  The mechanism of single-charge pumping using a dynamic quantum dot needs to
be precisely understood for high-accuracy and universal operation toward
applications to quantum current standards and quantum information devices. The
type of charge carrier (electron or hole) is an important factor for
determining the pumping accuracy, but it has been so far compared just using
different devices that could have different potential landscapes. Here, we
report measurements of a silicon ambipolar single-charge pump. It allows a
comparison between the single-electron and single-hole pumps that share the
entrance tunnel barrier, which is a critical part of the pumping operation. By
changing the frequency and temperature, we reveal that the entrance barrier has
a better energy selectivity in the single-hole pumping, leading to a pumping
error rate better than that in the single-electron pumping up to 400 MHz. This
result implies that the heavy effective mass of holes is related to the
superior characteristics in the single-hole pumping, which would be an
important finding for stably realizing accurate single-charge pumping
operation.
