Endre søk
Begrens søket
1234567 151 - 200 of 615
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 151.
    Iyer, Srinivasan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Effective tunability and realistic estimates of group index in plasmonic metamaterials exhibiting electromagnetically induced transparency2011Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 50, nr 21, s. 3958-3961Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the phenomenon of the electromagnetically induced transparency in planar and stacked plasmonic metamaterials (MMs) using the finite integration time domain and finite element methods. For such structures, the dependence of the tunability of the inherent structural resonances on geometry design is clarified. We also analyze the performance of recently demonstrated MM designs in terms of the achievable group refractive index and losses, which are of great interest for slowing light applications.

  • 152.
    Iyer, Srinivasan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Transmission resonances in periodic U-shaped metallic nanostructures2010Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 18, nr 17, s. 17719-17728Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The spectral response of crescent-like metallic nanostructures, a sub-class of U-shaped split-ring resonators, on a glass substrate at normal incidence is studied numerically. Also, the interpretation of transmission resonances arising from periodic conventional standard split-ring resonators with rectangular edges (SSRR) at normal incidence is revisited. In particular, we focus on one specific transmission resonance which is present for nano-crescents (NC) but absent in the case of SSRRs used for metamaterials. It is proposed that for a U-shaped metallic structure of arbitrary geometry, coupling of plasmonic eigen modes at all the surfaces of the three-dimensional structure is essential to be considered. The manner in which the coupling takes place between plasmonic modes at all the surfaces of the three-dimensional structure is what completely characterizes transmission resonances, and it is unique for each given resonance. (C) 2010 Optical Society of America

  • 153.
    Jaskorzynska, Bozena
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Song, Yi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Kvantelektronik och -optik, QEO.
    Zhu, Ning
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Wang, Zhechao
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Dielectric and Plasmon Slot Waveguides for Photonic Integration2009Inngår i: ICTON 2009: 11th International Conference on Transparent Optical Networks: 2009 11TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS, VOLS 1 AND 2, NEW YORK: IEEE , 2009, s. 653-656Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Slot waveguides formed either in high-index dielectrics or in metals attract great interest because they provide sub-wavelength confinement in the slot region. While this feature is very attractive for devices relying on stimulated emission or nonlinear effects, it does not necessarily improve the integration density. The spacing between dielectric slot waveguides is still limited by diffraction. Although for metal (plasmon) waveguides the total field can be shrunk far beyond the diffraction limit, the associated increase in propagation loss will set practical limits on both the minimum waveguide width and edge-to-edge separation. Here we compare the packing densities for 3D slot waveguides in silicon and plasmon waveguides in gold with a silicon slot. As a reference we also consider silicon photonic wire. We calculate center-to-center waveguide separations (pitch) versus cross-talk level. We show that at ca 24 dB/mu m cross-talk and requiring the attenuation length of at least 5 mu m, plasmon slot waveguides can be packed ca 3.5 times denser than silicon slot waveguides, and ca 2.5 times denser than photonic wires. We also show examples of the fabricated devices.

  • 154.
    Jaskorzynska, Bozena
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Lourdudoss, Sebastian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Olsson, Fredrik
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Active Si-based photonics via heterogeneous integration2008Inngår i: ICTON 2008: PROCEEDINGS OF 2008 10TH ANNIVERSARY INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS, VOL 2 / [ed] Marciniak, M, NEW YORK: IEEE , 2008, s. 30-33Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We review major breakthroughs in realizing silicon-based active components by heterogeneous integration with III-V semiconductors, or nonlinear organic materials. In more detail we describe examples of our concepts and technological approach addressing this goal. This includes designs for widely tunable filters and new routes for heteroepitaxy and selective area growth of InP on silicon.

  • 155. Jensen, J.
    et al.
    Sanz, R.
    Jaafar, M.
    Hernández-Vélez, M.
    Asenjo, A.
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Vázquez, M.
    Localized 56Fe+ ion implantation of TiO2 using anodic porous alumina2010Inngår i: Ion beams and nano-engineering, Materials Research Society, 2010, s. 3-8Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present result following localized ion implantation of rutile titanium dioxide (TiC2) using anodic porous alumina as a mask. The implantation were performed with 100 keV 56Fe+ ions using a fluence of 1.3-1016 ions/cm2. The surface modifications where studied by means of SEM, AFM/MFM and XRD. A well-defined hexagonal pattern of modified material in the near surface structure is observed. Local examination of the implanted areas revealed no clear magnetic signal. However, a variation in mechanical and electrostatic behavior between implanted and non-implanted zones is inferred from the variation in AFM signals.

  • 156.
    Junesand, Carl
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Wang, Zhechao
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Lourdudoss, Sebastian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    InP overgrowth on SiO2 for active photonic devices on silicon2010Inngår i: Proceedings of SPIE - The International Society for Optical Engineering, SPIE - International Society for Optical Engineering, 2010, Vol. 7606Konferansepaper (Fagfellevurdert)
    Abstract [en]

    ntegrationof III-V materials on silicon wafer for active photonic deviceshave previously been achieved by growing thick III-V layers ontop of silicon or by bonding the III-V stack layersonto a silicon wafer. Another way is the epitaxial lateralovergrowth (ELOG) of a thin III-V material from a seedlayer directly on the silicon wafer, which can be usedas a platform for the growth of active devices. Asa prestudy, we have investigated lateral overgrowth of InP byHydride Vapor Phase Epitaxy (HVPE) over SiO2 masks of differentthickness on InP substrates from openings in the mask. Openingswhich varied in direction, width and separation were made withE-beam lithography allowing a good dimension control even for nano-sizedopenings (down to 100 nm wide). This mimics overgrowth ofInP on top of SiO2/Si waveguides. By optimizing the growthconditions in terms of growth temperature and partial pressure ofthe source gases with respect to the opening direction, separationand width, we show that a thin (~200 nm) layerof InP with good morphology and crystalline quality can begrown laterally on top of SiO2. Due to the thingrown InP layer, amplification structures on top of it canbe well integrated with the underlying silicon waveguides. The proposedELOG technology provides a promising integration platform for hybrid InP/siliconactive devices.

  • 157.
    Junique, Stéphane
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Surface-normal multiple quantum well electroabsorption modulators: for optical signal processing and asymmetric free-space communication2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Electroabsorption is the physical phenomenon by which the absorption of light in a medium can be controlled by applying an electric field. The Quantum–Confined Stark Effect, which makes the absorption band–edge in quantum wells very field–dependent, together with the strong absorption peak provided by excitons, are the physical foundations for the success of electroabsorption modulators based on quantum well structures in telecommunication networks.

    This thesis describes the design and fabrication of surface–normal electroabsorption modulation devices. The techniques needed to understand the design and fabrication of surface–normal multiple quantum well optical modulators are introduced, as are the various characterisation techniques used during and after the fabrication.

    Devices for several types of applications have been designed, fabricated, characterised and in some cases integrated into optical systems:

    – Two–dimensional arrays of 128´128 pixel amplitude modulators grown on GaAs substrates have been fabricated and characterised. Speeds of up to 11700 frames per second were demonstrated, limited by the output electronics of the computer interface.

    – Large–area modulators grown on GaAs substrates for free–space optical communication were developed, with an active area of 2cm2 and a modulation speed of several megahertz. Contrast ratios up to 5:1 on full modulator areas were measured. Problems limiting the yield and modulation speed of such devices have been studied, and solutions to overcome them have been demonstrated.

    – Large–area devices grown on InP substrates for free–space optical communication have been developed. Contrast ratios of up to 2:1 for transmissive types have been demonstrated.

    – Devices consisting of two rows of pixels, grown on GaAs substrates, with an active area of 22mm´5mm, divided into 64 or 128 pixels per row have been developed. These amplitude modulation devices were designed for optical signal processing applications.

    – One variant of these optical signal processing devices was also characterised as a ternary, binary amplitude and binary phase modulator array.

    – The use of GaAs multiple quantum well optical modulators in a free–space optical retro–communication system has been studied. An opto–mechanical design for a modulating retro–reflector is described, allowing a large field of view in one direction using reflecting, resonant–cavity modulators for high contrast ratios.

  • 158.
    Jänes, Peter
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Photonic Devices and Applications based on Intersubband Transitions and Electromagnetically Induced Transparency2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Although photonic devices have experienced a rapid development lately, there is still room for substantial improvements in performance. From a telecommunications perspective, improvements in speed, size, integration and power consumption are desired. There is also a general interest in photonic devices with new functionalities. Being a key component in fiber-optic systems, high-speed optical modulators often initiate the development towards higher bit-rates. The technology of current state-of-the-art modulators has matured suggesting new paths of development. In this thesis we investigate the potential of modulators based on intersubband (IS) transitions in quantum wells (QWs). Specific QW designs are suggested and complete modulator structures are simulated. IS absorption is also experimentally characterized. Absorption linewidth is critical for IS modulator performance since narrow linewidth implies high bandwidth and/or small driving voltage. High material quality is important, since linewidth is typically limited by well-width fluctuations and interface roughness.

    A mid-IR AlGaAs/GaAs-modulator is proposed having a RC-limited bandwidth of 130 GHz and a peak-to-peak voltage of 0.9 V. Experimentally, Stark shift is measured in InAlAs/InAlGaAs/InGaAs step QWs at λ ~ 6 μm predicting that an IS modulator based on this material would have a bandwidth of 90 GHz and a peak-to-peak voltage of 0.9 V. IS absorption at 1.55 μm requires material combinations with high conduction-band offset. Simulations of an InGaAs/InAlAs/AlAsSb-modulator predict a bandwidth of 90 GHz and a peak-to-peak voltage of 2.0 V. Experimental studies of IS absorption in AlN/GaN QWs are presented. IS absorption at 1.5-3.4 μm with linewidth below 100 meV is measured for well widths between 15-54 Å. Subpeaks corresponding to well-width fluctuations on the monolayer scale are identified with linewidths of ~60 meV. Agreement between theoretical calculations and measured spectra is encouraging. Theoretical simulations together with measured absorption linewidths suggest that high performance IS modulators operating at 1.55 μm are realizable.

    Photonic devices with new functionalities are addressed by investigating electromagnetically induced transparency (EIT) theoretically and considering potential applications based on EIT. Simulations of two-dimensional pulse-propagation based on the Maxwell-Bloch equations are performed with a focus on storing and reading out optical pulses. We explicitly formulate the phase-matching conditions for reading out stored pulses in a new direction and propose a serial-to-parallel converter based on this.

    For slow-light devices, e.g. optical buffers, we identify and analyze two main limitations on the medium bandwidth; the frequency dependent absorption and the group velocity dispersion. Since large bandwidth and large delay are contradictory requirements, the delay bandwidth product is considered. Analytical expressions are derived and analyzed and verified by simulations on pulse propagation. Insertion of parameters relevant for semiconductors indicates that development of materials with long coherence times are necessary for realizing optical buffers based on EIT.

  • 159.
    Jänes, Peter
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Tidström, Jonas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Thylén, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Limits on optical pulse compression and delay bandwidth product in electromagnetically induced transparency media2005Inngår i: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 23, nr 11, s. 3893-3899Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Delay bandwidth products (DBPs) and physical pulselengths obtainable in media exhibiting electromagnetically induced transparency (EIT) are analyzed. The study is performed in stationary media as well as for dynamic storing of light pulses in such media. In the latter case; the dispersion inherent in storage and readout of the pulses is analyzed. It is shown that absorption and the group velocity dispersion (GVD) are limiting factors. Analytical expressions for the minimum compressed 'pulselength and DBP are derived, and these expressions show good agreement with simulations of pulse propagation in EIT media.

  • 160. Jönsson, P. E.
    et al.
    Mathieu, Roland
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Wernsdorfer, W.
    Tkachuk, A. M.
    Barbara, B.
    Absence of conventional spin-glass transition in the Ising dipolar system LiHo(x)Y(1-x)F(4)2007Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 98, nr 25, s. 256403-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The magnetic properties of single crystals of LiHo(x)Y(1-x)F(4) with x=16.5% and x=4.5% were recorded down to 35 mK using a micro-SQUID magnetometer. While this system is considered as the archetypal quantum spin glass, the detailed analysis of our magnetization data indicates the absence of a phase transition, not only in a transverse applied magnetic field, but also without field. A zero-Kelvin phase transition is also unlikely, as the magnetization seems to follow a noncritical exponential dependence on the temperature. Our analysis thus unmasks the true, short-ranged nature of the magnetic properties of the LiHo(x)Y(1-x)F(4) system, validating recent theoretical investigations suggesting the lack of phase transition in this system.

  • 161. Karim, A.
    et al.
    Hansson, G. V.
    Linnarsson, Margareta
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Influence of Er and O concentrations on the microstructure and luminescence of Si:Er/O LEDs2008Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 100, nr Part 4, s. 042010-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Erbium(Er)/Oxygen(O) doped Silicon (Si) layers grown by molecular beam epitaxy (MBE), can be used for fabricating Si-based light emitting diodes. The electroluminescence intensity from these layers depends sensitively on the formation of specific types of Er/O precipitates inside the Si host. We have performed a detailed microstructure analysis of MBE-grown Er/O doped Si layers using electron microscopy and combined it with secondary ion mass spectrometry (SIMS) measurements as well as electroluminescence studies. Two types of microstructures are observed in different samples with specific Er and O concentrations and grown using Er and Si co-evaporation in O ambient. The first type of microstructure consists of planar precipitates along (311) planes mostly initiated at the onset of the growth of the Si: Er/O layer. The second characteristic type of microstructure observed contain round precipitates of Er/O. Using analytical microscopy techniques it was revealed that the round precipitates contain a higher ratio of Er to O as compared to the planar precipitates of the first type. The planar precipitates normally result in structures with high electroluminescence intensity while the structures with round precipitates have low intensity.

  • 162.
    Karlsson, A.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Bjork, G.
    On the modulation bandwidth of semiconductor microcavity lasers1994Inngår i: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 6, s. 1312-1314Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The small signal injection current modulation bandwidth of vertical cavity microlasers in the conventional macroscopic regime and in the microscopic regime of "controlled spontaneous emission" is investigated. A microlaser, under constraint of nonlinear gain or current density limitations, is found to have the same intrinsic modulation bandwidth as conventional edge-emitting lasers with the same cavity losses and photon density.<>

  • 163.
    Karlsson, Anders
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Microcavity lasers in communication applications: Present status and prospects1994Inngår i: Proceedings of European Conference on Optical Communication, Firenze, Italy, Sept 26 - 30, 1994, 1994Konferansepaper (Fagfellevurdert)
  • 164.
    Karlsson, Stefan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Yu, Yichuan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Liu, C.P.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Chuang, C.H.
    Kjebon, Olle
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Westergren, Urban
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Tsegaye, Tedros
    Seeds, A.J.
    A Packaged Reflective Electroabsorption Modulator/Detector with Optimized Dynamic Range2005Inngår i: Broadband Europe 2005, Bordeaux, 2005Konferansepaper (Fagfellevurdert)
  • 165.
    Karlsson, Stefan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Yu, Yichuan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Liu, C.P.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Chuang, C.H.
    Westergren, Urban
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Tsegaye, Tedros
    Krysa, A. B.
    Roberts, J.S.
    Seeds, A. J.
    A Packaged Resonant Electroabsorption Transceiver for Fiber-Radio Applications2005Inngår i: Photonics in Wireless Communication, PWCom 2005, Särö, 2005Konferansepaper (Fagfellevurdert)
  • 166. Kellock, H.
    et al.
    Setälä, T.
    Shirai, T.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Higher-order ghost imaging with partially polarized classical light2011Inngår i: Proc SPIE Int Soc Opt Eng, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Visibility, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) are quantities that characterize the quality of the image in ghost (or correlation) imaging. The visibility in quantum and classical ghost imaging with scalar light is known to improve as the order of imaging increases. Recently also electromagnetic ghost imaging has started to attract attention. In this work we analyze the effects of both the order of imaging and the degree of polarization (P) of the illumination on the image quality parameters. The source is a classical, partially polarized, random electromagnetic field obeying Gaussian statistics. The beam is split into several (N) parts which are directed either into the object or reference arms and the associated intensity correlations are calculated. When N > 2, more than one reference arm may exist which contributes to the background. We consider two different definitions for the visibility, as well as the SNR and CNR, and examine their attainable limiting values in second- and higher-order ghost imaging as a function of the degree of polarization. Both expressions of the visibility behave in a similar manner; they increase with the order of imaging and the degree of polarization. In second-order imaging the SNR decreases, due to increased noise, as P increases, while the CNR remains essentially constant. We emphasize that the exact numerical values depend on the definitions used and on the number of object arms in the setup.

  • 167. Kellock, Henri
    et al.
    Setälä, Tero
    Shirai, Tomohiro
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Image quality in double- and triple-intensity ghost imaging with classical partially polarized light2012Inngår i: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 29, nr 11, s. 2459-2468Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Classical ghost imaging is a correlation-imaging technique in which the image of the object is found through intensity correlations of light. We analyze three different quality parameters, namely the visibility, the signal-to-noise ratio (SNR), and the contrast-to-noise ratio (CNR), to assess the performance of double-and triple-intensity correlation-imaging setups. The source is a random partially polarized beam of light obeying Gaussian statistics, and the image quality is evaluated as a function of the degree of polarization (DoP). We show that the visibility improves when the DoP and the order of imaging increase, while the SNR behaves oppositely. The CNR is for the most part independent of DoP and the imaging order. The results are important for the development of new imaging devices using partially polarized light.

  • 168.
    Kim, Jang. Yong
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Processing and on-wafer test of ferroelectric film microwave varactors2006Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Applied physics letters, Vol. 88, nr 19, s. 192905-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present comparative characteristics of microwave variable capacitors (varactors) fabricated on Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), and Ba0.5Sr0.5TiO3 (BST) ferroelectric films grown by rf-magnetron sputtering (NKN) and pulsed laser deposition (ATN and BST) techniques on the sapphire. Two port 2 mu m finger gap coplanar waveguide interdigital capacitors (CPWIDCs) were defined on ferroelectric films surface by photolithographic lift-off technique. Deembedding method was employed to extract properties of CPWIDC from the S parameters measured in microwave range up to 40 GHz. BST films on sapphire substrates show superior tunability of 26% (20 GHz, 200 kV/cm), whereas ATN films possess the lowest tan delta=0.06 at 20 GHz and extremely low dispersion of 4.3% in a whole frequency range of 45 MHz-40 GHz.

  • 169.
    Kim, Jang-Yong
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Processing and On-Wafer Test of Ferroelectric Film Microwave Varactors2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Microwave materials have been widely used in a variety of applications ranging from communication devices to military satellite services, and the study of materials properties at microwave frequencies and the development of functional microwave materials have always been among the most active areas in solid-state physics, materials science, electrical and electronic engineering. In recent years, the increasing requirements for the development of high speed, high frequency circuits and systems require complete understanding of the properties of materials function at microwave frequencies. Ferroelectric materials usually have high dielectric constant, and their dielectric properties are temperature and electric field dependent. The change in permittivity as a function of electric field is the key to a wide range of applications. Ferroelectric materials can be used to fabricate capacitors for electronic industry because of their high dielectric constant, and this is important in the trend toward miniaturization and high functionality of electronic products. The simple tunable passive component based on ferroelectric films is a varactor which can be made as a planar structure and used for electrically tunable microwave integrated circuits. It is an important task to sinter highly tunable and low loss ferroelectrics, fabricate and test the properties of microwave ferroelectric components.

    This thesis shows experimental results on growth, crystalline and microwave properties of Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), Ba0.5Sr0.5TiO3 (BST) as well as AgTaO3 (ATO), and AgNbO3 (ANO) thin films. The films were grown by Pulsed Laser Deposition (PLD) and rf-magnetron sputtering techniques from stoichiometric high density ceramic NKN, ATN, ATO, ANO and BST targets onto LaAlO3 (LAO), Al2O3 (r-cut sapphire), Nd:YAlO3 single crystals and amorphous glass substrates. Advanced X-ray diffraction examinations showed NKN, ATN, BST films on LAO substrates grow epitaxially, whereas films on r-cut sapphire were found to be preferentially (00l) oriented.

    Coplanar waveguide 2 µm finger gap interdigital capacitor (CPWIDC) structures were fabricated by photolithography process and metal lift-off technique. On-wafer tests up to 40 GHz were performed to characterize microwave properties of the ferromagnetic film CPWIDC devices. The measurement setup is composed of network analyzer, probe station, and microwave G-S-G probes. External electric field was applied to planar capacitors to measure tunability. Original de-embedding technique has been developed to calculate capacitance, loss tan δ, and tunability of varactors from the measured S-parameters.

    NKN film interdigital capacitors on Nd:YAlO3 showed superior performance compared to ATN in the microwave range from 1 to 40 GHz. Within this range, the voltage tunability (40V, 200 kV/cm) was about 29%, loss tangent ~ 0.13, K-factor = tunability/tan δ from 152% @ 10GHz to 46% @ 40GHz. The ATN/sapphire CPWIDCs showed the lowest dispersion ~ 4.3% in whole frequency range from 1 to 40 GHz, voltage tunability 4.7% @ 20GHz and 200 kV/cm, lowest loss tangent ~ 0.068 @ 20GHz, K-factor = tunability/tan δ ranged from 124% @ 10GHz to 35% @ 40GHz.

    BST film CPWIDCs on sapphire showed frequency about 17%, the highest voltage tunability ~ 22.2%, loss tangent ~ 0.137 @ 20GHz, and K-factor = 281% @ 10GHz to 95% @ 40GHz.

  • 170.
    Kim, Jang-Yong
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    AgTa0.5Nb0.5O3 thin film coplanar waveguide microwave capacitors2005Inngår i: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 77, s. 13-20Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    400 nm thick AgTa0.5Nb0.5O3 (ATN) films have been prepared by pulsed laser depositiontechnique on LaAlO3 (001) and sapphire (Al2O3-0112, r -cut) single crystal substrates.Comprehensive X-ray diffraction analysis showed epitaxial quality of ATN/LaAlO3films and preferentially (001) orientation of ATN/Al2O3 films. Voltage tunable microwavecapacitors were fabricated by lift-off technique on the surface of ferroelectricfilms. Microwave on-wafer tests were performed in the range from 1 to 40 GHz. Frequencydispersion is about 4.3%, voltage tunability is 4.7% @ 20 GHz and 200 kV/cm,loss tangent ∼0.068 @ 20 GHz, K-factor=tunability/tanδ is ranged from 124% @10 GHz to 35% @ 40 GHz.

  • 171.
    Kim, Jang-Yong
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    AgTaO3 and AgNbO3 thin films by pulsed laser deposition2006Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, nr 2, s. 615-618Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silver tantalate AgTaO3 (ATO) and silver niobate AgNbO3 (ANO) films have been grown on to the LaAlO3 (001) and sapphire Al2O3 (0112, r-cut) single crystals by pulsed laser deposition technique from stoichiometric ATO and ANO targets. X-ray diffraction study revealed epitaxial quality of ATO and ANO films on the LaAlO3 (00 1) Whereas on the sapphire r-cut substrate they are preferential (I 10) and (00 1) oriented. To characterize microwave films properties in the range from I to 40 GHz, coplanar line interdigital capacitors were fabricated by photolithography and lift-off technique. ANO film capacitors show superior properties: frequency dispersion was as low as 13%, voltage tunability (40 V, 200 kV/ cm) was about 4.6% at 20 GHz, loss tangent similar to 0.106 at 20 GHz, K-factor-tunability/tan delta from 49% @ 10 GHz to 33% at 40 GHz.

  • 172.
    Kim, Jang-Yong
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Microwave properties of AgTa0.5Nb0.5O3 thin film varactors on various substrates2007Inngår i: 2006 15TH IEEE INTERNATIONAL SYMPOSIUM ON APPLICATIONS OF FERROELECTRICS, New York: IEEE , 2007, s. 363-366Konferansepaper (Fagfellevurdert)
    Abstract [en]

    400nm thick AgTa0.5Nb0.5O3 (ATN) films have been sintered by pulsed laser deposition technique on LaAlO3 (001), sapphire (Al2O3-01 (1) under bar2, r-cut) single crystal substrates and Coming 7059 Glass. Photolithography and metal lift-off technique were used to fabricate tunable Coplanar Waveguide Interdigital Capacitors (CPWIDCs). On-wafer test of varactors was performed with microwave network analyzer and G-S-G microwave probe. ATN/LaAlO3 capacitors demonstrated the highest tunability (similar to 5.8%@20GHz), ATN/Glass showed the best flat dispersion (similar to 3.9%) and ATN/ Al2O3 showed the lowest loss tangent (similar to 0.06@20GHz) in the microwave range from 1 to 40 GHz.

  • 173.
    Kim, Jang-Yong
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Grishin, Alexander M.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Niobate-tantalate thin films microwave varactors2006Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Thin solid films, Vol. 515, nr 2, s. 619-622Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present comparative characteristics of microwave variable capacitors (varactors) fabricated on Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN) and Ba0.5Sr0.5TiO3 (BST) ferroclectric films sintered by pulsed laser deposition technique. Two port 2 mu m finger gap coplanar waveguide interdigital capacitive (CPWIDC) structures were defined on ferroelectric films surface by a standard lift off technique. Results of the microwave on-wafer tests performed in frequency range 1 to 40 GHz have been examined with a de-embedding technique to extract device characteristics from the measured S-parameters. The frequency dispersion of capacitance was 37%, 4.3%, and 17%; the voltage tunability (200 kV/cm) 22%, 4.7%, and 22% at 20 GHz; loss tangent similar to 0.23, 0.068, and 0.137 at 20 GHz for NKN/Nd:YAlO3, ATN/Al2O3, and BST/Al2O3 films capacitors.

  • 174.
    Kjebon, Olle
    et al.
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Akram, Nadeem
    KTH, Tidigare Institutioner, Mikroelektronik och informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    40 Gb/s transmission experiment using directly modulated 1.55 mu m DBR lasers2003Inngår i: Conference Proceedings - International Conference on Indium Phosphide and Related Materials, 2003, s. 495-498Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Directly modulated two section 1.55 mum InGaAsP DBR lasers were used for 40 Gb/s error free operation back-to-back and through 1 km of standard single mode fiber.

  • 175.
    Kjebon, Olle
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Transmission at 20 Gb/s with directly modulated DBR lasers over 30 km standard fiber2002Inngår i: Optical Communication, 2002. ECOC 2002. 28th European Conference on, 2002, Vol. 1, s. 1-2Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Transmission of 20 Gb/s NRZ over 30 km of standard fiber was accomplished with directly modulated DBR lasers at 1.55 mum. Experiments were performed without dispersion compensation and optical amplification and a negative penalty was observed

  • 176.
    Kjebon, Olle
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Lourdudoss, S.
    Nilsson, S.
    Stalnacke, B.
    Backbom, L.
    Two-section InGaAsP DBR-lasers at 1.55 mu;m wavelength with 31 GHz direct modulation bandwidth1997Inngår i: Indium Phosphide and Related Materials, 1997., International Conference on, 1997, s. 665-668Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The small signal modulation response of two-section InGaAsP DBR-lasers at 1.55 mu;m wavelength was investigated. The response was fitted to a general transfer function and it was found that for almost all lasers the response could be described by a three pole model consisting of the laser response from the standard rate equations and an additional first order low pass roll-off. The lasers exhibited reduced damping and increased resonance frequency due to what we believe is detuned loading. This led to a maximum bandwidth of 30 GHz for lasers described by the three pole model. Some lasers exhibited an additional effect which we believe is cavity resonant enhancement of one of the modulation side-bands. This effect increased the maximum -3dB bandwidth to 31 GHz but could not be described by a three pole model

  • 177.
    Kjebon, Olle
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Lourdudoss, Sebastian
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Nilsson, Stefan
    KTH, Tidigare Institutioner, Elektronik.
    Stålnacke, Björn
    KTH, Tidigare Institutioner, Elektronik.
    Modulation response measurements and evaluation of MQW InGaAsP lasers of various designs1996Inngår i: Proc. SPIE, Vol. 2684, 1996, s. 138-152Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Resultsfrom modulation measurements of 40 high-speed multi quantum well (MQW)lasers ((lambda) equals 1.55 micrometer) of various designs are presented.By fitting the careful calibrated measurements, both magnitude and phase,to an analytical transfer function we were able to determineif a certain laser was limited by thermal effects, parasitic-likeeffects, or nonlinear gain effects. We found that most ofthe devices in the study were limited by thermal effectsand/or contact parasitics. The parasitics were found to be determinedby the width of the high-doped contact layer and claddinglayers below the metallic contact. It was also found thata high doping of the separate confinement heterostructure (SCH) layersdecreases the damping of the relaxation peak since it facilitatesthe carrier transport. Improved contact design and high doped SCH-layersresulted in modulation bandwidths of around 24 GHz.

  • 178. Kjellberg, T.
    et al.
    Nilsson, S.
    Klinga, T.
    Broberg, B.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Investigation on the spectral characteristics of DFB lasers with different grating configurations made by electron-beam lithography1993Inngår i: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 11, s. 1405-1415Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The single-mode stability for distributed-feedback (DFB) lasers with various electron-beam-written grating configurations has been investigated theoretically and experimentally, for both as-cleaved and AR-coated lasers. Other laser properties interesting for coherent and multichannel communications systems, such as linewidth and tunability, have also briefly been investigated. Lasers with more sophisticated grating structures, such as an optimized multiple phase-shifted or a corrugation-pitch-modulated grating, did not exhibit performance significantly superior to that of lambda;/4-shifted DFB lasers with an appropriate coupling coefficient. Antireflection (AR)-coating of the end facets proved indispensable for obtaining a high yield for lasers with single-mode operation at high output power and for reducing the large chip-to-chip variation seen for the as-cleaved lasers. A theoretical investigation of the effect of end reflections on the stopband and of the problem of determining the coupling coefficient was also made

  • 179. Kjellberg, T.
    et al.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    The effect of stitching errors on the spectral characteristics of DFB lasers fabricated using electron beam lithography1992Inngår i: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 10, s. 1256-1266Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Field stitching errors and their effect on the single-mode characteristics of distributed feedback (DFB) lasers fabricated using electron beam lithography were investigated. The stitching errors are associated with small-area, high-resolution electron beam exposure, which has the potential advantage of high-speed writing of laser gratings. Measurements show that the errors are composed of a systematic and a stochastic part. Their effect on the gain margin was simulated both for lambda;/4 phase-shifted and optimized multiple-phase-shifted DFB lasers. Simulations show that the lasers are insensitive to the systematic part of the stitching errors if the number of errors is large enough. The stochastic part was found to give rise to a variation in gain margin of the DFB lasers. It is concluded that the field stitching accuracy in the high-resolution mode of a commercial system for electron beam lithography is sufficient to provide a high yield of single-mode lasers. However, it is essential that certain precautions be taken considering exposure conditions and that a fault tolerant laser design be used

  • 180. Kjellberg, Torgil
    et al.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Nilsson, Stefan
    Broberg, Bjoern
    Effect of stitching errors on the performance of DFB lasers fabricated using e-beam lithography (Poster Paper)1992Inngår i: Electron-Beam, X-Ray, and Ion-Beam Submicrometer Lithographies for Manufacturing II, Vol. 1671, s. 191-200Artikkel i tidsskrift (Fagfellevurdert)
  • 181. Klimov, A. B.
    et al.
    Romero, J. L.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Sánchez-Soto, L. L.
    Discrete phase-space structures and mutually unbiased bases2007Inngår i: Arithmetic of Finite Fields, Proceedings, Springer Berlin/Heidelberg, 2007, s. 333-345Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We propose a unifying phase-space approach to the construction of mutually unbiased bases for an n-qubit system. It is based on an explicit classification of the geometrical structures compatible with the notion of unbiasedness. These consist of bundles of discrete curves intersecting only at the origin and satisfying certain additional conditions. The effect of local transformations is also studied.

  • 182. Klimov, A. B.
    et al.
    Sanchez-Soto, L. L.
    Yustas, E. C.
    Soderholm, J.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Distance-based degrees of polarization for a quantum field2005Inngår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 72, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is well established that unpolarized light is invariant with respect to any SU(2) polarization transformation. This requirement fully characterizes the set of density matrices representing unpolarized states. We introduce the degree of polarization of a quantum state as its distance to the set of unpolarized states. We use two different candidates of distance, namely the Hilbert-Schmidt and the Bures metric, showing that they induce fundamentally different degrees of polarization. We apply these notions to relevant field states and we demonstrate that they avoid some of the problems arising with the classical definition.

  • 183. Klimov, Andrei B.
    et al.
    Romero, Jose L.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Sanchez-Soto, Luis L.
    Geometrical approach to mutually unbiased bases2007Inngår i: Journal of Physics a-Mathematical and Theoretical, ISSN 1751-8113, Vol. 40, nr 14, s. 3987-3998Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose a unifying phase-space approach to the construction of mutually unbiased bases for a two-qubit system. It is based on an explicit classification of the geometrical structures compatible with the notion of unbiasedness. These consist of bundles of discrete curves intersecting only at the origin and satisfying certain additional properties. We also consider the feasible transformations between different kinds of curves and show that they correspond to local rotations around the Bloch-sphere principal axes. We suggest how to generalize the method to systems in dimensions that are powers of a prime.

  • 184. Kodash, V. Y.
    et al.
    Groza, J. R.
    Aldica, G.
    Toprak, Muhammet
    Li, Shanghua
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Muhammed, Mamoun
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Field-activated sintering of skutterudites2007Inngår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 57, nr 6, s. 509-511Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Skutterudite (Co0.92Ni0.08)4Sb11.88Te0.12 powder has been consolidated under an applied electrical field using a field-assisted sintering technique (FAST). The low FAST sintering temperature and relatively high heating rate considerably reduce grain growth during sintering.

  • 185. Korhonen, Minna
    et al.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Turunen, Jari
    Genty, Goery
    Elementary field representation of supercontinuum2013Inngår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 30, nr 1, s. 21-26Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe the second-order coherence functions of supercontinuum (SC) in terms of elementary fields that can be obtained from measurable average quantities. The representation is based on the partition of the second-order correlation functions of SC into quasi-coherent and quasi-stationary contributions. Numerical simulations of statistical ensembles of SC pulses with different coherence properties are used to illustrate the elementary field model. Comparison with the SC coherent-mode expansion is presented, and we also simulate the propagation of the elementary fields in a dispersive fiber to demonstrate the benefits of the model.

  • 186.
    Kothe, Christian
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Entanglement quantification through local observable correlations2007Inngår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a significantly improved scheme of entanglement detection inspired by local uncertainty relations for a system consisting of two qubits. Developing the underlying idea of local uncertainty relations, namely correlations, we demonstrate that it is possible to define a measure which is invariant under local unitary transformations and which is based only on local measurements. It is quite simple to implement experimentally and it allows entanglement quantification in a certain range for mixed states and exactly for pure states, without first obtaining full knowledge (e.g., through tomography) of the state.

  • 187. Kreter, A.
    et al.
    Brezinsek, S.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Emmoth, Birger
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Freisinger, M.
    Pelicon, P.
    Philipps, V.
    Schmitz, O.
    Sundelin, Per
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Sergienko, G.
    Deuterium retention in different carbon materials exposed in TEXTOR:  2008Inngår i: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY, Bristol: IOP PUBLISHING LTD , 2008, Vol. 100, nr PART 6, s. 062024-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    CFC NB31, CFC DMS780 and fine-grain graphite EK98 were simultaneously exposed in the SOL of TEXTOR in order to measure the retention of deuterium in the material bulk. After exposure, the samples were analysed by thermal desorption spectrometry and nuclear reaction analysis with a conventional beam as well as with a microbeam. The deuterium retention amounts (2-4).10(21) D/m(2) for the incident fluence of similar to 2.10(25) D/m(2). The retention values are similar for both CFC materials and lower by similar to 20-40% for EK98. The retention in all three materials scales roughly with a square root of incident fluence without saturation for the range of fluences obtained. The majority of deuterium is stored in a surface layer of <8 mu m. However, in NB31 deuterium is detectable as deep as 80 mu m. The in-bulk retention estimated for a TEXTOR experimental campaign of approximate to 7500 s of plasma has a contribution of approximate to 10% to the total retention, which is dominated by deuterium-carbon co-deposition.

  • 188. Lee, H. L. T.
    et al.
    Ram, R. J.
    Kjebon, Olle
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Bandwidth enhancement and chirp reduction in DBR lasers by strong optical injection2000Inngår i: Lasers and Electro-Optics, 2000. (CLEO 2000). Conference on, 2000, s. 99-100Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We have observed modulation bandwidth enhancement to 28 GHz and evidence of reduced chirp, beyond the optimally tuned free running case, in strongly injection-locked DBR lasers. Bandwidth enhancement occurs because the total modal photon density depends on the phase between the master and slave fields, which varies during modulation due to the dependence of index on carrier density. This results in an increased coupling between the carriers and photons, giving an effectively higher differential gain. This effect appears to be stronger than the similar amplitude-phase coupling that occurs with detuned loading. Chirp reduction occurs only for very strong injection, which can be explained by the fact that chirp reduction can only be achieved for modulation frequencies less than the locking range, which increases with injected power. For higher frequencies, the chirp reduction due to detuned loading dominates

  • 189. Lee, H. L. T.
    et al.
    Ram, R. J.
    Kjebon, Olle
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Schatz, Richard
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Enhanced direct modulation efficiency by FM to IM conversion2000Inngår i: Microwave Photonics, 2000. MWP 2000. International Topical Meeting on, 2000, s. 105-108Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Enhanced modulation efficiency of a directly modulated, high speed DBR laser of up to 400% has been demonstrated using FM to IM conversion in optical fiber. The link noise figure is improved by 8 dB and the dynamic range by 3 dB at 10 GHz

  • 190.
    Lee, Hyung-Seok
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Fabrication and Characterization of Silicon Carbide Power Bipolar Junction Transistors2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Silicon carbide bipolar junction transistors (BJTs) are attractive power switching devices because of the unique material properties of SiC with high breakdown electric field, high thermal conductivity and high saturated drift velocity of electrons. The SiC BJT has potential for very low specific on-resistances and this together with high temperature operation makes it very suitable for applications with high power densities. For SiC BJTs the common emitter current gain (β), the specific on-resistance (RSP_ON), and the breakdown voltage are important to optimize for competition with silicon based power devices. In this thesis, power SiC BJTs with high current gain β ≈ 60 , low on-resistance RSP_ON ≈ 5 mΩcm2, and high breakdown voltage BVCEO ≈ 1200 V have been demonstrated. The 1200 V SiC BJT that has been demonstrated has about 80 % lower on-state power losses compared to a typical 1200 V Si IGBT chip.

    A continuous epitaxial growth of the base-emitter layers has been used to reduce interface defects and thus improve the current gain. A significant influence of surface recombination on the current gain was identified by comparing the experiments with device simulations. In order to reduce the surface recombination, different passivation layers were investigated in SiC BJTs, and thermal oxidation in N2O ambient was identified as an efficient passivation method to increase the current gain.

    To obtain a low contact resistance, especially to the p-type base contact, is one critical issue to fabricate SiC power BJTs with low on-resistance. Low temperature anneal (~ 800 oC) of a p-type Ni/Ti/Al contact on 4H-SiC has been demonstrated. The contact resistivity on the ion implanted base region of the BJT was 1.3 × 10-4 Ωcm2 after annealing. The Ni/Ti/Al p-type ohmic contact was adapted to 4H-SiC BJTs fabrication indicating that the base contact plays a role for achieving a low on-resistance of SiC BJTs.

    To achieve a high breakdown voltage, optimized junction termination is important in a power device. A guard ring assisted Junction Termination Extension (JTE) structure was used to improve the breakdown voltage of the SiC BJTs. The highest breakdown voltage of the fabricated SiC BJTs was obtained for devices with guard ring assisted JTE using the base contact implant step for a simultaneous formation of guard rings.

    As a new approach to fabricate SiC BJTs, epitaxial regrowth of an extrinsic base layer was demonstrated. SiC BJTs without any ion implantation were successfully demonstrated using epitaxial regrowth of a highly doped p-type region and an etched JTE using the epitaxial base. A maximum current gain of 42 was measured for a 1.8 mm × 1.8 mm BJT with a stable and reproducible open base breakdown voltage of 1800 V.

  • 191.
    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), 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), Mikroelektronik och Informationsteknik, IMIT.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    High-Current-Gain SiC BJTs With Regrown Extrinsic Base and Etched JTE2008Inngår i: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 55, nr 8, s. 1894-1898Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes successful fabrication of 4H-SiC bipolar junction transistors (BJTs) with a regrown extrinsic base layer and an etched junction termination extension (JTE). Large-area 4H-SiC BJTs measuring 1.8 x 1.8 nun (with an active area of 3.24 mm') showed a common emitter current gain 0 of 42, specific on-resistance Rsp ON of 9 mQ - em', and open-base breakdown voltage BVcEO of-1.75 kV at room temperature. The key to successful fabrication of high-current-gain SiC BJTs with a regrown extrinsic base is efficient removal of the p+ regrown layer from the surface of the emitter-base junction. The BJT with p+ regrown layer has the advantage of lower base contact resistivity and current gain that is less sensitive to the distance between the emitter edge and the base contact, compared to a BJT with ion-implanted base. Fabrication of BJTs without ion implantation means less lifetime-reducing defects, and in addition, the surface morphology is improved since high-temperature annealing becomes unnecessary. BJTs with flat-surface junction termination that combine etched regrown layers show about 250 V higher breakdown voltage than BJTs; with only etched flat-surface JTE.

  • 192.
    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)).

  • 193.
    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.

  • 194.
    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), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Low-forward-voltage-drop 4H-SiC BJTs without base contact implantation2008Inngår i: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 55, nr 8, s. 1907-1911Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bipolar junction transistors (BJTs) of 4H-SiC, with a low collector--emitter forward voltage drop YCE, have been fabricated without base contact implantation. A comparison of BJTs on the same wafer with and without base contact implantation shows less than 10% higher VcE for the BJTs without base contact implantation. Omitting the base contact implantation eliminates high concentrations of implantation-induced defects that act as recombination centers. This is advantageous because it allows a shorter distance Wp+ between the emitter edge and the base contact, without affecting the current gain when no base contact implantation is used. The BJTs without contact implantation show a constant current gain as Wp+ was reduced from 3 to I pm, whereas the gain decreased by 45% for the BJTs with base contact implantation for the same reduction of Wp+. A key to the successful fabrication of low-forward-voltage-drop SiC BJTs without base contact implantation is the formation of low-resistivity Ni/Ti/Al ohmic contacts to the base. The contact resistivity on the base region (N-A approximate to 4 x 10(17) cm(-3)) was measured with linear transmission line method structures to PC = 1.9 X 10(-3) Omega cm(2), whereas the contact resistivity with the base contact implantation was PC = 1.3 x 10-4 Omega cm(2), both after rapid thermal processing annealing at 800 degrees C.

  • 195.
    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.
    Allerstam, F.
    Department of Microtechnology and Nanoscience, Chalmers University of Technology.
    Sveinbjörnsson, Einar Ö.
    Department of Microtechnology and Nanoscience, Chalmers University of Technology.
    Surface passivation oxide effects on the current gain of 4H-SiC bipolar junction transistors2008Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, nr 8, s. 082113-1-082113-3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Effects of surface recombination on the common emitter current gain have been studied in 4H-silicon carbide (SiC) bipolar junction transistors (BJTs) with passivation formed by conventional dry oxidation and with passivation formed by dry oxidation in nitrous oxide (N2O) ambient. A gradual reduction of the current gain was found after removal of the passivation oxide followed by air exposure. Comparison of the measurement results for two different passivated BJTs indicates that the BJTs with passivation by dry oxidation in nitrous oxide (N2O) ambient show a half order of magnitude reduction of base current, resulting in a half order of magnitude increase of current gain at low currents. This improvement of current gain is attributed to reduced surface recombination caused by reduced interface trap densities at the base-emitter junction sidewall.

  • 196.
    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), Integrerade komponenter och kretsar.
    Zetterling, Carl-Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Halvledarmaterial, HMA.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Allerstam, Fredrik
    Department of Microtechnology and Nanoscience, Chalmers University of Technology.
    Sveinbjörnsson, Einar Ö.
    Department of Microtechnology and Nanoscience, Chalmers University of TechnologyDepartment of Microtechnology and Nanoscience, Chalmers University of Technology.
    1200-V 5.2-m Omega center dot cm(2) 4H-SiC BJTs with a high common-emitter current gain2007Inngår i: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 28, nr 11, s. 1007-1009Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This letter presents fabrication of a power 4H-SiC bipolar junction transistor (BJT) with a high open-base breakdown voltage BVCEO approximate to 1200 V, a low specific ON-resistance R-SP_ON approximate to 5.2 m Omega . cm(2), and a high common-emitter current. gain beta approximate to 60. The high gain of the BJT is attributed to reduced surface recombination that has been obtained using passivation by thermal silicon dioxide grown in nitrous oxide (N2O) ambient. Reference BJTs with passivation by conventional dry thermal oxidation show a clearly lower current gain and a more pronounced emitter-size effect. BJTs with junction termination by a guard-ring-assisted junction-termination extension (JTE) show about 400 V higher breakdown voltage compared with BJTs with a conventional JTE.

  • 197.
    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.
    Heinze, Birk
    Chemnitz University of Technology.
    Lutz, Josef
    Chemnitz University of Technology.
    Influence of the base contact on the electrical characteristics of SiC BJTs2007Inngår i: 19th International Symposium on Power Semiconductor Devices and ICs, ISPSD'07: Jeju Island; 27 May 2007 through 31 May 2007, 2007, s. 153-156Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we have investigated how the specific on-resistance and common emitter current gain of SiC BJTs depend on the base contact resistance. The on-state characteristics of SiC BJTs were investigated before and after base contact annealing at different temperatures. The common emitter current gain and specific on-resistance was improved by 23 % and 300 % compared to the values of before base contact annealing, respectively. Large area SiC BJTs (active area 0.0324 cm(2)), have been measured up to 34 A collector current in pulsed mode showing a gain of 35, and a specific on-resistance of 2 8.79 m Omega center dot cm(2)

  • 198.
    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.

  • 199. Li, J.
    et al.
    Thylén, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. IQSL, Hewlett-Packard Laboratories, United States .
    Bratkovski, A.
    Wang, S. -Y
    Williams, S.
    Sub-wavelengh sized optical cavity resonators with fishnet2009Inngår i: 2009 Conference on Lasers and Electro-Optics and 2009 Conference on Quantum Electronics and Laser Science Conference, CLEO/QELS, 2009, s. 5224514-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An optical cavity resonator of deep sub-wavelength size is demonstrated numerically by inserting a single layer of "fishnet" structure of next refractive index into a Fabry-Perot cavity composed of two gold films.

  • 200. Li, J.
    et al.
    Thylén, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. Hewlett-Packard Research Lab, United States .
    Wang, S. -Y
    Comment on "stability and quality factor of a one-dimensional subwavelength cavity resonator containing a left-handed material"2009Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, nr 20, s. 207101-Artikkel i tidsskrift (Fagfellevurdert)
1234567 151 - 200 of 615
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf