Enhanced Valley Splitting in Si Layers with Oscillatory Ge Concentration

TL;DR

This paper explores how oscillatory germanium concentration in silicon layers can enhance valley splitting, potentially improving silicon-based qubits for quantum computing by analyzing the underlying theory and model calculations.

Contribution

It introduces a theoretical framework and model calculations for the Wiggle Well architecture, demonstrating how oscillatory Ge concentration affects valley splitting in silicon.

Findings

Valley splitting depends on the wavelength of Ge oscillations.

A selection rule limits the effectiveness of the Wiggle Well.

Model calculations quantify the magnitude of valley splitting enhancement.

Abstract

The valley degeneracy in Si qubit devices presents problems for their use in quantum information processing. It is possible to lift this degeneracy by using the Wiggle Well architecture, in which an oscillatory Ge concentration couples the valleys. This paper presents the basic theory of this phenomenon together with model calculations using the empirical pseudopotential theory to obtain the overall magnitude of this effect and its dependence on the wavelength of the concentration oscillations. We derive an important selection rule which can limit the effectiveness of the Wiggle Well in certain circumstances.