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  • 151.
    Bladh, Mats
    et al.
    Linköping University, Department of Thematic Studies, Technology and Social Change. Linköping University, Faculty of Arts and Sciences.
    Syväjärvi, MikaelLinköping University, The Institute of Technology. Linköping University, Department of Thematic Studies. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    New Lighting—New LEDs: Aspects on light-emitting diodes from social and material science perspectives2010Collection (editor) (Other academic)
    Abstract [en]

    The papers published in this volume were presented at Sveriges Energiting 2010 (The Swedish Energy Parliament 2010) in Älvsjö south of Stockholm in March 16-17. Sveriges Energiting is Sweden’s largest scene for discussion of energy and climate related activities. It gathered about 2300 participants and had a broad range of energy related issues covered, such as transport, future energy systems, industrial energy, energy and climate, energy efficiency and many more, including several on lighting. One session was initiated and organized by me: “New Lighting—New LEDs”.

    I hope this kind of cooperation between lighting researchers will continue in the future. One step in this direction is Nordic Light Emitting Diode Initiative (NORLED), initiated by Professor Mikael Syväjärvi, Linköping University. The aim of the NORLED project is to develop an innovative and industrially feasible white LED technology for general lighting. The project consortium is composed of partners from Sweden, Denmark, Germany and Norway.

    Linköping, September 2010

    Mats Bladh

  • 152.
    Blomqvist, A
    et al.
    Sandvik Tooling.
    Århammar, Cecilia
    Uppsala University.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Silvearv, Fredrik
    Uppsala University.
    Norgren, Susanne
    Sandvik Mining and Construction.
    Ahuja, R
    Uppsala University.
    Understanding the catalytic effects of H2S on CVD-growth of α-alumina: Thermodynamic gas-phase simulations and density functional theory2011In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 7, p. 1771-1779Article in journal (Refereed)
    Abstract [en]

    The catalytic effect of H2S on the AlCl3/H2/CO2/HCl chemical vapor deposition (CVD) process has been investigatedon an atomistic scale. We apply a combined approach with thermodynamic modeling and densityfunctional theory and show that H2S acts as mediator for the oxygenation of the Al-surface which will inturn increase the growth rate of Al2O3. Furthermore we suggest surface terminations for the three investigatedsurfaces. The oxygen surface is found to be hydrogenated, in agreement with a number of previous works.The aluminum surfaces are Cl-terminated in the studied CVD-process. Furthermore, we find that the AlClOmolecule is a reactive transition state molecule which interacts strongly with the aluminum and oxygensurfaces.

  • 153.
    Blumenschein, N.
    et al.
    North Carolina State University, USA.
    Slomski, M.
    North Carolina State University, USA.
    Paskov, Plamen P.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. North Carolina State University, USA.
    Kaess, F.
    North Carolina State University, USA.
    Breckenridge, M.
    North Carolina State University, USA.
    Muth, J. F.
    North Carolina State University, USA.
    Paskova, T.
    North Carolina State University, USA.
    Thermal conductivity of bulk and thin film β-Ga2O3 measured by the 3ω technique2018In: Oxide-based Materials and Devices IX / [ed] David J. Rogers, David C. Look, Ferechteh H. Teharani, SPIE - International Society for Optical Engineering, 2018, Vol. 10533, p. 105332G-1-105332G-8Conference paper (Refereed)
  • 154. Bockstedte, M.
    et al.
    Gali, A.
    Umeda, T.
    Nguyen, Son Tien
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Isoya, J.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Signature of the negative Carbon Vacancy-Antisite complex2006In: Materials Science Forum, Vols. 527-529, 2006, Vol. 527-529, p. 539-542Conference paper (Refereed)
  • 155.
    Bohnen, T.
    et al.
    Radboud University Nijmegen.
    Yazdi, Gholamreza
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    van Dreumel, G W G
    Radboud University Nijmegen.
    Hageman, P R
    Radboud University Nijmegen.
    Vlieg, E.
    Radboud University Nijmegen.
    Algra, R E
    Radboud University Nijmegen.
    Verheijen, M A
    Philips Res Labs.
    Edgar, J H
    Kansas State University.
    ScAlN nanowires: A cathodoluminescence study2009In: JOURNAL OF CRYSTAL GROWTH, ISSN 0022-0248, Vol. 311, no 11, p. 3147-3151Article in journal (Refereed)
    Abstract [en]

    Wurtzite ScAlN nanowires, grown on a scandium nitride (ScN) thin film by hydride vapor phase epitaxy (HVPE), were analyzed by energy dispersive analysis of X-rays (EDX), CL, high resolution transmission electron spectroscopy (HRTEM), and scanning electron microscopy (SEM). The wires were grown along the [0 0 0 1] axis, had an average length of 1 mu m, a diameter between 50 and 150 run, and a ScAlN composition with a 95:5 Al:Sc ratio. Cathodoluminescence studies on the individual wires showed a sharp emission near 2.4 eV, originating from the Sc atoms in the aluminum nitride (AlN) matrix. The formation of such a semiconducting ScAlN alloy could present a new alternative to InAlN for optoelectronic applications operating in the 200-550 nm range.

  • 156.
    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.

  • 157.
    Booker, Ian Don
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Carrier Lifetime Relevant Deep Levels in SiC2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Silicon carbide (SiC) is currently under development for high power bipolar devices such as insulated gate bipolar transistors (IGBTs). A major issue for these devices is the charge carrier lifetime, which, in the absence of structural defects such as dislocations, is influenced by point defects and their associated deep levels. These defects provide energy levels within the bandgap and may act as either recombination or trapping centers, depending on whether they interact with both conduction and valence band or only one of the two bands. Of all deep levels know in 4H-SiC, the intrinsic carbon vacancy related Z1/2 is the most problematic since it is a very effective recombination center which is unavoidably formed during growth. Its concentration in the epilayer can be decreased for the production of high voltage devices by injecting interstitial carbon, for example by oxidation, which, however, results in the formation of other new deep levels.

    Apart from intrinsic crystal flaws, extrinsic defects such as transition metals may also produce deep levels within the bandgap, which in literature have so far only been shown to produce trapping effects.

    The focus of the thesis is the transient electrical and optical characterization of deep levels in SiC and their influence on the carrier lifetime. For this purpose, deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS) variations were used in combination with time-resolved photoluminescence (TRPL). Paper 1 deals with a lifetime limiting deep level related to Fe-incorporation in n-type 4H-SiC during growth and papers 2 and 3 focus on identifying the main intrinsic recombination center in p-type 4H-SiC. In paper 4, the details of the charge carrier capture behavior of the deeper donor levels of the carbon vacancy, EH6/7, are investigated. Paper 5 deals with trapping effects created by unwanted incorporation of high amounts of boron during growth of n-type 4H-SiC which hinders the measurement of the carrier lifetime by room temperature TRPL. Finally, paper 6 is concerned with the characterization of oxidation-induced deep levels created in n- and p-type 4H- and 6H-SiC as a side-product of lifetime improvement by oxidation.

    In paper 1, the appearance of a new recombination center in n-type 4H-SiC, the RB1 level is discussed and the material is analyzed using room temperature TRPL, DLTS and pnjunction DLTS. The level appears to originate from a reactor contamination with Fe, a transition metal that generally leads to the formation of several trapping centers in the bandgap. Here it is found that under specific circumstances beneficial to the growth of high-quality material with a low Z1/2 concentration, the Fe incorporation also creates an additional recombination center capable of limiting the carrier lifetime.

    In paper 2, all deep levels found in p-type 4H-SiC grown at Linköping University which are accessible by DLTS and MCTS are investigated with regard to their efficiency as recombination centers. We find that none of the detectable levels is able to reduce carrier lifetime in p-type significantly, which points to the lifetime killer being located in the top half of the bandgap and having a large hole to electron capture cross section ratio (such as Z1/2, which is found in n-type material), making it undetectable by DLTS and MCTS.

    Paper 3 compares carrier lifetimes measured by temperature-dependent TRPL measurements in n- and p-type 4H-SiC and it is shown that the lifetime development over a large temperature range (77 - 1000 K) is similar in both types. This is interpreted as a further indication that the carbon vacancy related Z1/2 level is the main lifetime killer in p-type.

    In paper 4, the hole and electron capture cross sections of the near midgap deep levels EH6/7 are characterized. Both levels are capable of rapid electron capture but have only small hole capture rates, making them insignificant as recombination centers, despite their advantageous position near midgap.

    Minority carrier trapping by boron, which is both a p-type dopant and an unavoidable contaminant in 4H-SiC grown by CVD, is investigated in paper 5. Since even the shallow boron acceptor levels are relatively deep in the bandgap, minority trap and-release effects are detectable in room-temperature TRPL measurements. In case a high density of boron exists in n-type 4H-SiC, for example leached out from damaged graphite reactor parts during growth, we demonstrate that these trapping effects may be misinterpreted in room temperature TRPL measurements as a long free carrier lifetime.

    Paper 6 uses MCTS, DLTS, and room temperature TRPL to characterize the oxidation induced deep levels ON1 and ON2 in n- and p-type 4H- and their counterparts OS1-OS3 in 6H-SiC. The levels are found to all be positive-U, coupled two-levels defects which trap electrons efficiently but exhibit very inefficient hole capture once the defect is fully occupied by electrons. It is shown that these levels are incapable of significantly influencing carrier lifetime in epilayers which underwent high temperature lifetime enhancement oxidations. Due to their high density after oxidation and their high thermal stability they may, however, act to compensate n-type doping in low-doped material.

    List of papers
    1. Carrier Lifetime Controlling Defects Z(1/2) and RB1 in Standard and Chlorinated Chemistry Grown 4H-SiC
    Open this publication in new window or tab >>Carrier Lifetime Controlling Defects Z(1/2) and RB1 in Standard and Chlorinated Chemistry Grown 4H-SiC
    Show others...
    2014 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 8, p. 4104-4110Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2014
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:liu:diva-110278 (URN)10.1021/cg5007154 (DOI)000340080400049 ()
    Note

    Funding Agencies|The Swedish Energy Agency; Swedish Research Council (VR); Swedish Foundation for Strategic Research (SSF); LG Innotek

    Available from: 2014-09-05 Created: 2014-09-05 Last updated: 2017-12-05Bibliographically approved
    2. Electron and hole capture cross sections of deep levels accessible by DLTS and MCTS in p-type 4H-SiC
    Open this publication in new window or tab >>Electron and hole capture cross sections of deep levels accessible by DLTS and MCTS in p-type 4H-SiC
    (English)Manuscript (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.

    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-121542 (URN)
    Available from: 2015-09-24 Created: 2015-09-24 Last updated: 2015-09-24
    3. Carrier lifetime in p- and n-type 4H-SiC
    Open this publication in new window or tab >>Carrier lifetime in p- and n-type 4H-SiC
    Show others...
    (English)Manuscript (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.

    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-121543 (URN)
    Available from: 2015-09-24 Created: 2015-09-24 Last updated: 2015-09-24
    4. Donor and double donor transitions of the carbon vacancy related EH6/7 deep level in 4H-SiC
    Open this publication in new window or tab >>Donor and double donor transitions of the carbon vacancy related EH6/7 deep level in 4H-SiC
    Show others...
    2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 23, article id 235703Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2016
    Keywords
    4H-SiC, DLTS, MCTS, Carbon vacancy, EH6/7; Z1/2, UT-1, Negative-U, Trap Auger, Deep level
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-121544 (URN)10.1063/1.4954006 (DOI)000379038800035 ()
    Funder
    Swedish Foundation for Strategic Research Swedish Research Council
    Note

    At the time for thesis presentation publication was in status: Manuscript

    Funding agencies: Swedish Foundation for Strategic Research (SSF); Swedish Research Council (VR)

    Available from: 2015-09-24 Created: 2015-09-24 Last updated: 2017-12-01Bibliographically approved
    5. Shallow boron, the deep D-center and their influence on carrier lifetime in n- and p-type 4H-SiC
    Open this publication in new window or tab >>Shallow boron, the deep D-center and their influence on carrier lifetime in n- and p-type 4H-SiC
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The shallow boron and deep D-center are analyzed by minority carrier transient spectroscopy (MCTS), deep level transient spectroscopy (DLTS) and optical-electrical MCTS in n-type 4H-SiC with varying concentrations of boron, and in p-type 4H-SiC. MCTS, using high resolution correlation functions, shows the D-center to be composed of two closely overlapping peaks, referred to as D(a) and D(b), both most likely originating from the same defect located on inequivalent lattice sites. The hole capture cross sections of the D center are derived from DLTS filling pulse measurements in p-type material. The electron capture behavior of the D-center is analyzed by optical-electrical MCTS, and we find the center to be a pure hole trap, unable to act as a recombination center, with electron capture cross sections smaller than 1·10-23 cm2. The shallow boron peak is found to be composed of two or more overlapping levels in high resolution MCTS spectra. The shallow levels are further demonstrated to produce minority carrier trapping and detrapping effects in n-type 4H-SiC, which result in long time-resolved photoluminescence (TRPL) transients with microsecond decay constants, even in material containing high concentrations of the lifetime killing center Z1/2.

    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-121545 (URN)
    Available from: 2015-09-24 Created: 2015-09-24 Last updated: 2015-09-24
    6. Oxidation-induced deep levels in n- and p-type 4H- and 6H-SiC and their influence on carrier lifetime
    Open this publication in new window or tab >>Oxidation-induced deep levels in n- and p-type 4H- and 6H-SiC and their influence on carrier lifetime
    Show others...
    2016 (English)In: Physical Review Applied, ISSN 2331-7019, Vol. 6, no 1, p. 1-15, article id 014010Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    American Physical Society, 2016
    Keywords
    Time-resolved photoluminescence, Deep level transient spectroscopy, Minority carrier transient spectroscopy, Lifetime enhancement, Oxidation; Recombination center, 4H-SiC, 6H-SiC
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-121546 (URN)10.1103/PhysRevApplied.6.014010 (DOI)000380125700001 ()
    Funder
    Swedish Foundation for Strategic Research Swedish Research Council
    Note

    At the time for thesis presentation publication was in status: Manuscript

    Available from: 2015-09-24 Created: 2015-09-24 Last updated: 2018-09-01Bibliographically approved
  • 158.
    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.

  • 159.
    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.

  • 160.
    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.

  • 161.
    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.

  • 162.
    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.

  • 163.
    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.

  • 164.
    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.

  • 165.
    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.

  • 166.
    Booker, Ian Don
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yazdanfar, Milan
    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.
    Shallow boron, the deep D-center and their influence on carrier lifetime in n- and p-type 4H-SiCManuscript (preprint) (Other academic)
    Abstract [en]

    The shallow boron and deep D-center are analyzed by minority carrier transient spectroscopy (MCTS), deep level transient spectroscopy (DLTS) and optical-electrical MCTS in n-type 4H-SiC with varying concentrations of boron, and in p-type 4H-SiC. MCTS, using high resolution correlation functions, shows the D-center to be composed of two closely overlapping peaks, referred to as D(a) and D(b), both most likely originating from the same defect located on inequivalent lattice sites. The hole capture cross sections of the D center are derived from DLTS filling pulse measurements in p-type material. The electron capture behavior of the D-center is analyzed by optical-electrical MCTS, and we find the center to be a pure hole trap, unable to act as a recombination center, with electron capture cross sections smaller than 1·10-23 cm2. The shallow boron peak is found to be composed of two or more overlapping levels in high resolution MCTS spectra. The shallow levels are further demonstrated to produce minority carrier trapping and detrapping effects in n-type 4H-SiC, which result in long time-resolved photoluminescence (TRPL) transients with microsecond decay constants, even in material containing high concentrations of the lifetime killing center Z1/2.

  • 167.
    Boosalis, A.
    et al.
    University of Nebraska, USA .
    Hofmann, T.
    University of Nebraska, USA.
    Darakchieva, Vanya
    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.
    Schubert, M.
    University of Nebraska, USA .
    Visible to vacuum ultraviolet dielectric functions of epitaxial graphene on 3C and 4H SiC polytypes determined by spectroscopic ellipsometry2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 1Article in journal (Refereed)
    Abstract [en]

    Spectroscopic ellipsometry measurements in the visible to vacuum-ultraviolet spectra (3.5-9.5 eV) are performed to determine the dielectric function of epitaxial graphene on SiC polytypes, including 4H (C-face and Si-face) and 3C SiC (Si-face). The model dielectric function of graphene is composed of two harmonic oscillators and allows the determination of graphene quality, morphology, and strain. A characteristic van Hove singularity at 4.5 eV is present in the dielectric function of all samples, in agreement with observations on exfoliated as well as chemical vapor deposited graphene in the visible range. Model dielectric function analysis suggests that none of our graphene layers experience a significant degree of strain. Graphene grown on the Si-face of 4H SiC exhibits a dielectric function most similar to theoretical predictions for graphene. The carbon buffer layer common for graphene on Si-faces is found to increase polarizability of graphene in the investigated spectrum.

  • 168.
    Boosalis, Alexander
    et al.
    Department of Electrical Engineering, University of Nebraska–Lincoln, Lincoln, Nebraska, U.S.A..
    Hofmann, Tino
    Department of Electrical Engineering, University of Nebraska–Lincoln, Lincoln, Nebraska, U.S.A..
    Darakchieva, Vanya
    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.
    Tiwald, Tom
    J.A. Woollam Co., Lincoln, Nebraska, U.S.A..
    Schubert, Mathias
    Department of Electrical Engineering, University of Nebraska–Lincoln, Lincoln, Nebraska, U.S.A..
    Spectroscopic Mapping Ellipsometry of Graphene Grown on 3C SiC2012In: MRS Proceedings Volume 1407, 2012, p. aa20-43Conference paper (Refereed)
    Abstract [en]

    Spectroscopic mapping ellipsometry measurements in the visible spectrum (1.25 to 5.35 eV) are performed to determine the lateral variations of epitaxial graphene properties as grown on 3C SiC. Data taken in the visible spectrum is sensitive to both the Drude absorption of free charge carriers and the characteristic exciton enhanced van Hove singularity at 5 eV. Subsequent analysis with simple oscillator models allows the determination of physical parameters such as free charge carrier scattering time and local graphene thickness with a lateral resolution of 50 microns.

  • 169.
    Bosma, Tom
    et al.
    Univ Groningen, Netherlands.
    Lof, Gerrit J. J.
    Univ Groningen, Netherlands.
    Gilardoni, Carmem M.
    Univ Groningen, Netherlands.
    Zwier, Olger V
    Univ Groningen, Netherlands.
    Hendriks, Freddie
    Univ Groningen, Netherlands.
    Magnusson, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Norstel AB, Sweden.
    Ellison, Alexandre
    Norstel AB, Sweden.
    Gällström, Andreas
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Saab Dynam AB, SE-58188 Linkoping, Sweden.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Havenith, Remco W. A.
    Univ Groningen, Netherlands; Univ Groningen, Netherlands; Univ Ghent, Belgium.
    van der Wal, Caspar H.
    Univ Groningen, Netherlands.
    Identification and tunable optical coherent control of transition-metal spins in silicon carbide2018In: NPJ QUANTUM INFORMATION, ISSN 2056-6387, Vol. 4, article id 48Article in journal (Refereed)
    Abstract [en]

    Color centers in wide-bandgap semiconductors are attractive systems for quantum technologies since they can combine long-coherent electronic spin and bright optical properties. Several suitable centers have been identified, most famously the nitrogen-vacancy defect in diamond. However, integration in communication technology is hindered by the fact that their optical transitions lie outside telecom wavelength bands. Several transition-metal impurities in silicon carbide do emit at and near telecom wavelengths, but knowledge about their spin and optical properties is incomplete. We present all-optical identification and coherent control of molybdenum-impurity spins in silicon carbide with transitions at near-infrared wavelengths. Our results identify spin S= 1/2 for both the electronic ground and excited state, with highly anisotropic spin properties that we apply for implementing optical control of ground-state spin coherence. Our results show optical lifetimes of similar to 60 ns and inhomogeneous spin dephasing times of similar to 0.3 mu S, establishing relevance for quantum spin-photon interfacing.

  • 170.
    Bouhafs, Chamseddine
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Structural and Electronic Properties of Graphene on 4H- and 3C-SiC2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Graphene is a one-atom-tick carbon layer arranged in a honeycomb lattice. Graphene was first experimentally demonstrated by Andre Geim and Konstantin Novoselov in 2004 using mechanical exfoliation of highly oriented pyrolytic graphite (exfoliated graphene flakes), for which they received the Nobel Prize in Physics in 2010. Exfoliated graphene flakes show outstanding electronic properties, e.g., very high free charge carrier mobility parameters and ballistic transport at room temperature. This makes graphene a suitable material for next generation radio-frequency and terahertz electronic devices. Such applications require fabrication methods of large-area graphene compatible with electronic industry. Graphene grown by sublimation on silicon carbide (SiC) offers a viable route towards production of large-area, electronic-grade material on semi-insulating substrate without the need of transfer. Despite the intense investigations in the field, uniform wafer-scale graphene with very high-quality that matches the properties of exfoliated graphene has not been achieved yet. The key point is to identify and control how the substrate affects graphene uniformity, thickness, layer stacking, structural and electronic properties. Of particular interest is to understand the effects of SiC surface polarity and polytype on graphene properties in order to achieve large-area material with tailored properties for electronic applications. The main objectives of this thesis are to address these issues by investigating the structural and electronic properties of epitaxial graphene grown on 4HSiC and 3C-SiC substrates with different surface polarities. The first part of the thesis includes a general description of the properties of graphene, bilayer graphene and graphite. Then, the properties of epitaxial graphene on SiC by sublimation are detailed. The experimental techniques used to characterize graphene are described. A summary of all papers and contribution to the field is presented at the end of Part I. Part II consists of seven papers.

    List of papers
    1. Structural properties and dielectric function of graphene grown by high-temperature sublimation on 4H-SiC(000-1)
    Open this publication in new window or tab >>Structural properties and dielectric function of graphene grown by high-temperature sublimation on 4H-SiC(000-1)
    Show others...
    2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 8, p. 085701-Article in journal (Refereed) Published
    Abstract [en]

    Understanding and controlling growth of graphene on the carbon face (C-face) of SiC presents a significant challenge. In this work, we study the structural, vibrational, and dielectric function properties of graphene grown on the C-face of 4H-SiC by high-temperature sublimation in an argon atmosphere. The effect of growth temperature on the graphene number of layers and crystallite size is investigated and discussed in relation to graphene coverage and thickness homogeneity. An amorphous carbon layer at the interface between SiC and the graphene is identified, and its evolution with growth temperature is established. Atomic force microscopy, micro-Raman scattering spectroscopy, spectroscopic ellipsometry, and high-resolution cross-sectional transmission electron microscopy are combined to determine and correlate thickness, stacking order, dielectric function, and interface properties of graphene. The role of surface defects and growth temperature on the graphene growth mechanism and stacking is discussed, and a conclusion about the critical factors to achieve decoupled graphene layers is drawn. (C) 2015 AIP Publishing LLC.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2015
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-117253 (URN)10.1063/1.4908216 (DOI)000351132500070 ()
    Note

    Funding Agencies|Marie Curie actions [264613-NetFISiC]; Swedish Research Council (VR) [2011-4447, 2013-5580]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program [2011-03486]; Swedish foundation for strategic research (SSF) [FFL12-0181]; FP7 EU project Nano-Rf [FP7-ICT-2011-8]; French ANR under the Grafonics Project [ANR-10-NANO-0004]; European Union Seventh Framework Programme under Graphene Flagship [604391]; Knut and Alice Wallenbergs foundation

    Available from: 2015-04-22 Created: 2015-04-21 Last updated: 2017-12-04
    2. Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
    Open this publication in new window or tab >>Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
    Show others...
    2017 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 357-360Article in journal (Refereed) Published
    Abstract [en]

    Cavity-enhanced optical Hall effect at terahertz (THz) frequencies is employed to determine the free charge carrier properties in epitaxial graphene (EG) with different number of layers grown by high-temperature sublimation on 4H-SiC(0001). We find that one monolayer (ML) EG possesses p-type conductivity with a free hole concentration in the low 1012 cmᅵᅵᅵ2 range and a free hole mobility parameter as high as 1550 cm2/Vs. We also find that 6 ML EG shows n-type doping behavior with a much lower free electron mobility parameter of 470 cm2/Vs and an order of magnitude higher free electron density in the low 1013 cmᅵᅵᅵ2 range. The observed differences are discussed. The cavity-enhanced THz optical Hall effect is demonstrated to be an excellent tool for contactless access to the type of free charge carriers and their properties in two-dimensional materials such as EG.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    THz optical Hall effect, Epitaxial graphene, Free charge carrier properties
    National Category
    Physical Sciences Condensed Matter Physics Atom and Molecular Physics and Optics Ceramics
    Identifiers
    urn:nbn:se:liu:diva-132407 (URN)10.1016/j.apsusc.2016.10.023 (DOI)000408756700015 ()
    Note

    Funding agencies: Swedish Research Council (VR) [2013-5580]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program [2011-03486, 2014-04712]; Swedish foundation for strategic research (SSF) [FFL12-0181, RIF14-055]

    Available from: 2016-11-09 Created: 2016-11-09 Last updated: 2019-03-05Bibliographically approved
  • 171.
    Bouhafs, Chamseddine
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Persson, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Tiberj, A.
    University of Montpellier 2, France.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Paillet, M.
    University of Montpellier 2, France.
    Zahab, A. -A.
    University of Montpellier 2, France.
    Landois, P.
    University of Montpellier 2, France.
    Juillaguet, S.
    University of Montpellier 2, France.
    Schoeche, S.
    University of Nebraska, NE 68588 USA; University of Nebraska, NE 68588 USA.
    Schubert, M.
    University of Nebraska, NE 68588 USA; University of Nebraska, NE 68588 USA.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Structural properties and dielectric function of graphene grown by high-temperature sublimation on 4H-SiC(000-1)2015In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 8, p. 085701-Article in journal (Refereed)
    Abstract [en]

    Understanding and controlling growth of graphene on the carbon face (C-face) of SiC presents a significant challenge. In this work, we study the structural, vibrational, and dielectric function properties of graphene grown on the C-face of 4H-SiC by high-temperature sublimation in an argon atmosphere. The effect of growth temperature on the graphene number of layers and crystallite size is investigated and discussed in relation to graphene coverage and thickness homogeneity. An amorphous carbon layer at the interface between SiC and the graphene is identified, and its evolution with growth temperature is established. Atomic force microscopy, micro-Raman scattering spectroscopy, spectroscopic ellipsometry, and high-resolution cross-sectional transmission electron microscopy are combined to determine and correlate thickness, stacking order, dielectric function, and interface properties of graphene. The role of surface defects and growth temperature on the graphene growth mechanism and stacking is discussed, and a conclusion about the critical factors to achieve decoupled graphene layers is drawn. (C) 2015 AIP Publishing LLC.

  • 172.
    Bouhafs, Chamseddine
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Stanishev, Vallery
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Zakharov, A. A.
    Lund University, Sweden.
    Hofmann, Tino
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska, USA.
    Kuhne, Philipp
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. University of Nebraska, USA.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Decoupling and ordering of multilayer graphene on C-face 3C-SiC(111)2016In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 109, no 20, article id 203102Article in journal (Refereed)
    Abstract [en]

    We show experimentally that few layer graphene (FLG) grown on the carbon terminated surface (C-face) of 3C-SiC(111) is composed of decoupled graphene sheets. Landau level spectroscopy on FLG graphene is performed using the infrared optical Hall effect. We find that Landau level transitions in the FLG exhibit polarization preserving selection rules and the transition energies obey a square-root dependence on the magnetic field strength. These results show that FLG on C-face 3C-SiC(111) behave effectively as a single layer graphene with linearly dispersing bands (Dirac cones) at the graphene K point. We estimate from the Landau level spectroscopy an upper limit of the Fermi energy of about 60 meV in the FLG, which corresponds to a carrier density below 2.5 x 10(11) cm(-2). Low-energy electron diffraction mu-LEED) reveals the presence of azimuthally rotated graphene domains with a typical size of amp;lt;= 200 nm.mu-LEED mapping suggests that the azimuth rotation occurs between adjacent domains within the same sheet rather than vertically in the stack. Published by AIP Publishing.

  • 173.
    Bouhafs, Chamseddine
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Zakharov, A. A.
    Lund University, Sweden.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Giannazzo, F.
    CNR IMM, Italy.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Stanishev, Vallery
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Kuhne, Philipp
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Hofmann, Tino
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska Lincoln, NE 68588 USA.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska Lincoln, NE 68588 USA.
    Roccaforte, F.
    CNR IMM, Italy.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Multi-scale investigation of interface properties, stacking order and decoupling of few layer graphene on C-face 4H-SiC2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 116, p. 722-732Article in journal (Refereed)
    Abstract [en]

    In this work, we report a multi-scale investigation using several nano-, micro and macro-scale techniques of few layer graphene (FLG) sample consisting of large monolayer (ML) and bilayer (BL) areas grown on C-face 4H-SiC (000-1) by high-temperature sublimation. Single 1 x 1 diffraction patterns are observed by micro-low-energy electron diffraction for ML, BL and trilayer graphene with no indication of out-of-plane rotational disorder. A SiOx layer is identified between graphene and SiC by X-ray photoelectron emission spectroscopy and reflectance measurements. The chemical composition of the interface layer changes towards SiO2 and its thickness increases with aging in normal ambient conditions. The formation mechanism of the interface layer is discussed. It is shown by torsion resonance conductive atomic force microscopy that the interface layer causes the formation of non-ideal Schottky contact between ML graphene and SiC. This is attributed to the presence of a large density of interface states. Mid-infrared optical Hall effect measurements revealed Landau-level transitions in FLG that have a square-root dependence on magnetic field, which evidences a stack of decoupled graphene sheets. Contrary to previous works on decoupled C-face graphene, our BL and FLG are composed of ordered decoupled graphene layers without out-of-plane rotation. (C) 2017 Elsevier Ltd. All rights reserved.

  • 174.
    Boukhvalov, D W
    et al.
    Korea Institute Adv Study.
    Virojanadara, Chariya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Penetration of alkali atoms throughout a graphene membrane: theoretical modeling2012In: NANOSCALE, ISSN 2040-3364, Vol. 4, no 5, p. 1749-1753Article in journal (Refereed)
    Abstract [en]

    Theoretical studies of penetration of various alkali atoms (Li, Na, Rb, Cs) throughout a graphene membrane grown on a silicon carbide substrate are reported and compared with recent experimental results. Results of first principles modeling demonstrate a rather low (about 0.8 eV) energy barrier for the formation of temporary defects in the carbon layer required for the penetration of Li at a high concentration of adatoms, a higher (about 2 eV) barrier for Na, and barriers above 4 eV for Rb and Cs. Experiments prove migration of lithium adatoms from the graphene surface to the buffer layer and SiC substrate at room temperature, sodium at 100 degrees C and impenetrability of the graphene membrane for Rb and Cs. Differences between epitaxial and free-standing graphene for the penetration of alkali ions are also discussed.

  • 175.
    Briley, Chad
    et al.
    University of Nebraska, NE 68588 USA.
    Mock, Alyssa
    University of Nebraska, NE 68588 USA.
    Korlacki, Rafal
    University of Nebraska, NE 68588 USA.
    Hofmann, Tino
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska, NE 68588 USA.
    Schubert, Eva
    University of Nebraska, NE 68588 USA.
    Schubert, Mathias
    University of Nebraska, NE 68588 USA.
    Effects of annealing and conformal alumina passivation on anisotropy and hysteresis of magneto-optical properties of cobalt slanted columnar thin films2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 320-324Article in journal (Refereed)
    Abstract [en]

    We present magneto-optical dielectric tensor data of cobalt and cobalt oxide slanted columnar thin films obtained by vector magneto-optical generalized ellipsometry. Room-temperature hysteresis magnetization measurements were performed in longitudinal and polar Kerr geometries on samples prior to and after a heat treatment process with and without a conformal Al2O3 passivation coating. The samples have been characterized by generalized ellipsometry, scanning electron microscopy, and Raman spectroscopy in conjuncture with density functional theory. We observe strongly anisotropic hysteresis behaviors, which depend on the nanocolumn and magnetizing field orientations. We find that deposited cobalt films that have been exposed to heat treatment and subsequent atmospheric oxidation into Co3O4, when not conformally passivated, reveal no measurable magneto-optical properties while cobalt films with passivation coatings retain highly anisotropic magneto-optical properties (C) 2016 Published by Elsevier B.V.

  • 176. Brillson, L.J.
    et al.
    Tumakha, S.P.
    Gao, M.
    Ewing, D.J.
    Porter, L.M.
    Okojie, R.S.
    Zhang, M.
    Pirouz, P.
    Wahab, Qamar Ul
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Ma, X.
    Sudharshan, T.S.
    Onishi, T.
    Tsukimoto, S.
    Murakami, M.
    The impact of surface defects on SiC Schottky and ohmic contact formation2005In: International Semiconductor Device Research Symposium,2005, 2005Conference paper (Refereed)
  • 177.
    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.

  • 178. 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.

  • 179. Brosselard, P.
    et al.
    Henry, Anne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Pérez-Tomás, A.
    Montserrat, J.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Godignon, P.
    Bipolar Diode on 4H-SiC P+-Substrate2009In: Materials Science Forum, Vols. 600-603, 2009Conference paper (Other academic)
    Abstract [en]

        

  • 180.
    Brosselard, P
    et al.
    Centro Nacional de Microelectrónica, CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain .
    Jorda, X
    Centro Nacional de Microelectrónica, CNM-CSIC, Campus UAB, 08193 Bellaterra, Barcelona, Spain .
    Vellvehi, M
    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 .
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lambert, B
    ESA/ESTEC, Keplerlaan 1, 2200 AG Noordwijk ZH, Netherlands .
    High temperature behaviour of 3.5 kV 4H-SiC JBS diodes2007In: Proceedings of the International Symposium on Power Semiconductor Devices and ICs, 2007, p. 285-288Conference paper (Refereed)
    Abstract [en]

    4H-SiC JBS diodes have been manufactured on a Norstel epitaxied N/N + substrate using a JTE as edge termination. A breakdown voltage higherthan 3.5 kV has been measured on 0.16 and 2.56 mm 2 diodes. The leakage current in the 25°C-300°C temperature range depends on the bipolar/Schottky ratio whereas in forward mode its impact is minor. Diodes have been stressed in DC mode to show that the 2.56 mm 2 diodes have a slight forward voltage degradation independently of the layout. In switching mode, the recovery charge is only 20 nC for a 4A current switched at 300°C.

  • 181.
    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.

  • 182. 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)
  • 183.
    Burnett, Tim L
    et al.
    National Phys Lab, England .
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kazakova, Olga
    National Phys Lab, England .
    Identification of epitaxial graphene domains and adsorbed species in ambient conditions using quantified topography measurements2012In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, no 5, p. 054308-Article in journal (Refereed)
    Abstract [en]

    We discuss general limitations of topographical studies of epitaxial graphene in ambient conditions, in particular, when an accurate determination of the layers thickness is required. We demonstrate that the histogram method is the most accurate for measurements of small vertical distances (andlt;0.5 nm) and generally should be applied to epitaxial graphene and similar types of samples in order to get the correct and reproducible values. Experimental determination of the step height between different domains of epitaxial graphene shows excellent agreement with the predicted values once the adsorption of a 2D monolayer is taken into account on top of the one layer graphene. In contrast to general limitations of AFM topography, electrostatic force microscopy imaging allows a straightforward identification of domains of epitaxial graphene of different thickness.

  • 184.
    Burnett, Tim
    et al.
    National Physics Lab, Teddington, England .
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kazakova, Olga
    National Physics Lab, Teddington, England .
    Mapping of Local Electrical Properties in Epitaxial Graphene Using Electrostatic Force Microscopy2011In: NANO LETTERS, ISSN 1530-6984, Vol. 11, no 6, p. 2324-2328Article in journal (Refereed)
    Abstract [en]

    Local electrical characterization of epitaxial graphene grown on 4H-SiC (0001) using electrostatic force microscopy (EFM) in ambient conditions and at elevated temperatures is presented. EFM provides a straightforward identification of graphene with different numbers of layers on the substrate where topographical determination is hindered by adsorbates. Novel EFM spectroscopy has been developed measuring the EFM phase as a function of the electrical DC bias, establishing a rigorous way to distinguish graphene domains and facilitating optimization of EFM imaging.

  • 185.
    Buyanova, Irina A.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Hai, P.N.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Xin, H.P.
    Department of Electrical and Computer Engineering, University of California, San Diego, CA 92093-0407, United States.
    Tu, C.W.
    Department of Electrical and Computer Engineering, University of California, San Diego, CA 92093-0407, United States.
    Optical properties of GaNAs/GaAs structures2001In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 82, no 1-3, p. 143-147Article in journal (Refereed)
    Abstract [en]

    We review our recent results on optical characterization of MBE-grown GaNAs/GaAs quantum structures with N content up to 4.5%, by employing photoluminescence (PL), PL excitation, and time-resolved PL spectroscopies. The dominant PL mechanism has been determined as recombination of excitons trapped by potential fluctuations of the band edge, due to composition disorder and strain nonuniformity of the alloy. The estimated value of the localization potential is around 60 meV for the low-temperature grown structures and can be reduced by increasing the growth temperature or using post-growth rapid thermal annealing (RTA). © 2001 Elsevier Science S.A.

  • 186.
    Buyanova, Irina A
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Hallberg, T
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Swedish Def Res Estab, S-58111 Linkoping, Sweden Inst Solid State & Semicond Phys, Minsk 220072, Byelarus Univ Lund, S-22100 Lund, Sweden.
    Murin, LI
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Swedish Def Res Estab, S-58111 Linkoping, Sweden Inst Solid State & Semicond Phys, Minsk 220072, Byelarus Univ Lund, S-22100 Lund, Sweden.
    Markevich, VP
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Swedish Def Res Estab, S-58111 Linkoping, Sweden Inst Solid State & Semicond Phys, Minsk 220072, Byelarus Univ Lund, S-22100 Lund, Sweden.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Lindstrom, JL
    Effect of high-temperature electron irradiation on the formation of radiative defects in silicon1999In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 274, p. 528-531Article in journal (Refereed)
    Abstract [en]

    Defect formation processes in silicon caused by electron irradiation performed at elevated temperatures are studied in detail using photoluminescence (PL) spectroscopy. The use of high temperature during electron irradiation has been found to affect considerably the defect formation process, In particular, several new unknown excitonic PL lines were discovered in carbon-rich Si wafers subjected to electron irradiation at temperatures higher than 450 degrees C, The dominant new luminescent center gives rise to a bound exciton PL emission at 0.961 eV. The center is shown to be efficiently created by electron irradiation at temperatures from 450 degrees C up to 600 degrees C. The electronic structure of the 0.961 eV PL center can be described as a pseudodonor case, where the hole is strongly bound at a level 187 meV above the valence band, while the electron is a effective-mass-like particle weakly bound by approximate to 21 meV in the BE state, (C) 1999 Elsevier Science B.V. All rights reserved.

  • 187.
    Buyanova, Irina A.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Lindstrom, J.L.
    Lindström, J.L., Solid State Physics, Univ. of Lund, Box 118, S-221 00, Lund, Sweden.
    Hallberg, T.
    Murin, L.I.
    Inst. Solid Stt. Semiconduct. Phys., 220072, Minsk, Belarus.
    Markevich, V.P.
    Inst. Solid Stt. Semiconduct. Phys., 220072, Minsk, Belarus.
    Photoluminescence characterization of defects created in electron-irradiated silicon at elevated temperatures2000In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 72, no 2, p. 146-149Article in journal (Refereed)
    Abstract [en]

    Photoluminescence (PL) spectroscopy is employed to investigate radiative defects created in Si during electron-irradiation at elevated temperatures. The use of high temperature during electron irradiation has been found to affect considerably the defect formation process. The effect critically depends on the temperature of the irradiation as well as doping of the samples. For carbon-lean Si wafers high temperature electron irradiation stimulates the formation of extended defects, such as dislocations and precipitates. For carbon-rich Si wafers the increase of irradiation temperature up to 300°C enhances the formation of the known carbon-related defects. In addition, several new excitonic PL lines were observed after electron irradiation at T = 450°C. The dominant new PL center gives rise to a BE PL emission at 0.961 eV. The electronic structure of the 0.961 eV defect is discussed based on temperature-dependent and magneto-optical studies.

  • 188.
    Buyanova, Irina
    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.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Izadifard, Morteza
    Physics Department, Shahrood University of Technology, Shahrood, Iran .
    Hong, Y.G.
    Department of Electrical and Computer Engineering, University of California, La Jolla, CA, USA.
    Tu, C.W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, CA, USA.
    Role of nitrogen in photoluminescence up-conversion in GaInNP/GaAs heterostructures2007In: AIP Conference Proceedings / Volume 893 / [ed] Wolfgang Jantsch, Friedrich Schaffler, American Institute of Physics (AIP), 2007, p. 381-382Conference paper (Other academic)
    Abstract [en]

    Alloying of disordered GaInP with nitrogen is shown to lead to very efficient PLU in GaInNP/GaAs heterostructures grown by gas source molecular beam epitaxy (GS‐MBE). This is attributed to the N‐induced changes in the band alignment at the GaInNP/GaAs heterointerface from the type I for the N‐free structure to the type II in the samples with N compositions exceeding 0.5%. Based on the performed excitation power dependent measurements, a possible mechanism for the energy upconversion is suggested as being due to the two‐step two‐photon absorption. The photon recycling effect is shown to be important for the structures with N=1%, from time‐resolved PL measurements. © 2007 American Institute of Physics

  • 189.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Thaler, G.
    Frazier, R.
    Abernathy, C. R.
    Pearton, S. J.
    Kim, J.
    Ren, F.
    Kyrychenko, F. V.
    Stanton, C. J.
    Pan, C.-C.
    Chen, G.-T.
    Chyi, J.-I.
    Zavada, J. M.
    Optical study of spin injection dynamics in InGaN/GaN quantum wells with GaMnN injection layers2004In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 22, no 6, p. 2668-2672Article in journal (Refereed)
    Abstract [en]

     The spin injection dynamics of GaMnN/InGaN multiquantum well (MQW) light emitting diodes (LEDs) grown by molecular beam epitaxy were examined using picosecond-transient and circularly polarized photoluminescence (PL) measurements. Even with the presence of a room temperature ferromagnetic GaMnN spin injector, the LEDs are shown to exhibit very low efficiency of spin injection. Based on resonant optical orientation spectroscopy, the spin loss in the structures is shown to be largely due to fast spin relaxation within the InGaN MQW, which itself destroys any spin polarization generated by optical spin orientation or electrical spin injection. Typical photoluminescence decay times were 20-40 ns in both commercial GaN MQW LEDs with emission wavelengths between 420-470 nm and in the GaMnN/InGaN multi-quantum well MQW LEDs. In the wurtzite InGaN/GaN system, biaxial strain at the interfaces give rise to large piezoelectric fields directed along the growth axis. This built-in piezofield breaks the reflection symmetry of confining potential leading to the presence of a large Rashba term in the conduction band Hamiltonian which is responsible for the short spin relaxation times.

  • 190.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Rawal, S.
    Norton, D.P.
    Pearton, S.J.
    Osinsky, A.
    Dong, J.W.
    Mechanism for radiative recombination in ZnCdO alloys2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 26Article in journal (Refereed)
    Abstract [en]

    Temperature dependent cw- and time-resolved photoluminescence combined with absorption measurements are employed to evaluate the origin of radiative recombination in ZnCdO alloys grown by molecular-beam epitaxy. The near-band-edge emission is attributed to recombination of excitons localized within band tail states likely caused by nonuniformity in Cd distribution. Energy transfer between the tail states is argued to occur via tunneling of localized excitons. The transfer is shown to be facilitated by increasing Cd content due to a reduction of the exciton binding energy and, therefore, an increase of the exciton Bohr radius in the alloys with a high Cd content. © 2007 American Institute of Physics.

  • 191.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Rawal, S.
    Norton, D.P.
    Pearton, S.J.
    Osinsky, A.
    Dong, J.W.
    Origin of near-band-edge emission in ZnCdO alloys2007In: 2007 MRS Fall Meeting,2007, 2007, p. 319-Conference paper (Other academic)
  • 192.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    New insight on electronic properties of GaNP alloy2005In: 27th Int. Conf. on the Physics of Semicond,2004, 2005, p. 271-Conference paper (Other academic)
  • 193.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Optical and electronic properties of GaInNP alloys - a new material for lattice matching to GaAs2004In: Physics and applications of dilute nitrides / [ed] Irina A. Buyanova and Weimin M. Chen, Kerala, India: Research Signpost , 2004, 1, p. -442Chapter in book (Other academic)
    Abstract [en]

    Since their development in the 1990s, it has been discovered that diluted nitrides have intriguing properties that are not only distinct from those of conventional semiconductor materials, but also are conducive to various applications in optoelectronics and photonics. The book examines these applications and presents a broad and in-depth look at the basic electronic and optical properties of diluted nitrides.

    The aim of Physics and Applications of Diluted Nitrides is to provide graduate students, researchers and engineers with a comprehensive overview of the present knowledge and future perspectives of diluted nitrides.

    Co-authored by a group of leading scientists in the field, this book brings the reader up to speed on the development and current state of diluted nitride applications, as well as the technologies to be developed in the near future.

  • 194.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Ivill, M.P.
    Pate, R.
    Norton, D.P.
    Pearton, S.J.
    Dong, J.W.
    Osinsky, A.
    Hertog, B.
    Dabiran, A.M.
    Chow, P.P.
    Optical characterization of ZnMnO-based dilute magnetic semiconductor structures2006In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 24, no 1, p. 259-262Article in journal (Refereed)
    Abstract [en]

    n -type ZnMnO spin injection layers were grown by pulsed laser deposition on top of n-ZnMgOZnOp-AlGaNp-GaN hybrid spin light-emitting diode (LED) structures synthesized by molecular-beam epitaxy. Both the ZnMnOZnMgOZnOAlGaNGaN structures and control ZnMnO samples show no or very low (up to 10% at the lowest temperatures) optical (spin) polarization at zero field or 5 T, respectively. This indicates difficulties in generating spin polarization by optical spin orientation or possible efficient spin losses. The results are similar to those found earlier for GaMnNInGaNAlGaN spin-LED structures and indicate that these wide-band-gap dilute magnetic semiconductors with weak spin-orbit interaction and hexagonal symmetry are not attractive for spin-LED applications. © 2006 American Vacuum Society.

  • 195.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Pearton, S.J.
    Bihler, C.
    Brandt, M.S.
    Hong, Y.G.
    Tu, C.W.
    Hydrogen passivation of nitrogen in GaNAs and GaNP alloys: How many H atoms are required for each N atom?2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 2, p. 021920-Article in journal (Refereed)
    Abstract [en]

    Secondary ion mass spectrometry and photoluminescence are employed to evaluate the origin and efficiency of hydrogen passivation of nitrogen in GaNAs and GaNP. The hydrogen profiles are found to closely follow the N distributions, providing unambiguous evidence for their preferential binding as the dominant mechanism for neutralization of N-induced modifications in the electronic structure of the materials. Though the exact number of H atoms involved in passivation may depend on the conditions of the H treatment and the host matrixes, it is generally found that more than three H atoms are required to bind to a N atom to achieve full passivation for both alloys. © 2007 American Institute of Physics.

  • 196.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Electronic Properties of Ga(In)NAs Alloys2001In: MRS Internet journal of nitride semiconductor research, ISSN 1092-5783, E-ISSN 1092-5783, Vol. 6Article in journal (Refereed)
    Abstract [en]

     A brief review on the present knowledge of the electronic properties of the Ga(In)NAs ternary and quaternary alloys is given mainly from an experimental perspective. The discussion is focused on Ga(In)NAs with low N composition (< 10 %), where a large amount of experimental work has been done. Important fundamental electronic properties of the material system are analyzed with the emphasis on the nature of the giant band gap bowing in the alloy and nitrogen-induced modifications of the electronic structure of the conduction band. The current knowledge of the key material parameters, relevant for the device applications, such as electron effective mass, recombination processes and band alignment in Ga(In)NAs/GaAs heterostructures, is also reviewed.

  • 197.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Toropov, A. A.
    Terentev, Ya. V.
    Sorokin, S. V.
    Lebedev, A. V.
    Ivanov, S. V.
    Kopev, P. S.
    On the spin injection in ZnMnSe/ZnCdSe heterostructures2002Conference paper (Refereed)
    Abstract [en]

     We present results from a detailed study of spin injection in thin II-VI wide band gap semiconductor heterostructures by magnetooptical spectroscopy. It is shown that efficient spin alignment can be achieved in a diluted magnetic semiconductor barrier (a layer of ZnMnSe or ZnMnSe/CdSe superlattice) as thin as 10 nm. Rather efficient spin injection from such a thin spin aligner to a non-magnetic quantum well is demonstrated, even when the tunneling energy barrier is as thick as 10 nm. The effect of spin relaxation process on spin injection is also closely examined.

  • 198.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Xin, H. P.
    Tu, C. W.
    Effect of Growth Conditions on the Photoluminescence of GaNAs/GaAs Quantum Structures1999In: Joint International Meeting the 196th Meeting of The Electrochemical Society ECS and the 1999 Fall Meeting of The Electrochemical Society of Japan ECSJ,1999, 1999, p. 774-Conference paper (Other academic)
  • 199.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Xin, H. P.
    Tu, C. W.
    Effect of growth temperature on photoluminescence of GaNAs/GaAs quantum well structures1999In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 75, no 24, p. 3781-Article in journal (Refereed)
    Abstract [en]

     The effect of growth temperature on the optical properties of GaAs/GaNxAs1-x quantum wells is studied in detail using photoluminescence (PL) spectroscopies. An increase in growth temperature up to 580 °C is shown to improve the optical quality of the structures, while still allowing one to achieve high (>3%) N incorporation. This conclusion is based on: (i) an observed increase in intensity of the GaNAs-related near-band-edge emission; (ii) a reduction in band-edge potential fluctuations, deduced from the analysis of the PL line shape; and (iii) a decrease in concentration of some extended defects detected under resonant excitation of the GaNAs. The thermal quenching of the GaNAs-related PL emission, however, is almost independent of the growth temperature and is attributed to a thermal activation of an efficient nonradiative recombination channel located in the GaNAs layers.

  • 200.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Xin, H. P.
    Tu, C. W.
    Photoluminescence characterization of GaNAs/GaAs structures grown by molecular beam epitaxy2000In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 75, no 2-3, p. 166-169Article in journal (Refereed)
    Abstract [en]

    A number of optical spectroscopies, including photoluminescence (PL), PL excitation and cathodoluminescence, are employed for characterization of GaNAs epilayers and GaAs/GaNxAs1-x quantum well structures grown by gas source molecular beam epitaxy at low temperature. The existence of strong potential fluctuations in the band edge of the GaNAs alloy is concluded, even for the samples with high optical quality, from a detailed analysis of the characteristic properties of the GaNAs-related PL emission. Based on the observed similarity in the PL properties between the GaNAs epilayers and the QW structures, the potential fluctuations are suggested to be mainly due to composition disorder and strain nonuniformity of the alloy. ⌐ 2000 Elsevier Science S.A. All rights reserved.

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