Precision measurement of an electron pump at 2 GHz

TL;DR

This study demonstrates a silicon electron pump operating at 2 GHz with high precision, revealing a stable current plateau and highlighting potential limitations in current traceability methods for small currents.

Contribution

First demonstration of a silicon tunable-barrier electron pump at 2 GHz with sub-ppm measurement uncertainty over an extended period.

Findings

Pump current plateau flat to 0.1 ppm

Offset of 0.2 ppm from expected current

Uncertainty limited by current traceability chain

Abstract

A well-characterised sample of silicon tunable-barrier electron pump has been operated at a frequency of 2 GHz using a custom drive waveform, generating a pump current of 320 pA. Precision measurements of the current were made as a function of pump control parameters, using a blind protocol, over a 7-week campaign. The combined standard uncertainty for each 10 hour measurement was 0.1 parts per million. The pump current exhibits a plateau along the exit gate voltage flat to approximately 0.1 parts per million, but offset from ef by 0.2 parts per million. This offset may be a sign of errors in the current traceability chain, indicating a limit to the accuracy of small current scaling using existing methods based on cryogenic current comparators.