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  • 1.
    Anghel, Clara
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Dong, Qian
    Rundgren, John
    Hultquist, Gunnar
    Saeki, Isao
    Limbäck, Magnus
    Gas-tight oxides – Reality or just a Hope2006Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 522-523, s. 93-101Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A better understanding of the transport properties of gases in oxides is certainly very important in many applications. In the case of metals, a general protection measure against corrosion implies formation of a dense metal oxide scale. The scale should act as a barrier against gas transport and consequently it needs to be gas-tight. This is often assumed but rarely, if ever, confirmed. Hence there is a need for characterization of micro- and/or meso- pores formed especially during the early oxidation stage of metallic materials. This paper presents a novel and relatively straightforward method for characterization of gas release from an oxide previously equilibrated in a controlled atmosphere. The geometry of the sample is approximated to be a plate. The plate can be self-supporting or constitute a scale on a substrate. A mathematical model for calculation of diffusivity and gas content is given for this geometry. A desorption experiment, involving a mass spectrometer placed in ultra high vacuum, can be used to determine diffusivity and amount of gas released with aid of the mathematical model. The method is validated in measurements of diffusivity and solubility of He in quartz and applied in characterization of two Zr-oxides and one Fe oxide. From the outgassed amounts of water and nitrogen the H2O/N-2 molar ratio can be used to estimate an effective pore size in oxides.

  • 2.
    Barsoum, Zuheir
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Residual stress predictin and relaxation in welded tubular joints under constant cyclic loading2006Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 524-525, s. 323-330Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper three-dimensional welding simulations were carried out in FE software ANSYS in order to predict transient temperatures and the residual stresses in a three pass welded tubular joints. The thermal analysis and the moving heat source were verified with temperature measurements and the computed residual stresses were verified with hole drilling measurements. Then residual stress relaxation analyses were carried out on the tubular structure, with similar load cases as in earlier fatigue testing on the same tubular joint structures.

  • 3.
    Bergman, Ola
    et al.
    Research and Development, Höganäs AB.
    Lindqvist, Björn
    Tech Center, Höganäs (China) Ltd., Qingpu, Shanghai.
    Bengtsson, Sven
    Research and Development, Höganäs AB.
    Influence of sintering parameters on the mechanical performance of PM steels pre-alloyed with chromium2007Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 534-536, s. 545-548Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Powder grades pre-alloyed with 1.5-3 wt% chromium are suitable for PM steel components in high performance applications. These materials can be successfully sintered at the conventional temperature 1120 degrees C, although well-monitored sintering atmospheres with low oxygen partial pressures (< 10(-17)-10(-18) atm) are required to avoid oxidation. Mechanical properties of the Cr-alloyed PM grades are enhanced by a higher sintering temperature in the range 1120-1250 degrees C, due to positive effects from pore rounding, increased density and more effective oxide reduction. A material consisting of Astaloy CrM, which is pre-alloyed with 3 wt% Cr and 0.5 wt% Mo, and 0.6 wt% graphite obtains an ultimate tensile strength of 1470 MPa combined with an impact strength of 31 J at density 7.1 g/cm(3), after sintering at 1250 degrees C followed by cooling at 2.5 degrees C/s and tempering.

  • 4. Bora, T.
    et al.
    Kyaw, H. H.
    Dutta, Joydeep
    Water Research Center, Sultan Qaboos University.
    Plasmon resonance enhanced zinc oxide photoelectrodes for improvement in performance of dye sensitized solar cells2014Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 771, s. 91-101Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanocomposites of vertically aligned zinc oxide (ZnO) nanorod arrays incorporated with gold (Au) nanoparticles have been used as photoelectrodes to fabricate dye sensitized solar cells (DSSCs). Due to the surface plasmon resonance of the Au nanoparticles, the nanocomposite photoelectrodes demonstrate enhancement in the visible light absorption resulting in ~8% higher photocurrent compared to ZnO photoelectrode based DSSCs fabricated without any Au nanoparticles. In addition to the higher optical absorption due to the gold nanoparticles, a Schottky barrier forms at the ZnO/Au interface preventing the back electron transfer from the conduction band of the semiconductor nanorods to the redox electrolyte providing improvement in the charge separation at the nanocomposite photoelectrode. Upon incorporation of Au nanoparticles, the overall efficiency of the DSSC increased from 2. 41% to 3. 27%. The role of Au nanoparticles on the performance of the DSSCs for varying concentration of the Au nanoparticles as well as the post-growth annealing treatment of the nanocomposite photoelectrode is reported.

  • 5.
    Buono, Benedetto
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Ghandi, Reza
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Malm, B. Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Current Gain Degradation in 4H-SiC Power BJTs2011Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 679-680, s. 702-705Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    SiC airs are very attractive for high power application, but long term stability is still problematic and it could prohibit commercial production of these devices. The aim of this paper is to investigate the current gain degradation in BJTs with no significant degradation of the on-resistance. Electrical measurements and simulations have been used to characterize the behavior of the BJT during the stress test. Current gain degradation occurs, the gain drops from 58 before stress to 43 after 40 hours, and, moreover, the knee current shows fluctuations in its value during the first 20 hours. Current gain degradation has been attributed to increased interface traps or reduced lifetime in the base-emitter region or small stacking faults in the base-emitter region, while fluctuations of the knee current might be due to stacking faults in the collector region.

  • 6.
    Buono, Benedetto
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Ghandi, Reza
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Malm, B. Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Temperature Modeling and Characterization of the Current Gain in 4H-SiC Power BJTs2010Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 645-648, s. 1061-1064Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The current gain of 4H-SiC BJTs has been modeled using interface traps between SIC and SiO2 to describe surface recombination, by a positive temperature dependence of the carrier lifetime in the base region and by bandgap narrowing in the emitter region. The interface traps have been modeled by one single level at 1 eV above the valence band, with capture cross section of 1 x 10(-15) cm(2) and concentration of 2 x 10(12) cm(-2). The temperature behavior of SiC BJTs has been simulated and the results have been compared with measurements. An analysis of the carrier concentration has been performed in order to describe the mechanisms for fall-off of the current gain at high collector current. At room temperature high injection in the base and forward biasing of the base-collector junction occur simultaneously causing an abrupt drop of the current gain. At higher temperatures high injection in the base is alleviated by the higher ionization degree of the aluminum dopants, and then forward biasing of the base-collector junction is the only acting mechanism for the current gain fall-off at high collector current. This mechanism and the negative temperature dependence of the carrier mobility can also explain the reduction of the knee current for gain fall-off with increasing temperature. Simulations with different emitter widths have been also performed and analyzed to characterize the emitter size effect. Higher current density caused by reducing the emitter width introduces higher carrier recombination in the emitter region, leading to a reduction of the current gain.

  • 7.
    Buono, Benedetto
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Ghandi, Reza
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Malm, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Investigation of Current Gain Degradation in 4H-SiC Power BJTs2012Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 717-720, s. 1131-1134Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The current gain degradation of 4H-SiC BJTs with no significant drift of the on-resistance is investigated. Electrical stress on devices with different emitter widths suggests that the device design can influence the degradation behavior. Analysis of the base current extrapolated from the Gummel plot indicates that the reduction of the carrier lifetime in the base region could be the cause for the degradation of the gain. However, analysis of the base current of the base-emitter diode shows that the degradation of the passivation layer could also influence the reduction of the current gain.

  • 8.
    Buono, Benedetto
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Lee, Hyung-Seok
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl -Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Simulations of Open Emitter Breakdown Voltage in SiC BJTs with non Implanted JTE2009Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 615-617, s. 841-844Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ion implantation for selective doping of SiC is problematic due to damage generation during the process and low activation of dopants. In SiC bipolar junction transistor (BJT) the junction termination extension (JTE) can be formed without ion implantation using instead a controlled etching into the epitaxial base. This etched JTE is advantageous because it eliminates ion implantation induced damage and the need for high temperature annealing. However, the dose, which is controlled by the etched base thickness and doping concentration, plays a crucial role. In order to find the optimum parameters, device simulations of different etched base thicknesses have been performed using the software Sentaurus Device. A surface passivation layer consisting of silicon dioxide, considering interface traps and fixed trapped charge, has been included in the analysis by simulations. Moreover a comparison with measured data for fabricated SiC BJTs has been performed.

  • 9. Dahlquist, Fanny
    et al.
    Svedberg, J. -O
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Breitholtz, Bo
    Lendenmann, Heinz
    2.8 kV, forward drop JBS diode with low leakage2000Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 338-342, s. 1179-1182Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High voltage Schottky-, Junction Barrier Schottky (JBS)- and PiN-diodes with an implanted JTE termination have been fabricated on the same 4H-SiC wafer. Blocking voltages of 2.5-2.8 kV were reached for JBS and PiN diodes while the Schottky diodes reach about 2.0 kV. It is shown that the JBS design increases the blocking voltage effectively compared to the Schottky device with less than 10% increase in on-state static losses. Also, a comparison of static losses to a PiN diode gives a decrease of 40% for the JBS. The leakage current is also lowered by two decades compared to the Schottky device at its blocking voltage. Temperature measurements show that the low leakage current is maintained up to at least 225 °C.

  • 10. Dahlquist, Fanny
    et al.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Rottner, K.
    Junction barrier Schottky diodes in 4H-SiC and 6H-SiC1998Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 264-268, nr PART 2, s. 1061-1064Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Junction Barrier Schottky (JBS) diode in silicon carbide is a promising candidate for a low-leakage power rectifier for high switching frequencies and elevated temperature operation. It has the advantage of a low forward voltage drop while keeping a low leakage current at high blocking voltage. JBS devices have been fabricated in 4H SiC and 6H SiC and then electrically characterised in comparison with pn and Schottky diodes on the same wafer. The JBS devices reached blocking voltages up to 1.0 kV at a leakage current density of 13 ÎŒA/cm2 and the forward conduction was limited by an on-resistance close to the theoretical value.

  • 11.
    Danielsson, Erik
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Lee, Hyung-Seok
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schöner, Adolf
    Acreo AB.
    Hallin, Christer
    Department of Physics and Measurement Technology, Linköping University.
    A 4H-SiC BJT with an Epitaxially Regrown Extrinsic Base Layer2005Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 483-485, s. 905-908Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    4H-SiC BJTs were fabricated using epitaxial regrowth instead of ion implantation to form a highly doped extrinsic base layer necessary for a good base ohmic contact. A remaining p(+) regrowth spacer at the edge of the base-emitter junction is proposed to explain a low current gain of 6 for the BJTs. A breakdown voltage of 1000 V was obtained for devices with Al implanted JTE.

  • 12.
    Danielsson, Erik
    et al.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Domeij, Martin
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Zetterling, Carl-Mikael
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Östling, Mikael
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Schöner, Adolf
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Extrinsic base design of SiC bipolar transistors2004Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 457-460, nr II, s. 1117-1120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The SiC npn bipolar junction transistor (BJT) is a very promising device for high voltage and high power switches. The SiC BJT has, due to junction voltage cancellation, potentially a low on-resistance. However, the high resistivity in the base layer can induce a locally forward biased base collector junction and a premature current from the base to collector at on-state. In this work we propose a new technique to fabricate the extrinsic base using regrowth of the extrinsic base layer. This technique can put the highly doped region of the extrinsic base a few tenths of a micron from the intrinsic region. We also propose a new mobility model in our simulations to correctly account for the ionized impurities in minority carrier transport and elevated temperature.

  • 13. Danielsson, Erik
    et al.
    Harris, C. I.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Thermal stability of sputtered TiN as metal gate on 4H-SiC1998Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 264-268, nr PART 2, s. 805-808Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    MOS-structures were made with TiN as metal gate on 4H-SiC. The thermal stability and electrical properties of this gate was determined by CV-measurements. Comparison with Al gates showed that TiN worked well as a gate metal on 4H-SiC. The hysteresis and density of the interface states were comparable for the two gate types. The n-type samples had low leakage and a flatband voltage of a few volts, while the p-type samples had high leakage and a fiatband voltage of around -20 V. The structure showed poor characteristics after a 700°C anneal for one hour, which is probably caused by the formation of titanium silicide. The TiN films had a lower content of nitrogen than expected, which could influence the stability.

  • 14. Danielsson, Erik
    et al.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Forsberg, U.
    Janzen, E.
    Investigation of thermal properties in fabricated 4H-SiC high-power bipolar transistors2002Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 389-393, nr 2, s. 1337-1340Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silicon Carbide bipolar junction transistors have been fabricated and investigated. The transistors had a maximmn current gain of approximately 10 times, and a breakdown voltage of up to 600 V. When operated at high power densities the device showed a clear self-heating effect, decreasing the current gain. The junction temperature was extracted during self-heating to approximately 150 °C, using the assumption that the current gain only depends on temperature. Thermal images of a device under operation were also recorded using an infrared camera, showing a significant temperature increase in the vicinity of the device. Physical device simulations have been used to analyze the measured data. The thermal conductivity is fitted to model the measured self-heating, and the lifetime in the base is fitted against the measurement of the current gain.

  • 15. Danielsson, Erik
    et al.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Lee, S. K.
    Linthicum, K. J.
    Thomson, D. B.
    Nam, O. -H
    Davis, R. F.
    Dry etching and metallization schemes in a GaN/SiC heterojunction device process2000Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 338-342, s. 1049-1052Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Dry etching and metallization schemes are described for a GaN/SiC heterojunction. GaN was reactive ion etched in a chlorine based chemistry (Cl2/Ar), and an ICP etch was used on 4H-SiC using a fluorine based chemistry (SF6/Ar/O2). The etch rates obtained on GaN was above 400 nm/min. High sample temperature from self heating and large dc-bias was the probable cause for the high etch rate. The ICP etch rate on SiC approached 320 nm/min, and the etch selectivity to GaN was &gt;100. The metallization was based on Ti for both n-GaN and p-SiC. TLM and Kelvin structures were used to extract the specific contact resistivity, ρC. After a 950 °C anneal in N2 ρC on the GaN samples were below 1·10-6 Ωcm2 for sputtered contacts in room temperature, and an order of magnitude higher with evaporation. On p-SiC no ohmic behavior was found with a doping of 4·1018 cm-3, but the same contact metallization on highly doped areas (&gt;1020 cm-3) showed ohmic behavior with ρC below 10-4 Ωcm2.

  • 16.
    Domeij, Martin
    et al.
    KTH, Tidigare Institutioner                               , Elektronik.
    Breitholtz, Bo
    KTH, Tidigare Institutioner                               , Elektronik.
    Linnros, Jan
    KTH, Tidigare Institutioner                               , Elektronik.
    Östling, Mikael
    KTH, Tidigare Institutioner                               , Elektronik.
    Reverse Recovery and Avalance Injection in High Voltage SiC PIN Diodes1998Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 264-268, s. 1041-Artikkel i tidsskrift (Annet vitenskapelig)
  • 17.
    Domeij, Martin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Danielsson, Erik
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Lee, Hyung-Seok
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Current gain of 4H-SiC bipolar transistors including the effect of interface states2005Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 483, s. 889-892Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The current gain (&beta;) of 4H-SiC BJTs as function of collector current (I-C) has been investigated by DC and pulsed measurements and by device simulations. A measured monotonic increase of &beta; with I-C agrees well with simulations using a constant distribution of interface states at the 4H-SiC/SiO2 interface along the etched side-wall of the base-emitter junction. Simulations using only bulk recombination, on the other hand, are in poor agreement with the measurements. The interface states degrade the simulated current gain by combined effects of localized recombination and trapped charge that influence the surface potential. Additionally, bandgap narrowing has a significant impact by reducing the peak current gain by about 50% in simulations.

  • 18.
    Domeij, Martin
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Lee, Hyung-Seok
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schoner, A.
    Current gain dependence on emitter width in 4H-SiC BJTs2006Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 527-529, s. 1425-1428Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper reports the fabrication of epitaxial 4H-SiC bipolar junction transistors (BJTs) with a maximum current gain beta = 64 and a breakdown voltage of 1100 V. The high beta value is attributed to high material quality obtained after a continuous epitaxial growth of the base-emitter junction. The current gain of the BJTs increases with increasing emitter width indicating a significant influence of surface recombination. This "emitter-size" effect is in good agreement with device simulations including recombination in interface states at the etched termination of the base-emitter junction.

  • 19.
    Elahipanah, Hossein
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Salemi, Arash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Buono, Benedetto
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Process variation tolerant 4H-SiC power devices utilizing trench structures2013Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 740-742, s. 809-812Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silicon carbide (SiC) is one of the most attractive semiconductors for high voltage applications. The breakdown voltage of SiC-based devices highly depends on the variation of the fabrication process including doping of the epilayers and the etching steps. In this paper, we show a way to diminish this variability by employing novel trench structures. The influence of the process variations in terms of doping concentration and etching has been studied and compared with conventional devices. The breakdown voltage variation (ΔVBr) of 450 V and 2100 V is obtained for the ±20% variation of doping concentration of the devices with and without the trench structures, respectively. For ±20% variation in etching steps, the maximum ΔVBR of 380 V is obtained for the device with trench structures in comparison to 1800 V for the conventional structure without trench structures. These results show that the breakdown voltage variation is significantly reduced by utilizing the proposed structure.

  • 20.
    Elahipanah, Hossein
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik.
    Salemi, Arash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik.
    Zetteling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik.
    Modification of Etched Junction Termination Extension for the High Voltage 4H-SiC Power Devices2016Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 858, s. 978-981Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    High voltage 4H-SiC bipolar junction transistors (BJTs) with modified etched junction termination extension (JTE) are fabricated and optimized in terms of the length and remaining dose of JTEs. It is found that the JTE1 is the most effective one in spreading the electric field. Hence, for a given total termination length, a decremental JTE length from the innermost edge to the outermost mesa edge of the device results in better modification of the electric field. A breakdown voltage of 4.95 kV is measured for the modified device, which shows ~20% improvement of the termination efficiency for no extra cost or extra process step. Equal-size BJTs by interdigitated-emitter with different number of fingers and cell pitches are fabricated. It is presented that the maximum current gain decreases by having more fingers while the maximum current gain is achieved at higher current density.

  • 21.
    Elahipanah, Hossein
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Salemi, Arash
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    4.5-kV 20-mΩ. cm2 Implantation-Free 4H-SiC BJT with Trench Structures on the Junction Termination Extension2015Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 821, s. 838-841Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A single-mask junction termination extension withtrench structures is formed to realize a 4.5 kV implantation-free 4H-SiCbipolar junction transistor (BJT). The trench structures are formed on the baselayer with dry etching using a single mask. The electric field distributionalong the structure is controlled by the number and dimensions of the trenches.The electric field is distributed by the trench structures and thus the electricfield crowding at the base and mesa edges is diminished. The design isoptimized in terms of the depth, width, spacing, and number of the trenches toachieve a breakdown voltage (VB) of 4.5 kV, which is 85% of thetheoretical value. Higher efficiency is obtainable with finer lithographicresolution leading to smaller pitch, and higher number and narrower trenches.The specific on-resistance (RON) of 20 mΩ.cm2 is measuredfor the small-area BJT with active area of 0.04 mm2. The BV-RONof the fabricated device is very close to the SiC limit and by far exceeds thebest SiC MOSFETs.

  • 22.
    Eriksson, K. G. Peter
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Lee, Hyung-Seok
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    A Simple and Reliable Electrical Method for Measuring the Junction Temperature and Thermal Resistance of 4H-SiC Power Bipolar Junction Transistors2009Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 600-603, s. 1171-1174Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To determine the maximum allowed power dissipation in a power transistor, it is important to determine the relationship between junction temperature and power dissipation. This work presents a new method for measuring the junction temperature in a SiC bipolar junction transistor (BJT) that is self-heated during DC forward conduction. The method also enables extraction of the thermal resistance between junction and ambient by measurements of the junction temperature as function of DC power dissipation. The basic principle of the method is to determine the temperature dependent IN characteristics of the transistor under pulsed conditions with negligible self-heating, and compare these results with DC measurements with self-heating. Consistent results were obtained from two independent temperature measurements using the temperature dependence of the current gain, and the temperature dependence of the base-emitter IN characteristics, respectively.

  • 23.
    Esteve, Romain
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Schöner, A.
    Reshanov, S.A.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Comparative study of thermal oxides and post-oxidized depositedoxides on n-type free standing 3C-SiC2010Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 645-648, s. 829-832Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electrical properties of oxides fabricated on n-type 3C-SiC (001) using wet oxidationand an advanced oxidation process combining SiO 2 deposition with rapid post oxidation steps havebeen compared. Two alternative SiO 2 deposition techniques have been studied: the plasmaenhanced chemical vapor deposition (PECVD) and the low pressure chemical vapor deposition(LPCVD). The post-oxidized PECVD oxide is been demonstrated to be beneficial in terms ofinterface traps density and reliability.

  • 24.
    Ghandi, Reza
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Buono, Benedetto
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    High Voltage, Low On-resistance 4H-SiC BJTs with Improved Junction Termination Extension2011Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 679-680, s. 706-709Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, implantation-free 4H-SiC bipolar transistors with two-zone etched-JTE and improved surface passivation are fabricated. This design provides a stable open-base breakdown voltage of 2.8 kV which is about 75% of the parallel plane breakdown voltage. The small area devices shows a maximum dc current gain of 55 at Ic=0.33 A (J(C)=825 A/cm(2)) and V-CESAT = 1.05 V at Ic = 0.107 A that corresponds to a low ON-resistance of 4 m Omega.cm(2). The large area device shows a maximum dc current gain of 52 at Ic = 9.36 A (J(C)=312 A/cm(2)) and V-CESAT = 1.14 V at Ic = 5 A that corresponds to an ON-resistance of 6.8 m Omega.cm(2). Also these devices demonstrate a negative temperature coefficient of the current gain (beta=26 at 200 degrees C) and positive temperature coefficient of the ON-resistance (R-ON = 10.2 m Omega.cm(2)).

  • 25.
    Ghandi, Reza
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Esteve, R.
    Buono, Benedetto
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Schoner, A.
    Han, J.
    Dimitrijev, S.
    Reshanov, S. A.
    Zetterling, Carl -Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Experimental evaluation of different passivation layers on the performance of 3kV 4H-SiC BJTs2010Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 645-648, nr Part 1-2, s. 661-664Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, the electrical performance in terms of maximum current gain, ON-resistance and blocking capability has been compared for 4H-SiC BJTs passivated with different surface passivation layers. Variation in BJT performance has been correlated to densities of interface traps and fixed oxide charge, as evaluated through MOS capacitors. Six different methods were used to fabricate SiO2 surface passivation on BJT samples from the same wafer. The highest current gain was obtained for PECVD deposited SiO2 which was annealed in N2O ambient at 1100 degrees C during 3 hours. Variations in breakdown voltage for different surface passivations were also found, and this is attributed to differences in fixed oxide charge that can affect the optimum dose of the high voltage JTE termination.

  • 26.
    Ghandi, Reza
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Lee, Hyung-Seok
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Buono, Benedetto
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl - Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Implantation-Free Low on-resistance 4H-SiC BJTs with Common-Emitter Current Gain of 50 and High Blocking Capability2009Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 615-617, s. 833-836Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, high voltage blocking (2.7 kV) implantation-free SiC Bipolar Junction Transistors with low on-state resistance (12 m Omega-cm(2)) and high common-emitter current gain of 50 have been fabricated. A graded base doping was implemented to provide a low resistive ohmic contact to the epitaxial base. This design features a fully depleted base layer close to the breakdown voltage providing an efficient epitaxial JTE without ion implantation. Eliminating all ion implantation steps in this approach is beneficial for avoiding high temperature dopant activation annealing and for avoiding generation of life-time killing defects that reduces the current gain. Also in this process large area transistors showed common-emitter current gain of 38 and open-base breakdown voltage of 2 kV.

  • 27.
    Ghandi, Reza
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Lee, Hyung-Seok
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Backside Nickel Based Ohmic Contacts to n-type Silicon Carbide2009Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 600-603, s. 635-638Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work focuses on Ni ohmic contacts to the C-face (backside) of n-type 4H-SiC substrates. Low-resistive ohmic contacts to the wafer backside are important especially for vertical power devices. Ni contacts were deposited using E-beam evaporation and annealed at different temperatures (700-1050 degrees C) in RTP to obtain optimum conditions for forming low resistive ohmic contacts. Our results indicate that 1 min annealing at temperatures between 950 and 1000 degrees C provides high quality ohmic contacts with a contact resistivity of 2.3x10(-5) Omega cm(2). Also our XRD results show that different Ni silicide phases appear in this annealing temperature range.

  • 28.
    Hedayati, Raheleh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT). KTH University.
    Lanni, Luigia
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Shakir, Muhammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Salemi, Arash
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    High Temperature Bipolar Master-Slave Comparator and Frequency Divider in 4H-SiC Technology2017Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 897, s. 681-684Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper demonstrates a fully integrated master-slave emitter-coupled logic (ECL)comparator and a frequency divider implemented in 4H-SiC bipolar technology. The comparator consists of two latch stages, two level shifters and an output buffer stage. The circuits have been tested up to 500 °C. The single ended output swing of the comparator is -7.73 V at 25 °C and-7.63 V at 500 °C with a -15 V supply voltage. The comparator consumes 585 mW at 25 °C. The frequency divider consisting of two latches shows a relatively constant output voltage swing over the wide temperature range. The output voltage swing is 7.62 V at 25 °C and 7.32 V at 500 °C.

  • 29. Hofmeister, H.
    et al.
    Dutta, J.
    Hofmann, H.
    Nanoscale ordering in amorphous silicon powders formed by plasma induced reaction of silane1997Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 235-238, nr 2, s. 595-600Artikkel i tidsskrift (Fagfellevurdert)
  • 30. Kang, M. -S
    et al.
    Lee, J. -H
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Bahng, W.
    Kim, N. -K
    Koo, S. -M
    Metal work-function and doping-concentration dependent barrier height of Ni-contacts to 4H-SiC with metal-embedded nano-particles2012Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 717-720, s. 857-860Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigated the effect of the metal work-function and doping concentration on the barrier height of Ni-contacts with embedded nano-particles (NPs) on 4H-SiC surfaces. Both n-type epitaxial layers with N-D=1x10(16) cm(-3), and layers doped by phosphorus implantation to a doping concentration of similar to 1x10(19) cm(-3) are used. The barrier height is reduced with increasing doping concentration and the silver (Ag) nano-particles (R similar to 18.5 nm) further enhance the local electric field of the electrical contacts to 4H-SiC in comparison to gold (Au) nano-particles (R similar to 20.2 nm). In the case of ion-implanted samples, the barrier height of the fabricated SiC diode structures with embedded Ag-NPs was significantly reduced by similar to 0.09 eV and similar to 0.25 eV compared to the samples with Au-NPs and the sample without NPs, respectively.

  • 31.
    Kargarrazi, Saleh
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Lanni, Luigia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Design and characterization of 500°c schmitt trigger in 4H-SiC2015Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 821-823, s. 897-901Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two versions of Schmitt trigger, an emitter-coupled and an operational amplifier (opamp)-based, are implemented in 4H-SiC bipolar technology and tested up to 500 °C. The former benefits the simplicity, smaller footprint, and fewer number of devices, whereas the latter provides better promise for high temperature applications, thanks to its more stable temperature characteristics. In addition, the measurements in the range 25 °C - 500 °C, shows that the opamp-based version provides negative and positive slew rates of 4.8 V/μs and 8.3 V/μs, ~8 and ~3 times higher than that of the emitter-coupled version, which are 1.7 V/μs and 1 V/μs.

  • 32.
    Karlsson, Ulf O
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Jukna, Arturas
    Balevicius, Saulius
    Parseliunas, J
    Electric properties and irradiation of a pulse-laser-excited miniature magnetic-dipole antenna2002Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 384, s. 313-316Artikkel i tidsskrift (Fagfellevurdert)
  • 33. Kobayashi, M.
    et al.
    Uchida, H.
    Minami, A.
    Sakata, A.
    Esteve, Romain
    Schöner, A.
    3C-SiC MOSFET with High Channel Mobility and CVD Gate Oxide2011Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 679-680, s. 645-648Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    3C-SiC MOSFET with 200 cm2/Vs channel mobility was fabricated. High performance device processes were adopted, including room temperature implantation with resist mask, polysilicon-metal gates, aluminium interconnects with titanium and titanium nitride and a specially developed activation anneal at 1600°C in Ar to get a smooth 3C-SiC surface and hence the expected high channel mobility. CVD deposited oxide with post oxidation annealing was investigated to reduce unwanted oxide charges and hence to get a better gate oxide integrity compared to thermally grown oxides. 3C-SiC MOSFETs with 600 V blocking voltage and 10 A drain current were fabricated using the improved processes described above. The MOSFETs assembled with TO-220 PKG indicated specific on-resistances of 5 to 7 mΩcm2.

  • 34. Koo, S. -M
    et al.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Forsberg, U.
    Janzen, E.
    Simulation and Measurement of Switching Characteristics of 4H-SiC Buried-Gate JFETs2003Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 433-436, s. 773-776Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Buried-gate junction field-effect transistors (JFETs) have been fabricated in 4H polytype silicon carbide (SiC). The dynamic switching characteristics of the JFETs in a circuit with inductive load have been characterized. The drain voltage rise/fall time of ∌30 ns and 25 ns have been observed for turn-off and turn-on, respectively. The results have been compared to numerical mixed-mode circuit simulations with finite element structures.

  • 35. Koo, S. -M
    et al.
    Lee, S. -K
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Forsberg, U.
    Janzen, E.
    Influence of trenching effect on the characteristics of buried-gate SiC junction field-effect transistors2002Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 389-393, nr 2, s. 1235-1238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Two different structures of junction field-effect transistors in 4H-SiC, with and without trenching effect in the channel region, have been fabricated and characterized. The devices formed with metal mask show a trenching profile (>∌0.2 Όm) after dry etch in the channel groove region and exhibited static induction transistor (SIT)-like characteristics in the sub-threshold region of I-V curves as the channel thickness decreases. The devices without trenching effect have been processed by using a wet-etched oxide mask resulting in a sloped dry-etch profile (Ξ=∌30°) in the channel, and consequently showed well-saturated drain characteristics for all the channel thicknesses. The conduction mechanisms in these JFETs are examined by the potential profiles from two dimensional numerical simulations.

  • 36.
    Koo, Sang-Mo
    et al.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Zetterling, Carl-Mikael
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Lee, Hyung-Seok
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Östling, Mikael
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    SiC JMOSFETs for high-temperature stable circuit operation2004Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 457-460, s. 1445-1448Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    4H-SiC junction-gated and metal-oxide-semiconductor field effect transistors (JMOSFETs) have been fabricated for high temperature stable circuit operation. The JMOSFETs have shown the feasibility for operating with constant on and off current levels from room temperature up to 300 degreesC. Moreover, by accumulating the channel using the MOS gate, over 2.5 times higher current density than normal JFET operation has been achieved. The temperature dependent I-V and the sub-threshold characteristics have been studied by using 2-dimensional simulation.

  • 37. Kurose, T.
    et al.
    Kuroki, S. -I
    Ishikawa, S.
    Maeda, T.
    Sezaki, H.
    Makino, T.
    Ohshima, T.
    Östling, Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Zetterling, Carl-Mikael
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Integrerade komponenter och kretsar.
    Low-parasitic-capacitance self-aligned 4H-SiC nMOSFETs for harsh environment electronics2018Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 924, s. 971-974Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Low-parasitic-capacitance 4H-SiC nMOSFETs using a novel self-aligned process were suggested and demonstrated. In these nMOSFETs, device characteristics including parasitic capacitances (gate-source, gate-drain, drain-source capacitance) were investigated and low parasitic capacitance was achieved by the self-aligned structure

  • 38.
    Lanni, Luigia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Ghandi, Reza
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Malm, B. Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Measurements and simulations of lateral PNP transistors in a SiC NPN BJT technology for high temperature integrated circuits2011Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 679-680, s. 758-761Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, a 4H-SiC lateral PNP transistor fabricated in a high voltage NPN technology has been simulated and characterized. The possibility of fabricating a lateral PNP with a current gain larger than 1 has been investigated. Device and circuit level solutions have been performed.

  • 39.
    Lanni, Luigia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Ghandi, Reza
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Malm, B. Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Bipolar integrated OR-NOR gate in 4H-SiC2012Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 717-720, s. 1257-1260Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An integrated bipolar OR-NOR gate based on emitter coupled logic (ECL) is demonstrated in 4H-SiC. Operated from 27 up to 300 °C on -15 V supply voltage the logic gate exhibits stable noise margins (NMs) of about 1 V in the entire temperature range, and high and low output voltage levels that move towards positive voltages when the temperature increases: from -3 up to -2.7 V and from -5.4 up to -5.1 V respectively. In the same temperature range transistor current gain (β) goes from 46 down to 21.

  • 40.
    Lanni, Luigia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Malm, B. Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    SiC Etching and Sacrificial Oxidation Effects on the Performance of 4H-SiC BJTs2014Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 778-780, s. 1005-1008Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Performance of 4H-SiC BJTs fabricated on a single 100mm wafer with different SiC etching and sacrificial oxidation procedures is compared in terms of peak current gain in relation to base intrinsic sheet resistance. The best performance was achieved when device mesas were defined by inductively coupled plasma etching and a dry sacrificial oxide was grown at 1100 °C.

  • 41.
    Lanni, Luigia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Malm, Bengt Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    High-temperature characterization of 4H-SiC darlington transistors for low voltage applications2013Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 740-742, s. 966-969Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    4H-SiC bipolar Darlington transistors (D-BJTs) for low voltage applications have been fabricated, simulated and characterized up to 300 °C, where they exhibit a current gain of 460. The influence on D-BJT current gain of relative current capability of driver and output BJTs has been investigated, and the collector resistance has been identified as the main limitation for the D-BJTs.

  • 42.
    Lanni, Luigia
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Malm, Bengt Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    ECL-based SiC logic circuits for extreme temperatures2015Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 821-823, s. 910-913Artikkel i tidsskrift (Fagfellevurdert)
  • 43.
    Lee, Hyung-Seok
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Danielsson, Erik
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Electrical characteristics of 4H-SiC BJTs at elevated temperatures2005Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 483-485, s. 897-900Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The DCI-V characteristics of 4H-SiC BJTs have been studied in the temperature range 25 &DEG; C to 300 &DEG; C. The DC current gain at 300 &DEG; C decreased 56% compared to its value at 25 &DEG; C. Under high power operation, the SiC BJTs were strongly influenced by self-heating, which significantly limits the performance of device. Pulsed measurements were performed and compared to DC measurements to distinguish the effects of self-heating. From DC IN measurements, the junction temperature and thermal resistance were extracted to 102 &DEG; C and 19 &DEG; C/W respectively for a power level of 7.3 W at ambient temperature 25 &DEG; C.

  • 44.
    Lee, Hyung-Seok
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Ghandi, Reza
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Allerstam, F.
    Sveinbjörnsson, E. Ö.
    1200 V 4H-SiC BJTs with a Common Emitter Current Gain of 60 and Low On-resistance2009Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 600-603, s. 1151-1154Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper reports a 4H-SiC bipolar junction transistor (BJT) with a breakdown voltage (BVCEO) of 1200 V, a maximum current gain (beta) of 60 and the low on-resistance (Rsp-on)of 5.2 m Omega cm(2). The high gain is attributed to an improved surface passivation SiO2 layer which was grown in N2O ambient in a diffusion furnace. The SiC BJTs with passivation oxide grown in N2O ambient show less emitter size dependence than reference SiC BJTs, with conventional SiO2 passivation, due to a reduced surface recombination current. SiC BJT devices with an active area of 1.8 mm x 1.8 mm showed a current gain of 53 in pulsed mode and a forward voltage drop Of V-CE=2V at I-C=15 A (J(C)=460 A/cm(2)).

  • 45.
    Lee, Hyung-Seok
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    4H-SiC power BJTs with high current gain and low on-resistance2007Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 556-557, s. 767-770Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    4H-SiC BJTs have been fabricated with varying geometrical designs. The maximum value of the current gain was about 30 at I-c=85 mA, V-CE=14 V and room temperature (RT) for a 20 mu m emitter width structure. A collector-emitter voltage drop V-CE of 2 V at a forward collector current 55 mA (J(C) = 128 A/cm(2)) was obtained and a specific on-resistance of 15.4 m Omega center dot cm(2) was extracted at RT. Optimum emitter finger widths and base-contact implant distances were derived from measurement. The temperature dependent DC IN characteristics of the BJTs have been studied resulting in 45 % reduction of the gain and 75 % increase of the on-resistance at 225 degrees C compared to RT. Forward-bias stress on SiC BJTs was investigated and about 20 % reduction of the initial current gain was found after 27.5 hours. Resistive switching measurements with packaged SiC BJTs were performed showing a resistive fast turn-on with a VCE fall-time of 90 ns. The results indicate that significantly faster switching can be obtained by actively controlling the base current.

  • 46.
    Lee, Hyung-Seok
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Lu, J
    Investigation of TiW contacts to 4H-SiC bipolar junction devices2006Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 527-529, s. 887-890Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One important challenge in SiC Bipolar Junction Transistor (BJT) fabrication is to form good ohmic contacts to both n-type and p-type SiC. In this paper, we have examined contact study in a SiC BJT process with sputter deposition of titanium tungsten contacts to both n-type and p-type regions followed by annealing at different temperatures between 750 T and 950 T. The contacts were characterized using linear transmission line method (LTLM) structures. To see the formation of compound phases, X-ray Diffraction (XRD) theta-2 theta scans were performed before and after annealing. The results indicate that 5 minutes annealing at 950 T of the n(+) contact is sufficient whereas the p(+) contacts remain non-ohmic after 30 minutes annealing. The n(+) emitter structure contact resistivity after 5 min annealing with 750 degrees C and 950 degrees C was 1.08 x 10(-3) Omega cm(2) and 4.08 x 10(-4) Omega cm(2), respectively. Small amorphous regions of silicon and carbon as well as titanium tungsten carbide regions were observed by high-resolution transmission electron microscopy (HRTEM), whereas less carbide formation and no amorphous regions were found in a sample with unsuccessful formation of TiW ohmic contacts.

  • 47.
    Lee, Hyung-Seok
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Domeij, Martin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Sveinbjörnsson, Einar Ö.
    Department of Microtechnology and Nanoscience, Chalmers University of Technology.
    A comparative study of surface passivation on SiC BJTs with high current gain2007Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 556-557, s. 631-634Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of the different types of passivation layers on the current gain of SiC BJTs has been investigated. Measurements have been compared for BJTs passivated with thermal SiO2, plasma deposited (PECVD) SiO2 and BJTs without passivation. The maximum DC current gain of BJTs with thermal SiO2 was about 62 at I-c=20 mA and V-ce=40 V. On the other hand, the BJTs with a passivation by PECVD SiO2 had a DC current gain of only 25. The surface recombination current was extracted from measurements with BJTs of different emitter widths. The surface recombination current of BJTs with a thermally grown oxide was about 25% lower than unpassivated BJTs and 65% lower than that of PECVD passivated BJTs.

  • 48.
    Lee, Hyung-Seok
    et al.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Koo, Sang-Mo
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Zetterling, Carl-Mikael
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Danielsson, Erik
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Domeij, Martin
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Östling, Mikael
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Simulation study of 4H-SiC junction-gated MOSFETs from 300 K to 773 K2004Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 457-460, s. 1437-1440Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electrical characteristics of 4H-SiC junction gated MOSFETs (JMOSFETs) have been investigated by 2-dimensional device simulations. The results have been compared with measured data from 300 K to 573 K. and applied to predict the device performance up to 773 K. Simulation results predict a decrease of the saturation current to 7.5% of its room temperature value as the temperature increases from 300 K to 773 K. However, by applying a proper voltage on the top MOS gate, carrier accumulation can be used to compensate for the reduced mobility and a constant drain current can be maintained over the whole temperature range (300 K - 773 K), where the main deviations for different temperatures are at low drain voltages before the drain current saturates.

  • 49. Lee, J. -H
    et al.
    Ahn, J. -J
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Koo, S. -M
    Local anodic oxidation of phosphorus-implanted 4H-SiC by atomic force microscopy2012Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 717-720, s. 905-908Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, local oxidation behavior in phosphorus ion-implanted 4H-SiC has been investigated by using atomic force microscopy (AFM). The AFM-local oxidation (LO) has been performed on the implanted samples, with and without activation anneal, using varying applied bias (15/20/25 V). It has been clearly shown that the post-implantation annealing process at 1650 °C has a great impact on the local oxidation rate by electrically activating the dopants and by modulating the surface roughness. In addition, the composition of resulting oxides changes depending on the doping level of SiC surfaces.

  • 50. Lee, S. -K
    et al.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Åberg, I.
    Magnusson, M. H.
    Deppert, K.
    Wernersson, L. -E
    Samuelson, L.
    Litwin, A.
    Reduction of the barrier height and enhancement of tunneling current of titanium contacts using embedded Au nano-particles on 4H and 6H silicon carbide2002Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 389-393, nr 2, s. 937-940Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated the electrical characteristics of Ti Schottky contacts with embedded Au nano-particles on various types of epilayers of SiC (4H- and 6H-SiC). From our current-voltage (I-V) and capacitance-voltage (C-V) measurements, we observed that Ti Schottky contacts with embedded Au nano-particles had 0.19 eV (n-4H-SiC) and 0.15 eV (n-6H-SiC) lower barrier height than those of particle free Ti Schottky contacts. In order to understand this reduction of the Schottky barrier height (SBH) for Ti Schottky contacts with embedded Au nano-particles, it has been proposed that SBH lowering is caused by an enhanced electric field due to the small size of the Au nano-particles and the large SBH difference. We have also tested these contacts on highly doped n-and p-type SiC material to study ohmic contacts using linear TLM measurements.

12 1 - 50 of 70
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