Low percolation density and charge noise with holes in germanium

TL;DR

This paper demonstrates that planar germanium heterostructures exhibit low disorder and charge noise, making them promising for scalable hole spin qubit arrays in quantum computing.

Contribution

The study introduces a method to engineer low-disorder Ge/SiGe heterostructures with buried Ge channels, achieving low percolation density and ultra-low charge noise for quantum dot applications.

Findings

Percolation density of 2.1×10^{10} cm^{-2} indicating low disorder

Charge noise below 0.2 μeV/√Hz at 1 Hz

Supports quiet operation of hole quantum dots

Abstract

We engineer planar Ge/SiGe heterostructures for low disorder and quiet hole quantum dot operation by positioning the strained Ge channel 55~nm below the semiconductor/dielectric interface. In heterostructure field effect transistors, we measure a percolation density for two-dimensional hole transport of $2.1\times10^{10}~\text{cm}^{-2}$, indicative of a very low disorder potential landscape experienced by holes in the buried Ge channel. These Ge heterostructures support quiet operation of hole quantum dots and we measure charge noise levels that are below the detection limit $\sqrt{S_\text{E}}=0.2~\mu \text{eV}/\sqrt{\text{Hz}}$ at 1 Hz. These results establish planar Ge as a promising platform for scaled two-dimensional spin qubit arrays.