  Semiconductor tunable barrier single-electron pumps can produce output
current of hundreds of picoamperes at sub ppm 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 understand the temperature effect 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 confidently
achieved in a $^4$He cryogenic system, further promoting utilization of the
revised quantum current standard across the national measurement institutes and
industries worldwide.
