A backgate for enhanced tunability of holes in planar germanium

TL;DR

This paper introduces a backgate in planar germanium heterostructures, allowing independent tuning of density and electric field, which enhances control over qubit properties for quantum computing applications.

Contribution

The work demonstrates a backgate implementation that enables independent control of density and electric field in planar germanium heterostructures, improving qubit property engineering.

Findings

Backgate enables independent control of density and electric field.

Enhanced tuning of effective mass, g-factor, and quantum lifetime.

Facilitates targeted tuning of bilayer quantum wells for denser qubit packing.

Abstract

Planar semiconductor heterostructures offer versatile device designs and are promising candidates for scalable quantum computing. Notably, heterostructures based on strained germanium have been extensively studied in recent years, with emphasis on their strong and tunable spin-orbit interaction, low effective mass, and high hole mobility. However, planar systems are still limited by the fact that the shape of the confinement potential is directly related to the density. In this work, we present the successful implementation of a backgate for a planar germanium heterostructure. The backgate, in combination with a topgate, enables independent control over the density and the electric field, which determines important state properties such as the effective mass, the $g$-factor and the quantum lifetime. This unparalleled degree of control paves the way towards engineering qubit properties and facilitates the targetted tuning of bilayer quantum wells, which promise denser qubit packing.