Quantized current by a silicon dual-gate bidirectional electron pump

Quantized current was observed in a silicon dual-gate bidirectional electron pump. The polarity of the pump current can be altered either by the DC voltages applied on the two-gate electrodes, or by the sign of the phase difference of the AC modulations added to the gate voltages. The pump current exhibits stepwise jumps as the amplitude of the AC modulation is increased, and the step height of the current jump is quantized in unit of ef, where f is the frequency of the AC modulation. An energy-potential scheme, based on that the potential energy of the central quantum dot can be modulated by the sum of the electrical potentials applied on the two-finger gates, reasonably explains the observations. The occurrence of the sequential switching on-and-off of the two multiple tunneling junction single-electron transistors is essential to the observation of the quantized current.