Quantum Magnetometer Achieves High Performance Using Scalable 4H-Silicon Carbide Technology

The development of highly sensitive and scalable magnetic field sensors is crucial for applications ranging from medical diagnostics to navigation. Researchers at Walter Schottky Institute and Württembergischer Chemisch-Technischer Verein have demonstrated a novel quantum magnetometer chip utilising proprietary 4H-silicon carbide technology. Led by P. A. Stuermer, D. Wirtitsch, and T. Steidl, alongside colleagues including R. Wörnle, J. Körber, and W. Schustereder, the team fabricated a device exhibiting sensitivities two to three orders of magnitude lower than existing confocal techniques. This advancement simplifies sensor architecture, improves performance, and streamlines optical processes, representing a significant step towards practical, next-generation silicon carbide sensing technologies. The use of wafer-scale fabrication techniques allows for reproducible, industry-grade manufacturing with precise control over key material properties.

Silicon Carbide Magnetometer with Optimized Color Centers

Scientists demonstrate a groundbreaking quantum magnetometer chip leveraging proprietary 4H-silicon carbide (SiC) technology, achieving unprecedented performance through industrially scalable fabrication techniques. The research team optimized V2 silicon vacancy color centers, controlling their depth and density with precision to enable reproducible, industry-grade manufacturing. This innovative approach integrates these color center ensembles into a planar silicon carbide waveguide, significantly simplifying fluorescence excitation and collection compared to conventional confocal microscopy methods. Experiments utilizing continuous-wave optically detected magnetic resonance, alongside Rabi, Ramsey, and Hahn-echo sequences, confirm the coherent capabilities of the large V2 center ensemble embedded within the device.

The study reveals a device exhibiting shot-noise limited sensitivities 2 to 3 orders of magnitude lower than those achieved with more complex confocal techniques, representing a substantial leap in magnetometer performance. This advancement is directly attributable to the streamlined architecture, enhanced sensitivity, and efficient optical signal handling facilitated by the SiC waveguide. By exploiting changes in the refractive index of silicon carbide with varying doping levels, the team created a monolithic waveguide structure with a n++ doped substrate, an intrinsically doped core, and a thin SiO2 layer, effectively confining light and maximizing signal extraction. This photonic design supports wavelengths from 780nm to 1200nm, efficiently guiding both excitation and fluorescence light from the V2 color centers with minimal loss.

Furthermore, the research establishes a design where the crystal axis of the silicon vacancies is perpendicular to the sensor plane, simplifying the implementation of radio-frequency (RF) excitation. Finite-element simulations using Ansys demonstrate the creation of a homogeneous B1 field across a substantial area of the chip using a 3μm metallization microstrip, driven by a current of 200mA at 70MHz. This configuration maximizes the interaction between the RF field and the spin system, enhancing the sensitivity of the magnetometer. The work opens new avenues for next-generation SiC-based quantum sensing technologies, offering a pathway towards high-volume, power-efficient, and highly sensitive magnetic field detection.

This breakthrough addresses key limitations of diamond-based quantum sensors, namely cost and compatibility with existing semiconductor manufacturing processes. Silicon carbide’s wide bandgap and stable defects provide advantageous quantum properties, while its compatibility with wafer-scale fabrication enables high-volume production. The integrated photonic waveguide not only enhances signal collection but also reduces energy consumption, making the device more competitive for practical applications. Collectively, these innovations simplify the quantum sensor architecture, paving the way for widespread adoption of SiC-based quantum sensing in diverse fields, including materials science, biotechnology, and beyond.

Silicon Carbide Waveguide Magnetometer Fabrication and Testing

The research team engineered a high-performance magnetometer chip utilising 4H-silicon carbide (SiC) technology and wafer-scale fabrication techniques. This approach focused on optimising V2 silicon vacancy colour centres, achieving precise control over their depth and density for reproducible, industry-grade fabrication. Scientists developed a planar silicon carbide waveguide integrating these colour centre ensembles, significantly simplifying fluorescence extraction and enhancing efficient excitation compared to conventional confocal microscopy. This waveguide exploits changes in the refractive index of SiC achieved through varying doping levels, employing a n++ doped substrate and a thin SiO2 layer to confine light within the core.

Experiments employed continuous-wave (CW) optically detected magnetic resonance measurements, supplemented by Rabi, Ramsey, and Hahn-echo sequences, to demonstrate the coherent capabilities of the embedded V2 centre ensemble. The system delivers a monolithic SiC waveguide, designed with an intrinsically doped core sandwiched between a heavily doped substrate and a silica layer, creating asymmetric modes and strong vertical confinement of light. This design ensures near-identical behaviour across wavelengths from approximately 785nm to 1100nm, crucial for efficient optical excitation at 785nm and detection of the 916nm zero-phonon line. The study pioneered a method for achieving shot-noise limited sensitivities 2-3 orders of magnitude lower than those obtained with complex confocal techniques.

This sensitivity enhancement stems from the increased ensemble density within the waveguide, which expands the active volume without compromising quantum properties. The innovative photonic design circumvents issues associated with increased crystal damage and reduced collection efficiency, streamlining optical excitation and collection. This advancement paves the way for next-generation SiC-based quantum sensing technologies, offering a scalable and power-efficient alternative to diamond-based systems.

Silicon Carbide Magnetometer Demonstrates Coherent Control

Scientists achieved a significant breakthrough in magnetometer technology with the development of a high-performance chip utilizing 4H-silicon carbide (SiC) and silicon vacancy (V2) color centers. The research team fabricated an industrially scalable device leveraging wafer-scale techniques to precisely control the depth and density of V2 centers, crucial for reproducible, industry-grade fabrication. Integration of these color center ensembles into a planar SiC waveguide streamlines fluorescence extraction, simplifying the architecture compared to conventional confocal methods. Experiments revealed coherent capabilities of the embedded V2 ensemble through continuous-wave optically detected magnetic resonance (CW-ODMR) measurements, alongside Rabi, Ramsey, and Hahn-echo sequences.

Data shows the device exhibits shot-noise limited sensitivities 2 to 3 orders of magnitude lower than those achieved with more complex confocal techniques. Proton implantation, optimized through simulation using the Stopping and Range of Ions in Matter (SRIM) model, demonstrated precise depth control, with peak depths of approximately 3μm achieved with 400 keV protons and 5μm with 600 keV protons. Confocal microscopy confirmed these results, revealing a V2 color center ribbon corresponding to the proton implantation peak. Continuous-wave ODMR measurements yielded a contrast of approximately 1 percent between the resonance peak and background, confirming successful generation of a dense V2 ensemble with a peak density of around 350 ±80 / μm3.

Low-temperature spectra, recorded at 8 K, clearly displayed the zero-phonon line (ZPL) at 916nm and its associated phononic sideband. Correlation of nitrogen doping concentration, measured via capacitance-voltage measurements, with ZPL fluorescence identified an optimal N-doping concentration of 1014-1015/cm3 for maximizing color center charge state. Waveguide SiC chips were fabricated using a high-volume 6-inch wafer process, incorporating a 9μm thick epitaxy layer optimized for nitrogen doping. CW-ODMR measurements performed on the V2 ensemble embedded within the planar waveguide, at 0 and 250 μT, were fitted with single and double Lorentzian functions, respectively. T1 measurements, conducted by initializing the system with a laser pulse and reading out fluorescence with a delayed second pulse, further characterized the coherence properties of the V2 ensemble within the waveguide structure.

Silicon Carbide Magnetometer Surpasses Confocal Sensitivity

This research demonstrates a significant advancement in silicon carbide (SiC)-based quantum sensing through the development of a high-performance magnetometer chip. By utilising wafer-scale fabrication to optimise V2 silicon vacancy colour centres within a planar SiC waveguide, the team achieved coherent control of a large ensemble of these centres. This innovative approach simplifies optical excitation and collection, resulting in sensitivities exceeding those of conventional confocal measurements by at least two orders of magnitude. The presented technology offers several advantages, including reduced power consumption and full compatibility with existing semiconductor manufacturing processes, a notable benefit compared to diamond-based systems.

The broadband photonic concept employed also suggests potential for application with other vacancy types, broadening the scope of this research. While acknowledging that current sensitivity measurements assume shot-noise as the primary noise source and do not account for electronic noise, the authors identify opportunities for further optimisation of pulse sequences and chip miniaturisation. Future work will focus on these areas, potentially enabling SiC-based quantum sensors to achieve performance comparable to diamond systems and facilitating the mass production of quantum sensing technology.