Universality of the tunable-barrier electron pump at the part-per-million level

We summarize the results of precision measurement campaigns on semiconductor tunable-barrier electron pumps undertaken at NPL, over the last 5 years. We have investigated pumps of 3 different designs, fabricated in GaAs and silicon and operated on the 1-electron plateau at frequencies from 230 MHz to 1 GHz. For all measurements we find the pump current equal to e×f within the ≈1 ppm standard uncertainty of the current measurement. This accumulated data strongly suggests that accurate quantized operation of the tunable-barrier pump is a universal property, insensitive to the detailed design of the device. The data includes previously unpublished results.