of an electron system can be measured using a metallic single-electron transistor (S ET). To demonstrate the method, a SET made of aluminum was fabricated on top of a GaAs/AlGaAs heterostructure containing a two-dimensional e lectron system (2DES). A change in the chemical potential of the 2DES causes a change in the contact voltage between the SET leads and the 2 DES below the SET island which affects the current flow through the SE T island. Tuning a voltage which is externally applied in series to th e contact voltage, the change in the intrinsic contact voltage can be compensated to keep the SET current constant. With this tuning voltage , the change of the chemical potential by the magnetic field is direct ly measured. The method described here is applicable to other material s and other parameters affecting the intrinsic contact voltages. (C) 1 997 American Institute of Physics.