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  • 1.
    Anderson, Christopher P.
    et al.
    Univ Chicago, IL 60637 USA.
    Bourassa, Alexandre
    Univ Chicago, IL 60637 USA.
    Miao, Kevin C.
    Univ Chicago, IL 60637 USA.
    Wolfowicz, Gary
    Univ Chicago, IL 60637 USA.
    Mintun, Peter J.
    Univ Chicago, IL 60637 USA.
    Crook, Alexander L.
    Univ Chicago, IL 60637 USA; Univ Chicago, IL 60637 USA.
    Abe, Hiroshi
    Natl Inst Quantum and Radiol Sci and Technol, Japan.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ohshima, Takeshi
    Natl Inst Quantum and Radiol Sci and Technol, Japan.
    Awschalom, David D.
    Univ Chicago, IL 60637 USA; Univ Chicago, IL 60637 USA; Argonne Natl Lab, IL 60439 USA; Argonne Natl Lab, IL 60439 USA.
    Electrical and optical control of single spins integrated in scalable semiconductor devices2019In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 366, no 6470, p. 1225-+Article in journal (Refereed)
    Abstract [en]

    Spin defects in silicon carbide have the advantage of exceptional electron spin coherence combined with a near-infrared spin-photon interface, all in a material amenable to modern semiconductor fabrication. Leveraging these advantages, we integrated highly coherent single neutral divacancy spins in commercially available p-i-n structures and fabricated diodes to modulate the local electrical environment of the defects. These devices enable deterministic charge-state control and broad Stark-shift tuning exceeding 850 gigahertz. We show that charge depletion results in a narrowing of the optical linewidths by more than 50-fold, approaching the lifetime limit. These results demonstrate a method for mitigating the ubiquitous problem of spectral diffusion in solid-state emitters by engineering the electrical environment while using classical semiconductor devices to control scalable, spin-based quantum systems.

  • 2.
    Anderson, Christopher P.
    et al.
    Univ Chicago, IL 60637 USA; Univ Chicago, IL 60637 USA.
    Glen, Elena O.
    Univ Chicago, IL 60637 USA.
    Zeledon, Cyrus
    Univ Chicago, IL 60637 USA.
    Bourassa, Alexandre
    Univ Chicago, IL 60637 USA.
    Jin, Yu
    Univ Chicago, IL 60637 USA.
    Zhu, Yizhi
    Univ Chicago, IL 60637 USA.
    Vorwerk, Christian
    Univ Chicago, IL 60637 USA.
    Crook, Alexander L.
    Univ Chicago, IL 60637 USA; Univ Chicago, IL 60637 USA.
    Abe, Hiroshi
    Natl Inst Quantum Sci & Technol, Japan.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ohshima, Takeshi
    Natl Inst Quantum Sci & Technol, Japan.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Galli, Giulia
    Univ Chicago, IL 60637 USA; Univ Chicago, IL 60637 USA; Argonne Natl Lab, IL 60439 USA.
    Awschalom, David D.
    Univ Chicago, IL 60637 USA; Univ Chicago, IL 60637 USA; Argonne Natl Lab, IL 60439 USA.
    Five-second coherence of a single spin with single-shot readout in silicon carbide2022In: Science Advances, E-ISSN 2375-2548, Vol. 8, no 5, article id eabm5912Article in journal (Refereed)
    Abstract [en]

    An outstanding hurdle for defect spin qubits in silicon carbide (SiC) is single-shot readout, a deterministic measurement of the quantum state. Here, we demonstrate single-shot readout of single defects in SiC via spin-to-charge conversion, whereby the defects spin state is mapped onto a long-lived charge state. With this technique, we achieve over 80% readout fidelity without pre- or postselection, resulting in a high signal-to-noise ratio that enables us to measure long spin coherence times. Combined with pulsed dynamical decoupling sequences in an isotopically purified host material, we report single-spin T-2 > 5 seconds, over two orders of magnitude greater than previously reported in this system. The mapping of these coherent spin states onto single charges unlocks both single-shot readout for scalable quantum nodes and opportunities for electrical readout via integration with semiconductor devices.

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  • 3.
    Arslan, Engin
    et al.
    Bilkent University, Turkey .
    Cakmakyapan, Semih
    Bilkent University, Turkey .
    Kazar, Ozgur
    Bilkent University, Turkey .
    Butun, Serkan
    Bilkent University, Turkey .
    Bora Lisesivdin, Sefer
    Gazi University, Turkey .
    Cinel, Neval A.
    Bilkent University, Turkey .
    Ertas, Gulay
    Bilkent University, Turkey .
    Ardali, Sukru
    Anadolu University, Turkey .
    Tiras, Engin
    Anadolu University, Turkey .
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ozbay, Ekmel
    Bilkent University, Turkey .
    SiC Substrate Effects on Electron Transport in the Epitaxial Graphene Layer2014In: ELECTRONIC MATERIALS LETTERS, ISSN 1738-8090, Vol. 10, no 2, p. 387-391Article in journal (Refereed)
    Abstract [en]

    Hall effect measurements on epitaxial graphene (EG) on SiC substrate have been carried out as a function of temperature. The mobility and concentration of electrons within the two-dimensional electron gas (2DEG) at the EG layers and within the underlying SiC substrate are readily separated and characterized by the simple parallel conduction extraction method (SPCEM). Two electron carriers are identified in the EG/SiC sample: one high-mobility carrier (3493 cm(2)/Vs at 300 K) and one low-mobility carrier (1115 cm(2)/Vs at 300 K). The high mobility carrier can be assigned to the graphene layers. The second carrier has been assigned to the SiC substrate.

  • 4.
    Astner, Thomas
    et al.
    Inst Quantum Opt & Quantum Informat IQOQI Vienna, Austria; Univ Wien, Austria.
    Koller, Philipp
    Inst Quantum Opt & Quantum Informat IQOQI Vienna, Austria; Univ Wien, Austria; Univ Vienna, Austria; Univ Vienna, Austria.
    Gilardoni, Carmem M.
    Univ Groningen, Netherlands.
    Hendriks, Joop
    Univ Groningen, Netherlands.
    Son, Nguyen Tien
    Univ Groningen, Netherlands.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    van der Wal, Caspar H.
    Univ Groningen, Netherlands.
    Trupke, Michael
    Inst Quantum Opt & Quantum Informat IQOQI Vienna, Austria; Univ Wien, Austria.
    Vanadium in silicon carbide: telecom-ready spin centres with long relaxation lifetimes and hyperfine-resolved optical transitions2024In: QUANTUM SCIENCE AND TECHNOLOGY, ISSN 2058-9565, Vol. 9, no 3, article id 035038Article in journal (Refereed)
    Abstract [en]

    Vanadium in silicon carbide (SiC) is emerging as an important candidate system for quantum technology due to its optical transitions in the telecom wavelength range. However, several key characteristics of this defect family including their spin relaxation lifetime (T1), charge state dynamics, and level structure are not fully understood. In this work, we determine the T1 of an ensemble of vanadium defects, demonstrating that it can be greatly enhanced at low temperature. We observe a large spin contrast exceeding 90% and long spin-relaxation times of up to 25 s at 100 mK, and of order 1 s at 1.3 K. These measurements are complemented by a characterization of the ensemble charge state dynamics. The stable electron spin furthermore enables high-resolution characterization of the systems' hyperfine level structure via two-photon magneto-spectroscopy. The acquired insights point towards high-performance spin-photon interfaces based on vanadium in SiC.

  • 5.
    Ayedh, Hussein M.
    et al.
    University of Oslo, Department of Physics, Center for Materials Science and Nanotechnology, N-0316 Oslo, NORWAY .
    Baathen, Marianne E.
    University of Oslo, Department of Physics, Center for Materials Science and Nanotechnology, N-0316 Oslo, NORWAY .
    Galeckas, Augustinas
    University of Oslo, Department of Physics, Center for Materials Science and Nanotechnology, N-0316 Oslo, NORWAY .
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Nipoti, Roberta
    CNR-IMM of Bologna, I-40129 Bologna, ITALY.
    Hallen, Anders
    Royal Institute of Technology, KTH, School of Information and Communication Technology, SE-164 40 Kista-Stockholm, SWEDEN.
    Svensson, Bengt G
    University of Oslo, Department of Physics, Center for Materials Science and Nanotechnology, N-0316 Oslo, NORWAY.
    (Invited) Controlling the Carbon Vacancy in 4H-SiC by Thermal Processing2018In: / [ed] Dudley, M; Bakowski, M; Shenai, K; Ohtani, N; Raghothamachar, B, Electrochemical Society, 2018, Vol. 86, no 12, p. 91-97Conference paper (Refereed)
    Abstract [en]

    The carbon vacancy (VC) is perhaps the most prominent point defect in silicon carbide (SiC) and it is an efficient charge carrier lifetime killer in high-purity epitaxial layers of 4H-SiC. The VC concentration needs to be controlled and minimized for optimum materials and device performance, and an approach based on post-growth thermal processing under C-rich ambient conditions is presented. It utilizes thermodynamic equilibration and after heat treatment at 1500 °C for 1 h, the VC concentration is shown to be reduced by a factor ~25 relative to that in as-grown state-of-the-art epi-layers. Concurrently, a considerable enhancement of the carrier lifetime occurs throughout the whole of >40 µm thick epi-layers.

  • 6.
    Babin, Charles
    et al.
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Stoehr, Rainer
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Morioka, Naoya
    Univ Stuttgart, Germany; Univ Stuttgart, Germany; Kyoto Univ, Japan.
    Linkewitz, Tobias
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Steidl, Timo
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Woernle, Raphael
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Liu, Di
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Hesselmeier, Erik
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Vorobyov, Vadim
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Denisenko, Andrej
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Hentschel, Mario
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Gobert, Christian
    Fraunhofer Inst Integrated Syst & Device Technol, Germany.
    Berwian, Patrick
    Fraunhofer Inst Integrated Syst & Device Technol, Germany.
    Astakhov, Georgy V
    Helmholtz Zentrum Dresden Rossendorf, Germany.
    Knolle, Wolfgang
    Leibniz Inst Surface Engn IOM, Germany.
    Majety, Sridhar
    Univ Calif Davis, CA 95616 USA.
    Saha, Pranta
    Univ Calif Davis, CA 95616 USA.
    Radulaski, Marina
    Univ Calif Davis, CA 95616 USA.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Kaiser, Florian
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Wrachtrup, Joerg
    Univ Stuttgart, Germany; Univ Stuttgart, Germany.
    Fabrication and nanophotonic waveguide integration of silicon carbide colour centres with preserved spin-optical coherence2022In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 21, p. 67-73Article in journal (Refereed)
    Abstract [en]

    Colour centres are a promising quantum information platform, but coherence degradation after integration in nanostructures has hindered scalability. Here, the authors show that waveguide-integrated V-Si centres in SiC maintain spin-optical coherences, enabling nuclear high-fidelity spin qubit operations. Optically addressable spin defects in silicon carbide (SiC) are an emerging platform for quantum information processing compatible with nanofabrication processes and device control used by the semiconductor industry. System scalability towards large-scale quantum networks demands integration into nanophotonic structures with efficient spin-photon interfaces. However, degradation of the spin-optical coherence after integration in nanophotonic structures has hindered the potential of most colour centre platforms. Here, we demonstrate the implantation of silicon vacancy centres (V-Si) in SiC without deterioration of their intrinsic spin-optical properties. In particular, we show nearly lifetime-limited photon emission and high spin-coherence times for single defects implanted in bulk as well as in nanophotonic waveguides created by reactive ion etching. Furthermore, we take advantage of the high spin-optical coherences of V-Si centres in waveguides to demonstrate controlled operations on nearby nuclear spin qubits, which is a crucial step towards fault-tolerant quantum information distribution based on cavity quantum electrodynamics.

  • 7.
    Bathen, M. E.
    et al.
    Univ Oslo, Norway.
    Coutinho, J.
    Univ Aveiro, Portugal.
    Ayedh, H. M.
    Univ Oslo, Norway.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Farkas, Ildiko
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Oberg, S.
    Lulea Univ Technol, Sweden.
    Frodason, Y. K.
    Univ Oslo, Norway.
    Svensson, B. G.
    Univ Oslo, Norway.
    Vines, L.
    Univ Oslo, Norway.
    Anisotropic and plane-selective migration of the carbon vacancy in SiC: Theory and experiment2019In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 1, article id 014103Article in journal (Refereed)
    Abstract [en]

    We investigate the migration mechanism of the carbon vacancy (V-C) in silicon carbide (SiC) using a combination of theoretical and experimental methodologies. The V-C, commonly present even in state-of-the-art epitaxial SiC material, is known to be a carrier lifetime killer and therefore strongly detrimental to device performance. The desire for V-C removal has prompted extensive investigations involving its stability and reactivity. Despite suggestions from theory that V(C )migrates exclusively on the C sublattice via vacancy-atom exchange, experimental support for such a picture is still unavailable. Moreover, the existence of two inequivalent locations for the vacancy in 4H-SiC [hexagonal, V-C(h), and pseudocubic, V-C(k)] and their consequences for V-C migration have not been considered so far. The first part of the paper presents a theoretical study of V(C )migration in 3C- and 4H-SiC. We employ a combination of nudged elastic band (NEB) and dimer methods to identify the migration mechanisms, transition state geometries, and respective energy barriers for V(C )migration. In 3C-SiC, V-C is found to migrate with an activation energy of E-A = 4.0 eV. In 4H-SiC, on the other hand, we anticipate that V-C migration is both anisotropic and basal-plane selective. The consequence of these effects is a slower diffusivity along the axial direction, with a predicted activation energy of E-A = 4.2 eV, and a striking preference for basal migration within the h plane with a barrier of E-A = 3.7 eV, to the detriment of the k-basal plane. Both effects are rationalized in terms of coordination and bond angle changes near the transition state. In the second part, we provide experimental data that corroborates the above theoretical picture. Anisotropic migration of V-C in 4H-SiC is demonstrated by deep level transient spectroscopy (DLTS) depth profiling of the Z(1/2) electron trap in annealed samples that were subject to ion implantation. Activation energies of E-A = (4.4 +/- 0.3) eV and E-A = (3.6 +/- 0.3) eV were found for V-C migration along the c and a directions, respectively, in excellent agreement with the analogous theoretical values. The corresponding prefactors of D-0 = 0.54 cm(2)/s and 0.017 cm(2)/s are in line with a simple jump process, as expected for a primary vacancy point defect.

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  • 8.
    Bathen, Marianne Etzelmueller
    et al.
    Swiss Fed Inst Technol, Switzerland; Univ Oslo, Norway.
    Kumar, Piyush
    Swiss Fed Inst Technol, Switzerland.
    Ghezellou, Misagh
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Belanche, Manuel
    Swiss Fed Inst Technol, Switzerland.
    Vines, Lasse
    Univ Oslo, Norway.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Grossner, Ulrike
    Swiss Fed Inst Technol, Switzerland.
    Dual configuration of shallow acceptor levels in 4H-SiC2024In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 177, article id 108360Article in journal (Refereed)
    Abstract [en]

    Acceptor dopants in 4H-SiC exhibit energy levels that are located deeper in the band gap than the thermal energy at room temperature (RT), resulting in incomplete ionization at RT. Therefore, a comprehensive understanding of the defect energetics and how the impurities are introduced into the material is imperative. Herein, we study impurity related defect levels in 4H-SiC epitaxial layers (epi-layers) grown by chemical vapor deposition (CVD) under various conditions using minority carrier transient spectroscopy (MCTS). We find two trap levels assigned to boron impurities, B and D, which are introduced to varying degrees depending on the growth conditions. A second acceptor level that was labeled X in the literature and attributed to impurity related defects is also observed. Importantly, both the B and X levels exhibit fine structure revealed by MCTS measurements. We attribute the fine structure to acceptor impurities at hexagonal and pseudo -cubic lattice sites in 4H-SiC, and tentatively assign the X peak to Al based on experimental findings and density functional theory calculations.

  • 9.
    Bergman, Peder
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Booker, Ian Don
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lilja, Louise
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Radial Variation of Measured Carrier Lifetimes in Epitaxial Layers Grown with Wafer Rotation2012In: Materials Science Forum Vols 717 - 720, Trans Tech Publications Inc., 2012, Vol. 717-720, p. 289-292Conference paper (Refereed)
    Abstract [en]

    In this report we present homoepitaxial growth of 4H-SiC on the Si-face of nominally on-axis substrates with diameter up to 100 mm in a hot-wall chemical vapor deposition reactor. A comparatively low carrier lifetime has been observed in these layers. Also, local variations in carrier lifetime are different from standard off-cut epilayers. The properties of layers were studied with more focus on charge carrier lifetime and its correlation with starting growth conditions, inhomogeneous surface morphology and different growth mechanisms.

  • 10.
    Bergman, Peder
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    ul-Hassan, Jawad
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Henry, Anne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Godignon, P.
    Brosselard, P.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Improved SiC Epitaxial Material for Bipolar Applications2008In: Proc. of MRS Spring Meeting 2008, 2008, p. D05-Conference paper (Refereed)
    Abstract [en]

    Epitaxial growth on Si-face nominally on-axis 4H-SiC substrates has been performed using horizontal Hot-wall chemical vapor deposition system. The formation of 3C inclusions is one of the main problem with growth on on-axis Si-face substrates. In situ surface preparation, starting growth parameters and growth temperature are found to play a vital role in the epilayer polytype stability. High quality epilayers with 100% 4H-SiC were obtained on full 2″ substrates. Different optical and structural techniques were used to characterize the material and to understand the growth mechanisms. It was found that the replication of the basal plane dislocation from the substrate into the epilayer can be eliminated through growth on on-axis substrates. Also, no other kind of structural defects were found in the grown epilayers. These layers have also been processed for simple PiN structures to observe any bipolar degradation. More than 70% of the diodes showed no forward voltage drift during 30 min operation at 100 A/cm2.

  • 11.
    Bernardin, Evans
    et al.
    University of South Florida, Tampa, FL, U.S.A..
    Frewin, Christopher L.
    University of Texas at Dallas, Dallas, TX, U.S.A.
    Dey, Abhishek
    University of South Florida, Tampa, FL, U.S.A..
    Everly, Richard
    University of South Florida, Tampa, FL, U.S.A..
    Ul Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Pancrazio, Joe
    University of Texas at Dallas, Dallas, TX, U.S.A.
    Saddow, Stephen E.
    University of South Florida, Tampa, FL, U.S.A..
    Development of an all-SiC neuronal interface device2016In: MRS Advances, E-ISSN 2059-8521, Vol. 1, no 55, p. 3679-3684Article in journal (Refereed)
    Abstract [en]

    The intracortical neural interface (INI) is a key component of brain machine interfaces (BMI) which offer the possibility to restore functions lost by patients due to severe trauma to the central or peripheral nervous system. Unfortunately today’s neural electrodes suffer from a variety of design flaws, mainly the use of non-biocompatible materials based on Si or W with polymer coatings to mask the underlying material. Silicon carbide (SiC) is a semiconductor that has been proven to be highly biocompatible, and this chemically inert, physically robust material system may provide the longevity and reliability needed for the INI community. The design, fabrication, and preliminary testing of a prototype all-SiC planar microelectrode array based on 4H-SiC with an amorphous silicon carbide (a-SiC) insulator is described. The fabrication of the planar microelectrode was performed utilizing a series of conventional micromachining steps. Preliminary data is presented which shows a proof of concept for an all-SiC microelectrode device.

  • 12.
    Bernardin, Evans K.
    et al.
    Univ S Florida, FL 33620 USA.
    Frewin, Christopher L.
    Univ Texas Dallas, TX 75080 USA.
    Everly, Richard
    USF, FL 33617 USA.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Saddow, Stephen E.
    Univ S Florida, FL 33620 USA.
    Correction: Demonstration of a Robust All-Silicon-Carbide Intracortical Neural Interface (vol 9, 412, 2018)2018In: Micromachines, E-ISSN 2072-666X, Vol. 9, no 9, article id 451Article in journal (Other academic)
    Abstract [en]

    n/a

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  • 13.
    Bernardin, Evans K.
    et al.
    Univ S Florida, FL 33620 USA.
    Frewin, Christopher L.
    Univ Texas Dallas, TX 75080 USA.
    Everly, Richard
    Nanotechnol Res and Educ Ctr USF, FL 33617 USA.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Saddow, Stephen E.
    Univ S Florida, FL 33620 USA.
    Demonstration of a Robust All-Silicon-Carbide Intracortical Neural Interface2018In: Micromachines, E-ISSN 2072-666X, Vol. 9, no 8, article id 412Article in journal (Refereed)
    Abstract [en]

    Intracortical neural interfaces (INI) have made impressive progress in recent years but still display questionable long-term reliability. Here, we report on the development and characterization of highly resilient monolithic silicon carbide (SiC) neural devices. SiC is a physically robust, biocompatible, and chemically inert semiconductor. The device support was micromachined from p-type SiC with conductors created from n-type SiC, simultaneously providing electrical isolation through the resulting p-n junction. Electrodes possessed geometric surface area (GSA) varying from 496 to 500 K m(2). Electrical characterization showed high-performance p-n diode behavior, with typical turn-on voltages of 2.3 V and reverse bias leakage below 1 nArms. Current leakage between adjacent electrodes was 7.5 nArms over a voltage range of -50 V to 50 V. The devices interacted electrochemically with a purely capacitive relationship at frequencies less than 10 kHz. Electrode impedance ranged from 675 +/- 130 k (GSA = 496 mu m(2)) to 46.5 +/- 4.80 k (GSA = 500 K mu m(2)). Since the all-SiC devices rely on the integration of only robust and highly compatible SiC material, they offer a promising solution to probe delamination and biological rejection associated with the use of multiple materials used in many current INI devices.

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  • 14.
    Booker, Ian D.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Farkas, Ildiko
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan G.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Chloride-based SiC growth on a-axis 4H-€“SiC substrates2016In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 480, p. 23-25Article in journal (Refereed)
    Abstract [en]

    Abstract SiC has, during the last few years, become increasingly important as a power-device material for high voltage applications. The thick, low-doped voltage-supporting epitaxial layer is normally grown by CVD on 4° off-cut 4H–SiC substrates at a growth rate of 5 – 10 ÎŒ m / h using silane (SiH4) and propane (C3H8) or ethylene (C2H4) as precursors. The concentrations of epitaxial defects and dislocations depend to a large extent on the underlying substrate but can also be influenced by the actual epitaxial growth process. Here we will present a study on the properties of the epitaxial layers grown by a Cl-based technique on an a-axis (90° off-cut from c-direction) 4H–SiC substrate.

  • 15.
    Booker, Ian Don
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Abdalla, Hassan
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Lilja, Louise
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Science Institute, University of Iceland, Reykjavik, Iceland.
    Oxidation-induced deep levels in n- and p-type 4H- and 6H-SiC and their influence on carrier lifetime2016In: Physical Review Applied, ISSN 2331-7019, Vol. 6, no 1, p. 1-15, article id 014010Article in journal (Refereed)
    Abstract [en]

    We present a complete analysis of the electron- and hole-capture and -emission processes of the deep levels ON1, ON2a, and ON2b in 4H-SiC and their 6H-SiC counterparts OS1a and OS1b through OS3a and OS3b, which are produced by lifetime enhancement oxidation or implantation and annealing techniques. The modeling is based on a simultaneous numerical fitting of multiple high-resolution capacitance deep-level transient spectroscopy spectra measured with different filling-pulse lengths in n- and p-type material. All defects are found to be double-donor-type positive-U two-level defects with very small hole-capture cross sections, making them recombination centers of low efficiency, in accordance with minority-carrier-lifetime measurements. Their behavior as trapping and weak recombination centers, their large concentrations resulting from the lifetime enhancement oxidations, and their high thermal stability, however, make it advisable to minimize their presence in active regions of devices, for example, the base layer of bipolar junction transistors.

  • 16.
    Booker, Ian Don
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Abdalla, Hassan
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, The Institute of Technology.
    Lilja, L.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Oxidation induced ON1, ON2a/b defects in 4H-SiC characterized by DLTS2014In: SILICON CARBIDE AND RELATED MATERIALS 2013, PTS 1 AND 2, Trans Tech Publications , 2014, Vol. 778-780, p. 281-284Conference paper (Refereed)
    Abstract [en]

    The deep levels ON1 and ON2a/b introduced by oxidation into 4H-SiC are characterized via standard DLTS and via filling pulse dependent DLTS measurements. Separation of the closely spaced ON2a/b defect is achieved by using a higher resolution correlation function (Gaver-Stehfest 4) and apparent energy level, apparent electron capture cross section and filling pulse measurement derived capture cross sections are given.

  • 17.
    Booker, Ian Don
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hallén,, Anders
    Royal Institute of Technology, Sweden.
    Sveinbjörnsson, Einar Ö.
    University of Iceland, Reykjavik, Iceland.
    Kordina, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Comparison of Post-Growth Carrier Lifetime Improvement Methods for 4H-SiC Epilayers2012In: Materials Science Forum Vols 717 - 720, Trans Tech Publications Inc., 2012, Vol. 717-720, p. 285-288Conference paper (Refereed)
    Abstract [en]

    We compare two methods for post-growth improvement of bulk carrier lifetime in 4H-SiC: dry oxidations and implantations with either C-12 or N-14, followed by high temperature anneals in Ar atmosphere. Application of these techniques to samples cut from the same wafer/epilayer yields 2- to 11-fold lifetime increases, with the implantation/annealing technive shown to give greater rnaximum lifetimes. The maximum lifetimes reached are similar to 5 mu s after C-12 implantation at 600 degrees C and annealing in Ar for 180 minutes at 1500 degrees C. At higher annealing temperatures the lifetimes decreases, a result which differs from reports in the literature.

  • 18.
    Booker, Ian Don
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    High-Resolution Time-Resolved Carrier Lifetime and Photoluminescence Mapping of 4H-SiC Epilayers2012In: Materials Science Forum Vols 717 - 720, Trans Tech Publications Inc., 2012, Vol. 717-720, p. 293-296Conference paper (Refereed)
    Abstract [en]

    We present a comparison between time-resolved carrier lifetime mappings of several samples and integrated near band edge intensity photoluminescence mappings using a pulsed laser. High-injection conditions and as-grown material are used, which generally allow for the assumption of a single exponential decay. The photoluminescence intensity under these circumstances is proportional to the carrier lifetime and the mappings can be used to detect lifetime-influencing defects in epilayers and give an estimate of the carrier lifetime variation over the wafer. Several examples for the defect detection capability of the system are given.

  • 19.
    Booker, Ian Don
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Science Institute, University of Iceland, Reykjavik, Iceland.
    Electron and hole capture cross sections of deep levels accessible by DLTS and MCTS in p-type 4H-SiCManuscript (preprint) (Other academic)
    Abstract [en]

    The effective electron (σn(T)) and hole (σn(T)) capture cross sections of the electrically active deep levels HK0, HK2, LB1 and EM1 found in as-grown, high temperature annealed and oxidized p-type 4H-SiC were measured by deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy (MCTS) and optical-electrical MCTS and DLTS (OE-MCTS and EO-DLTS) in an effort to determine the potential recombination centers in p-type material. Additionally, we also find the D-center, and the deep levels EH6/7, ON1 and ON2 in our samples, while the levels HK1, HK3 and HK4, reported in literature, are always below the detection limit. We further compare deep level concentrations and the timeresolved photoluminescence (TRPL) measured low injection (τLI) in samples annealed at up to 1920 °C. None of the detected deep levels possess σp(T):σn(T) ratios which could enable them to act as efficient recombination centers in the annealed epilayers, where τLI ranges from 1.2·10-6 s to less than 100·10-9 s. However, a clear anti-correlation between τLI and the EH6/7 concentration is found, which is linked to the main lifetime limiting center in n-type material, Z1/2, via their common origin, the carbon vacancy. Due to their large σp(T):σn(T) ratio, the Z1/2 deep levels are not detected by frontside illumination MCTS in p-type material. We thus conclude that the main lifetime limiting deep level(s) in p-type 4HSiC appear to be located in the upper half of the bandgap and are most likely either Z1/2, or other deep levels of intrinsic or partially intrinsic origin with a similar σp(T):σn(T) ratio.

  • 20.
    Booker, Ian Don
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Stenberg, Pontus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Science Institute, University of Iceland, Reykjavik, Iceland.
    Carrier lifetime in p- and n-type 4H-SiCManuscript (preprint) (Other academic)
    Abstract [en]

    Temperature-dependent time-resolved photoluminescence measurements made in the temperature range from 77 K to 1000 K on free-standing as grown n-type 4H-SiC and p-type 4H-SiC epilayers, which are either as-grown or annealed at 1000 °C, 1400 °C or 1700 °C, are analyzed. The development of the instantaneous carrier lifetime over temperature, calculated from the decay curves of all n- and p-type samples, is found to be identical in the entire temperature range. With increasing annealing temperature only the magnitude of the lifetime in p-type 4H-SiC decreases while the trend remains identical to that in the as-grown n-type sample. Annealing thus only increases the density of the main recombination center which appears to control lifetime in as-grown n- and p-type material. The results implies that the lifetime in all samples may be governed by the same intrinsic defect, which we suggest to be Z1/2.

  • 21.
    Booker, Ian Don
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Son, Nguyen Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Stenberg, Pontus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Science Institute, University of Iceland, Reykjavik, Iceland.
    Donor and double donor transitions of the carbon vacancy related EH6/7 deep level in 4H-SiC2016In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 23, article id 235703Article in journal (Refereed)
    Abstract [en]

    Using medium- and high-resolution multi-spectra fitting of deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy (MCTS), optical O-DLTS and optical-electrical (OE)-MCTS measurements, we show that the EH6∕7 deep level in 4H-SiC is composed of two strongly overlapping, two electron emission processes with thermal activation energies of 1.49 eV and 1.58 eV for EH6 and 1.48 eV and 1.66 eV for EH7. The electron emission peaks of EH7 completely overlap while the emission peaks of EH6 occur offset at slightly different temperatures in the spectra. OE-MCTS measurements of the hole capture cross section σp 0(T) in p-type samples reveal a trap-Auger process, whereby hole capture into the defect occupied by two electrons leads to a recombination event and the ejection of the second electron into the conduction band. Values of the hole and electron capture cross sections σn(T) and σp(T) differ strongly due to the donor like nature of the deep levels and while all σn(T) have a negative temperature dependence, the σp(T) appear to be temperature independent. Average values at the DLTS measurement temperature (∼600 K) are σn 2+(T) ≈ 1 × 10−14 cm2, σn +(T) ≈ 1 × 10−14 cm2, and σp 0(T) ≈ 9 × 10−18 cm2 for EH6 and σn 2+(T) ≈ 2 × 10−14 cm2, σn +(T) ≈ 2 × 10−14 cm2, σp 0(T) ≈ 1 × 10−20 cm2 for EH7. Since EH7 has already been identified as a donor transition of the carbon vacancy, we propose that the EH6∕7 center in total represents the overlapping first and second donor transitions of the carbon vacancy defects on both inequivalent lattice sites.

  • 22.
    Booker, Ian Don
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ul Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lilja, Louise
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Beyer, Franziska
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, J. Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Danielsson, Örjan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kordina, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Carrier Lifetime Controlling Defects Z(1/2) and RB1 in Standard and Chlorinated Chemistry Grown 4H-SiC2014In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 8, p. 4104-4110Article in journal (Refereed)
    Abstract [en]

    4H-SiC epilayers grown by standard and chlorinated chemistry were analyzed for their minority carrier lifetime and deep level recombination centers using time-resolved photoluminescence (TRPL) and standard deep level transient spectroscopy (DLTS). Next to the well-known Z(1/2) deep level a second effective lifetime killer, RB1 (activation energy 1.05 eV, electron capture cross section 2 x 10(-16) cm(2), suggested hole capture cross section (5 +/- 2) x 10(-15) cm(2)), is detected in chloride chemistry grown epilayers. Junction-DLTS and bulk recombination simulations are used to confirm the lifetime killing properties of this level. The measured RB1 concentration appears to be a function of the iron-related Fe1 level concentration, which is unintentionally introduced via the corrosion of reactor steel parts by the chlorinated chemistry. Reactor design and the growth zone temperature profile are thought to enable the formation of RB1 in the presence of iron contamination under conditions otherwise optimal for growth of material with very low Z(1/2) concentrations. The RB1 defect is either an intrinsic defect similar to RD1/2 or EH5 or a complex involving iron. Control of these corrosion issues allows the growth of material at a high growth rate and with high minority carrier lifetime based on Z(1/2) as the only bulk recombination center.

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  • 23.
    Bosma, Tom
    et al.
    Univ Groningen, Netherlands.
    Hendriks, Joop
    Univ Groningen, Netherlands.
    Ghezellou, Misagh
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    van der Wal, Caspar H.
    Univ Groningen, Netherlands.
    Broadband single-mode planar waveguides in monolithic 4H-SiC2022In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 131, no 2, article id 025703Article in journal (Refereed)
    Abstract [en]

    Color-center defects in silicon carbide promise opto-electronic quantum applications in several fields, such as computing, sensing, and communication. In order to scale down and combine these functionalities with the existing silicon device platforms, it is crucial to consider SiC integrated optics. In recent years, many examples of SiC photonic platforms have been shown, like photonic crystal cavities, film-on-insulator waveguides, and micro-ring resonators. However, all these examples rely on separating thin films of SiC from substrate wafers. This introduces significant surface roughness, strain, and defects in the material, which greatly affects the homogeneity of the optical properties of color centers. Here, we present and test a method for fabricating monolithic single-crystal integrated-photonic devices in SiC: tuning optical properties via charge carrier concentration. We fabricated monolithic SiC n-i-n and p-i-n junctions where the intrinsic layer acts as waveguide core, and demonstrate the waveguide functionality for these samples. The propagation losses are below 14 dB/cm. These waveguide types allow for addressing color centers over a broad wavelength range with low strain-induced inhomogeneity of the optical-transition frequencies. Furthermore, we expect that our findings open the road to fabricating waveguides and devices based on p-i-n junctions, which will allow for integrated electrostatic and radio frequency control together with high-intensity optical control of defects in silicon carbide.

  • 24.
    Bourassa, Alexandre
    et al.
    Univ Chicago, IL 60637 USA.
    Anderson, Christopher P.
    Univ Chicago, IL 60637 USA.
    Miao, Kevin C.
    Univ Chicago, IL 60637 USA.
    Onizhuk, Mykyta
    Univ Chicago, IL 60637 USA.
    Ma, He
    Univ Chicago, IL 60637 USA.
    Crook, Alexander L.
    Univ Chicago, IL 60637 USA.
    Abe, Hiroshi
    Natl Inst Quantum & Radiol Sci & Technol, Japan.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ohshima, Takeshi
    Natl Inst Quantum & Radiol Sci & Technol, Japan.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Galli, Giulia
    Univ Chicago, IL 60637 USA; Argonne Natl Lab, IL 60439 USA; Argonne Natl Lab, IL 60439 USA.
    Awschalom, David D.
    Univ Chicago, IL 60637 USA; Argonne Natl Lab, IL 60439 USA; Argonne Natl Lab, IL 60439 USA.
    Entanglement and control of single nuclear spins in isotopically engineered silicon carbide2020In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 19, no 12, p. 1319-1325Article in journal (Refereed)
    Abstract [en]

    Isotope engineering of silicon carbide leads to control of nuclear spins associated with single divacancy centres and extended electron spin coherence. Nuclear spins in the solid state are both a cause of decoherence and a valuable resource for spin qubits. In this work, we demonstrate control of isolated(29)Si nuclear spins in silicon carbide (SiC) to create an entangled state between an optically active divacancy spin and a strongly coupled nuclear register. We then show how isotopic engineering of SiC unlocks control of single weakly coupled nuclear spins and present an ab initio method to predict the optimal isotopic fraction that maximizes the number of usable nuclear memories. We bolster these results by reporting high-fidelity electron spin control (F = 99.984(1)%), alongside extended coherence times (Hahn-echoT(2) = 2.3 ms, dynamical decouplingT(2)(DD) > 14.5 ms), and a >40-fold increase in Ramsey spin dephasing time (T-2*) from isotopic purification. Overall, this work underlines the importance of controlling the nuclear environment in solid-state systems and links single photon emitters with nuclear registers in an industrially scalable material.

  • 25.
    Brosselard, P
    et al.
    Centro Nacional de Microelectrónica, CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain .
    Berthou, M
    Centro Nacional de Microelectrónica, CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain .
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Jorda, X
    Centro Nacional de Microelectrónica, CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain .
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Montserrat, J
    Centro Nacional de Microelectrónica, CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain .
    Godignon, P
    Centro Nacional de Microelectrónica, CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain .
    Millan, J
    Centro Nacional de Microelectrónica, CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain .
    Comparison between 3.3kV 4H-SiC schottky and bipolar diodes2008In: IET Seminar Digest, Volume 2008, Issue 2, 2008, 2008, p. 87-91Conference paper (Refereed)
    Abstract [en]

    Silicon Carbide Schottky and bipolar diodes have been fabricated with a breakdown voltage of 3.3kV. Diodes have been packaged and measured up to 300°C. The Schottky diode shows an increase of voltage drop with temperature and a reverse recovery charge independent from temperature. The PiN diode reverse recovery charge is ×20 at 300°C compared to that of the Schottky diode. 55% of the stressed bipolar diodes at 20A show a very small forward voltage drift. Theswitching losses of these stressed diodes are reduced by 20%. Substrate quality enhancement makes large SiC component fabrication possible (25mm 2 Schottky diodes) and bipolar components show very small tension drift with temperature.

  • 26. Brosselard, P.
    et al.
    Camara, N.
    ul-Hassan, Jawad
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Jordà, X.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Montserrat, J.
    Millán, J.
    3.3 kV-10A 4H-SiC PiN diodes2009In: Materials Science Forum, Vols. 600-603, Trans Tech Publ. , 2009, p. 991-994Conference paper (Refereed)
    Abstract [en]

    An innovative process has been developed by Linköping University to prepare the 4HSiC substrate surface before epitaxial growth. The processed PiN diodes have been characterized in forward and reverse mode at different temperature. The larger diodes (2.56 mm2) have a very low leakage current around 20 nA @ 500V for temperatures up to 300°C. A performant yield (68%) was obtained on these larger diodes have a breakdown voltage superior to 500V. Electroluminescence characteristics have been done on these devices and they show that there is no generation of Stacking Faults during the bipolar conduction.

  • 27.
    Brosselard, P
    et al.
    Centre Nacl Microelect IMB CNM CSIC.
    Perez-Tomas, A
    Centre Nacl Microelect IMB CNM CSIC.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Camara, N
    Centre Nacl Microelect IMB CNM CSIC.
    Jorda, X
    Centre Nacl Microelect IMB CNM CSIC.
    Vellvehi, M
    Centre Nacl Microelect IMB CNM CSIC.
    Godignon, P
    Centre Nacl Microelect IMB CNM CSIC.
    Millan, J
    Centre Nacl Microelect IMB CNM CSIC.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Low loss, large area 4.5 kV 4H-SiC PIN diodes with reduced forward voltage drift2009In: SEMICONDUCTOR SCIENCE AND TECHNOLOGY, ISSN 0268-1242, Vol. 24, no 9, p. 095004-Article in journal (Refereed)
    Abstract [en]

    4H-SiC PIN diodes have been fabricated on a Norstel P+/N/N+ substrate with a combination of Mesa and JTE as edge termination. A breakdown voltage of 4.5 kV has been measured at 1 mu A for devices with an active area of 2.6 mm(2). The differential on-resistance at 15 A (600 A cm(-2)) was of only 1.7 m Omega cm(2) (25 degrees C) and 1.9 m Omega cm(2) at 300 degrees C. The reduced recovery charge was of 300 nC for a switched current of 15 A (500 V) at 300 degrees C. 20% of the diodes showed no degradation at all after 60 h of dc stress (25-225 degrees C). Other 30% of the diodes exhibit a reduced voltage shift below 1 V. For those diodes, the leakage current remains unaffected after the dc stress. Electroluminescence investigations reveal a very low density of stacking faults after the dc stress. The manufacturing yield evidences the efficiency of the substrate surface preparation and our technological process.

  • 28. Brosselard, P.
    et al.
    Tomas, A.P.
    Camara, N.
    ul-Hassan, Jawad
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Jorda, X.
    Vellvehi, M.
    Godignon, P.
    Millan, J.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    The effect of the temperature on the bipolar degradation of 3.3 kV 4H-SiC PiN diodes2008In: 20th International Symposium on Power Semiconductor Devices ICs,2008, Proceedings of the 20th International Symposium on Power Semiconductor Devices & ICs: Institute of Electrical and Electronics Engineers ( IEEE ) , 2008, p. 237-Conference paper (Refereed)
  • 29.
    Christle, David J.
    et al.
    University of Chicago, IL 60637 USA; University of Calif Santa Barbara, CA 93106 USA.
    Falk, Abram L.
    University of Chicago, IL 60637 USA.
    Andrich, Paolo
    University of Chicago, IL 60637 USA; University of Calif Santa Barbara, CA 93106 USA.
    Klimov, Paul V.
    University of Chicago, IL 60637 USA; University of Calif Santa Barbara, CA 93106 USA.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Tien Son, Nguyen
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ohshima, Takeshi
    Japan Atom Energy Agency, Japan.
    Awschalom, David D.
    University of Chicago, IL 60637 USA; University of Calif Santa Barbara, CA 93106 USA.
    Isolated electron spins in silicon carbide with millisecond coherence times2015In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 14, no 2, p. 160-163Article in journal (Refereed)
    Abstract [en]

    The elimination of defects from SiC has facilitated its move to the forefront of the optoelectronics and power-electronics industries(1). Nonetheless, because certain SiC defects have electronic states with sharp optical and spin transitions, they are increasingly recognized as a platform for quantum information and nanoscale sensing(2-16). Here, we show that individual electron spins in high-purity monocrystalline 4H-SiC can be isolated and coherently controlled. Bound to neutral divacancy defects(2,3), these states exhibit exceptionally long ensemble Hahn-echo spin coherence times, exceeding 1 ms. Coherent control of single spins in a material amenable to advanced growth and microfabrication techniques is an exciting route towards wafer-scale quantum technologies.

  • 30.
    Christle, David J.
    et al.
    University of Chicago, IL 60637 USA.
    Klimov, Paul V.
    University of Chicago, IL 60637 USA.
    de las Casas, Charles F.
    University of Chicago, IL 60637 USA.
    Szasz, Krisztian
    Hungarian Academic Science, Hungary.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Hungarian Academic Science, Hungary.
    Jokubavicius, Valdas
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Koehl, William F.
    University of Chicago, IL 60637 USA.
    Ohshima, Takeshi
    National Institute Quantum and Radiol Science and Technology, Japan.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Gali, Adam
    Hungarian Academic Science, Hungary; Budapest University of Technology and Econ, Hungary.
    Awschalom, David D.
    University of Chicago, IL 60637 USA.
    Isolated Spin Qubits in SiC with a High-Fidelity Infrared Spin-to-Photon Interface2017In: Physical Review X, E-ISSN 2160-3308, Vol. 7, no 2, article id 21046Article in journal (Refereed)
    Abstract [en]

    The divacancies in SiC are a family of paramagnetic defects that show promise for quantum communication technologies due to their long-lived electron spin coherence and their optical addressability at near-telecom wavelengths. Nonetheless, a high-fidelity spin-photon interface, which is a crucial prerequisite for such technologies, has not yet been demonstrated. Here, we demonstrate that such an interface exists in isolated divacancies in epitaxial films of 3C-SiC and 4H-SiC. Our data show that divacancies in 4H-SiC have minimal undesirable spin mixing, and that the optical linewidths in our current sample are already similar to those of recent remote entanglement demonstrations in other systems. Moreover, we find that 3C-SiC divacancies have a millisecond Hahn-echo spin coherence time, which is among the longest measured in a naturally isotopic solid. The presence of defects with these properties in a commercial semiconductor that can be heteroepitaxially grown as a thin film on Si shows promise for future quantum networks based on SiC defects.

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  • 31.
    Ciechonski, Rafal
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Structural instabilities in growth of SiC crystals2005In: Journal of Crystal Growth, ISSN 0022-0248, Vol. 275, no 1-2, p. e461-e466Article in journal (Refereed)
    Abstract [en]

    Misoriented grains, which may occur on the growth front of 6H–SiC boules have been studied in relation to their appearance during sublimation growth. The effect was obtained by applying growth conditions at which the source powder was gradually approaching graphitisation and the vapour becoming C-rich. The high off-orientation of the grains is demonstrated through etching in molten KOH and transmission light optical microscopy. Micropipes propagating in the single crystal area and facing the misoriented grain have been studied, and it is shown that they may either be terminated at the grain or their propagation is altered to be parallel with the grain boundary. It has been found that the polytype of the grains may switch from 6H to 4H, which is explained by the change of the Si/C ratio in the vapour.

  • 32.
    Cilibrizzi, Pasquale
    et al.
    Heriot Watt Univ, Scotland.
    Arshad, Muhammad Junaid
    Heriot Watt Univ, Scotland.
    Tissot, Benedikt
    Univ Konstanz, Germany.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Astner, Thomas
    Austrian Acad Sci, Austria.
    Koller, Philipp
    Austrian Acad Sci, Austria.
    Ghezellou, Misagh
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    White, Daniel
    Heriot Watt Univ, Scotland.
    Bekker, Christiaan
    Heriot Watt Univ, Scotland.
    Burkard, Guido
    Univ Konstanz, Germany.
    Trupke, Michael
    Austrian Acad Sci, Austria.
    Bonato, Cristian
    Heriot Watt Univ, Scotland.
    Ultra-narrow inhomogeneous spectral distribution of telecom-wavelength vanadium centres in isotopically-enriched silicon carbide2023In: Nature Communications, E-ISSN 2041-1723, Vol. 14, no 1, article id 8448Article in journal (Refereed)
    Abstract [en]

    Spin-active quantum emitters have emerged as a leading platform for quantum technologies. However, one of their major limitations is the large spread in optical emission frequencies, which typically extends over tens of GHz. Here, we investigate single V4+ vanadium centres in 4H-SiC, which feature telecom-wavelength emission and a coherent S = 1/2 spin state. We perform spectroscopy on single emitters and report the observation of spin-dependent optical transitions, a key requirement for spin-photon interfaces. By engineering the isotopic composition of the SiC matrix, we reduce the inhomogeneous spectral distribution of different emitters down to 100 MHz, significantly smaller than any other single quantum emitter. Additionally, we tailor the dopant concentration to stabilise the telecom-wavelength V4+ charge state, thereby extending its lifetime by at least two orders of magnitude. These results bolster the prospects for single V emitters in SiC as material nodes in scalable telecom quantum networks. Several solid-state defect platforms have been proposed for application as a spin-photon interface in quantum communication networks. Here the authors report spin-selective optical transitions and narrow inhomogeneous spectral distribution of V centers in isotopically-enriched SiC emitting in the telecom O-band.

  • 33.
    Civrac, Gabriel
    et al.
    University of Lyon, France .
    Laariedh, Farah
    University of Lyon, France .
    Thierry-jebali, Nicolas
    University of Lyon, France .
    Lazar, Mihai
    University of Lyon, France .
    Planson, Dominique
    University of Lyon, France .
    Brosselard, Pierre
    University of Lyon, France .
    ul Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vergne, Bertrand
    French-German Research Institute of Saint-Louis (ISL), France.
    Scharnholz, Sigo
    German Research Institute of Saint-Louis (ISL), France.
    600 V PiN diodes fabricated using on-axis 4H silicon carbide2012In: Materials Science Forum Vol 717 - 720, Trans Tech Publications Inc., 2012, Vol. 717-720, p. 969-972Conference paper (Refereed)
    Abstract [en]

    This paper reports the fabrication and electrical characterization of PiN diodes on an on-axis grown epitaxial layer. TCAD simulations have been performed in order to design their architecture. Some of these diodes have a breakdown voltage around 600 V. A comparison is made with similar diodes fabricated on off-cut grown layers. Computer simulations are used to explain lower breakdown voltages than those expected.

  • 34.
    de las Casas, Charles F.
    et al.
    University of Chicago, IL 60637 USA.
    Christle, David J.
    University of Chicago, IL 60637 USA.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ohshima, Takeshi
    National Institute Quantum and Radiol Science and Technology, Japan.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Awschalom, David D.
    University of Chicago, IL 60637 USA.
    Stark tuning and electrical charge state control of single divacancies in silicon carbide2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 111, no 26, article id 262403Article in journal (Refereed)
    Abstract [en]

    Neutrally charged divacancies in silicon carbide (SiC) are paramagnetic color centers whose long coherence times and near-telecom operating wavelengths make them promising for scalable quantum communication technologies compatible with existing fiber optic networks. However, local strain inhomogeneity can randomly perturb their optical transition frequencies, which degrades the indistinguishability of photons emitted from separate defects and hinders their coupling to optical cavities. Here, we show that electric fields can be used to tune the optical transition frequencies of single neutral divacancy defects in 4H-SiC over a range of several GHz via the DC Stark effect. The same technique can also control the charge state of the defect on microsecond timescales, which we use to stabilize unstable or non-neutral divacancies into their neutral charge state. Using fluorescence-based charge state detection, we show that both 975 nm and 1130 nm excitation can prepare their neutral charge state with near unity efficiency. (C) 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons. org/licenses/by/4.0/).

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  • 35.
    Dheilly, Nicolas
    et al.
    Université de Lyon, INSA-Lyon, Ampere UMR5005, Villeurbanne, France.
    Planson, Dominique
    Université de Lyon, INSA-Lyon, Ampere UMR5005, Villeurbanne, France.
    Brosselard, Pierre
    Centro Nacional de Microelectrónica, Campus UAB, Bellaterra, Spain.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Bevilacqua, Pascal
    Université de Lyon, INSA-Lyon, Ampere UMR5005, Villeurbanne, France.
    Tournier, Dominique
    Université de Lyon, INSA-Lyon, Ampere UMR5005, Villeurbanne, France.
    Montserrat, Josep
    Centro Nacional de Microelectrónica, Campus UAB, Bellaterra, Spain.
    Raynaud, Christophe
    Université de Lyon, INSA-Lyon, Ampere UMR5005, Villeurbanne, France.
    Morel, Hervé
    Université de Lyon, INSA-Lyon, Ampere UMR5005, Villeurbanne, France.
    Measurement of Carrier Lifetime Temperature Dependence in 3.3kV 4H-SiC PiN Diodes Using OCVD Technique2009In: Silicon Carbide and Related Materials 2008, Trans Tech Publications Ltd , 2009, Vol. 615, p. 703-706Conference paper (Refereed)
    Abstract [en]

    This paper reports on the influence of temperature on the electrical carrier lifetime of a 3.3 kV 4H-SiC PiN diode processed with a new generation of SiC material. The Open Circuit Voltage Decay (OCVD) is used to evaluate ambipolar lifetime evolution versus temperature. The paper presents a description of the setup, electrical measurements and extraction fittings. The ambipolar lifetime is found to rise from 600 ns at 30 °C to 3.5 μs at 150 °C.

  • 36.
    Etzelmueller Bathen, Marianne
    et al.
    Univ Oslo, Norway.
    Linnarsson, Margareta
    KTH Royal Inst Technol, Sweden.
    Ghezellou, Misagh
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Vines, Lasse
    Univ Oslo, Norway.
    Influence of Carbon Cap on Self-Diffusion in Silicon Carbide2020In: Crystals, ISSN 2073-4352, Vol. 10, no 9, article id 752Article in journal (Refereed)
    Abstract [en]

    Self-diffusion of carbon (C-12 and C-13) and silicon (Si-28 and Si-30) in 4H silicon carbide has been investigated by utilizing a structure containing an isotope purified 4H-(SiC)-Si-28-C-12 epitaxial layer grown on an n-type (0001) 4H-SiC substrate, and finally covered by a carbon capping layer (C-cap). The C-13 and Si-30 isotope profiles were monitored using secondary ion mass spectrometry (SIMS) following successive heat treatments performed at 2300-2450 degrees C in Ar atmosphere using an inductively heated furnace. The 30Si profiles show little redistribution within the studied temperature range, with the extracted diffusion lengths for Si being within the error bar for surface roughening during annealing, as determined by profilometer measurements. On the other hand, a significant diffusion of C-13 was observed into the isotope purified layer from both the substrate and the C-cap. A diffusivity of D=8.3x106e(-10.4/kBT) cm(2)/s for C-13 was extracted, in contrast to previous findings that yielded lower both pre-factors and activation energies for C self-diffusion in SiC. The discrepancy between the present measurements and previous theoretical and experimental works is ascribed to the presence of the C-cap, which is responsible for continuous injection of C interstitials during annealing, and thereby suppressing the vacancy mediated diffusion.

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  • 37.
    Frewin, Christopher L.
    et al.
    University of Texas Dallas, TX 75080 USA.
    Bernardin, Evans
    University of S Florida, FL 33612 USA.
    Deku, Felix
    University of Texas Dallas, TX 75080 USA.
    Everly, Richard
    USF, FL 33617 USA.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Pancrazio, Joseph J.
    University of Texas Dallas, TX 75080 USA.
    Saddow, Stephen E.
    University of S Florida, FL 33612 USA.
    Silicon Carbide As a Robust Neural Interface (Invited)2016In: GALLIUM NITRIDE AND SILICON CARBIDE POWER TECHNOLOGIES 6, ELECTROCHEMICAL SOC INC , 2016, Vol. 75, no 12, p. 39-45Conference paper (Refereed)
    Abstract [en]

    The intracortical neural interface (INI) could be a key component of brain machine interfaces (BMI), devices which offer the possibility of restored physiological neurological functionality for patients suffering from severe trauma to the central or peripheral nervous system. Unfortunately the main components of the INI, microelectrodes, have not shown appropriate long-term reliability due to multiple biological, material, and mechanical issues. Silicon carbide (SiC) is a semiconductor that is completely chemically inert within the physiological environment and can be micromachined using the same methods as with Si microdevices. We are proposing that a SiC material system may provide the improved longevity and reliability for INI devices. The design, fabrication, and preliminary electrical and electrochemical testing of an all-SiC prototype microelectrode array based on 4H-SiC, with an amorphous silicon carbide (a-SiC) insulator, is described. The fabrication of the planar microelectrode was performed utilizing a series of conventional micromachining steps. Preliminary electrochemical data are presented which show that these prototype electrodes display suitable performance.

  • 38.
    Ghezellou, Misagh
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Kumar, Piyush
    Advanced Power Semiconductor Laboratory, ETH Zürich, 8092 Zürich, Switzerland.
    Bathen, Marianne E.
    Advanced Power Semiconductor Laboratory, ETH Zürich, 8092 Zürich, Switzerland.
    Karsthof, Robert
    Department of Physics, University of Oslo, 0316 Oslo, Norway.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Science Institute, University of Iceland, IS-107 Reykjavík, Iceland.
    Grossner, Ulrike
    Advanced Power Semiconductor Laboratory, ETH Zürich, 8092 Zürich, Switzerland.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Vines, Lasse
    Department of Physics, University of Oslo, 0316 Oslo, Norway.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    The role of boron related defects in limiting charge carrier lifetime in 4H–SiC epitaxial layers2023In: APL Materials, E-ISSN 2166-532X, Vol. 11, no 3, article id 031107Article in journal (Refereed)
    Abstract [en]

    One of the main challenges in realizing 4H–SiC (silicon carbide)-based bipolar devices is the improvement of minority carrier lifetime in as-grown epitaxial layers. Although Z1/2 has been identified as the dominant carrier lifetime limiting defect, we report on B-related centers being another dominant source of recombination and acting as lifetime limiting defects in 4H–SiC epitaxial layers. Combining time-resolved photoluminescence (TRPL) measurement in near band edge emission and 530 nm, deep level transient spectroscopy, and minority carrier transient spectroscopy (MCTS), it was found that B related deep levels in the lower half of the bandgap are responsible for killing the minority carriers in n-type, 4H–SiC epitaxial layers when the concentration of Z1/2 is already low. The impact of these centers on the charge carrier dynamics is investigated by correlating the MCTS results with temperature-dependent TRPL decay measurements. It is shown that the influence of shallow B acceptors on the minority carrier lifetime becomes neutralized at temperatures above ∼422 K. Instead, the deep B related acceptor level, known as the D-center, remains active until temperatures above ∼570 K. Moreover, a correlation between the deep level concentrations, minority carrier lifetimes, and growth parameters indicates that intentional nitrogen doping hinders the formation of deep B acceptor levels. Furthermore, tuning growth parameters, including growth temperature and C/Si ratio, is shown to be crucial for improving the minority carrier lifetime in as-grown 4H–SiC epitaxial layers.

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  • 39.
    Ghezellou, Misagh
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Influence of Different Hydrocarbons on Chemical Vapor Deposition Growth and Surface Morphological Defects in 4H‐SiC Epitaxial Layers2024In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951Article in journal (Refereed)
    Abstract [en]

    Controlled epitaxial growth of 4H-SiC is essential for advancing both power electronics and quantum technologies. This study explores how different carbon sources—methane and propane—affect the surface morphology of these epitaxial layers. By varying C/Si ratios and using the two mentioned hydrocarbons as the carbon source in chloride-based epitaxial growth of 4H-SiC layers, it is unveiled that methane results in an exceptionally smooth surface. However, it pronounces surface irregularities such as short step bunching and dislocation-related etch pits. Moreover, methane amplifies the overgrowth of triangular defects with the 4H polytype. In contrast, the introduction of propane causes a step-bunched surface together with inclined line-like surface morphological defects. Notably, a majority of the triangular defects exhibit a pure 3C character without an overgrown 4H polytype. It is shown that these outcomes could be attributed to different sticking coefficients and diffusivity of the molecular species resulting from different carbon sources on the 4H-SiC surface during the epitaxial growth. This research also uncovers the underlying origins and mechanisms responsible for various surface morphological defects.

  • 40.
    Gogova, Daniela
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ghezellou, Misagh
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Tran, Dat Q.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Richter, Steffen
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Solid State Physics and NanoLund, Lund University, P. O. Box 118, 221 00 Lund, Sweden.
    Papamichail, Alexis
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Persson, Axel R.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kordina, Olof
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Hilfiker, Matthew
    Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA.
    Paskov, Plamen P.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Solid State Physics and NanoLund, Lund University, P. O. Box 118, 221 00 Lund, Sweden.
    Epitaxial growth of β-Ga2O3 by hot-wall MOCVD2022In: AIP Advances, E-ISSN 2158-3226, Vol. 12, no 5, article id 055022Article in journal (Refereed)
    Abstract [en]

    The hot-wall metalorganic chemical vapor deposition (MOCVD) concept, previously shown to enable superior material quality and high performance devices based on wide bandgap semiconductors, such as Ga(Al)N and SiC, has been applied to the epitaxial growth of beta-Ga2O3. Epitaxial beta-Ga2O3 layers at high growth rates (above 1 mu m/h), at low reagent flows, and at reduced growth temperatures (740 degrees C) are demonstrated. A high crystalline quality epitaxial material on a c-plane sapphire substrate is attained as corroborated by a combination of x-ray diffraction, high-resolution scanning transmission electron microscopy, and spectroscopic ellipsometry measurements. The hot-wall MOCVD process is transferred to homoepitaxy, and single-crystalline homoepitaxial beta-Ga2O3 layers are demonstrated with a 201 rocking curve width of 118 arc sec, which is comparable to those of the edge-defined film-fed grown (201) beta-Ga2O3 substrates, indicative of similar dislocation densities for epilayers and substrates. Hence, hot-wall MOCVD is proposed as a prospective growth method to be further explored for the fabrication of beta-Ga2O3.

  • 41.
    Hassan, Jawad
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lilja, Louise
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Booker, Ian Don
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Influence of Growth Mechanism on Carrier Lifetime in on-axis Homoepitaxial Layers of 4H-SiC2012In: Materials Science Forum Vols 717 - 720, Trans Tech Publications Inc., 2012, Vol. 717-720, p. 157-160Conference paper (Refereed)
    Abstract [en]

    In this report we present homoepitaxial growth of 4H-SiC on Si-face, nominally on-axis substrates with diameters up to 76 mm in a hot-wall chemical vapor deposition reactor. A comparatively low carrier lifetime has been observed in these layers; local variations in carrier lifetime are different from standard epilayers on off-cut substrates. The properties of the layers were studied with focus on charge carrier lifetime and its correlation with starting growth conditions, inhomogeneities of surface morphology and different growth mechanisms.

  • 42.
    Hassan, Jawad
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Scajev, Patrik
    Institute of Applied Research, Vilnius University, Vilnius, Lithuania.
    Jarasiunas, Kestutis
    Institute of Applied Research, Vilnius University, Vilnius, Lithuania.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Optically Detected Temperature Dependences of Carrier Lifetime and Diffusion Coefficient in 4H- and 3C-SiC2011In: Materials Science Forum (Volumes 679 - 680), Trans Tech Publications Inc., 2011, p. 205-208Conference paper (Refereed)
    Abstract [en]

    Free carrier dynamics has been studied in 4H- and 3C-SiC in a wide temperature range using time-resolved photoluminescence, free carrier absorption, and light induced transient grating techniques. Considerably high carrier lifetime was observed in 3C-SiC epitaxial layers grown on 4H-SiC substrates using hot-wall CVD with respect to previously reported values for 3C-SiC grown either on Si or on 6H-SiC substrates. The temperature dependences of carrier lifetime and diffusion coefficient for 4H- and 3C-SiC were compared. Shorter photoluminescence decay time with respect to free carrier absorption decay time was observed in the same 4H-SiC sample, while these techniques revealed similar trends in the carrier lifetime temperature dependencies. However, the latter dependences for hot-wall CVD-grown 3C layers were found different if measured by time resolved photoluminescence and free carrier absorption techniques.

  • 43.
    Heiler, Jonah
    et al.
    Univ Stuttgart, Germany; Luxembourg Inst Sci & Technol LIST, Luxembourg; Univ Luxembourg, Luxembourg.
    Koerber, Jonathan
    Univ Stuttgart, Germany.
    Hesselmeier, Erik
    Univ Stuttgart, Germany.
    Kuna, Pierre
    Univ Stuttgart, Germany.
    Stoehr, Rainer
    Univ Stuttgart, Germany.
    Fuchs, Philipp
    Univ Saarland, Germany.
    Ghezellou, Misagh
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Knolle, Wolfgang
    Leibniz Inst Surface Engn IOM, Germany.
    Becher, Christoph
    Univ Saarland, Germany.
    Kaiser, Florian
    Univ Stuttgart, Germany; Luxembourg Inst Sci & Technol LIST, Luxembourg; Univ Luxembourg, Luxembourg.
    Wrachtrup, Joerg
    Univ Stuttgart, Germany; Max Planck Inst Solid State Res, Germany.
    Spectral stability of V2 centres in sub-micron 4H-SiC membranes2024In: NPJ QUANTUM MATERIALS, ISSN 2397-4648, Vol. 9, no 1, article id 34Article in journal (Refereed)
    Abstract [en]

    Colour centres in silicon carbide emerge as a promising semiconductor quantum technology platform with excellent spin-optical coherences. However, recent efforts towards maximising the photonic efficiency via integration into nanophotonic structures proved to be challenging due to reduced spectral stabilities. Here, we provide a large-scale systematic investigation on silicon vacancy centres in thin silicon carbide membranes with thicknesses down to 0.25 mu m. Our membrane fabrication process involves a combination of chemical mechanical polishing, reactive ion etching, and subsequent annealing. This leads to highly reproducible membranes with roughness values of 3-4 A, as well as negligible surface fluorescence. We find that silicon vacancy centres show close-to lifetime limited optical linewidths with almost no signs of spectral wandering down to membrane thicknesses of similar to 0.7 mu m. For silicon vacancy centres in thinner membranes down to 0.25 mu m, we observe spectral wandering, however, optical linewidths remain below 200 MHz, which is compatible with spin-selective excitation schemes. Our work clearly shows that silicon vacancy centres can be integrated into sub-micron silicon carbide membranes, which opens the avenue towards obtaining the necessary improvements in photon extraction efficiency based on nanophotonic structuring.

  • 44.
    Heiler, Jonah
    et al.
    Univ Stuttgart, Germany; Luxembourg Inst Sci & Technol LIST, Luxembourg; Univ Luxembourg, Luxembourg.
    Korber, Jonathan
    Univ Stuttgart, Germany.
    Hesselmeier, Erik
    Univ Stuttgart, Germany.
    Kuna, Pierre
    Univ Stuttgart, Germany.
    Stohr, Rainer
    Univ Stuttgart, Germany.
    Fuchs, Philipp
    Univ Saarland, Germany.
    Ghezellou, Misagh
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Knolle, Wolfgang
    Leibniz Inst Surface Engn IOM, Germany.
    Becher, Christoph
    Univ Saarland, Germany.
    Kaiser, Florian
    Univ Stuttgart, Germany; Luxembourg Inst Sci & Technol LIST, Luxembourg; Univ Luxembourg, Luxembourg.
    Wrachtrup, Jorg
    Univ Stuttgart, Germany; Max Planck Inst Solid State Res, Germany.
    Correction: Spectral stability of V2 centres in sub-micron 4H-SiC membranes (vol 9, 34, 2024)2024In: NPJ QUANTUM MATERIALS, ISSN 2397-4648, Vol. 9, no 1, article id 39Article in journal (Other academic)
  • 45.
    Henry, Anne
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Leone, Stefano
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kordina, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, J. Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Epitaxial growth on on-axis substrates2012In: Silicon Carbide Epitaxy / [ed] Francesco La Via, Kerala, India: Research Signpost, 2012, p. 97-119Chapter in book (Refereed)
    Abstract [en]

    SiC epitaxial growth using the Chemical Vapour Deposition (CVD) technique on nominally on-axis substrate is presented. Both standard and chloride-based chemistry have been used with the aim to obtain high quality layers suitable for device fabrication. Both homoepitaxy (4H on 4H) and heteroepitaxy (3C on hexag onal substrate) are addressed.

    Download full text (pdf)
    Epitaxial growth on on-axis substrates
  • 46.
    Henry, Anne
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    ul-Hassan, Jawad
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Hallin, Christer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Thick Silicon Carbide Homoepitaxial Layers Grown by CVD Techniques2006In: Chemical Vapor Deposition, ISSN 0948-1907, E-ISSN 1521-3862, Vol. 12, no 8-9, p. 475-482Article in journal (Refereed)
  • 47.
    Henry, Anne
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Beyer, Franziska
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Andersson, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Godignon, P.
    Thick epilayers for power devices2007In: Materials Science Forum, vol. 556-557, Trans Tech Publications , 2007, p. 47-Conference paper (Refereed)
    Abstract [en]

    Growth of thick epitaxial SiC layers needed for high power devices is presented for horizontal hot-wall CVD (HWCVD) reactors. We demonstrate thickness of epilayer of 100 μm and more with good morphology, low-doping with no doping variation through the whole thick layer and reasonable carrier lifetime which mainly depends on the substrate quality. Typical epidefects are described and their density can dramatically be reduced when choosing correctly the growth conditions as well as the polishing of the surface prior to the growth. The control of the doping and thickness uniformities as well as the run-to-run reproducibility is also presented. Various characterization techniques such as optical microscopy, AFM, reflectance, CV, PL and minority carrier lifetime have been used. Results of high-voltage SiC Schottky power devices are presented.

  • 48.
    Hesselmeier, Erik
    et al.
    3rd Institute of Physics, IQST, and Research Centre SCoPE, University of Stuttgart, Stuttgart, Germany.
    Kuna, Pierre
    3rd Institute of Physics, IQST, and Research Centre SCoPE, University of Stuttgart, Stuttgart, Germany.
    Takács, István
    Eötvös Loránd University, Egyetem tér 1-3, Budapest, H-1053, Hungary; Eötvös Loránd University, Egyetem tér 1-3, Budapest, H-1053, Hungary.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Eötvös Loránd University, Egyetem tér 1-3, Budapest, H-1053, Hungary; Eötvös Loránd University, Egyetem tér 1-3, Budapest, H-1053, Hungary.
    Knolle, Wolfgang
    Department of Sensoric Surfaces and Functional Interfaces, Leibniz-Institute of Surface Engineering (IOM), Permoserstraße 15, Leipzig, 04318, Germany.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ghezellou, Misagh
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Dasari, Durga
    3rd Institute of Physics, IQST, and Research Centre SCoPE, University of Stuttgart, Stuttgart, Germany.
    Kaiser, Florian
    Materials Research and Technology (MRT) Department, Luxembourg Institute of Science and Technology (LIST), Belvaux, 4422, Luxembourg; University of Luxembourg, 41 rue du Brill, Belvaux, L-4422, Luxembourg.
    Vorobyov, Vadim
    3rd Institute of Physics, IQST, and Research Centre SCoPE, University of Stuttgart, Stuttgart, Germany.
    Wrachtrup, Jörg
    3rd Institute of Physics, IQST, and Research Centre SCoPE, University of Stuttgart, Stuttgart, Germany; Max Planck Institute for solid state physics, Heisenbergstraße 1, Stuttgart, 70569, Germany.
    Qudit-Based Spectroscopy for Measurement and Control of Nuclear-Spin Qubits in Silicon Carbide2024In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 132, no 9, article id 090601Article in journal (Refereed)
    Abstract [en]

    Nuclear spins with hyperfine coupling to single electron spins are highly valuable quantum bits. Here we probe and characterize the particularly rich nuclear-spin environment around single silicon vacancy color centers (V2) in 4H-SiC. By using the electron spin-3/2 qudit as a four level sensor, we identify several sets of Si29 and C13 nuclear spins through their hyperfine interaction. We extract the major components of their hyperfine coupling via optical detected nuclear magnetic resonance, and assign them to shells in the crystal via the density function theory simulations. We utilize the ground-state level anticrossing of the electron spin for dynamic nuclear polarization and achieve a nuclear-spin polarization of up to 98±6%. We show that this scheme can be used to detect the nuclear magnetic resonance signal of individual spins and demonstrate their coherent control. Our work provides a detailed set of parameters and first steps for future use of SiC as a multiqubit memory and quantum computing platform.

  • 49.
    Ivanov, Ivan Gueorguiev
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ul Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Zakharov, Alexei A.
    Lund University, Sweden .
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Layer-number determination in graphene on SiC by reflectance mapping2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 77, p. 492-500Article in journal (Refereed)
    Abstract [en]

    We report a simple, handy and affordable optical approach for precise number-of-layers determination of graphene on SiC based on monitoring the power of the laser beam reflected from the sample (reflectance mapping) in a slightly modified micro-Raman setup. Reflectance mapping is compatible with simultaneous Raman mapping. We find experimentally that the reflectance of graphene on SiC normalized to the reflectivity of bare substrate (the contrast) increases linearly with similar to 1.7% per layer for up to 12 layers, in agreement with theory The wavelength dependence of the contrast in the visible is investigated using the concept of ideal fermions and compared with existing experimental data for the optical constants of graphene. We argue also that the observed contrast is insensitive to the doping condition of the sample, as well as to the type of sample (graphene on C- or Si-face of 4H or 6H SiC, hydrogen-intercalated graphene). The possibility to extend the precise layer counting to similar to 50 layers makes reflectivity mapping superior to low-energy electron microscopy (limited to similar to 10 layers) in quantitative evaluation of graphene on the C-face of SiC. The method is applicable for graphene on other insulating or semiconducting substrates.

    Download full text (pdf)
    Layer-number determination in graphene on SiC by reflectance mapping
  • 50.
    Ivanov, Ivan Gueorguiev
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    ul-Hassan, Jawad
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Henry, Anne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Temperature Dependence and Selective Excitation of the Phosphorus Related Photoluminescence in 4H-SiC2009In: Materials Science Forum, Vols. 615-617, Trans Tech Publications , 2009, p. 263-266Conference paper (Refereed)
    Abstract [en]

    The paper presents experimental data on the temperature dependence and the excitation properties of the phosphorus-related photoluminescence in 4H SiC. Two main sets of phonon replicas can be observed with selective excitation, which are attributed to two of the no-phonon lines observed in the spectrum. Some of the excited states are also attributed to one of the no-phonon lines on the ground of the selectively excited spectra. A tentative explanation of the observed features in terms of multiple bound excitons is proposed.

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