Operation of a three-junction single-electron pump with on-chip resistors

We report on the operation of a single-electron pump (comprising three Al/AlOx/Al tunnel junctions and two gates) connected to the bias electrodes through the compact on-chip Cr resistors, R≈60 kΩ>Rk=h/e2≈26 kΩ. The function of the resistors in this so-called R pump was to suppress electron cotunneling, the process which otherwise severely deteriorates the performance of few-junction single-electron devices. When a harmonic ac drive of frequency f of several MHz was applied to the gates, the current–voltage curve of the R pump exhibited remarkably horizontal current steps at I=ef. We show that the use of the resistors is capable of substantially increasing the accuracy of the pump in comparison to operation of the pump without resistors.