Si/SiGe quantum dot with superconducting single-electron transistor charge sensor

TL;DR

This paper presents a robust fabrication process for Si/SiGe quantum dots integrated with a superconducting single-electron transistor charge sensor, enabling precise charge state detection at cryogenic temperatures.

Contribution

It introduces a novel fabrication method combining deep mesa etch and AlOx backfill to reduce gate leakage in Si/SiGe quantum dot devices with integrated S-SET sensors.

Findings

Successful suppression of gate leakage current.

Observation of Coulomb oscillations at 0.3 K.

Confirmed coupling between S-SET and quantum dot.

Abstract

We report a robust process for fabrication of surface-gated Si/SiGe quantum dots (QDs) with an integrated superconducting single-electron transistor (S-SET) charge sensor. A combination of a deep mesa etch and AlOx backfill is used to reduce gate leakage. After the leakage current is suppressed, Coulomb oscillations of the QD and the current-voltage characteristics of the S-SET are observed at a temperature of 0.3 K. Coupling of the S-SET to the QD is confirmed by using the S-SET to perform sensing of the QD charge state.