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Vibronic States and Their Effect on the Temperature and Strain Dependence of Silicon-Vacancy Qubits in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mn>4</mml:mn><mml:mi>H</mml:mi></mml:math> - <mml:math xmlns:mml="http://www.w3.org/1998/Math/Mat...more
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We will review recent demonstrations of single photon emission in different silicon carbide (SiC) polytypes, in both bulk and nano-structured form. Due to well established doping, and micro- and nanofabrication procedures deep defects... more
We will review recent demonstrations of single photon emission in different silicon carbide (SiC) polytypes, in both bulk and nano-structured form. Due to well established doping, and micro- and nanofabrication procedures deep defects photoluminescence (PL) can be electrically excited and incorporated in SiC nanomaterials. Finally we will report on preliminary results to incorporate near infrared defects in SiC nanoparticles.
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Defects are common in many materials and some were regarded for years as detrimental. Recently with the advent of ultra-sensitive detectors, quantum optical single spin magnetic resonance protocols and advanced material synthesis and... more
Defects are common in many materials and some were regarded for years as detrimental. Recently with the advent of ultra-sensitive detectors, quantum optical single spin magnetic resonance protocols and advanced material synthesis and doping, diamond intra-band gap defects and their nanostructured counterpart are revealed to be a disruptive discovery for the future of nanoscale sensing and quantum technologies[1]. We will report on recently studied optical centres in another wide-band gap semiconductor, such as silicon carbide (SiC). SiC harbors paramagnetic defects whose quantum properties were recently unraveled [2-7]. As occurred for similar diamond point defects[1], we have recently identified a bright single photon emission in 4H-SiC. We will show more recent results on single defects SiC nanoparticles [8], nanotetrapods [9] and other SiC quantum emission [10] providing novel information on their physics and atomistic structure. The fundamental understanding of these defects is essential for their engineering and deployment in next generation multifunctional sensors and in quantum nano- photonics. We will discuss the potential designs of photonics cavities to further enhance some of these single photon sources
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Color centers that emit light at telecommunication wavelengths are promising candidates for future quantum technologies. A pressing challenge for the broad use of these color centers is the typically low collection efficiency from bulk... more
Color centers that emit light at telecommunication wavelengths are promising candidates for future quantum technologies. A pressing challenge for the broad use of these color centers is the typically low collection efficiency from bulk samples. Here, we demonstrate enhancements of the emission collection efficiency for Er3+ incorporated into 4H-SiC surface nano-pillars fabricated using a scalable top-down approach. Optimal Er ion implantation and annealing strategies are investigated in detail. The substitutional fraction of Er atoms in the SiC lattice is closely correlated with the peak photoluminescence intensity. This intensity is further enhanced via spatial wave-guiding once the surface is patterned with nano-pillars. These results have broad applicability for use with other color centers in SiC and also demonstrate a step toward a scalable protocol for fabricating photonic quantum devices with enhanced emission characteristics.
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We report on a bistable defect known as M-center, here introduced in n-type 4H-SiC by 2 MeV He ion implantation. Deep levels of the M-center are investigated by means of junction spectroscopy techniques, namely, deep level transient... more
We report on a bistable defect known as M-center, here introduced in n-type 4H-SiC by 2 MeV He ion implantation. Deep levels of the M-center are investigated by means of junction spectroscopy techniques, namely, deep level transient spectroscopy (DLTS) and isothermal DLTS. In addition to previously reported three deep levels arising from the M-center (labeled as M1, M2, and M3), we provide direct evidence on the existence of a fourth transition (labeled as M4) with an activation energy of 0.86 eV. Activation energies and apparent capture cross sections for all four metastable defects are determined. From first-principles calculations, it is shown that the observed features of the M-center, including the charge state character, transition levels, bi-stability dynamics, and annealing, are all accounted for by a carbon self-interstitial.
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We present a study of electrically active radiation-induced defects formed in 4H-SiC epitaxial layers following irradiation with fast neutrons, as well as 600 keV H+and 2 MeV He++ion implantations. We also look at electron emission... more
We present a study of electrically active radiation-induced defects formed in 4H-SiC epitaxial layers following irradiation with fast neutrons, as well as 600 keV H+and 2 MeV He++ion implantations. We also look at electron emission energies and mechanisms of the carbon vacancy in 4H-SiC by means of first-principles modelling. Combining the relative stability of carbon vacancies at different sites with the relative amplitude of the observed Laplace-DLTS peaks, we were able to connect Z1and Z2to emissions from double negatively charged carbon vacancies located at theh- andk-sites, respectively.
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We present results from combined Laplace-Deep Level Transient Spectroscopy (Laplace-DLTS) and density functional theory studies of the carbon vacancy (VC) in n-type 4H-SiC. Using Laplace-DLTS, we were able to distinguish two previously... more
We present results from combined Laplace-Deep Level Transient Spectroscopy (Laplace-DLTS) and density functional theory studies of the carbon vacancy (VC) in n-type 4H-SiC. Using Laplace-DLTS, we were able to distinguish two previously unresolved sub-lattice-inequivalent emissions, causing the broad Z1/2 peak at 290 K that is commonly observed by conventional DLTS in n-type 4H-SiC. This peak has two components with activation energies for electron emission of 0.58 eV and 0.65 eV. We compared these results with the acceptor levels of VC obtained by means of hybrid density functional supercell calculations. The calculations support the assignment of the Z1/2 signal to a superposition of emission peaks from double negatively charged VC defects. Taking into account the measured and calculated energy levels, the calculated relative stability of VC in hexagonal (h) and cubic (k) lattice sites, as well as the observed relative amplitude of the Laplace-DLTS peaks, we assign Z1 and Z2 to VC(...
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Deep levels introduced by low‐energy (200 keV) electron irradiation in n‐type 4H‐SiC epitaxial layers grown by chemical vapour deposition were studied by deep level transient spectroscopy (DLTS) and photoexcitation electron paramagnetic... more
Deep levels introduced by low‐energy (200 keV) electron irradiation in n‐type 4H‐SiC epitaxial layers grown by chemical vapour deposition were studied by deep level transient spectroscopy (DLTS) and photoexcitation electron paramagnetic resonance (photo‐EPR). After irradiation, several DLTS levels, EH1, EH3, Z1/2, EH5 and EH6/7, often reported in irradiated 4H‐SiC, were observed. In irradiated freestanding films from the same wafer, the EPR signals of the carbon vacancy in the positive and negative charge states, VC+ and VC‐, respectively, can be observed simultaneously under illumination with light of certain photon energies. Comparing the ionization energies obtained from DLTS and photo‐EPR, we suggest that the EH6/7 (at ∼EC – 1.6 eV) and EH5 (at ∼EC – 1.0 eV) electron traps may be related to the single donor (+ | 0) and the double acceptor (1– | 2–) level of VC, respectively. Judging from the relative intensity of the DLTS signals, the EH6/7 level may also be contributed to by ot...
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ABSTRACT Optical detection of magnetic resonance (ODMR) was used to study defects in electron-irradiated ZnO substrates. In addition to the shallow donor and the Zn vacancy, several ODMR centers with an effective electron spin S=12 were... more
ABSTRACT Optical detection of magnetic resonance (ODMR) was used to study defects in electron-irradiated ZnO substrates. In addition to the shallow donor and the Zn vacancy, several ODMR centers with an effective electron spin S=12 were detected. Among these, the axial LU3 and non-axial LU4 centers are shown to be dominating recombination centers. The annealing behavior of radiation-induced defects was studied and possible defect models are discussed.
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Quantum systems combining indistinguishable photon generation and spin-based quantum information processing are essential for remote quantum applications and networking. However, identification of suitable systems in scalable platforms... more
Quantum systems combining indistinguishable photon generation and spin-based quantum information processing are essential for remote quantum applications and networking. However, identification of suitable systems in scalable platforms remains a challenge. Here, we investigate the silicon vacancy centre in silicon carbide and demonstrate controlled emission of indistinguishable and distinguishable photons via coherent spin manipulation. Using strong off-resonant excitation and collecting zero-phonon line photons, we show a two-photon interference contrast close to 90% in Hong-Ou-Mandel type experiments. Further, we exploit the system’s intimate spin-photon relation to spin-control the colour and indistinguishability of consecutively emitted photons. Our results provide a deep insight into the system’s spin-phonon-photon physics and underline the potential of the industrially compatible silicon carbide platform for measurement-based entanglement distribution and photonic cluster stat...
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Scalable quantum networking requires quantum systems with quantum processing capabilities. Solid state spin systems with reliable spin–optical interfaces are a leading hardware in this regard. However, available systems suffer from large... more
Scalable quantum networking requires quantum systems with quantum processing capabilities. Solid state spin systems with reliable spin–optical interfaces are a leading hardware in this regard. However, available systems suffer from large electron–phonon interaction or fast spin dephasing. Here, we demonstrate that the negatively charged silicon-vacancy centre in silicon carbide is immune to both drawbacks. Thanks to its 4A2 symmetry in ground and excited states, optical resonances are stable with near-Fourier-transform-limited linewidths, allowing exploitation of the spin selectivity of the optical transitions. In combination with millisecond-long spin coherence times originating from the high-purity crystal, we demonstrate high-fidelity optical initialization and coherent spin control, which we exploit to show coherent coupling to single nuclear spins with ∼1 kHz resolution. The summary of our findings makes this defect a prime candidate for realising memory-assisted quantum networ...
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We provide direct evidence that the broad Z1/2 peak, commonly observed by conventional deep level transient spectroscopy in as-grown and at high concentrations in radiation damaged 4H-SiC, has two components, namely, Z1 and Z2, with... more
We provide direct evidence that the broad Z1/2 peak, commonly observed by conventional deep level transient spectroscopy in as-grown and at high concentrations in radiation damaged 4H-SiC, has two components, namely, Z1 and Z2, with activation energies for electron emissions of 0.59 and 0.67 eV, respectively. We assign these components to Z1/2=→Z1/2−+e−→Z1/20+2e− transition sequences from negative-U ordered acceptor levels of carbon vacancy (VC) defects at hexagonal/pseudo-cubic sites, respectively. By employing short filling pulses at lower temperatures, we were able to characterize the first acceptor level of VC on both sub-lattice sites. Activation energies for electron emission of 0.48 and 0.41 eV were determined for Z1(−/0) and Z2(−/0) transitions, respectively. Based on trap filling kinetics and capture barrier calculations, we investigated the two-step transitions from neutral to doubly negatively charged Z1 and Z2. Positions of the first and second acceptor levels of VC at b...
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ABSTRACT Recently, InGaP/GaAs/Ge 3-junction solar cells are widely used for space because of their higher conversion efficiency and better radiation-resistance compared to GaAs and Si solar cells. In this study, effects of base carrier... more
ABSTRACT Recently, InGaP/GaAs/Ge 3-junction solar cells are widely used for space because of their higher conversion efficiency and better radiation-resistance compared to GaAs and Si solar cells. In this study, effects of base carrier concentration in GaAs and InGaP sub-cells upon their radiation resistance are analyzed by using radiative recombination lifetime and damage constant K for minority-carrier lifetime of GaAs and InGaP. In addition, analytical results are also compared with the experimental results of InGaP solar cells irradiated with 1-MeV electrons, 30-keV and 200-keV protons. In low irradiation fluence, n-on-p structure cells are found to be more radiation resistant than p-on-n structure cells. Better radiation-resistance of sub-cells can be realized by optimal design based on fundamental approach for radiative and non-radiative recombination properties of InGaP and radiation-resistance of InGaP/GaAs/Ge 3-junction cells will also be improved by optimal design of sub cells.
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ABSTRACT The native and radiation induced defects in lattice mismatched In0.16GaAs and In0.56Ga0.44P are investigated. Subjecting lattice mismatched In0.16GaAs devices to thermal cycle annealing after growth shows a marked improvement in... more
ABSTRACT The native and radiation induced defects in lattice mismatched In0.16GaAs and In0.56Ga0.44P are investigated. Subjecting lattice mismatched In0.16GaAs devices to thermal cycle annealing after growth shows a marked improvement in the open circuit voltage and a related trend is observed from deep level transient spectroscopy (DLTS) measurements as a reduction in the electronic defect density. The role of these native defects in the evolution of the defect levels under 1 MeV electron irradiation is presented and compared to data from lattice mismatched In0.56Ga0.44P devices.
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ABSTRACT 30 keV proton irradiation effects on AlInGaP cells and diodes as a new top cell for high efficiency III-V multijunction (MJ) space solar cells are presented here for the first time. New defects such as two majority-carrier (hole)... more
ABSTRACT 30 keV proton irradiation effects on AlInGaP cells and diodes as a new top cell for high efficiency III-V multijunction (MJ) space solar cells are presented here for the first time. New defects such as two majority-carrier (hole) traps HP1 (EV+1.57 eV, NT=3.9×1014cm-3), HP2 (EV+1.19 eV, NT=2.6×1014cm-3) and two minority-carrier (electron) traps EP1, EP2 (EC-0.71 eV, NT=2.9×1015cm-3) were observed in p-AlInGaP irradiated with a dose of 1 ×1012cm×2 by DLTS measurements. In as-grown samples, the E1 trap appears in both of majority- and minority-carrier DLTS scans, and is attributed to the DX center. The change of remaining factor (VOC, ISC, FF, Pmax) in the AlInGaP cell with 30 keV proton fluence is evaluated. As the proton fluence increases over 1×1010cm-2, the Pmax of the cell decreases rapidly due to the degradation in the fill-factor. At the proton fluence of 1×1010cm-2, the short-circuit current rises above the initial value interestingly due to the depletion layer broadening with the majority-carrier removal, and is degraded gradually over 1×1010cm-2. On comparing the VOC, ISC in the AlInGaP cell (0.6 μm) and InGaP cell (0.6 μm) with proton fluence, AlInGaP shows the higher radiation tolerance than InGaP.
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EPR spectra originating from phosphorus shallow donors occupying silicon sites in 3C-, 4H-, and 6H-SiC are identified by using CVD grown films in which the interference from the signals from the nitrogen shallow donors is practically... more
EPR spectra originating from phosphorus shallow donors occupying silicon sites in 3C-, 4H-, and 6H-SiC are identified by using CVD grown films in which the interference from the signals from the nitrogen shallow donors is practically absent. Phosphorus donors occupying both silicon and carbon sites are observed in high-energy phosphorus ion implanted semi-insulating 6H-SiC which was also free from the interference from the signals from the nitrogen shallow donors.
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Anomalous degradation of Si space solar cells for the ETS-VI satellite suggests the importance of understanding the origins of radiation-induced defects in Si, because such defects are responsible for carrier removal, type conversion and... more
Anomalous degradation of Si space solar cells for the ETS-VI satellite suggests the importance of understanding the origins of radiation-induced defects in Si, because such defects are responsible for carrier removal, type conversion and reduction in minority-carrier lifetime. Effects of impurities on generation of radiation-induced defects in Si have been studied using measurements of DLTS and minority-carrier lifetime. Boron concentration
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... Dalia Elfiky1,*, Masafumi Yamaguchi1, Takuo Sasaki1, Tatsuya Takamoto2, Chiharu Morioka3 Mitsuru Imaizumi3, Takeshi Ohshima4, Shin-ichiro Sato4, Mohamed Elnawawy5, Tarek Eldesuky6 and Ahmed Ghitas7 1. Toyota Technological Institute,... more
... Dalia Elfiky1,*, Masafumi Yamaguchi1, Takuo Sasaki1, Tatsuya Takamoto2, Chiharu Morioka3 Mitsuru Imaizumi3, Takeshi Ohshima4, Shin-ichiro Sato4, Mohamed Elnawawy5, Tarek Eldesuky6 and Ahmed Ghitas7 1. Toyota Technological Institute, Nagoya, Japan. ...
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The present study explored first time the better radiation tolerance of gallium-doped silicon solar cells as compared to conventional boron-doped silicon solar cells after heavy fluence of 1MeV electron irradiation. One of the approaches... more
The present study explored first time the better radiation tolerance of gallium-doped silicon solar cells as compared to conventional boron-doped silicon solar cells after heavy fluence of 1MeV electron irradiation. One of the approaches to improve the end of life of silicon solar cells is by increasing the effective base carrier concentrations. Analysis of the carrier removal rate RC in