Depletion-mode Quantum Dots in Intrinsic Silicon

TL;DR

This paper demonstrates the fabrication and electrical characterization of depletion-mode quantum dots in intrinsic silicon using a simple single-layer process, revealing Coulomb oscillations and a method to deactivate fixed charge.

Contribution

It introduces a depletion-mode quantum dot design in intrinsic silicon that simplifies fabrication and includes a novel method to deactivate fixed charge in the dielectric stack.

Findings

Coulomb oscillations with charging energies of 10-15 meV and 3-5 meV observed.

Deactivation of fixed charge using deep ultraviolet light demonstrated.

Depletion-mode design avoids complex multilayer architectures.

Abstract

We report the fabrication and electrical characterization of depletion-mode quantum dots in a two-dimensional hole gas (2DHG) in intrinsic silicon. We use fixed charge in a SiO$_2$/Al$_2$O$_3$ dielectric stack to induce a 2DHG at the Si/SiO$_2$ interface. Fabrication of the gate structures is accomplished with a single layer metallization process. Transport spectroscopy reveals regular Coulomb oscillations with charging energies of 10-15 meV and 3-5 meV for the few- and many-hole regimes, respectively. This depletion-mode design avoids complex multilayer architectures requiring precision alignment, and allows to adopt directly best practices already developed for depletion dots in other material systems. We also demonstrate a method to deactivate fixed charge in the SiO$_2$/Al$_2$O$_3$ dielectric stack using deep ultraviolet light, which may become an important procedure to avoid unwanted 2DHG build-up in Si MOS quantum bits.