Germanium Quantum Well Interface for Stronger Hole Rashba Coupling

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Solution Overview

Problem

The hole linear Rashba spin-orbit coupling effect in semiconductor quantum wells is unobservable in experiments, hindering the rapid manipulation of hole spin qubits in gate-defined quantum dots, which is crucial for quantum computation.

Innovation Solution

A method is developed to enhance the hole linear Rashba spin-orbit coupling effect by inserting one or more silicon monolayers at the interface between the well and barrier of a germanium quantum well, using a silicon-germanium alloy or superlattice barrier, compatible with the CMOS process, to increase the Rashba strength by an order of magnitude.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional germanium quantum well structure is used, then the structure is simple and compatible with existing processes, but the hole linear Rashba spin-orbit coupling effect is unobservable

Engineering Contradiction:

ImproveRashba effect strengthVSAvoidquantum well structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by inserting silicon atomic layers specifically at the interface regions between the germanium quantum well and aluminum gallium arsenide barriers, while keeping other regions of the structure conventional. This localized modification at the interfaces creates the necessary structural inversion asymmetry to generate observable Rashba effect without redesigning the entire quantum well structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements asymmetry by introducing silicon atomic layers at the quantum well interfaces, which creates structural inversion asymmetry. This asymmetry is the fundamental requirement for generating the Rashba spin-orbit coupling effect, transforming the symmetric conventional quantum well into an asymmetric structure that produces the desired physical effect.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If silicon atomic layers are inserted at the quantum well interfaces to enhance Rashba effect, then the Rashba strength increases by an order of magnitude, but the manufacturing process becomes more complex

Engineering Contradiction:

ImproveRashba effect strengthVSAvoidfabrication process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by incorporating silicon atomic layers during the epitaxial growth process itself, rather than adding them as a separate post-processing step. The silicon layers are grown in-situ along with the germanium quantum well and aluminum gallium arsenide barriers, ensuring precise atomic-layer control and interface quality while maintaining compatibility with existing CMOS fabrication processes.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If the quantum well structure is modified to enhance spin-orbit coupling, then the control rate of spin qubits improves, but the device structure becomes more complex

Engineering Contradiction:

Improvespin qubit control rateVSAvoidquantum well structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach significantly improves the control rate of spin qubits by enhancing the linear Rashba parameter, making it compatible with microelectronic CMOS processes and enabling rapid control of spin qubits in quantum computing.

Implementation Method 1

The Rashba effect is caused by the structural inversion asymmetry due to low-dimensional system interfaces and can be tuned by an external electric field. The driving force of the fast manipulation of hole qubits is demonstrated to be the linear Rashba spin-orbit coupling effect.

Methodology Applied

Scientific EffectRashba effect:

Data Source

PatentUS20230395705A1Method for Fabricating Semiconductor Structure Having Enhanced Hole Linear Rashba Spin-Orbit Coupling Effect

Publication Date: 2023.12.07 INST OF SEMICONDUCTORS - CHINESE ACAD OF SCI

AI summary

A method for fabricating a semiconductor structure having an enhanced hole linear Rashba spin-orbit coupling effect includes: providing a substrate; and growing a germanium quantum well on the substrate. A silicon atomic layer is inserted at an interface between a well and a barrier of the germanium quantum well. The silicon atomic layer includes one or more monolayers.