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  • 1.
    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.

  • 2.
    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: ECS Transactions, ISSN 1938-5862, E-ISSN 1938-6737, ECS Transactions, Vol. 86, no 12, p. 91-97Article in journal (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.

  • 3.
    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.

  • 4.
    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.

  • 5.
    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.

  • 6.
    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, 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.

  • 7.
    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, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 9, no 9, article id 451Article in journal (Refereed)
    Abstract [en]

    n/a

  • 8.
    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, ISSN 2072-666X, 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.

  • 9.
    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.

  • 10.
    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.

  • 11.
    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.

  • 12.
    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.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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.

  • 16.
    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.

  • 17.
    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.

  • 18.
    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.

  • 19. 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.

  • 20.
    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.

  • 21. 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)
  • 22.
    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.

  • 23.
    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, ISSN 2160-3308, 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.

  • 24.
    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.

  • 25.
    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.

  • 26.
    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/).

  • 27.
    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.

  • 28.
    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.

  • 29.
    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.

  • 30.
    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.

  • 31.
    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.

  • 32.
    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)
  • 33.
    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.

  • 34.
    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.

  • 35.
    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.

  • 36.
    Ivanov, Ivan Gueorguiev
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yazdanfar, Milan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lundqvist, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Chen, Jr-Tai
    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.
    Stenberg, Pontus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Liljedahl, Rickard
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Son, Nguyen Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ager, Joel W. III
    Lawrence Berkeley National Laboratory, Berkeley, California, USA.
    Kordina, Olle
    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.
    High-Resolution Raman and Luminescence Spectroscopy of Isotope-Pure (SiC)-Si-28-C-12, Natural and C-13 - Enriched 4H-SIC2014In: Silicon Carbide and Related Materials 2013, PTS 1 AND 2, Trans Tech Publications Inc., 2014, Vol. 778-780, p. 471-474Conference paper (Refereed)
    Abstract [en]

    The optical properties of isotope-pure (SiC)-Si-28-C-12, natural SiC and enriched with C-13 isotope samples of the 4H polytype are studied by means of Raman and photoluminescence spectroscopies. The phonon energies of the Raman active phonons at the Gamma point and the phonons at the M point of the Brillouin zone are experimentally determined. The excitonic bandgaps of the samples are accurately derived using tunable laser excitation and the phonon energies obtained from the photoluminescence spectra. Qualitative comparison with previously reported results on isotope-controlled Si is presented.

  • 37.
    Janzén, Erik
    et al.
    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.
    Danielsson, Örjan
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Forsberg, Urban
    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.
    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.
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Kakanakova-Gueorguie, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Persson, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Wahab, Qamar Ul
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    SiC and III-nitride Growth in a Hot-wall CVD Reactor2005In: Materials Science Forum, ISSN 0255-5476, volume 483-485, Trans Tech Publications , 2005, Vol. 483-485, p. 61-66Conference paper (Refereed)
  • 38.
    Johansson, Leif
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Xia, Chao
    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.
    Zarharov, Alexei A.
    MAX-lab, Lund University, Lund 22100, Sweden.
    Watcharinyanon, Somsakul
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositza
    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.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Is the Registry Between Adjacent Graphene Layers Grown on C-Face SiC Different Compared to That on Si-Face SiC2013In: Crystals, ISSN 2073-4352, Vol. 3, no 1, p. 1-13Article in journal (Refereed)
    Abstract [en]

    Graphene grown on C-face SiC substrates using two procedures, high and low growth temperature and different ambients, was investigated using Low Energy Electron Microscopy (LEEM), X-ray Photo Electron Electron Microscopy (XPEEM), selected area Low Energy Electron Diffraction (μ-LEED) and selected area Photo Electron Spectroscopy (μ-PES). Both types of samples showed formation of μm-sized grains of graphene. The sharp (1 × 1) μ-LEED pattern and six Dirac cones observed in constant energy photoelectron angular distribution patterns from a grain showed that adjacent layers are not rotated relative to each other, but that adjacent grains in general have different azimuthal orientations. Diffraction spots from the SiC substrate appeared in μ-LEED patterns collected at higher energies, showing that the rotation angle between graphene and SiC varied. C 1s spectra collected did not show any hint of a carbon interface layer. A hydrogen treatment applied was found to have a detrimental effect on the graphene quality for both types of samples, since the graphene domain/grain size was drastically reduced. From hydrogen treated samples, μ-LEED showed at first a clear (1 × 1) pattern, but within minutes, a pattern containing strong superstructure spots, indicating the presence of twisted graphene layers. The LEED electron beam was found to induce local desorption of hydrogen. Heating a hydrogenated C-face graphene sample did not restore the quality of the original as-grown sample.

  • 39.
    Kallinger, B.
    et al.
    Fraunhofer IISB, Erlangen, Germany.
    Rommel, M.
    Fraunhofer IISB, Erlangen, Germany.
    Lilja, Louise
    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.
    Booker, Ian Don
    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.
    Comparison of carrier lifetime measurements and mapping in 4H SIC using time resolved photoluminescence and μ-PCD2014In: SILICON CARBIDE AND RELATED MATERIALS 2013, PTS 1 AND 2, Stafa-Zurich, Switzerland: Trans Tech Publications , 2014, Vol. 778-780, p. 301-304Conference paper (Refereed)
    Abstract [en]

    Carrier lifetime measurements and wafer mappings have been done on several different 4H SiC epiwafers to compare two different measurement techniques, time-resolved photoluminescence and microwave induced photoconductivity decay. The absolute values of the decay time differ by a factor of two, as expected from recombination and measurement theory. Variations within each wafer are comparable with the two techniques. Both techniques are shown to be sensitive to substrate quality and distribution of extended defects.

  • 40.
    Karhu, Robin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Booker, Ian
    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.
    Janzén, Erik
    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.
    Long Charge Carrier Lifetime in As-Grown 4H-SiC Epilayer2016In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 858, p. 125-128Article in journal (Refereed)
    Abstract [en]

    Over 150 μm thick epilayers of 4H-SiC with long carrier lifetime have been grown with a chlorinated growth process. The carrier lifetime have been determined by time resolved photoluminescence (TRPL), the lifetime varies a lot between different areas of the sample. This study investigates the origins of lifetime variations in different regions using deep level transient spectroscopy (DLTS), low temperature photoluminescence (LTPL) and a combination of KOH etching and optical microscopy. From optical microscope images it is shown that the area with the shortest carrier lifetime corresponds to an area with high density of structural defects.

  • 41.
    Karhu, Robin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Booking, Ian
    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.
    Ivanov, Ivan
    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.
    The Role of Chlorine during High Growth Rate Epitaxy2015In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 821-823, p. 141-144Article in journal (Refereed)
    Abstract [en]

    The influence of chlorine has been investigated for high growth rates of 4H-SiC epilayers on 4o off-cut substrates. Samples were grown at a growth rate of approximately 50 and 100 μm/h and various Cl/Si ratios. The growth rate, net doping concentration and charge carrier lifetime have been studied as a function of Cl/Si ratio. This study shows some indications that a high Cl concentration in the growth cell leads to less availability of Si during the growth process.

  • 42.
    Karhu, Robin
    et al.
    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. Univ Iceland, Iceland.
    Magnusson, Bjorn
    Norstel AB, Sweden.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Danielsson, Örjan
    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.
    CVD growth and properties of on-axis vanadium doped semi-insulating 4H-SiC epilayers2019In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 125, no 4, article id 045702Article in journal (Refereed)
    Abstract [en]

    Highly resistive homoepitaxial layers of 4H-SiC have been grown on the Si-face of nominally on-axis, n-type substrates using chemical vapor deposition. Vanadium tetrachloride has been used as the V-dopant which is responsible for the high resistivity of the epilayers. 100% 4H-polytype was reproduced in the epilayers using the optimized on-axis growth process. The upper limit of vanadium tetrachloride flow rate was also established to achieve high resistivity epilayers free of 3C polytype inclusion. A resistivity of more than 1 x 10(5) Omega cm has been achieved in epilayers with a very low concentration of V (1 x 10(15) cm(-3)). Owing to the low concentration of V, superior epilayer structural quality was achieved compared to V-doped and standard high purity semi-insulating bulk grown material of similar resistivity. Epitaxial layers with varying vanadium tetrachloride flow have also been grown to study the influence of V concentration on the polytype stability, structural quality, and optical and electrical properties of epilayers. A clear correspondence has been observed in the flow-rates of vanadium tetrachloride, the atomic concentration of V, and electrical, optical, and structural properties of epilayers. Published under license by AIP Publishing.

  • 43.
    Khosa, R. Y.
    et al.
    Univ Iceland, Iceland; Univ Educ Lahore, Pakistan.
    Chen, Jr-Tai
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Pålsson, K.
    Univ Iceland, Iceland.
    Karhu, Robin
    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.
    Rorsman, N.
    Chalmers Univ Technol, Sweden.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Univ Iceland, Iceland.
    Electrical properties of 4H-SiC MIS capacitors with AlN gate dielectric grown by MOCVD2019In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 153, p. 52-58Article in journal (Refereed)
    Abstract [en]

    We report on the electrical properties of the AlN/4H-SiC interface using capacitance- and conductance-voltage (CV and GV) analysis of AlN/SiC MIS capacitors. The crystalline AlN layers are made by hot wall MOCVD. CV analysis at room temperature reveals an order of magnitude lower density of interface traps at the AlN/SiC interface than at nitrided SiO2/SiC interfaces. Electron trapping in bulk traps within the AlN is significant when the MIS capacitors are biased into accumulation resulting in a large flatband voltage shift towards higher gate voltage. This process is reversible and the electrons are fully released from the AlN layer if depletion bias is applied at elevated temperatures. Current-voltage (IV) analysis reveals that the breakdown electric field intensity across the AlN dielectric is 3-4 MV/cm and is limited by trap assisted leakage. By depositing an additional SiO2 layer on top of the AlN layer, it is possible to increase the breakdown voltage of the MIS capacitors significantly without having much impact on the quality of the AlN/SiC interface.

  • 44.
    Khosa, R. Y.
    et al.
    Univ Iceland, Iceland; Univ Educ Lahore, Pakistan.
    Chen, Jr-Tai
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Winters, M.
    Chalmers Univ Technol, Sweden.
    Palsson, K.
    Univ Iceland, Iceland.
    Karhu, Robin
    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.
    Rorsman, N.
    Chalmers Univ Technol, Sweden.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Univ Iceland, Iceland.
    Electrical characterization of high k-dielectrics for 4H-SiC MIS devices2019In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 98, p. 55-58Article in journal (Refereed)
    Abstract [en]

    We report promising results regarding the possible use of AlN or Al2O3 as a gate dielectric in 4H-SiC MISFETs. The crystalline AlN films are grown by hot wall metal organic chemical vapor deposition (MOCVD) at 1100 degrees C. The amorphous Al2O3 films are grown by repeated deposition and subsequent low temperature (200 degrees C) oxidation of thin Al layers using a hot plate. Our investigation shows a very low density of interface traps at the AlN/4H-SiC and the Al2O3/4H-SiC interface estimated from capacitance-voltage (CV) analysis of MIS capacitors. Current-voltage (IV) analysis shows that the breakdown electric field across the AlN or Al2O3 is similar to 3 MV/cm or similar to 5 MV/cm respectively. By depositing an additional SiO2 layer by plasma enhanced chemical vapor deposition at 300 degrees C on top of the AlN or Al2O3 layers, it is possible to increase the breakdown voltage of the MIS capacitors significantly without having pronounced impact on the quality of the AlN/SiC or Al2O3/SiC interfaces.

  • 45.
    Khosa, R. Y.
    et al.
    Univ Iceland, Iceland.
    Thorsteinsson, E. B.
    Univ Iceland, Iceland.
    Winters, M.
    Chalmers Univ Technol, Sweden.
    Rorsman, N.
    Chalmers Univ Technol, Sweden.
    Karhu, Robin
    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.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Univ Iceland, Iceland.
    Electrical characterization of amorphous Al2O3 dielectric films on n-type 4H-SiC2018In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 8, no 2, article id 025304Article in journal (Refereed)
    Abstract [en]

    We report on the electrical properties of Al2O3 films grown on 4H-SiC by successive thermal oxidation of thin Al layers at low temperatures (200 degrees C - 300 degrees C). MOS capacitors made using these films contain lower density of interface traps, are more immune to electron injection and exhibit higher breakdown field (5MV/cm) than Al2O3 films grown by atomic layer deposition (ALD) or rapid thermal processing (RTP). Furthermore, the interface state density is significantly lower than in MOS capacitors with nitrided thermal silicon dioxide, grown in N2O, serving as the gate dielectric. Deposition of an additional SiO2 film on the top of the Al2O3 layer increases the breakdown voltage of the MOS capacitors while maintaining low density of interface traps. We examine the origin of negative charges frequently encountered in Al2O3 films grown on SiC and find that these charges consist of trapped electrons which can be released from the Al2O3 layer by depletion bias stress and ultraviolet light exposure. This electron trapping needs to be reduced if Al2O3 is to be used as a gate dielectric in SiC MOS technology. (c) 2018 Author(s).

  • 46.
    Khosa, Rabia Y.
    et al.
    Science Institute, University of Iceland, Iceland.
    Chen, J. T.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Pálsson, K.
    Science Institute, University of Iceland, Iceland.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Rorsman, Niklas
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, Sweden.
    Sveinbjörnsson, Einar Ö.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Science Institute, University of Iceland, Iceland.
    Electrical Characterization of MOCVD Grown Single Crystalline AlN Thin Films on 4H-SiC2019In: Silicon Carbide and Related Materials 2018, Trans Tech Publications Ltd , 2019, Vol. 963, p. 460-464Conference paper (Refereed)
    Abstract [en]

    We report on a very low density of interface traps at the AlN/4H-SiC interface estimated from capacitance-voltage (CV) analysis of metal-insulator-semiconductor (MIS) capacitors. Single crystalline aluminum nitride (AlN) films are grown by metal organic chemical vapor deposition (MOCVD). Current-voltage (IV) analysis shows that the breakdown electric field across the AlN dielectric is 3 MV/cm. By depositing an additional SiO2 layer on top of the AlN layer it is possible to increase the breakdown voltage of the MIS capacitors significantly without having pronounced impact on the quality of the AlN/SiC interface.

  • 47.
    Khosa, Rabia Y.
    et al.
    Science Institute, University of Iceland, IS-107 Reykjavík, Iceland.
    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.
    Winters, Michael
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg, Sweden.
    ul-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.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Rorsman, Niklas
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg, Sweden.
    Low Density of Near-Interface Traps at the Al2O3/4H-SiC Interface with Al2O3 Made by Low Temperature Oxidation of Al2017In: Silicon Carbide and Related Materials 2016, Trans Tech Publications Ltd , 2017, Vol. 897, p. 135-138Conference paper (Refereed)
    Abstract [en]

    We report on a very low density (<5×1011 cm-2) of near-interface traps (NITs) at the Al2O3/4H-SiC interface estimated from capacitance-voltage (CV) analysis of MOS capacitors at different temperatures. The aluminum oxide (Al2O3) is grown by repeated deposition and subsequent low temperature (200°C) oxidation for 5 min of thin (1-2 nm) Al layers using a hot plate. We refer to this simple method as hot plate Al2O3. It is observed that the density of NITs is significantly lower in the hot plate Al2O3 samples than in samples with Al2O3 grown by atomic layer deposition (ALD) at 300°C and in reference samples with thermally grown silicon dioxide grown in O2 or N2O ambient.

  • 48.
    Li, Xun
    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.
    Kordina, Olof
    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.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Surface preparation of 4 degrees off-axis 4H-SIC substrate for epitaxial growth2013In: Materials Science Forum (Volumes 740 - 742), Trans Tech Publications Inc., 2013, p. 225-228Conference paper (Refereed)
    Abstract [en]

    Results of surface preparation on Si-face 4° off-cut 4H-SiC substrates are presented in this paper. The influences of two types of etchants, i.e. hydrogen chloride (HCl) and only hydrogen (H2), were investigated by Nomarski microscopy and AFM. The experiments were performed in a hot wall CVD reactor using a TaC coated susceptor. Four etching temperatures, including 1580 °C, 1600 °C, 1620 °C and 1640 °C, were studied. In-situ etching with only H2 as ambient atmosphere is found to be the optimal way for the SiC surface preparation. Using HCl at temperature higher than 1620 °C could degrade the substrates surface quality.

  • 49.
    Lilja, Louise
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Don Booker, Ian
    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.
    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.
    The influence of growth conditions on carrier lifetime in 4H-SiC epilayers2013In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 381, p. 43-50Article in journal (Refereed)
    Abstract [en]

    4H-SiC homoepitaxial layers have been grown in a horizontal hot-wall CVD (chemical vapor deposition) reactor and the measured carrier lifetimes have been correlated to the CVD growth conditions. Two different generations of reactors were compared, resulting in measured carrier lifetimes in two different orders of magnitude, from a few hundreds of ns to a few ms. The variations in measured carrier lifetime were correlated to deep level concentrations of the Z(1/2) center and the D-1 center, seen by photoluminescence. Decreasing the growth temperature clearly prolonged the carrier life time and showed lower Z(1/2) concentrations, where as lowering the growth rate only showed a small improvement of the carrier lifetime and no obvious tendencyin Z(1/2) defect concentrations, indicating that Z(1/2) is not the only defect limiting the carrier lifetime. Increasing the C/Si ratio resulted in decreasing Z(1/2) concentrations, indicating the carbon vacancy nature of the defect. However, carrier lifetime measurements showed maximum values for a C/Si ratio of 1 but otherwise an increasing tendency for increasing C/Si ratios. The reactor giving higher carrier lifetimes, correspondingly also showed lower Z(1/2) concentrations indicating the lifetime limiting property of Z(1/2). Furthermore, the D-1 defect intensity increased with growth temperature and decreased with increasing C/Si ratio, similar to the Z(1/2) concentration.

  • 50.
    Lilja, Louise
    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.
    Booker, Ian
    Department of Electronic Science and Engineering, Kyoto University, Japan.
    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.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Influence of n-Type Doping Levels on Carrier Lifetime in 4H-SiC Epitaxial Layers2017In: Silicon Carbide and Related Materials 2016, Trans Tech Publications Ltd , 2017, Vol. 897, p. 238-241Conference paper (Refereed)
    Abstract [en]

    In this study we have grown thick 4H-SiC epitaxial layers with different n-type doping levels in the range 1E15 cm-3 to mid 1E18 cm-3, in order to investigate the influence on carrier lifetime. The epilayers were grown with identical growth conditions except the doping level on comparable substrates, in order to minimize the influence of other parameters than the n-type doping level. We have found a drastic decrease in carrier lifetime with increasing n-type doping level. Epilayers were further characterized with low temperature photoluminescence and deep level transient spectroscopy.

123 1 - 50 of 104
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