Germanium electrostatic quantum dot with integrated charge detector in an MOS structure

TL;DR

This paper presents a novel Germanium-based electrostatic quantum dot with an integrated charge detector in an MOS structure, demonstrating single-charge detection despite modest mobility, and discusses potential improvements for device performance.

Contribution

The work introduces a new Germanium quantum dot device with integrated charge detection, utilizing a hybrid design and Al2O3/Germanium interface, advancing quantum dot fabrication in Ge.

Findings

Single-charge detection achieved with Germanium quantum dot

Device uses a two-level gate stack for electron and hole control

Potential for improved performance with multilayer interface

Abstract

We report the fabrication and characterization of an electrostatic quantum dot in pure Germanium with an integrated charge measurement transistor. The device uses the Al2O3/Germanium interface for the confinement of carriers in the Germanium and an hybrid design with an electron quantum dot and hole transistor for the charge detection. The hole transistor, using with NiGe source and drain contacts, despite the modest low temperature carrier mobility of 450 cm2/Vs, has shown a sensitivity to the dot electric potential sufficient to detect single charges tunneling in and out of the quantum dot. The device is realized with a two level gate stack, with the top level used to attract electrons and the lower one to define the electron confinement potential and accumulate the hole transistor. The possibility to improve the device operation using a Al2O3/SiGe/Ge multilayer for the confinement of electrons at a smoother interface is discussed.