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  • 1.
    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.

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

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

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  • 3.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    CVD growth of SiC for high-power and high-frequency applications2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Silicon Carbide (SiC) is a wide bandgap semiconductor that has attracted a lot of interest for electronic applications due to its high thermal conductivity, high saturation electron drift velocity and high critical electric field strength. In recent years commercial SiC devices have started to make their way into high and medium voltage applications.

    Despite the advancements in SiC growth over the years, several issues remain. One of these issues is that the bulk grown SiC wafers are not suitable for electronic applications due to the high background doping and high density of basal plane dislocations (BPD). Due to these problems SiC for electronic devices must be grown by homoepitaxy. The epitaxial growth is performed in chemical vapor deposition (CVD) reactors. In this work, growth has been performed in a horizontal hot-wall CVD (HWCVD) reactor. In these reactors it is possible to produce high-quality SiC epitaxial layers within a wide range of doping, both n- and p-type.

    SiC is a well-known example of polytypism, where the different polytypes exist as different stacking sequences of the Si-C bilayers. Polytypism makes polytype stability a problem during growth of SiC. To maintain polytype stability during homoepitaxy of the hexagonal polytypes the substrates are usually cut so that the angle between the surface normal and the c-axis is a few degrees, typically 4 or 8°. The off-cut creates a high density of micro-steps at the surface. These steps allow for the replication of the substrates polytype into the growing epitaxial layer, the growth will take place in a step-flow manner. However, there are some drawbacks with step-flow growth. One is that BPDs can replicate from the substrate into the epitaxial layer. Another problem is that 4H-SiC is often used as a substrate for growth of GaN epitaxial layers. The epitaxial growth of GaN has been developed on on-axis substrates (surface normal coincides with c-axis), so epitaxial 4H-SiC layers grown on off-axis substrates cannot be used as substrates for GaN epitaxial growth.

    In efforts to solve the problems with off-axis homoepitaxy of 4H-SiC, on-axis homoepitaxy has been developed. In this work, further development of wafer-scale on-axis homoepitaxy has been made. This development has been made on a Si-face of 4H-SiC substrates. The advances include highly resistive epilayers grown on on-axis substrates. In this thesis the ability to control the surface morphology of epitaxial layers grown on on-axis homoepitaxy is demonstrated. This work also includes growth of isotopically enriched 4H-SiC on on-axis substrates, this has been done to increase the thermal conductivity of the grown epitaxial layers.

    In (paper 1) on-axis homoepitaxy of 4H-SiC has been developed on 100 mm diameter substrates. This paper also contains comparisons between different precursors. In (paper 2) we have further developed on-axis homoepitaxy on 100 mm diameter wafers, by doping the epitaxial layers with vanadium. The vanadium doping of the epitaxial layers makes the layers highly resistive and thus suitable to use as a substrate for III-nitride growth. In (paper 3) we developed a method to control the surface morphology and reduce the as-grown surface roughness in samples grown on on-axis substrates. In (paper 4) we have increased the thermal conductivity of 4H-SiC epitaxial layers by growing the layers using isotopically enriched precursors. In (paper 5) we have investigated the role chlorine have in homoepitaxial growth of 4H-SiC. In (paper 6) we have investigated the charge carrier lifetime in as-grown samples and traced variations in lifetime to structural defects in the substrate. In (paper 7) we have investigated the formation mechanism of a morphological defect in homoepitaxial grown 4H-SiC.

    List of papers
    1. The Role of Chlorine during High Growth Rate Epitaxy
    Open this publication in new window or tab >>The Role of Chlorine during High Growth Rate Epitaxy
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    2015 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 821-823, p. 141-144Article in journal (Refereed) Published
    Abstract [en]

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

    Place, publisher, year, edition, pages
    Pfaffikon, Switzerland: Scientific.Net, 2015
    Keywords
    Chemical Vapor Deposition (CVD), Chlorine, Doping, Epitaxy, High Growth Rate
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-123951 (URN)10.4028/www.scientific.net/MSF.821-823.141 (DOI)
    Conference
    European Conference on Silicon Carbide & Related Materials, Grenoble, France, 21-25 September 2014
    Available from: 2016-01-14 Created: 2016-01-14 Last updated: 2019-02-14Bibliographically approved
    2. Long Charge Carrier Lifetime in As-Grown 4H-SiC Epilayer
    Open this publication in new window or tab >>Long Charge Carrier Lifetime in As-Grown 4H-SiC Epilayer
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    2016 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 858, p. 125-128Article in journal (Refereed) Published
    Abstract [en]

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

    Place, publisher, year, edition, pages
    Trans Tech Publications, 2016
    Keywords
    Carrier Lifetime, Chemical Vapor Deposition (CVD), Chlorine, Epitaxy
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-154468 (URN)10.4028/www.scientific.net/MSF.858.125 (DOI)2-s2.0-84971500767 (Scopus ID)
    Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2019-02-21Bibliographically approved
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    CVD growth of SiC for high-power and high-frequency applications
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  • 4.
    Karhu, Robin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Booker, Ian
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Long Charge Carrier Lifetime in As-Grown 4H-SiC Epilayer2016In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 858, p. 125-128Article in journal (Refereed)
    Abstract [en]

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

  • 5.
    Karhu, Robin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Booking, Ian
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    The Role of Chlorine during High Growth Rate Epitaxy2015In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 821-823, p. 141-144Article in journal (Refereed)
    Abstract [en]

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

  • 6.
    Karhu, Robin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ghezellou, Misagh
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    The Origin and Formation Mechanism of an Inclined Line-like Defect in 4H-SiC Epilayers2022In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 259, no 4, article id 2100512Article in journal (Refereed)
    Abstract [en]

    The origin and the formation mechanism of a surface morphological defect in 4H-SiC epilayers are reported. The defect appears on the surface of an epilayer as an inclined line-like feature at an angle of +/- 80 degrees to the step-flow direction [ 11 2 over bar 0 ] . The defect is confirmed to originate from a threading screw dislocation intersecting the surface and its orientation is controlled by the sign of the Burgers vector of the dislocation. The defect forms through the interaction of local spiral growth associated with threading screw dislocations and step-flow growth related to the substrate offcut. The defect mainly appears in the epilayers grown through chloride-based chemistry, where in situ surface preparation of the substrate is performed in H-2 + HCl at a relatively high temperature.

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  • 7.
    Karhu, Robin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Univ Iceland, Iceland.
    Magnusson, Bjorn
    Norstel AB, Sweden.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Danielsson, Örjan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    CVD growth and properties of on-axis vanadium doped semi-insulating 4H-SiC epilayers2019In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 125, no 4, article id 045702Article in journal (Refereed)
    Abstract [en]

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

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  • 8.
    Khosa, R. Y.
    et al.
    Univ Iceland, Iceland; Univ Educ Lahore, Pakistan.
    Chen, Jr-Tai
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Pålsson, K.
    Univ Iceland, Iceland.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Rorsman, N.
    Chalmers Univ Technol, Sweden.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Univ Iceland, Iceland.
    Electrical properties of 4H-SiC MIS capacitors with AlN gate dielectric grown by MOCVD2019In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 153, p. 52-58Article in journal (Refereed)
    Abstract [en]

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

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  • 9.
    Khosa, R. Y.
    et al.
    Univ Iceland, Iceland; Univ Educ Lahore, Pakistan.
    Chen, Jr-Tai
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Winters, M.
    Chalmers Univ Technol, Sweden.
    Palsson, K.
    Univ Iceland, Iceland.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Rorsman, N.
    Chalmers Univ Technol, Sweden.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Univ Iceland, Iceland.
    Electrical characterization of high k-dielectrics for 4H-SiC MIS devices2019In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 98, p. 55-58Article in journal (Refereed)
    Abstract [en]

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

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  • 10.
    Khosa, R. Y.
    et al.
    Univ Iceland, Iceland.
    Thorsteinsson, E. B.
    Univ Iceland, Iceland.
    Winters, M.
    Chalmers Univ Technol, Sweden.
    Rorsman, N.
    Chalmers Univ Technol, Sweden.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Univ Iceland, Iceland.
    Electrical characterization of amorphous Al2O3 dielectric films on n-type 4H-SiC2018In: AIP Advances, E-ISSN 2158-3226, Vol. 8, no 2, article id 025304Article in journal (Refereed)
    Abstract [en]

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

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  • 11.
    Khosa, Rabia Y.
    et al.
    Science Institute, University of Iceland, Iceland.
    Chen, J. T.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Pálsson, K.
    Science Institute, University of Iceland, Iceland.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Rorsman, Niklas
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, Sweden.
    Sveinbjörnsson, Einar Ö.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Science Institute, University of Iceland, Iceland.
    Electrical Characterization of MOCVD Grown Single Crystalline AlN Thin Films on 4H-SiC2019In: Silicon Carbide and Related Materials 2018, Trans Tech Publications Ltd , 2019, Vol. 963, p. 460-464Conference paper (Refereed)
    Abstract [en]

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

  • 12.
    Khosa, Rabia Y.
    et al.
    Science Institute, University of Iceland, IS-107 Reykjavík, Iceland.
    Sveinbjörnsson, Einar
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Science Institute, University of Iceland, IS-107 Reykjavík, Iceland.
    Winters, Michael
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg, Sweden.
    ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Rorsman, Niklas
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Göteborg, Sweden.
    Low Density of Near-Interface Traps at the Al2O3/4H-SiC Interface with Al2O3 Made by Low Temperature Oxidation of Al2017In: Silicon Carbide and Related Materials 2016, Trans Tech Publications Ltd , 2017, Vol. 897, p. 135-138Conference paper (Refereed)
    Abstract [en]

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

  • 13.
    Nagy, Roland
    et al.
    Univ Stuttgart, Germany; Inst Quantum Sci and Technol, Germany.
    Niethammer, Matthias
    Univ Stuttgart, Germany; Inst Quantum Sci and Technol, Germany.
    Widmann, Matthias
    Univ Stuttgart, Germany; Inst Quantum Sci and Technol, Germany.
    Chen, Yu-Chen
    Univ Stuttgart, Germany; Inst Quantum Sci and Technol, Germany.
    Udvarhelyi, Peter
    Hungarian Acad Sci, Hungary; Eotvos Lorand Univ, Hungary.
    Bonato, Cristian
    Heriot Watt Univ, Scotland.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    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.
    Maze, Jeronimo R.
    Pontificia Univ Catolica Chile, Chile; Pontificia Univ Catolica Chile, Chile.
    Ohshima, Takeshi
    Natl Inst Quantum and Radiol Sci and Technol, Japan.
    Soykal, Oney O.
    Naval Res Lab, DC 20375 USA.
    Gali, Adam
    Hungarian Acad Sci, Hungary; Budapest Univ Technol and Econ, Hungary.
    Lee, Sang-Yun
    Korea Inst Sci and Technol, South Korea.
    Kaiser, Florian
    Univ Stuttgart, Germany; Inst Quantum Sci and Technol, Germany.
    Wrachtrup, Joerg
    Univ Stuttgart, Germany; Inst Quantum Sci and Technol, Germany.
    High-fidelity spin and optical control of single silicon-vacancy centres in silicon carbide2019In: Nature Communications, E-ISSN 2041-1723, Vol. 10, article id 1954Article in journal (Refereed)
    Abstract [en]

    Scalable quantum networking requires quantum systems with quantum processing capabilities. Solid state spin systems with reliable spin-optical interfaces are a leading hardware in this regard. However, available systems suffer from large electron-phonon interaction or fast spin dephasing. Here, we demonstrate that the negatively charged silicon-vacancy centre in silicon carbide is immune to both drawbacks. Thanks to its (4)A(2) symmetry in ground and excited states, optical resonances are stable with near-Fourier-transform-limited linewidths, allowing exploitation of the spin selectivity of the optical transitions. In combination with millisecond-long spin coherence times originating from the high-purity crystal, we demonstrate high-fidelity optical initialization and coherent spin control, which we exploit to show coherent coupling to single nuclear spins with similar to 1 kHz resolution. The summary of our findings makes this defect a prime candidate for realising memory-assisted quantum network applications using semiconductor-based spin-to-photon interfaces and coherently coupled nuclear spins.

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  • 14.
    Spindlberger, L.
    et al.
    Johannes Kepler Univ Linz, Austria.
    Csore, A.
    Hungarian Acad Sci, Hungary.
    Thiering, G.
    Hungarian Acad Sci, Hungary.
    Putz, S.
    Univ Wien, Austria.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Fromherz, T.
    Johannes Kepler Univ Linz, Austria.
    Gali, A.
    Hungarian Acad Sci, Hungary; Univ Technol and Econ, Hungary.
    Trupke, M.
    Univ Wien, Austria.
    Optical Properties of Vanadium in 4H Silicon Carbide for Quantum Technology2019In: Physical Review Applied, E-ISSN 2331-7019, Vol. 12, no 1, article id 014015Article in journal (Refereed)
    Abstract [en]

    We study the optical properties of tetravalent-vanadium impurities in 4H silicon carbide. Light emission from two crystalline sites is observed at wavelengths of 1.28 and 1.33 mu m, with optical lifetimes of 163 and 43 ns, respectively, which remains stable up to 50 and 20 K, respectively. Moreover, spectrally broad photoluminescence is observed up to room temperature. Group-theory and ab initio density-functional supercell calculations enable unequivocal site assignment and shed light on the spectral features of the defects. Specifically, our numerical simulations indicate that the site assignment is reversed with respect to previous assumptions. Our calculations show that vanadium in silicon carbide has highly favorable properties for the generation of single photons in the telecommunication wavelength regime. Combined with the available electronic and nuclear degrees of freedom, vanadium presents all the ingredients required for a highly efficient spin-photon interface.

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  • 15.
    Stenberg, Pontus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Booker, Ian Don
    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.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Defects in silicon carbide grown by fluorinated chemical vapor deposition chemistry2018In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 535, p. 44-49Article in journal (Refereed)
    Abstract [en]

    Point defects in n- and p-type 4H-SiC grown by fluorinated chemical vapor deposition (CVD) have been characterized optically by photoluminescence (PL) and electrically by deep-level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS). The results are considered in comparison with defects observed in non-fluorinated CVD growth (e.g., using SiH4 instead of SiF4 as silicon precursor), in order to investigate whether specific fluorine-related defects form during the fluorinated CVD growth, which might prohibit the use of fluorinated chemistry for device-manufacturing purposes. Several new peaks identifying new defects appear in the PL of fluorinated-grown samples, which are not commonly observed neither in other halogenated chemistries, nor in the standard CVD chemistry using silane (SiH4). However, further investigation is needed in order to determine their origin and whether they are related to incorporation of F in the SiC lattice, or not. The electric characterization does not find any new electrically-active defects that can be related to F incorporation. Thus, we find no point defects prohibiting the use of fluorinated chemistry for device-making purposes.

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  • 16.
    Tia, Kai
    et al.
    Xi An Jiao Tong Univ, Peoples R China.
    Xia, Jinghua
    Global Energy Interconnect Res Inst Co Ltd, Peoples R China.
    Elgammal, Karim
    KTH Sch EECS, Sweden.
    Schoner, Adolf
    Ascatron AB, Sweden.
    Kaplan, Wlodek
    Ascatron AB, Sweden.
    Karhu, Robin
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ul-Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Hallen, Anders
    KTH Sch EECS, Sweden.
    Modelling the static on-state current voltage characteristics for a 10 kV 4H-SiC PiN diode2020In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 115, article id 105097Article in journal (Refereed)
    Abstract [en]

    A 10 kV 4H-SiC epitaxial PiN diode is fabricated and the measured static on-state current voltage characteristics are used to tune the physical models and parameters included in TCAD device simulations. From the measurements it is found that the on-state voltage drop decreases more than 0.5 V at a current density of 100 A/cm(2), as the temperature is raised from room temperature to 300 degrees C. The steep slope of the IV-curve is, furthermore, maintained at elevated temperatures in contrast to most silicon PiN structures, where the decrease in mobility at higher temperatures typically decreases the IV slope, resulting in an increased voltage drop. Physical device simulations, involving common models for bandgap, incomplete ionization, charge carrier lifetime and mobility, are systematically compared and optimized to obtain the best fit with measured data. The negative temperature dependence can be simulated with good precision although the fitting is very sensitive to the choice of mobility models and, in particular, the acceptor ionization energy.

  • 17.
    Ul-Hassan, Jawad
    et al.
    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.
    Wafer Scale On-Axis Homoepitaxial Growth of 4H-SiC(0001) for High-Power Devices: Influence of Different Gas Phase Chemistries and Growth Rate Limitations2019In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 19, no 6, p. 3288-3297Article in journal (Refereed)
    Abstract [en]

    On-axis homoepitaxy of 4H-SiC has the advantage of producing epilayers that are free of basal plane dislocations. Such layers can be highly beneficial for SiC-based high-power bipolar electronic devices which otherwise suffer from bipolar degradation phenomena related to basal plane dislocations in epilayers. In this study, we have developed on-axis homoepitaxy on the Si-face of 100 mm diameter 4H-SiC wafers with only 4H polytype in the epilayer excluding the edges of the wafer. We have also compared standard and chloride-based growth, the influence of different ambient conditions on surface preparation of the substrate, the influence of the histories of different growth cells, and the geometry of the susceptors regarding 4H-polytype stability in the epilayer. Substrate surface preparation, growth temperature, C/Si ratio, and Si/H ratio are found to be the most influential parameters to achieve homoepitaxy. On-axis homoepitaxial growth rate is limited to a very low value of amp;lt;10 mu m/h. We have performed a systematic study to understand the influence of different growth parameters and gas phase chemistries to determine whether on-axis growth rate can be enhanced and, if not, what the limiting factors are. Our experimental evidence suggests that the on-axis growth rate is not limited by the gas phase chemistry or diffusion, but it is limited by the surface kinetics. A significantly low step density on on-axis substrates lowers the surface reaction rates and limits the growth rate to lower values. It may not be possible to further improve the growth rate even with chloride-based growth using epitaxial growth conditions.

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