Silicon-charge-pump operation limit above and below liquid-helium temperature

Semiconductor tunable -barrier single -electron pumps can produce output current of hundreds of picoamperes at sub -parts -per -million precision, approaching the metrological requirement for the direct implementation of the current standard. Here we operate a silicon metal -oxide -semiconductor electron pump up to a temperature of 14 K to qualitatively understand the effect of temperature on charge -pumping accuracy. The uncertainty of the charge pump is tunnel limited below liquid -helium temperature, implying lowering the temperature further does not greatly suppress errors. Hence, highly accurate charge pumps could be achieved in a 4He cryogenic system, further promoting use of the revised quantum current standard across national measurement institutes and industries worldwide.