Isotopically Depleted Semiconductor Structures for Stable Spin Qubits
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Solution Overview
Problem
The presence of silicon atoms with mass number 29, which have a non-integer nuclear spin, degrades the performance of spin qubits in quantum computers by causing decoherence and instability.
Innovation Solution
Forming a semiconductor layer with a concentration of silicon atoms with mass number 29 reduced to less than natural abundance, typically below 100 parts per million, using epitaxial growth and annealing processes to enrich the layer with silicon atoms of mass number 28, which have a nuclear spin of zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If natural silicon material is used in the semiconductor layer, then the manufacturing process is simple and cost-effective, but the nuclear spin of silicon atoms with mass number 29 causes decoherence and instability of qubit spin states
Solution Approach 1:
The patent changes the isotopic composition parameter of the silicon material by reducing the concentration of silicon atoms with mass number 29 to less than natural abundance (typically below 100 parts per million). This parameter change eliminates the harmful nuclear spin interaction while maintaining the semiconductor functionality, thereby resolving the contradiction between qubit stability and manufacturing simplicity
Solution Approach 2:
The patent extracts or removes the harmful component (silicon atoms with mass number 29) from the semiconductor material. By depleting the concentration of this specific isotope through epitaxial growth and annealing processes, the harmful nuclear spin effect is eliminated while retaining the beneficial properties of silicon for quantum computing applications
2Reliability
If the concentration of silicon atoms with mass number 29 is reduced to below natural abundance, then qubit spin state decoherence is reduced, but the manufacturing process becomes more complex requiring epitaxial growth and annealing
Solution Approach 1:
The patent applies preliminary action by performing epitaxial growth with controlled isotopic composition and subsequent annealing processes before the quantum device is fully assembled and operational. These preparatory steps establish the required isotopic depletion in advance, preventing decoherence issues before they can affect device performance
Solution Approach 2:
The patent utilizes parameter changes through precise control of epitaxial growth conditions and annealing parameters to achieve the desired isotopic depletion. By adjusting temperature, time, and atmospheric conditions during these processes, the concentration of silicon atoms with mass number 29 is reduced to below natural abundance levels
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
The reduced concentration of silicon atoms with mass number 29 stabilizes qubit spin states, improving the functionality and reducing decoherence in quantum computers.
Implementation Method 1
using epitaxial growth and annealing processes to enrich the layer with silicon atoms of mass number 28
Implementation Method 2
using epitaxial growth and annealing processes to enrich the layer with silicon atoms of mass number 28
Data Source
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AI summary
Semiconductor structures (10) including isotopically-enriched silicon, germanium and/or silicon-germanium layers for use in spin qubit devices, as well as corresponding methods, are disclosed. The method comprises providing a silicon, germanium or silicon-germanium on insulator (SOI, GOI, SGOI) substrate (12, 14, 16) and depositing a layer of nuclear-spin free semiconductor material (18) thereon. A subsequent anneal causes 29-Si and/or 73-Ge to diffuse into the enriched layer, leaving the device layer with less nuclear spin isotopes. The resulting qubit device comprises a semiconductor device layer (12) having a concentration of a nuclear-spin carrying isotope that is less than a natural abundance of the first isotope and greater than zero parts per million.