NV-centers in SiC - A solution for quantum computing technology?

At a Glance

Metadata	Details
Publication Date	2023-01-26
Journal	Frontiers in Quantum Science and Technology
Authors	Khashayar Khazen, H. J. von Bardeleben
Institutions	Institut des NanoSciences de Paris, Sorbonne Université
Citations	18
Analysis	Full AI Review Included

Technical Documentation & Analysis: NV Centers in SiC vs. Diamond

Executive Summary

This documentation analyzes the comparative review of solid-state spin qubits (NV centers in Diamond vs. Divacancies/NV centers in SiC) to position 6CCVD’s high-purity MPCVD diamond as the superior platform for high-performance quantum technology.

Benchmark Performance: Diamond NV centers remain the gold standard for intrinsic qubit performance, demonstrating coherence times (T₂) up to 3.3 ms at Room Temperature (RT) and 1 second at 4K, significantly exceeding current SiC RT results (T₂ ≈ 20 µs for VV centers).
SiC Scalability vs. Diamond Purity: While SiC offers compatibility with established microelectronics infrastructure (300 mm wafers) and telecom wavelength operation (1200-1300 nm ZPL), the paper implicitly confirms that high-purity CVD diamond is necessary to achieve the highest intrinsic spin coherence and isolation.
Material Requirement: Achieving optimal qubit performance relies on ultra-low strain and high-purity host material to minimize electron-phonon interactions (low Huang-Rhys factor, 0.264-0.285 cited for SiC NV). 6CCVD’s Optical Grade Single Crystal Diamond (SCD) is engineered specifically for this requirement.
Telecom Wavelength Counterpoint: Although SiC NV centers operate in the telecom O-band (1289 nm), 6CCVD is actively supporting research into alternative diamond color centers (e.g., SiV, GeV) that also offer telecom compatibility while leveraging diamond’s superior intrinsic properties.
6CCVD Value Proposition: We provide the necessary high-quality, customizable MPCVD diamond substrates (SCD/PCD) and advanced processing (metalization, polishing) required to replicate and extend benchmark quantum computing and sensing research.

Technical Specifications

The following table summarizes key performance parameters extracted from the comparison of candidate defects, highlighting the benchmark performance of Diamond NV centers.

Parameter	Value	Unit	Context
NV^- Diamond ZPL	637	nm	Optical absorption/emission wavelength
NV^- Diamond ZFS (Ground State)	2.87	GHz	Zero-Field Splitting (D)
NV^- Diamond T₂ (RT, Ensemble)	3.3	ms	Achieved using multiple decoupling pulse sequences
NV^- Diamond T₂ (4K, Isolated)	1	s	Highest reported coherence time for this defect
NV^- Diamond Quantum Efficiency	82	%	High efficiency for optical readout
VV° 4H-SiC ZPL Range	1078 - 1132	nm	Near-infrared/Telecom range
NV° 3C-SiC ZPL	1289	nm	Well suited for Telecom O-band transition
VV° 4H-SiC T₂ (5K, Isolated)	5	s	Highest recorded T₂ for any solid-state qubit
NV° 4H-SiC Huang-Rhys Factor	0.264	-	Indicates weak electron-phonon coupling
SiC Substrate Availability	Up to 300	mm	Commercial availability for 4H-SiC polytype

Key Methodologies

The research relies on precise material engineering and defect creation techniques to isolate and control solid-state spin qubits.

Host Material Growth: Utilization of high-purity, low-defect SCD (Diamond) or epitaxial layers of 4H/3C-SiC polytypes, often isotopically purified (e.g., ¹²C) to minimize nuclear spin noise.
Defect Creation: Generation of vacancies (V) and nitrogen (N) defects via two primary methods:
- Ion Implantation: Introducing ¹⁴N or ¹⁵N atoms into the host lattice (Diamond or SiC).
- Electron Irradiation: High-energy electron beams (100 keV - 1 MeV) used primarily in SiC to create monovacancies, followed by thermal annealing.
Post-Processing Annealing: High-temperature annealing (T ≈ 600°C for Diamond NV; T = 850°C - 1,050°C for SiC VV) is required to mobilize vacancies and finalize the formation of the desired defect pairs (NV, VV).
Charge State Stabilization: Fermi level engineering, donor doping (e.g., Boron-Doped Diamond), or electric field gating is used to stabilize the negatively charged state (S = 1), which is required for qubit functionality.
Spin Control and Readout: Coherent manipulation is achieved using microwave (MW) pulses (Ramsey, Hahn echo) and optical excitation (e.g., 637 nm for Diamond NV) for spin initialization and photoluminescence (PL) readout.
Coherence Enhancement: Implementation of advanced decoupling MW pulse sequences and the use of isotopically pure materials to extend T₂ times by isolating the electron spin from environmental noise.

6CCVD Solutions & Capabilities

6CCVD provides the foundational MPCVD diamond materials and advanced processing services necessary to achieve and surpass the quantum performance benchmarks discussed in this paper. We address the limitations of early-stage CVD diamond fabrication cited in the research by offering highly standardized, scalable, and customizable substrates.

Applicable Materials

Material	Application Focus	Key Advantage
Optical Grade Single Crystal Diamond (SCD)	Benchmark Qubit Performance (NV centers), Quantum Sensing, Metrology.	Ultra-low strain, high purity, essential for achieving millisecond-to-second T₂ coherence times.
High-Purity Polycrystalline Diamond (PCD)	Large-Area Quantum Sensing, Cost-Effective Scalability, Heat Spreading.	Plates up to 125 mm, competing with large SiC wafers for scalable device integration.
Boron-Doped Diamond (BDD)	Charge State Control, Electrochemistry, Field Emitters.	Used for Fermi level engineering to stabilize the NV^- state and enable on-chip gating structures.

Customization Potential

6CCVD’s in-house capabilities directly support the advanced fabrication requirements for quantum devices, including those mentioned for SiC integration (nanocavities, on-chip waveguides).

Custom Dimensions and Thickness: We supply SCD and PCD plates/wafers up to 125 mm in diameter. Thickness is precisely controlled from 0.1 µm to 500 µm for active layers, and substrates are available up to 10 mm thick. This precision is vital for controlling ion implantation depth and defect placement.
Advanced Metalization Services: To facilitate on-chip microwave delivery and electric field gating, 6CCVD offers custom metalization stacks, including Au, Pt, Pd, Ti, W, and Cu, tailored to specific device architectures (e.g., Ti/Pt/Au contacts for gate structures).
Ultra-Smooth Polishing: Achieving high-fidelity optical interfaces (e.g., for coupling to nanocavities) requires exceptional surface quality. We guarantee surface roughness of Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD wafers.
Laser Cutting and Shaping: Custom geometries and precise dicing are available to integrate diamond into complex microelectronic or photonic circuits.

Engineering Support

6CCVD’s in-house PhD team specializes in defect engineering and material optimization for solid-state qubits. We can assist researchers in selecting the optimal SCD grade, controlling nitrogen concentration during growth, and defining post-growth annealing protocols required to replicate or extend the high-coherence results achieved for NV centers in Diamond. Our expertise ensures that the material platform maximizes the intrinsic quantum properties of the defect.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Spin S = 1 centers in diamond and recently in silicon carbide, have been identified as interesting solid-state qubits for various quantum technologies. The largely-studied case of the nitrogen vacancy center (NV) in diamond is considered as a suitable qubit for most applications, but it is also known to have important drawbacks. More recently it has been shown that divacancies (V Si V C )° and NV (V Si N C ) - centers in SiC can overcome many of these drawbacks such as compatibility with microelectronics technology, nanostructuring and n- and p-type doping. In particular, the 4H-SiC polytype is a widely used microelectronic semiconductor for power devices for which these issues are resolved and large-scale substrates (300mmm) are commercially available. The less studied 3C polytype, which can host the same centers (VV, NV), has an additional advantage, as it can be epitaxied on Si, which allows integration with Si technology. The spectral range in which optical manipulation and detection of the spin states are performed, is shifted from the visible, 632 nm for NV centers in diamond, to the near infrared 1200-1300 nm (telecom wavelength) for divacancies and NV centers in SiC. However, there are other crucial parameters for reliable information processing such as the spin-coherence times, deterministic placement on a chip and controlled defect concentrations. In this review, we revisit and compare some of the basic properties of NV centers in diamond and divacancies and NV centers in 4H and 3C-SiC.

Tech Support

Original Source

DOI: https://doi.org/10.3389/frqst.2023.1115039

References

2018 - One-second coherence for a single electron spin coupled to a multi-qubit nuclear-spin environment [Crossref]
2014 - First-principles theory of the luminescence lineshape for the triplet transition in Diamond NV Centres [Crossref]
2022 - Direct writing of divacancy centers in silicon carbide by femtosecond laser irradiation and subsequent thermal annealing [Crossref]
2022 - Five-second coherence of a single spin with single-shot readout in Silicon Carbide [Crossref]
2019 - Quantum supremacy using a programmable superconducting processor [Crossref]
2013 - Photo-induced ionization dynamics of the nitrogen vacancy defect in diamond investigated by single-shot charge state detection [Crossref]
2021 - Fabrication and nanophotonic waveguide integration of silicon carbide colour centres with preserved spin-optical coherence [Crossref]
2009 - Ultralong spin coherence time in isotopically engineered diamond [Crossref]
2013 - Solid-state electronic spin coherence time approaching one second [Crossref]
2020 - Quantum computers based on cold Atoms [Crossref]