Defects In Silicon Carbide Research Articles

All-optical nanoscale thermometry with silicon carbide color centers

All-optical thermometry plays a crucial role in precision temperature measurement across diverse fields. Quantum defects in solids are one of the most promising sensors due to their excellent sensitivity, stability, and biocompatibility. Yet, it faces limitations, such as the microwave heating effect and the complexity of spectral analysis. Addressing these challenges, we introduce a novel approach to nanoscale optical thermometry using quantum defects in silicon carbide (SiC), a material compatible with complementary metal-oxide-semiconductor (CMOS) processes. This method leverages the intensity ratio between anti-Stokes and Stokes emissions from SiC color centers, overcoming the drawbacks of traditional techniques such as optically detected magnetic resonance (ODMR) and zero-phonon line (ZPL) analysis. Our technique provides a real-time, highly sensitive (1.06% K−1), and diffraction-limited temperature sensing protocol, which potentially helps enhance thermal management in the future miniaturization of electronic components.

Exploring High-Spin Color Centers in Wide Band Gap Semiconductors SiC: A Comprehensive Magnetic Resonance Investigation (EPR and ENDOR Analysis).

High-spin defects (color centers) in wide-gap semiconductors are considered as a basis for the implementation of quantum technologies due to the unique combination of their spin, optical, charge, and coherent properties. A silicon carbide (SiC) crystal can act as a matrix for a wide variety of optically active vacancy-type defects, which manifest themselves as single-photon sources or spin qubits. Among the defects, the nitrogen-vacancy centers (NV) are of particular importance. This paper is devoted to the application of the photoinduced electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) techniques at a high-frequency range (94 GHz) to obtain unique information about the nature and properties of NV defects in SiC crystal of the hexagonal 4H and 6H polytypes. Selective excitation by microwave and radio frequency pulses makes it possible to determine the microscopic structure of the color center, the zero-field splitting constant (D = 1.2-1.3 GHz), the phase coherence time (T2), and the values of hyperfine (≈1.1 MHz) and quadrupole (Cq ≈ 2.45 MHz) interactions and to define the isotropic (a = -1.2 MHz) and anisotropic (b = 10-20 kHz) contributions of the electron-nuclear interaction. The obtained data are essential for the implementation of the NV defects in SiC as quantum registers, enabling the optical initialization of the electron spin to establish spin-photon interfaces. Moreover, the combination of optical, microwave, and radio frequency resonant effects on spin centers within a SiC crystal shows the potential for employing pulse EPR and ENDOR sequences to implement protocols for quantum computing algorithms and gates.

Optimum surface-passivation schemes for near-surface spin defects in silicon carbide

Optimum surface-passivation schemes for near-surface spin defects in silicon carbide

Experimental Generation of Spin-Photon Entanglement in Silicon Carbide.

A solid-state approach for quantum networks is advantageous, as it allows the integration of nanophotonics to enhance the photon emission and the utilization of weakly coupled nuclear spins for long-lived storage. Silicon carbide, specifically point defects within it, shows great promise in this regard due to the easy of availability and well-established nanofabrication techniques. Despite of remarkable progresses made, achieving spin-photon entanglement remains a crucial aspect to be realized. In this Letter, we experimentally generate entanglement between a silicon vacancy defect in silicon carbide and a scattered single photon in the zero-phonon line. The spin state is measured by detecting photons scattered in the phonon sideband. The photonic qubit is encoded in the time-bin degree of freedom and measured using an unbalanced Mach-Zehnder interferometer. Photonic correlations not only reveal the quality of the entanglement but also verify the deterministic nature of the entanglement creation process. By harnessing two pairs of such spin-photon entanglement, it becomes straightforward to entangle remote quantum nodes at long distance.

All-Electrical Readout of Coherently Controlled Spins in Silicon Carbide.

Spin defects in silicon carbide are promising candidates for quantum sensing applications as they exhibit long coherence times even at room temperature. However, spin readout methods that rely on fluorescence detection can be challenging due to poor photon collection efficiency. Here, we demonstrate coherent spin control and all-electrical readout of a small ensemble of spins in a SiC junction diode using pulsed electrically detected magnetic resonance. A lock-in detection scheme based on a three stage modulation cycle is implemented, significantly enhancing the signal-to-noise ratio. This technique enabled observation of coherent spin dynamics, specifically Rabi spin nutation, spin dephasing, and spin decoherence. The use of these protocols for magnetometry applications is evaluated.

Parametric magnon transduction to spin qubits.

The integration of heterogeneous modular units for building large-scale quantum networks requires engineering mechanisms that allow suitable transduction of quantum information. Magnon-based transducers are especially attractive due to their wide range of interactions and rich nonlinear dynamics, but most of the work to date has focused on linear magnon transduction in the traditional system composed of yttrium iron garnet and diamond, two materials with difficult integrability into wafer-scale quantum circuits. In this work, we present a different approach by using wafer-compatible materials to engineer a hybrid transducer that exploits magnon nonlinearities in a magnetic microdisc to address quantum spin defects in silicon carbide. The resulting interaction scheme points to the unique transduction behavior that can be obtained when complementing quantum systems with nonlinear magnonics.

Impact of carbon injection in 4H-SiC on defect formation and minority carrier lifetime

Point defects in silicon carbide (SiC) can act as charge carrier traps and have a pronounced impact on material properties such as the mobility and carrier lifetime. Prominent among these traps is the carbon vacancy (VC) with a demonstrated detrimental effect on the minority carrier lifetime in 4H-SiC epitaxial layers. Hence, a variety of methods for VC removal have been proposed. Common to all is that they involve some sort of C-injection into the epi-layer that leads to annihilation of VC with C interstitials (Ci) via the reaction Ci＋ VC→0̸. However, many studies on injection of Ci for removal of VC do not take into account the potential effect of any additional defects that are formed as a result of excess C in the material, including electrically active defects that introduce energy levels in the SiC band gap. Herein, we study the formation and impact of carbon related defects that are introduced in 4H-SiC epi-layers by injection of excess carbon. C-injection is achieved by annealing 4H-SiC epi-layers covered by a graphitized photoresist known as a C-cap at 1250°C for different durations. The resulting appearance of defects in the samples is monitored using deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS) measurements, which reveal the formation of both minority and majority carrier traps as a result of the C-injection. Intriguingly, the injected carbon is also found to interact with a perennially present impurity in 4H-SiC epi-layers and a potentially lifetime limiting defect, namely boron. Furthermore, we monitor the minority carrier lifetime as a function of C-injection time and depth from the surface using cross-sectional time-resolved photoluminescence (TRPL) measurements. Both the defect distributions and the minority carrier lifetime are found to depend strongly on the duration of the C-cap anneal, with a marked depth dependence being present for all samples studied. The moderate temperature C-cap annealing treatment is proposed as a method for enhancing the carrier lifetime in n-type 4H-SiC epi-layers for power device applications.

Ultralong‐Term High‐Density Data Storage with Atomic Defects in SiC

AbstractThere is an urgent need to increase the global data storage capacity, as current approaches lag behind the exponential growth of data generation driven by the Internet, social media, and cloud technologies. In addition to increasing storage density, new solutions should provide long‐term data archiving that goes far beyond traditional magnetic memory, optical disks, and solid‐state drives. Here, a concept of energy‐efficient, ultralong, high‐density data archiving is proposed, based on optically active atomic‐size defects in a radiation resistance material, silicon carbide (SiC). The information is written in these defects by focused ion beams and read using photoluminescence or cathodoluminescence. The temperature‐dependent deactivation of these defects suggests a retention time minimum over a few generations under ambient conditions. With near‐infrared laser excitation, grayscale encoding and multi‐layer data storage, the areal density corresponds to that of Blu‐ray discs. Furthermore, it is demonstrated that the areal density limitation of conventional optical data storage media due to the light diffraction can be overcome by focused electron‐beam excitation.

Photoinduced EPR and ENDOR studies of the divacancies and nitrogen-vacancy defects in silicon carbide

Photoinduced EPR and ENDOR studies of the divacancies and nitrogen-vacancy defects in silicon carbide

Characteristics of interacting carbon-antisite-vacancies in 4H silicon carbide

Spin defects in semiconductors have demonstrated promising electronic structures for potential applications in quantum computing and sensing. Among various proposed quantum byte systems, spin defects in silicon carbide have attracted significant attention due to several advantages they offer over other options. In this study, we investigate carbon-antisite-vacancy defects in 4H silicon carbide through ab initio density functional theory calculations. With the HSE06 functionals, the ab initio computation can predict much more accurate electronic structures. However, the corresponding computational cost is high, especially for supercells consisting of several hundreds of atoms. In this investigation, the carbon-antisite-vacancy defect is studied by using a high-performance computing cluster, with a specific focus on supercells that encompass two such defects. The extension of a single carbon-antisite-vacancy defect is depicted by referring to the spin density distribution. Different defect types show similar spin density patterns. Based on the single defect characteristics, supercells with paired carbon-antisite-vacancy defects are created. It is found that the binding energy can reach 2 eV for overlapping defects. In the case of insignificant overlap of the corresponding single defects, the ground state magnetic moment is 4 µB, accompanied by a negligible binding energy. However, if there is a significant overlap of the spin density, the magnetic moment changes to 2 µB. These findings can serve as helpful references for the study of spin defects in 4H silicon carbide, particularly in the potential carbon-antisite-vacancy application research.

The influence of helium-induced defects on the migration of strontium implanted into SiC above critical amorphization temperature

The presence of radiation-induced defects and the high temperature of implantation are breeding grounds for helium (He) to accumulate and form He-induced defects (bubbles, blisters, craters, and cavities) in silicon carbide (SiC). In this work, the influence of He-induced defects on the migration of strontium (Sr) implanted into SiC was investigated. Sr-ions of 360 keV were implanted into polycrystalline SiC to a fluence of 2 × 1016 Sr-ions/cm2 at 600°C (Sr-SiC). Some of the Sr-SiC samples were then co-implanted with He-ions of 21.5 keV to a fluence of 1 × 1017 He-ions/cm2 at 350°C (Sr + He-SiC). The Sr-SiC and Sr + He-SiC samples were annealed for 5 h at 1,000°C. The as-implanted and annealed samples were characterized by Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and Rutherford backscattered spectrometry (RBS). Implantation of Sr retained some defects in SiC, while co-implantation of He resulted in the formation of He-bubbles, blisters, and craters (exfoliated blisters). Blisters close to the critical height and size were the first to exfoliate after annealing. He-bubbles grew larger after annealing owing to the capture of more vacancies. In the co-implanted samples, Sr was located in three regions: the crystalline region (near the surface), the bubble region (where the projected range of Sr was located), and the damage region toward the bulk. Annealing the Sr + He-SiC caused the migration of Sr towards the bulk, while no migration was observed in the Sr-SiC samples. The migration was governed by “vacancy migration driven by strain fileds.”

Analysis of the microscopic characteristics of periodic structure arrays on silicon carbide fabricated by femtosecond laser

The fabrication of large dimension structures (800 μm × 800 μm) featuring fine and coarse ripple patterns, nano particle structures, and V-shaped grooves was achieved on silicon carbide (SiC) through the use of femtosecond laser. The X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy (Raman) were performed on sample surface to investigate the atomic bond, residual stress and lattice disorder. XPS analysis revealed that an increase in laser fluence resulted in an increase in the content of C=O bond, while the content of O–C=O bond decreased. The C–C (sp2) bond was destroyed, while the unstable C–C (sp3) bond increased. Additionally, there was a decrease in the content of Si–Si bond and Si–C bond, and an increase in the content of Si–O bond. The resulting oxide layer contributed to an improvement in the fracture toughness of the periodic array. XRD analysis results indicate that the technique is not sensitive to structural defects in SiC and surface contaminants caused by laser ablation. On the (0008) crystal plane, an increase in fluence resulted in an initial increase in lattice spacing, strain, and residual stress, followed by a plateau. The laser-modified area corresponded to a region of tensile stress, with the maximum tensile stress being 179.464 MPa. On the (0004) crystal plane, an increase in fluence resulted in varying degrees of increase in lattice spacing, strain, and residual stress. The residual tensile stress at the fine ripple and groove bottom was 0 and 14.623 MPa, respectively, while the residual tensile stress at the coarse ripple and nano particle structure was 277.847 MPa. The residual tensile stress increased with an increase in scanning interval. Raman analysis showed that the overall disorder increased with an increase in laser fluence, with a maximum degree of disorder being 0.548.

Oxygen-vacancy defect in 4H-SiC as a near-infrared emitter: An ab initio study

Optically active spin defects in semiconductors can serve as spin-to-photon interfaces, key components in quantum technologies. Silicon carbide (SiC) is a promising host of spin defects thanks to its wide bandgap and well-established crystal growth and device technologies. In this study, we investigated the oxygen-vacancy complexes as potential spin defects in SiC by means of ab initio calculations. We found that the OCVSi defect has a substantially low formation energy compared with its counterpart, OSiVC, regardless of the Fermi level position. The OCVSi defect is stable in its neutral charge state with a high-spin ground state (S = 1) within a wide energy range near the midgap energy. The zero-phonon line (ZPL) of the OCVSi0 defect lies in the near-infrared regime, 1.11–1.24 eV (1004–1117 nm). The radiative lifetime for the ZPL transition of the defect in kk configuration is fairly short (12.5 ns). Furthermore, the estimated Debye–Waller factor for the optical transition is 13.4%, indicating a large weight of ZPL in the photoluminescence spectrum. All together, we conclude that the OCVSi0 defect possesses desirable spin and optical properties and thus is potentially attractive as a quantum bit.

Fabrication and quantum sensing of spin defects in silicon carbide

In the past decade, color centers in silicon carbide (SiC) have emerged as promising platforms for various quantum information technologies. There are three main types of color centers in SiC: silicon-vacancy centers, divacancy centers, and nitrogen-vacancy centers. Their spin states can be polarized by laser and controlled by microwave. These spin defects have been applied in quantum photonics, quantum information processing, quantum networks, and quantum sensing. In this review, we first provide a brief overview of the progress in single-color center fabrications for the three types of spin defects, which form the foundation of color center-based quantum technology. We then discuss the achievements in various quantum sensing, such as magnetic field, electric field, temperature, strain, and pressure. Finally, we summarize the current state of fabrications and quantum sensing of spin defects in SiC and provide an outlook for future developments.

Formation of Paramagnetic Defects in the Synthesis of Silicon Carbide.

Silicon carbide (SiC) is a very promising platform for quantum information processing, as it can host room temperature solid state defect quantum bits. These room temperature quantum bits are realized by paramagnetic silicon vacancy and divacancy defects in SiC that are typically introduced by irradiation techniques. However, irradiation techniques often introduce unwanted defects near the target quantum bit defects that can be detrimental for the operation of quantum bits. Here, we demonstrate that by adding aluminum precursor to the silicon and carbon sources, quantum bit defects are created in the synthesis of SiC without any post treatments. We optimized the synthesis parameters to maximize the paramagnetic defect concentrations-including already established defect quantum bits-monitored by electron spin resonance spectroscopy.

Charge State Control over Point Defects in Sic Devices

Point defects in silicon carbide (SiC) are well positioned for integration with SiC based quantum photonic devices due to the maturity of SiC material and fabrication technology, the plethora of candidate quantum emitters that can be formed in SiC, and the potential for emission over a wide spectral range from the visible to the infrared. However, for each of the available color centers in SiC, only one of the charge states has displayed quantum emission, meaning that the emission strongly depends on the Fermi level and hence the doping concentration in the material. In this contribution, we discuss the methodology and mechanism for electrical charge-state control over point defects in SiC devices.

Cathodoluminescence Characterization of Point Defects Generated through Ion Implantations in 4H-SiC

The high quality of crystal growth and advanced fabrication technology of silicon carbide (SiC) in power electronics enables the control of optically active defects in SiC, such as silicon vacancies (VSi). In this paper, VSi are generated in hexagonal SiC (4H) samples through ion implantation of nitrogen or (and) aluminum, respectively the n- and p-type dopants for SiC. The presence of silicon vacancies within the samples is studied using cathodoluminescence at 80K. For 4H-SiC samples, the ZPL (zero phonon line) of the V1′ center of VSi is more intense than the one for the V1 center before annealing. The opposite is true after 900 °C annealing. ZPLs of the divacancy defect (VCVSi) are also visible after annealing.

Plasmonic-Enhanced Bright Single Spin Defects in Silicon Carbide Membranes.

Optically addressable spin defects in silicon carbide (SiC) have emerged as attractable platforms for various quantum technologies. However, the low photon count rate significantly limits their applications. We strongly enhanced the brightness by 7 times and spin-control strength by 14 times of single divacancy defects in 4H-SiC membranes using a surface plasmon generated by gold film coplanar waveguides. The mechanism of the plasmonic-enhanced effect is further studied by tuning the distance between single defects and the surface of the gold film. A three-energy-level model is used to determine the corresponding transition rates consistent with the enhanced brightness of single defects. Lifetime measurements also verified the coupling between defects and surface plasmons. Our scheme is low-cost, without complicated microfabrication and delicate structures, which is applicable for other spin defects in different materials. This work would promote developing spin-defect-based quantum applications in mature SiC materials.

On the interpretation of confocal spectral depth profiling of color center and carrier concentration by photoluminescence and Raman of implanted 4H–SiC

Point defects in silicon carbide (SiC) formed after ion implantation can serve as color centers for quantum sensing, or as donors or acceptors to provide carriers to influence electrical performance. Confocal spectroscopic characterization allows the determination of point defect-related optical and electrical properties without sample preparation or destruction. However, phenomena such as refraction and aberration can complicate the interpretation of the results of three-dimensional spectroscopy. Here, we used H+, N+ and He+ implantation to fabricate silicon vacancy (VSi) color centers in SiC and used confocal spectroscopy to characterize bulk and thin layer of VSi contained materials. 270 keV H+ is more advantageous than 150 keV N+ in preparing VSi due to the preservation of better lattice integrity. For thin-layer VSi samples, the photoluminescence intensity maxima of VSi were distributed at 2–6.5 μm above the surface. To explain such confusing phenomenon in depth profiles focusing on and above the surface the effective excitation volume and chromatic aberration are discussed and proposed for explanation of the results. Furthermore, the ion-implanted layer exhibits a non-negligible effect on the underlying signal during confocal spectral depth profiling, which is attributed to the refraction-related focus degradation.

Effects of surface roughness and single Shockley stacking fault expansion on the electroluminescence of 4H-SiC

The electroluminescence of a 4H silicon carbide (SiC) bipolar junction transistor was studied using the base-collector junction after a side-wall facet was exposed. This sidewall was ground and polished in sequential stages with increasing grit numbers. After each stage, an electrical stress test under forward bias was performed. Electroluminescence spectra with peaks at 390 nm, 445 nm and 500 nm were initially observed. These peaks were seen to evolve under operation and after changes to the surface condition. Expansion of single Shockley stacking faults (1SSFs) in the device was observed during forward biased operation as evidenced by the growth of the 420nm emission peak, while the broad 500 nm peak was seen to diminish with increasing surface smoothness. Defect-enabled radiative recombination in SiC is a useful pathway for SiC defect characterization and it offers a new opportunity for light emission from SiC.