Controlling the charging energy of arrays of tunnel junctions

Abstract We describe a new technique to control in situ charging energy of systems of coupled metallic or superconducting islands. To illustrate the technique, we have fabricated two-dimensional arrays of Al islands on GaAs/AlAs heterostructures. Each island is coupled to its nearest-neighbor by a submicron Al/AlO x /Al tunnel junction and to the three-dimensional electron gas (3DEG) located below the surface of the heterostructure by a capacitance C g . We vary C g , which dominates the charging energy of the array, by depleting the electrons in the 3DEG by means of a negative voltage applied to the array. With the array driven normal by a magnetic field, a decrease in C g increases in both the offset voltage and the period of the Coulomb blockade oscillations.