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  • 1. Abadei, S.
    et al.
    Gevorgian, S.
    Cho, C. R.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Low-frequency and microwave performances of laser-ablated epitaxial Na0.5K0.5NbO3 films on high-resistivity SiO2/Si substrates2002In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 91, no 4, p. 2267-2276Article in journal (Refereed)
    Abstract [en]

    The dielectric properties of laser-ablated 0.5-mum-thick c-axis epitaxial Na0.5K0.5NbO3 (NKN) films on high-resistivity (>7.7 kOmega cm) silicon SiO2/Si substrates are studied experimentally in the temperature interval of 30-320 K and at frequencies of 1.0 MHz-40 GHz. The films are grown by laser ablation from a stoichiometric target. For the measurements, planar 0.5-mum-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of NKN films. The slot width between the electrodes is 2.0 or 4.0 mum. At low frequencies (f<1.0 GHz), the structure performance is that of a typical metal-dielectric-semiconductor type, where two of this type of capacitor are connected back to back. At these frequencies, the large change in the capacitance (more than 10 times at 1.0 MHz), due to the applied dc field, is mainly due to the changes in depletion layer thickness at the surface of silicon. The associated losses are also large, tan delta>1. At microwave frequencies (f>10 GHz), the voltage dependence of the capacitance is given by the NKN film. More than a 13% capacitance change at 40 V dc bias and a Q factor of more than 15 are observed at 40 GHz, which make the structure useful for applications in electrically tunable millimeter-wave devices.

  • 2. Abadei, S.
    et al.
    Gevorgian, S.
    Cho, C. R.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Andreasson, J.
    Lindback, T.
    DC field dependent properties of Na0.5K0.5NbO3/SiO2/Si structures at millimeter-wave frequencies2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 13, p. 1900-1902Article in journal (Refereed)
    Abstract [en]

    Dielectric properties of laser-ablated 0.5-mum-thick c-axis epitaxial Na0.5K0.5NbO3 films on high-resistivity (7.7 Omega cm) silicon SiO2/Si substrate are studied experimentally at frequencies up to 40 GHz. For measurements, planar 0.5-mum-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of Na0.5K0.5NbO3 films. The slot width between the electrodes is 2 or 4 mum. 13% capacitance change at 40 V dc bias and Q factor more than 15 are observed at 40 GHz, which makes the structure useful for applications in electrically tunable millimeter-wave devices.

  • 3. Abdalla, M. A.
    et al.
    Frojdh, C.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A CMOS APS for dental X-ray imaging using scintillating sensors2001In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 460, no 1, p. 197-203Article in journal (Refereed)
    Abstract [en]

    In this paper we present an integrating CMOS Active Pixel Sensor (APS) circuit to be used with scintillator type X-ray sensors for intra oral dental X-ray imaging systems. Different pixel architectures were constructed to explore their performance characteristics and to study the feasibility of the development of such systems using the CMOS technology. A prototype 64 x 80 pixel array has been implemented in a CMOS 0.8 mum double poly n-well process with a pixel pitch of 50 mum. A spectral sensitivity measurement for the different pixels topologies, as well as measured X-ray direct absorption in the different APSs are presented. A measurement of the output signal showed a good linearity over a wide dynamic range. This chip showed that the very low sensitivity of the CMOS APSs to direct X-ray exposure adds a great advantage to the various CMOS advantages over CCD-based imaging systems,

  • 4. Abdalla, M. A.
    et al.
    Frojdh, C.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    An integrating CMOS APS for X-ray imaging with an in-pixel preamplifier2001In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 466, no 1, p. 232-236Article in journal (Refereed)
    Abstract [en]

    We present in this paper an integrating CMOS Active Pixel Sensor (APS) circuit coated with scintillator type sensors for intra-oral dental X-ray imaging systems. The photosensing element in the pixel is formed by the p-diffusion on the n-well diode. The advantage of this photosensor is its very low direct absorption of X-rays compared to the other available photosensing elements in the CMOS pixel. The pixel features an integrating capacitor in the feedback loop of a preamplifier of a finite gain in order to increase the optical sensitivity. To verify the effectiveness of this in-pixel preamplification, a prototype 32 x 80 element CMOS active pixel array was implemented in a 0.8 mum CMOS double poly, n-well process with a pixel pitch of 50 mum. Measured results confirmed the improved optical sensitivity performance of the APS. Various measurements on device performance are presented.

  • 5.
    Abdalla, Munir
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pixel Detectors and Electronics for High Energy Radiation Imaging2001Doctoral thesis, comprehensive summary (Other scientific)
  • 6. Aberg, D.
    et al.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pellegrino, P.
    Svensson, B. G.
    Nitrogen deactivation by implantation-induced defects in 4H-SiC epitaxial layers2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 19, p. 2908-2910Article in journal (Refereed)
    Abstract [en]

    Ion implantation causes free charge carrier reduction due to damage in the crystalline structure. Here, nitrogen-doped 4H silicon carbide (n type) epitaxial layers have been investigated using low ion doses in order to resolve the initial stage of the charge carrier reduction. It was found that the reduction of free carriers per ion-induced vacancy increases with increasing nitrogen content. Nitrogen is suggested to be deactivated through reaction with migrating point defects, and silicon vacancies or alternatively interstitials are proposed as the most likely candidates.

  • 7. Aberg, D.
    et al.
    Hallén, Anders.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Pellegrino, P.
    Svensson, B. G.
    Nitrogen passivation by implantation-induced point defects in 4H-SiC epitaxial layers2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 184, no 04-jan, p. 263-267Article in journal (Refereed)
    Abstract [en]

    Ion implantation causes damage to the crystal lattice resulting in the loss of free charge carriers. In this study, low dose implantations using different ions and implantation doses are made to resolve the initial carrier loss in nitrogen-doped epitaxial layers. A strong dependence of compensation on nitrogen concentration is seen, showing that nitrogen is passivated by implantation-induced point defects. An activation energy of 3.2 eV for the dissociation of the passivated nitrogen center is obtained.

  • 8. Aberg, J
    et al.
    Persson, S
    Hellberg, Per-Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zhang, Shi-Li
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Smith, U
    Ericson, F
    Engstrom, M
    Kaplan, W
    Electrical properties of the TiSi2-Si transition region in contacts: The influence of an interposed layer of Nb2001In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 90, no 5, p. 2380-2388Article in journal (Refereed)
    Abstract [en]

    The influence of an interposed ultrathin Nb layer between Ti and Si on the silicide formation and the electrical contact between the silicide formed and the Si substrate is investigated. The presence of the Nb interlayer results in the formation of ternary alloy (Nb,Ti)Si-2 in the C40 crystallographic structure adjacent to the Si substrate. Depending on the nature of the Si substrates and/or the amount of the initial Nb, the interfacial C40 (Nb,Ti)Si-2 leads, in turn, to either epitaxial growth of a highly faulted metastable C40 TiSi2 or formation of the desired C54 TiSi2 at a lower temperature than needed for it to form in reference samples with Ti deposited directly on Si. On p-type substrates doped to various concentrations, the Nb also leads to a considerably lower specific contact resistivity than that obtained in the reference samples: a twofold to fourfold reduction in the contact resistivity is found using cross-bridge Kelvin structures in combination with two-dimensional numerical simulation. As C40 (Nb,Ti)Si-2 forms at the interface when an interfacial Nb is present, the interface characterized is likely to represent the one between (Nb,Ti)Si-2 and Si. For the reference samples, the interface studied is between TiSi2 and Si.

  • 9. Aboelfotoh, M. O.
    et al.
    Frojdh, C.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Schottky-barrier behavior of metals on n- and p-type 6H-SiC2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 67, no 7Article in journal (Refereed)
    Abstract [en]

    The Schottky-barrier height of a number of metals (Ti, Ni, Cu, and Au) on n- and p-type Si-terminated 6H-SiC has been measured in the temperature range 150-500 K. It is found that the barrier height to n-type 6H-SiC does not exhibit a temperature dependence, while for p-type 6H-SiC the change in the barrier height with temperature follows very closely the change in the indirect energy gap in 6H-SiC. These results are inconsistent with models of Schottky-barrier formation based on the concept of a charge neutrality level. Furthermore, the present results cannot be reconciled with a defect pinning mechanism, contrary to the conclusions of earlier studies on III-V compound semiconductors. We suggest that chemical bonding at the metal-semiconductor interface plays an important role in determining the Schottky-barrier height.

  • 10. Adachi, N.
    et al.
    Denysenkov, V. P.
    Khartsev, Sergiy
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Okuda, T.
    Epitaxial Bi3Fe5O12(001) films grown by pulsed laser deposition and reactive ion beam sputtering techniques2000In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 88, no 5, p. 2734-2739Article in journal (Refereed)
    Abstract [en]

    We report on processing and comparative characterization of epitaxial Bi3Fe5O12 (BIG) films grown onto Gd-3(ScGa)(5)O-12[GSGG,(001)] single crystal using pulsed laser deposition (PLD) and reactive ion beam sputtering (RIBS) techniques. A very high deposition rate of about 0.8 mu m/h has been achieved in the PLD process. Comprehensive x-ray diffraction analyses reveal epitaxial quality both of the films: they are single phase, exclusively (001) oriented, the full width at half maximum of the rocking curve of (004) Bragg reflection is 0.06 deg for PLD and 0.05 deg for RIBS film, strongly in-plane textured with cube-on-cube film-to-substrate epitaxial relationship. Saturation magnetization 4 pi M-s and Faraday rotation at 635 nm were found to be 1400 Gs and -7.8 deg/mu m in PLD-BIG, and 1200 Gs and -6.9 deg/mu m in RIBS-BIG. Ferromagnetic resonance (FMR) measurements performed at 9.25 GHz yielded the gyromagnetic ratio gamma=1.797x10(7) l/s Oe, 1.826x10(7) l/s Oe; the constants of uniaxial magnetic anisotropy were K-u(*)=-8.66x10(4) erg/cm(3), -8.60x10(4) erg/cm(3); the cubic magnetic anisotropy K-1=-2.7x10(3) erg/cm(3),-3.8x10(3) erg/cm(3); and the FMR linewidth Delta H=25 and 34 Oe for PLD and RIBS films correspondingly. High Faraday rotation, low microwave loss, and low coercive field less than or equal to 40 Oe of BIG/GSGG(001) films promise their use in integrated magneto-optic applications.

  • 11. Adachi, N.
    et al.
    Okuda, T.
    Denysenkov, Vasyl
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jalali-Roudsar, Amir
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Grishin, Alexander
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Magnetic properties of single crystal film Bi3Fe5O12 prepared onto Sm3(Sc, Ga)5O12(111)2002In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 242, no Part 2, p. 775-777Article in journal (Refereed)
    Abstract [en]

    Magnetic properties of single crystal Bi3Fe5O12 has been investigated in the temperature range between 2 and 670K. The Sm3(Sc,Ga)5O12 wafer has been used for substrates. Due to the small contribution of the substrate's magnetization, the film's magnetization can be clearly estimated to be 2040G (0K) and the Curie temperature has been estimated to be around 650K.

  • 12.
    Adam, Constantin
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Stadler, Rolf
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Patterns for Routing and Self-Stabilization2004In: NOMS 2004: IEEE/IFIP NETWORK OPERATIONS AND MANAGMENT SYMPOSIUM - MANAGING NEXT GENERATION CONVERGENCE NETWORKS AND SERVICES, New York: IEEE , 2004, p. 61-74Conference paper (Refereed)
    Abstract [en]

    This paper contributes towards engineering self-stabilizing networks and Services. We propose the use of navigation patterns, which define how information for state updates is disseminated in the system, as fundamental building blocks for self-stabilizing systems. We present two navigation patterns for self-stabilization: the progaressive wave pattern and the stationary wave pattern. The progressive wave pattern defines the update dissemination in Internet routing systems running the DUAL and OSPF protocols. Similarly, the stationary wave pattern defines the interactions of peer nodes in structured-peer-to-peer systems, including Chord, Pastry, Tapestry, and CAN. It turns out that both patterns are related. They both disseminate information in form of waves, i.e, sets of messages that originate from single events. Patterns can be instrumented to obtain wave statistics, which enables monitoring the process of self-stabilization in a system. We focus on Internet routing and peer-to-peer systems in this work, since we believe that studying these (existing) systems can lead to engineering principles for self-stabilizing system in various application areas.

  • 13.
    Adiseno,
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Design Aspects of Fully Integrated Multiband Multistandard Front-End Receivers2003Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In this thesis, design aspects of fully integrated multibandmultistandard front-end receivers are investigated based onthree fundamental aspects: noise, linearity and operatingfrequency. System level studies were carried out to investigatethe effects of different modulation techniques, duplexing andmultiple access methods on the noise, linearity and selectivityperformance of the circuit. Based on these studies and thelow-cost consideration, zero-IF, low-IF and wideband-IFreceiver architectures are promising architectures. These havea common circuit topology in a direct connection between theLNA and the mixer, which has been explored in this work toimprove the overall RF-to-IF linearity. One front-end circuitapproach is used to achieve a low-cost solution, leading to anew multiband multistandard front-end receiver architecture.This architecture needs a circuit whose performance isadaptable due to different requirements specified in differentstandards, works across several RF-bands and uses a minimumamount ofexternal components.

    Five new circuit topologies suitable for a front-endreceiver consisting of an LNA and mixer (low-noise converter orLNC) were developed. A dual-loop wide-band feedback techniquewas applied in all circuits investigated in this thesis. Threeof the circuits were implemented in 0.18 mm RF-CMOS and 25 GHzbipolar technologies. Measurement results of the circuitsconfirmed the correctness of the design approach.

    The circuits were measured in several RF-bands, i.e. in the900 MHz, 1.8 GHz and 2.4 GHz bands, with S11 ranging from–9.2 dB to–17 dB. The circuits have a typicalperformance of 18-20 dB RF-to-IF gain, 3.5-4 dB DSB NF and upto +4.5 dBm IIP3. In addition, the circuit performance can beadjusted by varying the circuit’s first-stage biascurrent. The circuits may work at frequencies higher than 3GHz, as only 1.5 dB of attenuation is found at 3 GHz and nopeaking is noticed. In the CMOS circuit, the extrapolated gainat 5 GHz is about 15 dB which is consistent with the simulationresult. The die-area of each of the circuits is less than 1mm2.

  • 14.
    Adiseno,
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Design aspects of low-noise amplifiers in low-IF receivers for wireless applications2001Licentiate thesis, comprehensive summary (Other scientific)
  • 15. Adiseno,
    et al.
    Ismail, Mohammed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A wide-band RF front-end for multiband multistandard high-linearity low-IF wireless receivers2002In: IEEE Journal of Solid-State Circuits, ISSN 0018-9200, E-ISSN 1558-173X, Vol. 37, no 9, p. 1162-1168Article in journal (Refereed)
    Abstract [en]

    A wide-band radio-frequency (RF) front-end is designed with a balanced combined low-noise amplifier and a switching mixer (a low-noise converter) in RF Si-bipolar process with an f(T) of 25 GHz. The circuit achieves 20-dB conversion gain, higher than -4.5-dBm RF-to-IF IIP3 (+15.5-dBm OIP3) and less than 3.8-dB double-side-band noise figure in 900-MHz (e.g., GSM) and 1.9-GHz (e.g., WCDMA) frequency bands. The -1-dB compression point is -20 dBm at 13-mA dc current consumption from a single 5-V supply. The local-oscillator leakage to the input is less than -56 dBm in the 900-MHz band and less than -63 dBm in the 1.9-GHz band. The -3-dB bandwidth of the amplifier is larger than 3 GHz and a wide-band matching at the input with - 10 to -41-dB S-11 is achieved in the frequency bands of interest by applying a dual-loop wide-band active feedback. The die area is 0.69 x 0.9 mm(2). The circuit is suitable for area-efficient multiband multistandard low-IF receivers.

  • 16. Adiseno,
    et al.
    Ismail, Mohammed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Multiband high-linearity front-end receivers for wireless applications2002In: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 30, no 1, p. 59-67Article in journal (Refereed)
    Abstract [en]

    In this paper, a modified front-end receiver configuration, which consists of an LNA and mixer suitable for zero-IF or low-IF receivers, is presented. The idea is to achieve a better linearity for receivers by combining circuit and system level solutions. Three circuit topologies, two in bipolar and one in CMOS technology, are presented in this paper with their simulation results. One of the bipolar topologies has been implemented and measurement results are presented. An IIP3 of up to +0.6 dBm of a combined bipolar LNA and mixer is achieved, depending on frequency of interest and with an acceptable noise figure performance at a current consumption of less than 13 mA from 5 V supply voltage in one circuit and 3 V supply voltage in the other one. An IIP3 up to +5 dBm is achieved for the CMOS topology at a lower overall gain and acceptable noise figure (14.4 mA and 3 V). All circuits presented in this paper are wideband circuits, suitable for area-efficient multiband receivers.

  • 17. Aitken, Candice L.
    et al.
    Mahmoud, Faaiza
    McGuinness, Georgeann
    Kramer, Elissa L.
    Maguire, Gerald Q. Jr.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Noz, Marilyn E.
    New York University.
    Tumor localization and image registration of F-18FDG coincidence detection scans with computed tomographic scans2002In: Clinical Nuclear Medicine, ISSN 0363-9762, E-ISSN 1536-0229, Vol. 27, no 4, p. 275-282Article in journal (Refereed)
    Abstract [en]

    Purpose: The aim of this study was to determine the feasibility of registering routine clinical F-18 fluorodeoxyglucose (FDG) coincidence detection (CD) scans with computed tomographic (CT) scans for radiation treatment planning and case management. Methods: F-18 FDG CD and chest CT scans, performed in 10 randomly selected patients with confirmed or possible adenocarcinoma of the lung, were evaluated. The quality of the matches was verified by comparisons of the center-to-center distance between a region of interest (ROI) manually drawn on the CT slice and warped onto the CD slice with an ROI drawn manually directly on the CD slice. In addition, the overlap between the two ROIs was calculated. Results: All 10 F-18 FDG CD and CT scans were registered with good superimposition of soft tissue density on increased radionuclide activity. The center-to-center distance between the ROIs ranged from 0.29 mm to 8.08 mm, with an average center-to-center distance of 3.89 mm 2.42 mm (0.69 pixels +/- 0.34 pixels). The ROI overlap ranged from 77% to 99%, with an average of 90% +/- 5.6%. Conclusions: Although the use of F-18 FDG CD shows great promise for the identification of tumors, it shares the same drawbacks as those associated with radiolabeled monoclonal antibody SPECT and ligand-based positron emission tomographic scans in that anatomic markers are limited. This study shows that image registration is feasible and may improve the clinical relevance of CD images.

  • 18.
    Akram, Nadeem
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Lateral current injection (LCI) multiple quantum-well 1.55 mu m laser with improved gain uniformity across the active region2004In: Optical and quantum electronics, ISSN 0306-8919, E-ISSN 1572-817X, Vol. 36, no 9, p. 827-846Article in journal (Refereed)
    Abstract [en]

    A simulation study of lateral current injection 1.55 mum laser with strain-compensated multiple quantum-well (MQW) active region (InGaAsP well, InGaAlAs barrier) is presented using self-consistent 2D numerical simulations. The effects of different mesa width and p-doping in the QWs on the carrier and gain uniformity across the active region are explored. A high p-doping in the quantum wells is found to increases the carrier and gain non-uniformity across the active region. The QW region close to the n-contact side does not provide much gain at high optical powers. An asymmetric optical waveguide design is proposed to help reduce the gain non-uniformity across the active region. By shifting the optical modal peak toward the p-side, the modal overlap between the gain region and the optical mode is improved and a more even carrier and gain distribution is obtained. However, due to reduced bandgap of the quaternary InGaAsP p-cladding, an enhanced electron leakage out of the QWs into the p-cladding degrades the laser efficiency and increases the threshold current. Transient time - domain simulations are also performed to determine the small-signal modulation response of the laser promising a simulated high modulation bandwidth suitable for direct-modulation applications.

  • 19.
    Akram, Nadeem
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kjebon, Olle
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Influence of electrical parasitics and drive impedance on the laser modulation response2004In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 16, no 1, p. 21-23Article in journal (Refereed)
    Abstract [en]

    In this letter, we analyze the effects of electrical parasitics and drive impedance on the laser modulation response. It is found that for lasers with small active-region volume, e.g., vertical-cavity surface-emitting lasers, the finite drive impedance and/or the laser parasitic capacitance can significantly enhance the damping of the laser resonance peak at low bias. This is due to the voltage fluctuations across the laser diode active layer during modulation. It is also shown that the real pole of the small-signal response transfer function corresponding to the laser parasitic cutoff frequency is not fixed but decreases with the increased bias level.

  • 20.
    Akram, Nadeem
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Silfvenius, Christofer
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kjebon, Olle
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Design optimization of InGaAsP-InGaAlAs 1.55 mu m strain-compensated MQW lasers for direct modulation applications2004In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 19, no 5, p. 615-625Article in journal (Refereed)
    Abstract [en]

    In this paper, a simulation study of InGaAsP(well)/InGaAlAs(barrier) 1.55 mum strain-compensated multi-quantum well (MQW) lasers is presented. Due to a large conduction band discontinuity in this material system, a higher material gain and differential gain can be obtained from such a quantum well (QW) as compared to a traditional InGaAsP/InGaAsP quantum well. The deeper electron well should also improve elevated temperature operating characteristics and reduce the electron spillover from QWs. For MQWs, a uniform vertical distribution of holes is achieved due to a reduced effective hole confinement energy by optimizing the bandgap and the strain in the barriers. A large number of quantum wells can be uniformly pumped, reducing the carrier density in each individual well. A uniform and low carrier density in all the wells help reduce the total Auger recombination current. High p-doping in the active region is shown to enhance the carrier and gain non-uniformity in the MQWs. A simulated high modulation bandwidth has been demonstrated, promising directly modulated lasers as a low-cost source for short to medium distance (1-10 km) high speed optical links.

  • 21.
    Al Khatib, Lyad
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Performance anaalysis of wireless LAN access points2003Licentiate thesis, comprehensive summary (Other scientific)
  • 22.
    Anand, Srinivasan
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Mulot, Mikael
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Berrier, Audrey
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Ferrini, R.
    Houdre, R.
    Kamp, M.
    Forchel, A.
    Towards realization of high quality 2D-photonic crystals in InP/GaInAsP/InP2004In: 2004 International Conference on Indium Phosphide and Related Materials, Conference Proceedings, 2004, p. 311-313Conference paper (Refereed)
    Abstract [en]

    Two-dimensional photonic crystals (PhCs) were etched into InP/GaInAsP/InP planar waveguides using chlorine based chemical assisted ion beam etching (CAIBE). Etching mechanisms and process parameters crucial for high quality PhC definition are discussed, with special attention to the lag-effect. The processed PhCs were optically characterized by measuring transmission through simple slabs and one-dimensional cavities. The optical properties inside the photonic bandgap are much better compared to both previously reported CAME results and results obtained with other etching methods. In particular, we measured a record quality factor of 310 for one-dimensional cavities fabricated in this material system.

  • 23.
    Anand, Srinivasan
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Qiu, Min
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Mulot, Mikael
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Swillo, Marcin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jaskorzynska, Bozena
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Anders
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    High aspect ratio etching and characterization of 2D-photonic crystals in InP/InGaAsP/InP heterostructures2004In: Photonics: Design, Technology, And Packaging / [ed] Jagadish, C; Choquette, KD; Eggleton, BJ; Nener, BD; Nugent, KA, SPIE - International Society for Optical Engineering, 2004, p. 78-89Conference paper (Refereed)
    Abstract [en]

    We report on the fabrication and characterization of 2D photonic crystals (PhCs) in InP/InGaAsP/InP heterostructures. It is demonstrated that Ar/C12 based chemically assisted ion beam etching (CAIBE) is a very promising method to obtain high aspect ratio etching of PhCs in the InP-based materials. With this process, it is possible to obtain PC-holes as deep as 3 microns even for feature (PhC-hole) sizes as small as 200-250 nm. The optical characteristics of the fabricated PhC-based elements/devices such as line-defect waveguides, in-plane resonant cavities and drop-filter based on contra-directional coupling will be reported. The devices were measured using end-fire coupling and the obtained results were simulated using the 2D finite difference time domain (FDTD) method including an effective loss-approximation. The etched PhC-waveguides show low transmission losses, less than 1 dB/100 mum. A quality factor of 400 for a 6 micron long cavity with 6-hole mirrors is obtained. Finally, drop-functionality in a PhC-based filter using contra-directional coupling is demonstrated.

  • 24.
    Andersson, Magnus
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Lundqvist, Björn
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Rapp, Östen
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Vortex liquid-to-solid transition in underdoped YBa2Cu3O7-delta single crystals with B parallel to ab2003In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 388, p. 691-692Article in journal (Refereed)
    Abstract [en]

    A nearly magnetic field independent vortex liquid-to-solid transition has been observed in both the ab-plane and in the c-axis resistivity of underdoped YBa2Cu3O7-delta single crystals for magnetic fields Bparallel toab-plane. These observations suggest that intrinsic pinning caused by the superconducting layers do neither lead to a system of completely decoupled superconducting layers nor to a smectic vortex phase at high fields. A possible explanation may include a transition driven by changes in elastic properties (e.g., the shear modulus) of the vortex system.

  • 25.
    Andersson, Magnus
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Rydh, Andreas
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Rapp, Östen
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Scaling of the vortex-liquid resistivity in optimally doped and oxygen-deficient YBa2Cu3O7-delta single crystals2001In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 63, no 18, p. 1845111-1845119Article in journal (Refereed)
    Abstract [en]

    The consequences of a recently proposed model [A. Rydh. O. Rapp. and M. Andersson. Phys. Rev. Lett. 83. 1850 (1999)] for the vortex-liquid resistivity close to a vortex liquid-to-glass transition are anal-zed in detail. We find a detailed quantitative agreement between the model and resistivity measurements on disordered, optimally doped YBa2Cu3O7-delta single crystals. For temperatures below the superconducting transition temperature. a scaling of all measured resistivity curves in magnetic field (0<B12 T) is obtained. Possible ways of slightly modifying the model in order to fully describe resistivity measurements on more anisotropic underdoped oxygen-deficient YBa2Cu3O7-delta single crystals are suggested. The physical interpretation of the model and its connection to other models of the vortex-liquid resistivity are discussed. in particular, we find close connections to vortex glass models and to a generalized Coulomb gas model.

  • 26. Andrae, A S G
    et al.
    Möller, Patrik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Anderson, J
    Liu, J
    Uncertainty estimation by Monte Carlo simulation applied to life cycle inventory of cordless phones and microscale metallization processes2004In: IEEE transactions on electronics packaging manufacturing (Print), ISSN 1521-334X, E-ISSN 1558-0822, Vol. 27, no 4, p. 233-245Article in journal (Refereed)
    Abstract [en]

    This paper focuses on uncertainty analysis, that is, how the input data uncertainty affects the output data uncertainty in small but realistic product systems. The motivation for the study is to apply the Monte Carlo simulation for uncertainty estimation in life cycle inventory and environmental assessment of microelectronics applications. The present paper addresses the question whether there is an environmental advantage of using digital enhanced cordless telecommunications (DECT) phones instead of global system for mobile (GSM) phones in offices. This paper also addresses the environmental compatibility of electrochemical pattern replication (ECPR) compared to classical photolithography-based microscale metallization (CL) for pattern transfer. Both environmental assessments in this paper consider electricity consumption and CO2 emissions and the projects undertaken are two comparative studies of DECT phone/GSM phone and ECPR/CL, respectively. The research method used was probabilistic uncertainty modeling with a limited number of inventory parameters used in the MATLAB tool. For the DECT/GSM study the results reflects the longer DECT technical life which is an environmental advantage. For the electrochemical pattern replication (ECPR)/classical photolithography based microscale metallization (CL) study the results reflects the fewer number of process steps and the lower electricity consumption needed by the ECPR to reach the functional unit. The difference in results is large enough to be able to draw conclusions, as the processes, having the highest electricity consumption within the system boundaries have been determined. Based on an earlier work, a straightforward method to include uncertainty for input life cycle inventory data is used to quantify the influence of realistic errors for input data in two microelectronic applications. The conclusion is that the ECPR technology is more electricity efficient than CL in producing one layer of copper on a silicon wafer having a diameter of 20.32 cm. Furthermore, the longer technical life of a cordless DECT phone is reflected in an electricity/CO2 comparison with a GSM phone, if office use is considered. Reasonable uncertainty intervals, used for the input life cycle inventory data for the studied DECT/GSM and ECPR/CL system, does affect the outcome of calculation of emission of CO2, but not to the degree that conclusions are not valid. Different uncertainty intervals and probability distributions could apply for different types of data and the interrelated input data dependencies should be investigated. Today there exist very few life cycle inventory (LCI) data with the range of uncertainty for input and output elements. It must be emphasized that the upcoming LCI databases should have standard deviation characterized LCI data just as the Swiss ecoinvent LCI database. More inventory parameters and probability distributions characteristic for microsystems could be included and error analysis should be applied to future life inventory methodology, especially for future packaging concepts such as system-in-a-package and system-on-a-chip comparisons.

  • 27.
    Andrijevic, Goran
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Magnusson, Håkan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kämpe, Andreas
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Multistandard receiver for home networking and digital media2004In: 22ND NORCHIP CONFERENCE, PROCEEDINGS, NEW YORK: IEEE , 2004, p. 131-134Conference paper (Refereed)
    Abstract [en]

    We propose a fully integrated multistandard receiver architecture that fulfills coming media and networking needs of homes. The receiver uses a dual-IF architecture to cover receive bands from 170 MHz to 920 MHz and the Industrial, Scientific and Medical (ISM) band at 2.4GHz. Key performance values meet the DVB-T, Zigbee, Bluetooth and 802.11b requirements (Sensitivity -72.5dBm. available SNR=28dB. Noise Figure 6.7dB. Adjacent Channel Protection Ratio-ACPR=-44dB, IIP3 = -11 dBm).

  • 28.
    Andrijevic, Goran
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Magnusson, Håkan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Olsson, Håkan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A fully integrated low-IF DVB-T receiver architecture2004In: 2004 INTERNATIONAL SYMPOSIUM ON SYSTEM-ON-CHIP, PROCEEDINGS / [ed] Nurmi, J; Takala, J; Hamalainen, TD, 2004, p. 189-192Conference paper (Refereed)
    Abstract [en]

    We propose a fully integrated DVB-T receiver architecture for low cost CMOS implementation. The receiver uses a dual-IF architecture to cover the receive bands from 170 MHz to 862 MHz and a Low-IF of 4.57 MHz. Key performance values meet the DVB-T requirements with competitive performance (Sensitivity 72.5 dBm, Noise Figure 66 dB, Adjacent Channel Protection Ratio-ACPR=43dB, available SNR=28 dB) and suggest that low cost receivers are realistic in volume for the coming digital broadcasting systems.

  • 29. Andræ, A. S. G.
    et al.
    Möller, Patrik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Liu, J.
    Uncertainty estimation by Monte Carlo simulation applied to life cycle inventory of cordless phones and microscale metallization processes2004In: Proc.Int.Conf.Asian Green Electron., 2004, p. 206-217Conference paper (Refereed)
    Abstract [en]

    This paper addressed the question whether there is an environmental advantage of using DECT phones instead of GSM phones in offices. The paper also addresses the environmental compatibility of Electrochemical Pattern Replication (ECPR) compared to classical photolithography based microscale metallization (CL) for pattern transfer. Both environmental assessments consider electricity consumption and CO2 emissions. The projects undertaken were two comparative studies of DECT phone/GSM phone and ECPR/CL respectively. The research method used was probabilistic uncertainty modelling with a limited number of inventory parameters used in the MATLAB tool. Within the chosen system boundaries and with the uncertainties added to input data, the ECPR is to 100 % probability better than CL and the DECT phone is to 90% better than the GSM phone.

  • 30.
    Angulo Barrios, Carlos
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Gallium arsenide based buried heterostructure laser diodes with aluminium-free semi-insulating materials regrowth2002Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Semiconductor lasers based on gallium arsenide and relatedmaterials are widely used in applications such as opticalcommunication systems, sensing, compact disc players, distancemeasurement, etc. The performance of these lasers can beimproved using a buried heterostructure offering lateralcarrier and optical confinement. In particular, if theconfinement (burying) layer is implemented by epitaxialregrowth of an appropriate aluminium-free semi-insulating (SI)material, passivation of etched surfaces, reduced tendency tooxidation, low capacitance and integration feasibility areadditional advantages.

    The major impediment in the fabrication of GaAs/AlGaAsburied-heterostructure lasers is the spontaneous oxidation ofaluminium on the etched walls of the structure. Al-oxide actsas a mask and makes the regrowth process extremely challenging.In this work, a HCl gas-basedin-situcleaning technique is employed successfully toremove Al-oxide prior to regrowth of SI-GaInP:Fe and SI-GaAs:Fearound Al-containing laser mesas by Hydride Vapour PhaseEpitaxy. Excellent regrowth interfaces, without voids, areobtained, even around AlAs layers. Consequences of usinginadequate cleaning treatments are also presented. Regrowthmorphology aspects are discussed in terms of different growthmechanisms.

    Time-resolved photoluminescence characterisation indicates auniform Fe trap distribution throughout the regrown GaInP:Fe.Scanning capacitance microscopy measurements demonstrate thesemi-insulating nature of the regrown GaInP:Fe layer. Thepresence of EL2 defects in regrown GaAs:Fe makes more difficultthe interpretation of the characterisation results in the nearvicinity of the laser mesa.

    GaAs/AlGaAs buried-heterostructure lasers, both in-planelasers and vertical-cavity surface-emitting lasers, withGaInP:Fe as burying layer are demonstrated for the first time.The lasers exhibit good performance demonstrating thatSI-GaInP:Fe is an appropriate material to be used for thispurpose and the suitability of our cleaning and regrowth methodfor the fabrication of this type of semiconductor lasers.Device characterisation indicates negligible leakage currentalong the etched mesa sidewalls confirming a smooth regrowthinterface. Nevertheless, experimental and simulation resultsreveal that a significant part of the injected current is lostas leakage through the burying material. This is attributed todouble carrier injection into the SI-GaInP:Fe layer.Simulations also predict that the function of GaInP:Fe ascurrent blocking layer should be markedly improved in the caseof GaAs-based longer wavelength lasers.

    Keywords:semiconductor lasers, in-plane lasers, VCSELs,GaAs, GaInP, semi-insulating materials, hydride vapour phaseepitaxy, regrowth, buried heterostructure, leakage current,simulation.

  • 31.
    Armstrong, Joe
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Making reliable distributed systems in the presence of software errors2003Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    The work described in this thesis is the result of aresearch program started in 1981 to find better ways ofprogramming Telecom applications. These applications are largeprograms which despite careful testing will probably containmany errors when the program is put into service. We assumethat such programs do contain errors, and investigate methodsfor building reliable systems despite such errors.

    The research has resulted in the development of a newprogramming language (called Erlang), together with a designmethodology, and set of libraries for building robust systems(called OTP). At the time of writing the technology describedhere is used in a number of major Ericsson, and Nortelproducts. A number of small companies have also been formedwhich exploit the technology.

    The central problem addressed by this thesis is the problemof constructing reliablesystems from programs which maythemselves contain errors. Constructing such systems imposes anumber of requirements on any programming language that is tobe used for the construction. I discuss these languagerequirements, and show how they are satisfied by Erlang.

    Problems can be solved in a programming language, or in thestandard libraries which accompany the language. I argue howcertain of the requirements necessary to build a fault-tolerantsystem are solved in the language, and others are solved in thestandard libraries. Together these form a basis for buildingfault-tolerant software systems.

    No theory is complete without proof that the ideas work inpractice. To demonstrate that these ideas work in practice Ipresent a number of case studies of large commerciallysuccessful products which use this technology. At the time ofwriting the largest of these projects is a major Ericssonproduct, having over a million lines of Erlang code. Thisproduct (the AXD301) is thought to be one of the most reliableproducts ever made by Ericsson.

    Finally, I ask if the goal of finding better ways to programTelecom applications was fulfilled --- I also point to areaswhere I think the system could be improved.

  • 32. Artemov, A. N.
    et al.
    Drobotko, V. F.
    Grishin, Alexander M.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Khokhlov, V. A.
    Kosse, A. I.
    Levchenko, G. G.
    Medvedev, Y. V.
    Prokhorov, A. Y.
    Large effect of thermal processes on the susceptibility of YBCO film with transport current2004In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 403, no 3, p. 157-162Article in journal (Refereed)
    Abstract [en]

    The response of YBCO film with transport current to the weak alternating magnetic field was studied. The hysteresis of the temperature dependences of the response measured under cooling and heating was revealed. The qualitative explanation of this phenomenon is proposed. It is based on the fact that under certain conditions the superconductor with transport current has two steady states. It is found that the hysteresis arises only if transport current exceeds some finite value I-0.

  • 33.
    Arve, Per
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Jänes, Peter
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Thylén, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Propagation of two-dimensional pulses in electromagnetically induced transparency media2004In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 69, no 6, p. 063809-Article in journal (Refereed)
    Abstract [en]

    The propagation in two dimensions of "optical" pulses in electromagnetically induced transparency media is analyzed. Results are presented for coupled Maxwell-Bloch equations with slowly varying envelope approximation, for both adiabatic and nonadiabatic situations. The possibility of changing the direction of the pulse by a switch of control beam direction is investigated in detail.

  • 34. Asplund, C.
    et al.
    Mogg, S.
    Plaine, G.
    Salomonsson, F.
    Chitica, N.
    Hammar, Mattias
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Doping-induced losses in AlAs/GaAs distributed Bragg reflectors2001In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 90, no 2, p. 794-800Article in journal (Refereed)
    Abstract [en]

    We have studied n- and p-type doping-induced performance degradation of AlAs/GaAs distributed Bragg reflectors (DBRs) for applications in vertical cavity lasers (VCLs). Based on high-accuracy optical reflectance and triple-axis x-ray diffraction measurements on a variety of differently doped DBR structures grown by metalorganic vapor-phase epitaxy, a fitting procedure was employed to extract the doping-dependent optical loss. A striking observation is that the reflectance of these DBRs is much more sensitive to n- than p-type doping incorporation. While in the latter case the loss can be well accounted for by intervalence-band and free-carrier absorption, additional loss mechanisms must be considered for n-type DBRs. We relate the losses to doping-enhanced interdiffusion effects resulting in increased interface scattering. These findings should have important consequences for the design of VCLs, demonstrating the importance of reduced n-type doping concentrations and/or growth temperatures, or the application of alternative device concepts, e.g., employing intracavity contacts.

  • 35.
    Asplund, Carl
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Epitaxy of GaAs-based long-wavelength vertical cavity lasers2003Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Vertical cavity lasers (VCLs) are of great interest aslow-cost, high-performance light sources for fiber-opticcommunication systems. They have a number of advantages overconventional edge-emitting lasers, including low powerconsumption, efficient fiber coupling and wafer scalemanufacturing/testing. For high-speed data transmission overdistances up to a few hundred meters, VCLs (or arrays of VCLs)operating at 850 nm wavelength is today the technology ofchoice. While multimode fibers are successfully used in theseapplications, higher transmission bandwidth and longerdistances require single-mode fibres and longer wavelengths(1.3-1.55 µm). However, long-wavelength VCLs are as yetnot commercially available since no traditional materialssystem offers the required combination of bothhigh-index-contrast distributed Bragg reflectors (DBRs) andhigh-gain active regions. Earlier work on long-wavelength VCLshas therefore focused on hybrid techniques, such as waferfusion between InP-based QWs and AlGaAs DBRs, but more recentlythe main interest in this field has shifted towardsall-epitaxial GaAs-based devices employing novel 1.3-µmactive materials. Among these, strained GaInNAs/GaAs QWs aregenerally considered one of the most promising approaches andhave received a great deal of interest.

    The aim of this thesis is to investigate monolithicGaAs-based long-wavelength (>1.2 µm) VCLs with InGaAsor GaInNAs QW active regions. Laser structures - or partsthereof - have been grown by metal-organic vapor phase epitaxy(MOVPE) and characterized by various techniques, such ashigh-resolution x-ray diffraction (XRD), photoluminescence(PL), atomic force microscopy, and secondary ion massspectroscopy (SIMS). High accuracy reflectance measurementsrevealed that n-type doping is much more detrimental to theperformance of AlGaAs DBRs than previously anticipated. Asystematic investigation was also made of the deleteriouseffects of buried Al-containing layers, such as AlGaAs DBRs, onthe optical and structural properties of subsequently grownGaInNAs QWs. Both these problems, with their potential bearingon VCL fabrication, are reduced by lowering the DBR growthtemperature.

    Record-long emission wavelength InGaAs VCLs were fabricatedusing an extensive gain-cavity detuning. The cavity resonancecondition just below 1270 nm wavelength occurs at the farlong-wavelength side of the gain curve. Still, the gain is highenough to yield threshold currents in the low mA-regime and amaximum output power exceeding 1 mW, depending on devicediameter. Direct modulation experiments were performed on1260-nm devices at 10 Gb/s in a back-to-back configuration withopen, symmetric eye diagrams, indicating their potential foruse in high-speed transmission applications. These devices arein compliance with the wavelength requirements of emerging10-Gb/s Ethernet and SONET OC-192 standards and may turn out tobe a viable alternative to GaInNAs VCLs.

    Keywords:GaInNAs, InGaAs, quantum wells, MOVPE, MOCVD,vertical cavity laser, VCSEL, long-wavelength, epitaxy, XRD,DBR

  • 36.
    Asplund, Carl
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hammar, Mattias
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sundgren, Petrus
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Optimization of MOVPE-grown GaInNAs/GaAs quantum wells for 1.3-μm laser applications2002Conference paper (Refereed)
    Abstract [en]

    The effects of high group-V precursor flows during metal-organic vapor phase epitaxial growthof GaInNAs QWs are investigated. It is shown that photoluminescence line width, waferuniformity, and sensitivity to growth temperature can be improved using V/III ratios in excess of2000. Broad area GaInNAdGaAs SQW lasers with dimensions 100 x 820 pm2 grown under theseconditions have threshold current densities as low as 660 kA/cm2 at 1.26 pm emission wavelength.

  • 37.
    Asplund, Carl
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Sundgren, Petrus
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Mogg, Sebastian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hammar, Mattias
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Christiansson, Ulf
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Oscarsson, V.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Runnström, C.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Odling, E.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Malmquist, J.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    1260 nm InGaAs vertical-cavity lasers2002In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 38, no 13, p. 635-636Article in journal (Refereed)
    Abstract [en]

     The fabrication and performance of highly strained double-quantum well InGaAs/GaAs vertical-cavity lasers with record-long emission wavelength of 1260 nm at room temperature is reported. Depending on device diameter, the minimum threshold current is in the low mA-regime while the maximum output power exceeds 1 mW. The devices work continuous-wave over a wide temperature range of at least 10-120degrees C.

  • 38. Asplund, R.
    et al.
    Björk, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Reconstructing the discrete Wigner function and some properties of the measurement bases2001In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 6401, no 1Article in journal (Refereed)
    Abstract [en]

    We derive a direct reconstruction algorithm for the discrete Wigner function through different types of measurements. For a system described in a Hilbert space of dimension N=N-1...N-p, where the numbers N-i are prime, the reconstruction is accomplished with (N-1+1)...(N-p+1) factorable (local) von Neumann measurements. For the special case where the dimension is a power of a prime, the reconstruction can be performed in a much more efficient way using N+1 complementary measurements. If the system is composed of a number of smaller subsystems, these measurements will then in general be nonseparable.

  • 39. Asplund, R.
    et al.
    Björk, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Bourennane, M.
    An expectation value expansion of Hermitian operators in a discrete Hilbert space2001In: Journal of Optics B-Quantum and Semiclassical Optics, ISSN 1464-4266, E-ISSN 1741-3575, Vol. 3, no 3, p. 163-170Article in journal (Refereed)
    Abstract [en]

    We discuss a real-valued expansion of any Hermitian operator defined in a Hilbert space of finite dimension N, where N is a prime number, or an integer power of a prime. The expansion has a direct interpretation in terms of the operator expectation values for a set of complementary bases. The expansion can be said to be the complement of the discrete Wigner function. We expect the expansion to be of use in quantum information applications since qubits typically are represented by a discrete, and finite-dimensional, physical system of dimension N = 2(p), where p is the number of qubits involved. As a particular example we use the expansion to prove that an intermediate measurement basis (a Breidbart basis) cannot be found if the Hilbert space dimension is three or four.

  • 40.
    Atallah, Jad G.
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Elnaggar, Mohammed Ismail
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    A CMOS frequency synthesizer for multi-standard wireless devices2003In: Proceedings of the 46th IEEE International Midwest Symposium on Circuits & Systems: Vols 1-3 / [ed] Hamdy, N., NEW YORK: IEEE , 2003, p. 1138-1141Conference paper (Refereed)
    Abstract [en]

    This paper presents a CMOS frequency synthesizer for wireless transceivers that support several communication standards namely GSM, WCDMA, IEEE 802.11b, and Bluetooth. The architecture is based on a multi-stage phase-locked loop where each stage differs from the others in the parameters of its charge pump and loop filter. It is designed using mathematical models and refined through simulation using different software tools depending on the required perspective. The architecture and the components presented pave the way to provide a low cost, fully integrated implementation.

  • 41.
    Augustsson, Torsten
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Photonic wavelength selective devices based on multi-mode interference waveguides2001Doctoral thesis, comprehensive summary (Other scientific)
  • 42.
    Auvert, Marine
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Hjalmarsson, Håkan
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Johansson, Karl H.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Karlsson, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    On Router Control for Congestion Avoidance2002Conference paper (Refereed)
    Abstract [en]

    This short paper deals with active queue management for computer networks. The goal is to develop control mechanisms for routers in heterogeneous networks that reduce traffic fluctuations. The proposed control strategy operates with local information (such as estimated arrival rates) and actively use the buffers to smooth traffic, and thus it avoids the buildup and propagation of traffic bursts.

  • 43. Axnas, J.
    et al.
    Bryntse, I.
    Safonova, I.
    Rapp, Östen.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Magnetoconductivity of polycrystalline Hg,Tl-12232000In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 284, p. 1009-1010Article in journal (Refereed)
    Abstract [en]

    The magnetoconductivity of polycrystalline Hg1-xTlxBa2Ca2Cu3O8+delta With x = 0 and 0.2 has been measured above T-c and analysed in terms of superconducting fluctuations. Such studies are numerous and successful for Y- and Bi-based materials, but still rare for Hg- and Tl-based materials. Results for the coherence lengths and the role of the Maki-Thompson contribution are briefly discussed.

  • 44. Badaroglu, M.
    et al.
    Donnay, S.
    De Man, H. J.
    Zinzius, Y. A.
    Gielen, G. G. E.
    Sansen, W.
    Fonden, T.
    Signell, Svante
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Modeling and experimental verification of substrate noise generation in a 220-Kgates WLAN system-on-chip with multiple supplies2003In: IEEE Journal of Solid-State Circuits, ISSN 0018-9200, E-ISSN 1558-173X, Vol. 38, no 7, p. 1250-1260Article in journal (Refereed)
    Abstract [en]

    Substrate noise is a major obstacle for mixed-signal integration. While the power consumption scales linearly with the clock frequency, substrate noise does not have thin scaling due to the resonances in the transfer function of the supply current to the substrate. This paper addresses a practical technique to estimate the substrate noise frequency spectrum of a large mixed-mode System-on-Chip (SoC) with multiple supplies and embedded memories. The results have been verified with substrate noise measurements on a 60-MHz 220-Kgates telecom SoC implemented in a 0.3 mum CMOS process on an EPI-type substrate. We compute a linear chip-level substrate model together with the single-cycle representation of piecewise-linear noise sources of three. supply regions used in this ASIC. Based on this model we accurately estimate the four major resonances in the substrate poise spectrum and their relative magnitudes with 2 dB relative error at the major resonance with respect to measurements. We also present substrate noise measurements at different operating modes of the WLAN receiver. These measurements show that output I/O buffers generate significant substrate noise where an increase of 44% is measured for substrate noise peak-to-peak value due to the additional simultaneous switching of six output I/O buffers with already fully switching datapath and two output I/Os.

  • 45.
    Badel, Xavier
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Development of macropore arrays in silicon and related technologies for X-ray imaging applications2003Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Digital devices have started to replace photographic film inX-ray imaging applications. As compared to photographic films,these devices are more convenient to obtain images and tohandle, treat and store these images. The goal of the presentstudy is to develop macropore arrays and related silicontechnologies in order to fabricate X-ray imaging detectors formedical applications, and in particular for dentistry. Althougha few detectors are already available on the market, theirperformances, such as the X-ray sensitivity, can still beimproved. In addition, the image quality, defined by thespatial resolution and the signalto- noise ratio (SNR), shouldbe sufficiently high to enable diagnosis and, as regard to thepatient health, the X-ray dose should be reduced to aminimum.

    Three detector concepts were investigated. All of themrequire the formation of a macropore array in silicon as afirst step in the detector fabrication. Even though deepreactive ion etching was used to form these macropore arrays,silicon electrochemical etching in aqueous hydrofluoric acid(HF) solution has been more intensively studied. The porespacing was fixed to about 50 µm in order to achieve aspatial resolution of 10 lp/mm, as required in dentalapplication. Pore depths up to 420 µm with diameterranging from 10 to 40 µm, depending on the detectorconcept, have been achieved. Electrochemical etching of siliconis, indeed, a very promising technique to fabricate high aspectratio structures and damage-free macropore arrays. Thistechnique is based on a silicon dissolution reaction involvingthe species of the HF solution, silicon atoms and holes, thepositive charge carriers. As holes are the minority carriers inn-type silicon, they are usually photogenerated. However, wealso developed an alternative technique based on hole injectionfrom a forwardbiased p-n junction, and the possibility to formmacropore arrays and diverse threedimensional structures wasdemonstrated.

    The first detector concept investigated consists of asilicon charge-coupled device (CCD) in proximity with ascintillating guide screen. This screen is made of a siliconmacropore array filled with CsI(Tl), emitting photons at awavelength of 550 nm (green light) under X-ray exposure. Thevisible light is then reflected on the walls of the pores inorder to be detected by the CCD pixels. Both oxide and metalcan be used as a reflective layer. Such detectors were fullyfabricated and characterized, showing good spatial resolutionand comparable results with currently available detectorsconcerning the SNR and the X-ray dose. The second detectorstudied in this thesis uses photodiodes, instead of a CCD, inorder to detect the photons emitted from the scintillator. Thisconcept would lead to high charge collection efficiency sincethe diodes are formed in the silicon pore walls, making thedistance between the generation and detection points of thevisible photons short. However, this design implies two majordifficulties in the detector fabrication: formation of p-njunction in the pore walls and formation of contacts to thediodes. Thus, boron diffusion from a solid source andlow-pressure chemical vapor deposition of boron-dopedpoly-silicon were experimented. Both techniques were shown tobe successful. The last detector concept is based on thegeneration of electron/hole pairs in the semiconductor bulkunder X-ray exposure. The generated charges would then becollected by electrodes going through the bulk, requiringformation of deep and narrow pores. Siliconphoto-electrochemical etching was used and 425-µm deeppores with a diameter of 14 µm were formed, resulting inan aspect ratio of ~ 30 and an active area of 90 %.

  • 46.
    Badel, Xavier
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Galeckas, Augustinas
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Linnros, Jan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kleimann, P.
    LENAC, Université Claude Bernard Lyon-I, Villeurbanne.
    Fröjdh, C.
    Mitthögskolan, Department of Electronics.
    Petersson, C. Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Improvement of an X-ray imaging detector based on a scintillating guides screen2002In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 487, no 1-2, p. 129-135Article in journal (Refereed)
    Abstract [en]

    An X-ray imaging detector has been developed for dental applications. The principle of this detector is based on application of a silicon charge coupled device covered by a scintillating wave-guide screen. Previous studies of such a detector showed promising results concerning the spatial resolution but low performance in terms of signal to noise ratio (SNR) and sensitivity. Recent results confirm the wave-guiding properties of the matrix and show improvement of the detector in terms of response uniformity, sensitivity and SNR. The present study is focussed on the fabrication of the scintillating screen where the principal idea is to fill a matrix of Si pores with a CsI scintillator. The photoluminescence technique was used to prove the wave-guiding property of the matrix and to inspect the filling uniformity of the pores. The final detector was characterized by X-ray evaluation in terms of spatial resolution, light output and SNR. A sensor with a spatial resolution of 9 LP/mm and a SNR over 50 has been achieved using a standard dental X-ray source and doses in the order of those used at the moment by dentists (around 25 mR).

  • 47.
    Badel, Xavier
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kumar, R. T. R.
    Atomic Physics Division, Stockholm University.
    Kleinmann, P.
    LENAC, Univ. Claude Bernard Lyon-I, Villeurbanne.
    Linnros, Jan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Formation of ordered pore arrays at the nanoscale by electrochemical etching of n-type silicon2004In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 36, no 1/3, p. 245-254Article in journal (Refereed)
    Abstract [en]

    Electrochemical etching has been studied to structure n-type silicon substrates at the nanoscale. In this work, well-ordered pore arrays with diameters in the range of 150-500 nm and depths up to 50 mum have been fabricated. The pores were successfully formed by anodic etching in (100)oriented n-type silicon wafers of low-resistivity, typically 1 Omegacm, using aqueous hydrofluoric acid solutions. The lithographic step was performed in a thermally grown oxide using a stepper and dry oxide etching technique. Two types of oxide openings and pitch sizes were tested. The smallest oxide opening realised at this stage was 0.5 mum for a pitch of 1 mum. Stable pore formation was obtained and the smallest pore size obtained was about 200 nm with an aspect ratio close to 100.

  • 48.
    Badel, Xavier
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Linnros, Jan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Electrochemical etching of n-type silicon based on carrier injection from a back side p-n junction2003In: Electrochemical and solid-state letters, ISSN 1099-0062, E-ISSN 1944-8775, Vol. 6, no 6, p. C79-C81Article in journal (Refereed)
    Abstract [en]

    A technique for electrochemical etching of n-type silicon in aqueous hydrofluoric acid is presented. This technique differs from photoelectrochemical etching because the holes (positive carriers) needed for the dissolution reaction to occur, are not photogenerated. The principle developed here is to inject these positive carriers using a p-n junction under forward bias formed at the back side of the sample. Drift-diffusion of holes through the wafer thickness allows a chemical dissolution reaction at the interface with the electrolyte. To enable holes diffusing through the wafer the minority carrier lifetime must be sufficiently high making the technique well adapted for high resistivity silicon. However, extension to low resistivity wafers has been achieved. Results show the possibility of forming pore arrays and diverse 3D structures.

  • 49.
    Badel, Xavier
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Linnros, Jan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Janson, M. S.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Österman, J.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Formation of pn junctions in deep silicon pores for X-ray imaging detector applications2003In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 509, no 1-3, p. 96-101Article in journal (Refereed)
    Abstract [en]

    The formation of pn junctions in deep silicon pores has been studied for a new concept of X-ray imaging detectors. The sensitive part of the device is an array of CsI(Tl) columns formed by filling a silicon matrix of pores having pn junctions in their walls. Under X-ray illumination, the CsI(TI) scintillator emits photons that are collected by the pn junctions. Relatively high signal collection efficiency is expected. However, the formation of pn junctions inside pore walls represents a challenging step in the detector fabrication. In this work pore matrices were fabricated in n-type silicon by deep reactive ion etching and by photo-electrochemical etching. The pn junctions were formed either by boron diffusion or deposition of boron doped poly-silicon. Various techniques were used to analyze the transverse depth profiles of boron atoms at different pore depths. The study shows successful results for pn-junctions formed both by diffusion and by poly-silicon deposition.

  • 50.
    Badel, Xavier
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Linnros, Jan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kleimann, P
    Norlin, B
    Koskiahde, E
    Valpas, K
    Nenonen, S.
    Petersson, Sture
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Frojdh, C
    Metallized and oxidized silicon macropore arrays filled with a scintillator for CCD-based X-ray imaging detectors2004In: 2003 IEEE NUCLEAR SCIENCE SYMPOSIUM, CONFERENCE RECORD, VOLS 1-5, 2004, p. 1006-1010Conference paper (Refereed)
    Abstract [en]

    Silicon Charge Coupled Devices (CCD) covered with a scintillating film are now available on the market for use in digital medical imaging. However, these devices could still be improved in terms of sensitivity and especially spatial resolution by coating the CCD with an array of scintillating waveguides. In this work-, we fabricated such waveguides by first etching pores in silicon, then performing metallization or oxidation of the pore walls and finally filling the pores with CsI(TI). The resulting structures were observed using SEM and tested under X-ray exposure. The detector performances were also compared with simulations, indicating that the optimal pore depth for metallized macropore arrays is about 80 mum while it is around 350 mum for oxidized ones. This result, together with the roughness of the metal coating, explains why lower performances were measured experimentally with the metallized macropores. Indeed, our macropore arrays had depths in the range of 210-390 mum, which is favorable to oxidized structures.

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