Palladium gates for reproducible quantum dots in silicon

TL;DR

This paper introduces palladium gates as a novel material for creating reproducible, low-disorder quantum dots in silicon, enabling smaller device designs and advanced electron transport measurements.

Contribution

It demonstrates a new fabrication method replacing aluminium with palladium and aluminium oxide, leading to more reliable quantum dot formation and smaller device architectures.

Findings

Reproducible quantum dots with palladium gates

Ability to shrink gate design to two layers

Successful electron transport in the few-electron regime

Abstract

We replace the established aluminium gates for the formation of quantum dots in silicon with gates made from palladium. We study the morphology of both aluminium and palladium gates with transmission electron microscopy. The native aluminium oxide is found to be formed all around the aluminium gates, which could lead to the formation of unintentional dots. Therefore, we report on a novel fabrication route that replaces aluminium and its native oxide by palladium with atomic-layer-deposition-grown aluminium oxide. Using this approach, we show the formation of low-disorder gate-defined quantum dots, which are reproducibly fabricated. Furthermore, palladium enables us to further shrink the gate design, allowing us to perform electron transport measurements in the few-electron regime in devices comprising only two gate layers, a major technological advancement. It remains to be seen, whether the introduction of palladium gates can improve the excellent results on electron and nuclear spin qubits defined with an aluminium gate stack.