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

Executive Summary

This review compares solid-state spin qubits—specifically the Nitrogen Vacancy (NV) center in diamond, Divacancies (VV) in Silicon Carbide (SiC), and NV centers in SiC—concluding that NV centers in SiC are the most promising platform for scalable quantum technology.

CMOS Compatibility and Scalability: SiC qubits (3C and 4H polytypes) are fully compatible with existing microelectronics fabrication (CMOS), leveraging commercially available large-scale (300 mm) substrates, a major advantage over diamond.
Telecom Wavelength Operation: SiC NV centers operate in the near-infrared (1100-1300 nm), aligning perfectly with the telecom O-band, facilitating long-distance quantum communication via optical fibers.
Superior Defect Localization: NV centers in SiC allow for deterministic placement on a chip because the nitrogen atom (N_C) is immobile during the required 700°C annealing step, unlike the mobile vacancies required for VV formation.
High Coherence Potential: While NV-SiC T₂ times are still under optimization, related SiC divacancies (VV) have demonstrated the highest recorded coherence time for a solid-state qubit (T₂ = 5 s at 5 K), suggesting high potential for NV-SiC under optimized conditions.
Room-Temperature Functionality: SiC NV centers maintain spin polarization and allow optical readout at room temperature, making them suitable for quantum sensing and metrology applications.

Technical Specifications

Parameter	Value	Unit	Context
SiC NV ZPL Range	1,100-1,300	nm	Near-Infrared (Telecom O-band); Polytype dependent.
Diamond NV ZPL	637	nm	Visible light operation.
SiC VV T₂ Coherence (5 K)	5	s	Neutral divacancy (VV°) in isotopically purified 4H-SiC (Highest reported solid-state qubit T₂).
SiC NV T₂ Coherence (300 K)	~20	µs	Room Temperature (4H-SiC, conventional Hahn-echo).
Diamond NV T₂ Coherence (300 K)	3.3	ms	Room Temperature (using multiple decoupling pulses).
SiC NV ZFS (D) Range (4H)	1,282-1,442	MHz	Ground state ³A, configuration dependent (hh, kk, hk, kh).
SiC NV ZFS (D) (3C)	1,303	MHz	Ground state ³A, axial configuration.
Diamond NV ZFS (D)	2,800	MHz	Ground state ³A.
SiC NV Huang-Rhys Factor (3C)	0.285	-	Low electron-phonon coupling (indicates high quantum efficiency).
SiC NV Second Order Correlation (g²)	0.03	-	Single photon emitter demonstration.
SiC Band Gaps (E_G)	2.2 / 3.2	eV	3C-SiC / 4H-SiC (Large band gap ensures defect isolation).
SiC Wafer Size	300	mm	Commercially available large-scale substrates (4H-SiC).

Key Methodologies

The fabrication process for SiC NV centers is highly compatible with existing semiconductor manufacturing techniques, focusing on controlled defect generation and stabilization:

Host Material Preparation: Utilize high-quality Silicon Carbide epitaxial layers (4H-SiC for power electronics compatibility; 3C-SiC for integration on Si substrates).
Nitrogen Introduction: Nitrogen (N) atoms are introduced either via doping during growth or, preferably for localized qubits, via ion implantation (N¹⁴ or N¹⁵ isotopes).
Vacancy Generation: Silicon and Carbon monovacancies (V_Si, V_C) are generated using high-energy electron irradiation (E > 100 keV).
Defect Pairing (NV Formation): Post-irradiation thermal annealing is performed at moderate temperatures (~700°C). Crucially, at this temperature, the implanted N atom remains fixed, ensuring the V_C-N_C pair (NV center) forms precisely at the implantation site, enabling deterministic placement.
Charge State Stabilization: Fermi level engineering (e.g., donor doping, electric field gating) is applied to ensure the NV center is stabilized in the required negative charge state (NV^-, spin S=1) for qubit operation.
Addressability and Integration: Standard nanolithography (e-beam) is used on the SiC epitaxial layers to fabricate ordered arrays, resonant nanocavities, and on-chip nanowaveguides, enhancing photon collection and addressability.

Commercial Applications

The unique combination of telecom compatibility, CMOS integration, and room-temperature operation positions SiC NV centers for several high-value engineering and commercial applications:

Quantum Computing Hardware: Serving as the fundamental solid-state spin qubit for scalable quantum processors, leveraging the long coherence times achieved in SiC.
Quantum Communication and Networks: Enabling the construction of quantum repeaters and long-distance quantum entanglement transfer due to the emission wavelength matching standard optical fiber transmission windows (1.3 µm).
Quantum Sensing and Metrology: Utilizing the spin state sensitivity to external fields (magnetic, electric) for high-precision, room-temperature sensors integrated directly onto microelectronic chips.
Integrated Photonics: Fabrication of on-chip entangled photon sources and quantum light sources using SiC NV centers integrated into microdisk resonators and nanowaveguides.
Semiconductor Manufacturing: Leveraging the existing industrial infrastructure for 4H-SiC power devices and the ability to grow 3C-SiC epitaxially on cheap, large-scale Si wafers.

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

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