Quantum Dot Arrays in Silicon and Germanium

TL;DR

This paper demonstrates scalable quantum dot arrays in silicon and germanium platforms, showcasing charge sensing, array control, and integration potential for quantum computing applications.

Contribution

It introduces multi-layer fabrication of quantum dot arrays in SiMOS, Si/SiGe, and Ge/SiGe, with first-time charge sensing in Ge/SiGe and array tuning in Si/SiGe.

Findings

Successful fabrication of quantum dot arrays in three platforms.

Charge sensing achieved in Ge/SiGe for the first time.

Smallest capacitive cross talk observed in SiMOS.

Abstract

Electrons and holes confined in quantum dots define an excellent building block for quantum emergence, simulation, and computation. In order for quantum electronics to become practical, large numbers of quantum dots will be required, necessitating the fabrication of scaled structures such as linear and 2D arrays. Group IV semiconductors contain stable isotopes with zero nuclear spin and can thereby serve as excellent host for spins with long quantum coherence. Here we demonstrate group IV quantum dot arrays in silicon metal-oxide-semiconductor (SiMOS), strained silicon (Si/SiGe) and strained germanium (Ge/SiGe). We fabricate using a multi-layer technique to achieve tightly confined quantum dots and compare integration processes. While SiMOS can benefit from a larger temperature budget and Ge/SiGe can make ohmic contact to metals, the overlapping gate structure to define the quantum dots can be based on a nearly identical integration. We realize charge sensing in each platform, for the first time in Ge/SiGe, and demonstrate fully functional linear and two-dimensional arrays where all quantum dots can be depleted to the last charge state. In Si/SiGe, we tune a quintuple quantum dot using the N+1 method to simultaneously reach the few electron regime for each quantum dot. We compare capacitive cross talk and find it to be the smallest in SiMOS, relevant for the tuning of quantum dot arrays. These results constitute an excellent base for quantum computation with quantum dots and provide opportunities for each platform to be integrated with standard semiconductor manufacturing.