Noise in Al single electron transistors of stacked design

TL;DR

This study investigates noise characteristics in stacked Al single electron transistors, revealing unexpectedly low charge noise levels and identifying background charge fluctuations and tunnel junction conductance as key noise sources.

Contribution

It introduces a novel stacked design for Al single electron transistors and provides detailed noise analysis, highlighting the impact of device architecture on noise performance.

Findings

Charge noise levels are surprisingly low (2.5-7)*10E-5 e/√Hz at 10 Hz.

Background charge fluctuations are the primary noise source.

Tunnel junction conductance fluctuations can also dominate noise under certain conditions.

Abstract

We have fabricated and examined several Al single electron transistors whose small islands were positioned on top of a counter electrode and hence did not come into contact with a dielectric substrate. The equivalent charge noise figure of all transistors turned out to be surprisingly low, (2.5 - 7)*10E-5 e/sqrt(Hz) at f = 10 Hz. Although the lowest detected noise originates mostly from fluctuations of background charge, the noise contribution of the tunnel junction conductances was, on occasion, found to be dominant.