An ambipolar single-charge pump in silicon

TL;DR

This paper demonstrates a silicon ambipolar single-charge pump that compares electron and hole pumping, revealing that holes exhibit better energy selectivity and lower error rates at high frequencies, advancing quantum current standards.

Contribution

It provides the first direct comparison of electron and hole single-charge pumps sharing the same tunnel barrier, highlighting the advantages of hole-based pumping for accuracy.

Findings

Hole pumping shows better energy selectivity than electron pumping.

Pumping error rate for holes is lower than electrons up to 400 MHz.

Heavy effective mass of holes contributes to superior pumping characteristics.

Abstract

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.