Increasing Quantized Single-Electron Current Accuracy in a Tunable Barrier Pump by Two-Gate Modulation

Tunable barrier single-electron pumps (SEPs) have recently shown their great potential as high precision current source with direct link to the electron charge. The quantization of SEPs realized in gallium-arsenide semiconductors and driven by a single alternating control voltage routinely shows sub-ppm accuracy when applying high magnetic field. However, their accuracy without field is presently much lower. We now have found that modulation of two gates can increase accuracy in zero magnetic field and have confirmed the current quantization I=ef for a frequency of 84.5 MHz within the measurement uncertainty of less than 1 ppm.