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  • 1.
    Almström, Erland
    et al.
    KTH, Superseded Departments, Electronics.
    Kjebon, Olle
    KTH, Superseded Departments, Electronics.
    10Gb/s over 60 km standard single mode fibre at 1.55 μm with a direct modulated DBR laser1998In: Conference on optical fiber communication, feb 22-27, San Jose, CA, USA, 1998Conference paper (Other academic)
  • 2.
    Bakowski, Mietek
    KTH, Superseded Departments, Electronics.
    Effect of electron and Helium irradiation on the high current density IV behaviour of Si power diodes-modelling and experiment2004In: ISPSD '04: PROCEEDINGS OF THE 16TH INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES & ICS, TOKYO: INST ELECTR ENGINEERS JAPAN , 2004, p. 253-256Conference paper (Refereed)
    Abstract [en]

    A complex behaviour of the dynamic IV characteristics of electron and Helium irradiated fast Si diodes under surge current conditions have been modelled successfully using an experimentally based model of the temperature dependence of trapping parameters of dominant recombination centers. A special care has been taken to determine the thermal boundary conditions at the contacts. The correctness of the thermal boundary conditions and of the model and has been verified comparing the measured failure limit (SOA) of the diodes irradiated with varying electron dose and combination of electrons and Helium with the predicted SOA using the model of thermal instability based on the thermal generation of the intrinsic carriers due to the self-heating.

  • 3. Bokhari, S H
    et al.
    Ahmed, M
    bin Sohail, S
    Khan, R H
    Mirza, J A
    Ali, Muhammad
    KTH, Superseded Departments, Electronics.
    A networking laboratory for the developing world2004In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 42, no 2, p. 106-113Article in journal (Refereed)
    Abstract [en]

    Internet-based communication is assuming an increasingly important role in the developing world. It is thus crucial that students be exposed to contemporary networking equipment in a realistic setting, in order to connect theoretical material taught in lecture courses with the realities of physical hardware. To this end, a large computer networking laboratory has been set up to provide a realistic environment for teaching internetworking concepts. This laboratory provides university-level students with a testbed to experiment with fundamental issues of internetworking in a way that cannot be provided by simulators and to a degree of rigor not possible with the commonly available laboratory setups designed for technicians. We describe the motivations for setting up the laboratory, its network structure and equipment, and the type of experiments students conduct. The laboratory structure is influenced heavily by the limited funds-at our disposal - a common problem in the developing world. Many of the problems we faced in setting up our equipment (such as the crucial impact of proper electrical grounding on system performance) are not ordinarily encountered in developed nations. Our experiences are thus likely to be of value to others in the developing world who are contemplating setting up experimental facilities for teaching networking.

  • 4.
    Bourennane, Mohamed
    et al.
    KTH, Superseded Departments, Electronics.
    Ljunggren, Daniel
    KTH, Superseded Departments, Electronics.
    Karlsson, Anders
    KTH, Superseded Departments, Electronics.
    Jonsson, Per
    KTH, Superseded Departments, Electronics.
    Hening, A.
    KTH, Superseded Departments, Electronics.
    Peña Císcar, J.
    KTH, Superseded Departments, Electronics.
    Experimental long wavelength quantum cryptography: from single-photon transmission to key extraction protocols2000In: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 47, p. 563-579Article in journal (Refereed)
    Abstract [en]

    We present experiments on long wavelength (λ = 1.55 μm) 'plug and play' quantum cryptography systems. We discuss the performance of single-photon detectors at λ = 1.55 μm. Furthermore, we address the full implementation of the quantum cryptography protocol, discussing in detail the implementation of protocols for error correction and privacy amplification needed to get a secure key. We illustrate the theory with examples from a full software simulation to show the performance of the complete protocol in terms of final secure key creation rate

  • 5. Bowallius, O.
    et al.
    Anand, Srinivasan
    KTH, Superseded Departments, Electronics.
    Evaluation of different oxidation methods for silicon for scanning capacitance microscopy2001In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 4, no 03-jan, p. 81-84Article in journal (Refereed)
    Abstract [en]

    Different oxides, namely, native, thermal, and wet-chemical (H2SO4 + H2O2 based) oxides on Si are evaluated in the context of scanning capacitance microscopy (SCM). The samples investigated consisted of uniformly doped Si substrates and p-type epitaxial doping-staircase structures with concentrations ranging from 5 x 10(14) to 2 x 10(19) cm(-3) The bias for which the SCM signal (dC/dV) is maximised for the lowest doped region was used for comparing the different oxidation methods. It is shown that for a better evaluation of the surface oxide properties, it is essential to obtain dC/dV curves for a sufficiently large doping range. Best results in terms of low values of flat-band voltages (1 V), uniformity, and consistency across a large doping range were obtained for the wet-chemical oxide. For the native oxide case, the difference in the dC/dV peak bias Values obtained at regions doped to 5 x 10(14) to 10(17) cm(-3) was anomalously large and suggests appreciable distortion of the dC/dV curves. For the same oxidation procedure the full-width at half-maximum of the dC/dV curve obtained on the cleaved surface is typically 2 times larger than that on the planar (100) surface. It is most likely that interface states are responsible for the observed distortion.

  • 6. Bowallius, O.
    et al.
    Anand, Srinivasan
    KTH, Superseded Departments, Electronics.
    Nordell, N.
    Landgren, Gunnar
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, S.
    Scanning capacitance microscopy investigations of SiC structures2001In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 4, no 03-jan, p. 209-211Article in journal (Refereed)
    Abstract [en]

    We have applied scanning capacitance microscopy (SCM) to investigate SIC structures grown by vapour-phase epitaxy. The SCM technique is evaluated using n- and p-type doping staircase structures with doping concentrations ranging from 10(16) to 10(20) cm(-3). The n- and p-type doping was obtained by doping SiC with nitrogen and aluminium, respectively. The sample cross-sections for SCM were obtained by simple cleaving. For doping levels above 10(17) cm(-3) the SCM data are consistent with doping data obtained independently from secondary ion mass spectroscopy (SIMS). Treating the samples with diluted hydrofluoric acid significantly improves the SCM signal for the low-doped regions. The SCM technique has been used to investigate doping redistribution in patterned regrowth of n- and p-type SIC around dry-etched mesas. In both cases, contrast variations were seen close to the mesa walls, indicative of doping variations; lower and higher incorporation for p- and n-type, respectively. The observations are shown to be consistent with the expected trends in dopant incorporation in the SiC material.

  • 7.
    Campi, Roberta
    et al.
    KTH, Superseded Departments, Electronics.
    Marcinkevicius, Saulius
    KTH, Superseded Departments, Physics.
    Landgren, Gunnar
    KTH, Superseded Departments, Electronics.
    Studies on the carrier transport in InGaAlAdP/InGaAsP quantum well structures emitting at 1.3 μm2000In: Conference on Lasers and Electro-Optics Europe - Technical Digest, 2000, p. 141-Conference paper (Refereed)
    Abstract [en]

    A novel approach to improve high temperature performance in the IngaAsP lasers was examined by adding aluminum to the barrier,which allows to increase conduction band offset. To find optimal heterostructure parameters, different barrier material compositions were examined in structures with InGaAsP compressively strained wells and tensile strained InGaAlAsP barriers. The MQW structures were fabricated by low pressure MOVPE.

  • 8.
    Campi, Roberta
    et al.
    KTH, Superseded Departments, Electronics.
    Patel, Amit
    KTH, Superseded Departments, Electronics.
    Landgren, Gunnar
    KTH, Superseded Departments, Electronics.
    MOVPE growth of strained 1300 nm InGaAlAsP/ InGaAsP quantum well structures2000In: 12th International Conference on Indium Phosphide and Related Materials, 2000, p. 380-383Conference paper (Refereed)
    Abstract [en]

    In this work we propose novel 1.3 μm InGaAlAsP/InGaAsP MQW laser structures designed for high-temperature operation. The effects of aluminum on the band offsets and carrier confinement in MQW structures have been investigated. Epitaxial structures exhibited very high photoluminescence (PL) and sharp satellites in high-resolution x-ray diffraction. The carrier transport issues were further investigated using femtosecond time-resolved PL. Broad area lasers exhibited values of threshold current density of 261 A/cm-2 per quantum well and a slope efficiency of 0.25 W/A. The observed T0 values of 69 K for pure InGaAsP barriers increased to about 95 K for an Al content of about 12.5%, in accordance with expectations.

  • 9. Canning, John
    et al.
    Åslund, Mattias
    Ankiewicz, Adrian
    Dainese, Matteo
    KTH, Superseded Departments, Electronics.
    Fernando, Harendra
    KTH, Superseded Departments, Electronics.
    Sahu, Jayanta Kumar
    KTH, Superseded Departments, Electronics.
    Wosinski, Lech
    KTH, Superseded Departments, Electronics.
    Birefringence control in plasma-enhanced chemical vapor deposition planar waveguides by ultraviolet irradiation2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 24, p. 4296-4299Article in journal (Refereed)
    Abstract [en]

    Complete birefringence compensation is demonstrated in plasma-enhanced chemical vapor deposition waveguides by 193-nm postexposure. A single relaxation process dominates the decay in stress anisotropy, indicating that compressive stress from the substrate leads to an elastic stress anisotropy at the core.

  • 10. Carlstrom, C. F.
    et al.
    Anand, Srinivasan
    KTH, Superseded Departments, Electronics.
    Characterization of damage in InP dry etched using nitrogen containing chemistries2001In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 19, no 5, p. 1905-1910Article in journal (Refereed)
    Abstract [en]

    Etching of InP by different ion beam etching processes using chemistries containing nitrogen, such as nitrogen milling, N(CH3)(3) and Ar/N(CH3)(3) based reactive ion beam etching (RIBS), and N-2/CH4/H-2 based chemically assisted ion beam etching (CAIBE), is investigated. The residual surface damage is characterized using I-V characteristics of Au/InP metal-semiconductor (MS) contacts and photoluminescence (PL) yield measurements from near surface quantum wells and bulls InP. The contacts formed on as-etched surfaces, irrespective of the etch process, show ohmic behavior. On the other hand, although the PL yield is reduced for the different processes, the measured intensities show variations which are attributed to passivation of defects by hydrogen. Secondary ion mass spectroscopy (SIMS) was used to check (qualitatively) the presence of nitrogen in the etched and annealed InP samples. SIMS data show the presence of nitrogen in the near surface region of the etched samples, but nitrogen levels drop to background levels upon annealing at typical regrowth conditions (650 degreesC under phosphine flow). Interestingly, the annealing step results not only in a significant recovery of the PL yield, but also in a recovery of Schottky characteristics of the Au contacts formed on the annealed surfaces. These observations show that the etch-induced damage is significantly reduced by annealing and suggests recovery of the near-surface stoichiometry and possibly reduction of nitrogen-related defects.

  • 11.
    Domeij, Martin
    KTH, Superseded Departments, Electronics.
    Dynamic avalanche in Si and 4H-SiC power diodes1999Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Semiconductor power modules for the control of high currentsand high voltages have important applications in motor drives,traction and power transmission. Dynamic avalanche is of atechnological interest since it may limit the safe operatingarea for bipolar switching devices and for power diodes, whichare important integral parts of a power module. Dynamicavalanche is caused by a current-controlled space charge, whichmay enhance the electric field to the critical field strengthat voltages below the static breakdown voltage. Measurementsand simulations of reverse recovery at high power densitieswere performed for Si and 4H-SiC p+nn+power diodes to investigate the failure limitcaused by dynamic avalanche. A special optical measurementtechnique was used to eliminate influence of the junction edgeand thereby probe the bulk diode area.

    It was found experimentally that it is possible for Si powerdiodes to sustain dynamic avalanche at very high powerdensities (>1MW/cm2) during reverse recovery. It is proposed thatthese diodes eventually fail as a result of impact ionizationat the diode nn+junction, which according to device simulations,results in current filamentation and an excessive localizedheating. No temperature dependence was found for the failurelimit and similar results were obtained for diodes with andwithout carrier lifetime control. The high failure limitmeasured with the optical technique correlates with a very gooddynamic ruggedness in conventional electrical reverse recoverymeasurements. Device simulations indicate that a deep n+profile may improve the diode failure limit.

    A low failure limit close to the onset of dynamic avalanchewas found for another Si power diode, which had a structuredp-zone with a lowly doped p profile extending to the metalcontact in a fraction of the active area. A suggested failurecause for this diode is punch-through of a high electric fieldthrough the p region to the metal contact, an effect which maybe enhanced by an inhomogeneous current resulting from dynamicavalanche.

    Some of the investigated 4H-SiC p+nn+diodes showed no dynamic reduction of thebreakdown voltage in reverse recovery measurements. The highpredicted onset level of dynamic avalanche for 4H-SiC couldhowever not be reached, since breakdown at the junction edgelimited the static breakdown voltage to between 800 and 1200 V.A similarly processed test diode showed a clear avalanche inthe bulk during reverse recovery at 300 V, even though thediodes could block more than 2 kV in static measurements. Basedon device simulation, it is proposed that this largediscrepancy between static and dynamic breakdown voltage iscaused by temporary trapping of holes in deep donor levelswhich enhance the space charge and thus the peak electricfield. Deep hole traps were found in the vicinity of the pnjunction by DLTS measurements.

    Keywords:dynamic avalanche, power diode, failure limit,dynamic ruggedness, avalanche injection, silicon, siliconcarbide, impact ionization

  • 12.
    Domeij, Martin
    et al.
    KTH, Superseded Departments, Electronics.
    Breitholtz, Bo
    KTH, Superseded Departments, Electronics.
    Hillkirk, Leonardo
    KTH, Superseded Departments, Electronics.
    Linnros, Jan
    KTH, Superseded Departments, Electronics.
    Östling, Mikael
    KTH, Superseded Departments, Electronics.
    Dynamic avalanche in 3.3-kV Si power diodes1999In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 46, no 4, p. 781-786Article in journal (Refereed)
    Abstract [en]

    Measurements of the safe reverse recovery limit were performed for 3.3-kV Si power diodes using a novel optical experimental technique. In this experiment, influence of the junction termination is effectively eliminated by optical generation of a laterally-localized carrier plasma. The turn-off failures observed in measurements at two temperatures showed no temperature dependence and could not be reproduced in ordinary one-dimensional (1-D) or two-dimensional (2-D) device simulations. To simulate the stability of the current density toward current filamentation, two 1-D diodes with an area ratio 1:19 and a 10% difference in initial carrier plasma level, were simulated in parallel. This resulted in a strongly inhomogeneous current distribution, and a rapid reverse voltage fall resembling the measured turn-off failures. Inhomogeneous current distribution in these simulations appears as the current decay ceases due to impact ionization, in qualitative agreement with a current instability condition proposed by Wachutka [1].

  • 13.
    Domeij, Martin
    et al.
    KTH, Superseded Departments, Electronics.
    Breitholtz, Bo
    KTH, Superseded Departments, Electronics.
    Linnros, Jan
    KTH, Superseded Departments, Electronics.
    Ostling, Mikael
    KTH, Superseded Departments, Electronics.
    Avalanche injection in high voltage Si PiN diodes1997In: Physica scripta. T, ISSN 0281-1847, Vol. T69, p. 134-137Article in journal (Refereed)
    Abstract [en]

    An experimental technique using optical excitation by a YAG laser pulse for studying avalanche injection in power devices is demonstrated This technique enables the creation of high uniform excess carrier concentrations in an optically defined device volume, involving very little heating. A method for determining the onset of avalanche multiplication, by studying the time integral of the reverse recovery current, is proposed. A PiN diode is observed to turn off from avalanching at a dissipated power density of more than 200 kW/cm(2).

  • 14.
    Domeij, Martin
    et al.
    KTH, Superseded Departments, Electronics.
    Breitholtz, Bo
    KTH, Superseded Departments, Electronics.
    Linnros, Jan
    KTH, Superseded Departments, Electronics.
    Östling, Mikael
    KTH, Superseded Departments, Electronics.
    Avalanche Injection in High Voltage Si P-i-N Diodes Measurements and Device Simulations1997In: ISPSD '97: Proceedings of the International Symposium on Power Semiconductor Devices and ICs, 1997, p. 125-Conference paper (Other academic)
  • 15.
    Domeij, Martin
    et al.
    KTH, Superseded Departments, Electronics.
    Breitholtz, Bo
    KTH, Superseded Departments, Electronics.
    Linnros, Jan
    KTH, Superseded Departments, Electronics.
    Östling, Mikael
    KTH, Superseded Departments, Electronics.
    Reverse Recovery and Avalance Injection in High Voltage SiC PIN Diodes1998In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 264-268, p. 1041-Article in journal (Other academic)
  • 16.
    Domeij, Martin
    et al.
    KTH, Superseded Departments, Electronics.
    Breitholtz, Bo
    KTH, Superseded Departments, Electronics.
    Lutz, Josef
    Östling, Mikael
    KTH, Superseded Departments, Electronics.
    Dynamic avalanche in Si power diodes and impact ionization at the nn(+) junction2000In: Solid-State Electronics, ISSN 0038-1101, E-ISSN 1879-2405, Vol. 44, no 3, p. 477-485Article in journal (Refereed)
    Abstract [en]

    The reverse recovery failure limit was measured with an optical technique for power diodes which sustain high levels of dynamic avalanche. Measurements and simulations indicate that these diodes withstand dynamic avalanche at the pn-junction and eventually fail as a result of a strongly inhomogeneous current distribution caused by the onset of impact ionisation at the diode nn(+) junction - a mechanism similar to the reverse bias second breakdown of bipolar transistors.

  • 17.
    Domeij, Martin
    et al.
    KTH, Superseded Departments, Electronics.
    Breitholtz, Bo
    KTH, Superseded Departments, Electronics.
    Åberg, Denny
    KTH, Superseded Departments, Electronics.
    Martinez, Antonio
    KTH, Superseded Departments, Electronics.
    Bergman, P
    Dynamic avalanche and trapped charge in 4H-SiC diodes2000In: SILICON CARBIDE AND RELATED MATERIALS: 1999 PTS, 1 & 2 / [ed] Carter CH; Devaty RP; Rohrer GS, 2000, Vol. 338-3, p. 1327-1330Chapter in book (Other academic)
    Abstract [en]

    A dynamically reduced breakdown voltage from more than 2 kV under static conditions to 300 V during reverse recovery was measured for 4H-SiC p(+)nn(+) diodes. Device simulation indicates that deep hole-trapping donors in the n-base, close the pn junction, could explain the dynamically reduced breakdown voltage. Hole traps situated 0.66 eV above the valence band were found in the diode n-base by DLTS measurements.

  • 18.
    Domeij, Martin
    et al.
    KTH, Superseded Departments, Electronics.
    Breitholtz, Bo
    KTH, Superseded Departments, Electronics.
    Östling, Mikael
    KTH, Superseded Departments, Electronics.
    Lutz, Josef
    Stable dynamic avalanche in Si power diodes1999In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 74, no 21, p. 3170-3172Article in journal (Refereed)
    Abstract [en]

    A stable dynamic avalanche at a maximum power density of about 2.4 MW/cm(2) was measured in small areas of 3.3 kV Si power diodes, using an optical measurement technique, and very good dynamic ruggedness was verified in a conventional turn-off measurement. Device simulations of a diode with a shallow n(+) emitter indicate that impact ionization at the nn(+) junction can result in negative differential resistance (NDR) and current filamentation, whereas a deep n(+) emitter in the experimentally studied diode suppresses NDR. It is, therefore, proposed that the deep n(+) emitter is important for the stable dynamic avalanche.

  • 19. Doyle, J. P.
    et al.
    Abolfotoh, M. O.
    Linnarsson, Margareta K.
    KTH, Superseded Departments, Electronics.
    Svensson, B. G.
    Schoener, A.
    Nordell, Nils
    KTH, Superseded Departments, Electronics.
    Harris, C.
    Lindström, J. L.
    Janzen, E.
    Hemmingsson, C.
    Characterization of deep level defects in 4H and 6H SiC via DLTS, SIMS and MeV e-beam irradiation1996In: III-nitride, SiC and diamond materials for electronic devices: Proceedings of the Symposium, San Francisco, CA; UNITED STATES; 8-12 Apr. 1996., 1996, p. 519-524Conference paper (Refereed)
    Abstract [en]
    Electrically active defects in both 4H and 6H polytypes of SiC have been observed through the use of deep level transient spectroscopy (DLTS). Schottky contacts were grown by VPE with doping concentrations, the epitaxial layer having a doping concentration in the range of 10 exp 14/cu cm to 10 exp 17/cu cm. Numerous levels have been found in the as-grown n-type 6H-SiC samples, and SIMS and MeV electron irradiation have been employed to correlate the defect levels to impurities or structural defects. In contrast, only a single level is observed in the as-grown 4H-SiC samples.
  • 20.
    Doyle, J. P.
    et al.
    KTH, Superseded Departments, Electronics.
    Linnarsson, Margareta K.
    KTH, Superseded Departments, Electronics.
    Pellegrino, Paolo
    KTH, Superseded Departments, Electronics.
    Keskitalo, N.
    KTH, Superseded Departments, Electronics.
    Svensson, B. G.
    KTH, Superseded Departments, Electronics.
    Schöner, A.
    Nordell, N.
    Lindström, J. L.
    Electrically active point defects in n-type 4H–SiC1998In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 84, no 3, p. 61-68Article in journal (Refereed)
    Abstract [en]

    An electrically active defect has been observed at a level position of ∼ 0.70 eV below the conduction band edge (Ec) with an extrapolated capture cross section of ∼ 5×10−14 cm2 in epitaxial layers of 4H–SiC grown by vapor phase epitaxy with a concentration of approximately 1×1013 cm−3. Secondary ion mass spectrometry revealed no evidence of the transition metals Ti, V, and Cr. Furthermore, after electron irradiation with 2 MeV electrons, the 0.70 eV level is not observed to increase in concentration although three new levels are observed at approximately 0.32, 0.62, and 0.68 eV below Ec with extrapolated capture cross sections of 4×10−14, 4×10−14, and 5×10−15 cm2, respectively. However, the defects causing these levels are unstable and decay after a period of time at room temperature, resulting in the formation of the 0.70 eV level. Our results suggest strongly that the 0.70 eV level originates from a defect of intrinsic nature. The unstable behavior of the electron irradiation-induced defects at room temperature has not been observed in the 6H–SiC polytype.

  • 21.
    Hammar, M.
    et al.
    KTH, Superseded Departments, Electronics.
    Rodriguez Messmer, E.
    Luzuy, M.
    Anand, S.
    Lourdudoss, S.
    Landgren, G.
    Topography dependent doping distribution in selectively regrown InP studied by scanning capacitance microscopy1998In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 72, no 7, p. 815-817Article in journal (Refereed)
    Abstract [en]

    We have used scanning capacitance microscopy (SCM) to study the dopant distribution in regrown InP with high sensitivity and spatial resolution. Sulfur or iron doped InP was selectively regrown around n-doped InP mesas using hydride vapor phase epitaxy, and the resulting structure was imaged in cross section by SCM. For calibration purposes, reference layers with known doping levels were grown directly on top of the region of interest. Dramatic variations in the carrier concentration around the mesa, as well as pronounced differences in the behavior of S and Fe are observed. We correlate these findings to the growth and doping incorporation mechanisms. © 1998 American Institute of Physics.

  • 22.
    Hammar, M.
    et al.
    KTH, Superseded Departments, Electronics.
    Wennekes, F.
    Salomonsson, F.
    Bentell, J.
    Streubel, K.
    Rapp, S.
    Keiper, D.
    Westphalen, R.
    Systematics of electrical conductivity across InP to GaAs wafer fused interfaces1998In: Conference Proceedings - International Conference on Indium Phosphide and Related Materials, Tsukuba, Jpn, 1998, no Piscataway, NJ, United States, p. 801-804Conference paper (Refereed)
    Abstract [en]

    We report on the electrical and compositional characterization of wafer fused isotype heterojunctions between Zn, C or Si doped GaAs and Zn or Si doped InP. The junctions were characterized with current-voltage and secondary ion mass spectrometry (SIMS) measurements. It is demonstrated that very low-resistive junctions can be obtained in each case, but also that there is a strong influence from the detailed sample structure and processing conditions. SIMS was used to monitor the doping concentration across the interface as well as the impurity concentration of oxygen, carbon and iron.

  • 23. Happ, T. D.
    et al.
    Markard, A.
    Kamp, M.
    Forchel, A.
    Anand, Srinivasan
    KTH, Superseded Departments, Electronics.
    Single-mode operation of coupled-cavity lasers based on two-dimensional photonic crystals2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 79, no 25, p. 4091-4093Article in journal (Refereed)
    Abstract [en]

    We report the fabrication of short-cavity lasers with highly reflective two-dimensional photonic crystal mirrors on an InGaAsP/InP laser structure emitting at 1.57 mum. An intracavity photonic crystal mirror creates two coupled cavities, which provide additional longitudinal mode selection for stable single-mode operation with side-mode suppression ratios exceeding 35 dB. The shortest lasers with l=100 mum overall length have a threshold current of 13 mA and provide more than 4 mW power under continuous wave operation. Longer devices with l=200 mum deliver up to 9 mW. A maximum modulation bandwidth of 7.9 GHz was determined by relative intensity noise measurements.

  • 24. Ivanov, A M
    et al.
    Kalinina, E V
    Konstantinov, A O
    Onushkin, G A
    Strokan, N B
    Kholuyanov, G F
    Hallén, Anders
    KTH, Superseded Departments, Electronics.
    High-resolution short range ion detectors based on 4H-SiC films2004In: Technical physics letters, ISSN 1063-7850, E-ISSN 1090-6533, Vol. 30, no 7, p. 575-577Article in journal (Refereed)
    Abstract [en]

    The energy resolution of SiC detectors has been studied in application to the spectrometry of alpha particles with 5.1-5.5 MeV energies. The Schottky barrier structure of the detector was based on a CVD-grown epitaxial n-4H-SiC film with a thickness of 26 mum and an uncompensated donor concentration of (1-2) x 10(15) cm(-3). An energy resolution of 0.5% achieved for the first time with SiC detectors allows fine structure of the alpha particle spectrum to be revealed. The average energy of the electron-hole pair formation in 4H-SiC is estimated at 7.71 eV.

  • 25.
    Janson, M S
    et al.
    KTH, Superseded Departments, Electronics.
    Hallén, Anders
    KTH, Superseded Departments, Electronics.
    Linnarsson, Margareta K.
    KTH, Superseded Departments, Electronics.
    Nordell, Nils
    KTH, Superseded Departments, Electronics.
    Karlsson, S
    Svensson, B G
    Dissociation energy of the passivating hydrogen-aluminum complex in 4H-SiC2001In: Materials Science Forum, 2001, Vol. 353-356, p. 427-430Conference paper (Other academic)
    Abstract [en]

    The thermal stability of the passivating hydrogen-aluminum complex ((HAl)-H-2) in 4H-silicon carbide has been studied by determining the effective diffusion constant for hydrogen in an AI-doped epitaxial layer. Assuming a complex comprised of one H-2 and one AI acceptor ion, the extracted diffusivities provide the dissociation frequency of the complex. The extracted frequencies cover three orders of magnitude and yield a close to perfect fit to an Arrhenius equation with the extracted dissociation energy for the (HAl)-H-2-complex equal to 1.66 (+/-0.05) eV and a pre-exponential attempt frequency nu (0) = 1.7x10(13) s(-1) in good agreement with the expected value for a first order dissociation process.

  • 26.
    Janson, Martin S.
    et al.
    KTH, Superseded Departments, Electronics.
    Hallén, Anders
    KTH, Superseded Departments, Electronics.
    Linnarsson, Margareta K
    KTH, Superseded Departments, Electronics.
    Svensson, Bengt Gunnar
    KTH, Superseded Departments, Electronics.
    Nordell, Nils
    IMC, Sweden.
    Karlsson, S.
    Electric-field-assisted migration and accumulation of hydrogen in silicon carbide2000In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 61, no 11, p. 7195-7198Article in journal (Refereed)
    Abstract [en]

    The diffusion of deuterium (H-2) in epitaxial 4H-SiC layers with buried highly Al-acceptor doped regions has been studied by secondary ion mass spectrometry. H-2 was introduced in the near surface region by the use of 20-keV implantation after which the samples were thermally annealed. As a result, an anomalous accumulation of H-2 in the high doped layers was observed. To explain the accumulation kinetics, a model is proposed where positively charged H-2 ions are driven into the high doped layer and become trapped there by the strong electric field at the edges. This effect is important for other semiconductors as well, since hydrogen is a common impurity present at high concentrations in many semiconductors.

  • 27. Johansson, M.
    et al.
    Lofving, B.
    Hard, S.
    Thylén, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Mokhtari, M.
    Westergren, Urban
    KTH, Superseded Departments, Electronics.
    Pala, C.
    Study of an ultrafast analog-to-digital conversion scheme based on diffractive optics2000In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 39, no 17, p. 2881-2887Article in journal (Refereed)
    Abstract [en]

    A potentially ultrafast optical analog-to-digital (A/D) converter scheme is proposed and was partly studied experimentally. In the A/D converter scheme the input signal controls the wavelength of a diode laser, whose output beam is incident on a grating. The beam from the grating hits a diffractive optical element in an array. The wavelength determines which element is illuminated. Each element fans out a unique spot-pattern bit code to be read out in parallel by individual detectors. In the experiment all patterns but one from 64 array elements were read out correctly.

  • 28.
    Juhasz, Robert
    et al.
    KTH, Superseded Departments, Electronics.
    Kleimann, Pascal
    Linnros, Jan
    KTH, Superseded Departments, Electronics.
    Laser assisted electrochemical etching of silicon: simulations and experiment2001In: Pits and Pores II: Formation Properties and Significance for Advanced Materials, Pennington, NJ: Electrochemical Society , 2001, p. 500-508Chapter in book (Other academic)
  • 29.
    Juhasz, Robert
    et al.
    KTH, Superseded Departments, Electronics.
    Linnros, Jan
    KTH, Superseded Departments, Electronics.
    Three-dimensionally controlled size-reduction of silicon nanopillars by photoelectrochemical etching2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 20, p. 3118-3120Article in journal (Refereed)
    Abstract [en]

    Silicon nanopillars, fabricated by electron beam lithography and reactive ion etching, were size-reduced using laser-assisted electrochemical etching in a dilute hydrofluoric acid solution. The progressing size reduction was followed by scanning electron microscopy down to final diameters of similar to 15 nm. By varying the voltage bias, it was found that etching could be directed primarily at the pillar top (7 V) or at the pillar base (-0.6 V) whereas in an intermediate regime, conformal etching could be obtained. From the rate of volume change during etching, it was concluded that holes, participating in the dissolution reaction, were primarily generated within the pillar volume. The corresponding effective dissolution valence was similar to5-9, indicating substantial recombination losses within the pillar.

  • 30.
    Juhasz, Robert
    et al.
    KTH, Superseded Departments, Electronics.
    Linnros, Jan
    KTH, Superseded Departments, Electronics.
    Kleimann, Pascal
    Size reduction of silicon nanopillars by photo-electrochemical etching2001In: Materials Research Society Symposium Proceedings, ISSN 0272-9172, E-ISSN 1946-4274, Vol. 638, p. F851-F855Article in journal (Refereed)
    Abstract [en]

    Silicon nanopillars, formed by electron beam lithography, were electrochemically etched to provide controlled size reduction. The smallest dimensions achieved were pillars of 15 nm in diameter, restricted mainly by the scanning electron microscope used for characterization. The etch rate was mainly determined by the photogeneration of carriers, by the HF concentration and by the applied voltage bias. The applied bias also controlled the resulting shape of the pillars such that a high bias resulted in etching of the pillar top whereas a negative bias caused etching only at the pillar base. For 0 V, a relatively conform etching of the pillar was observed. We discuss these phenomena in terms of electropolishing or pore formation effects on a local scale.

  • 31. Kalinina, E.
    et al.
    Kholuyanov, G.
    Strel'chuk, A.
    Davydov, D.
    Hallén, Anders
    KTH, Superseded Departments, Electronics.
    Konstantinov, A.
    Nikiforov, A.
    Electrical study of fast neutron irradiated devices based on 4H-SiC CVD epitaxial layers2004In: SILICON CARBIDE AND RELATED MATERIALS 2003, PRTS 1 AND 2 / [ed] Madar, R; Camassel, J, 2004, Vol. 457-460, p. 705-708Conference paper (Refereed)
    Abstract [en]

    The radiation-induced defect formation in high purity 4H-SiC CVD epitaxial layers and changes in the electrical properties of diode structures based on its after irradiation with different fluences I MeV neutrons were investigated at temperatures as high as 700 K. The Z(1), deep center, typical for 4H-SiC, was observed both in the initial and irradiated samples. The presence and number of different deep levels increased with the neutron fluence. The rectifying properties of the diode structures disappeared after neutron irradiation with fluence of 6.2x10(14) cm(-2). However, the diode structures that had been degraded after irradiation with fast neutrons, recovered their properties at the temperature of 700 K.

  • 32. Kamp, M.
    et al.
    Happ, T.
    Mahnkopf, S.
    Duan, G.
    Anand, Srinivasan
    KTH, Superseded Departments, Electronics.
    Forchel, A.
    Semiconductor photonic crystals for optoelectronics2004In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 21, no 2-4, p. 802-808Article in journal (Refereed)
    Abstract [en]

    We present a number of designs for the integration of photonic crystals (PC) with active semiconductor devices. As a first step, the use of PC blocks as laser mirrors is demonstrated. Ridge-waveguide lasers with a length of 100 mum and two PC mirrors achieve threshold currents below 8 mA. In order to obtain single-mode operation, an intracavity PC mirror can be used, which effectively separates the laser into two coupled cavities. Lasing occurs where two modes of the cavities coincide, leading to single-mode operation with a side-mode suppression ratio (SMSR) of over 35 dB. We also present two full PC devices: a single-mode laser with a coupled resonant cavity waveguide (CROW) and a tunable laser. The CROW device consists of a chain of 40 hexagonal cavities formed in a block of PC, with a total length of 140 mum. Low threshold, single-mode operation with over 40 dB SMSR is demonstrated. Coupled cavities are used for the tunable PC laser, which covers a tuning range of over 30 nm.

  • 33. Kamp, M.
    et al.
    Zimmermann, J.
    Anand, Srinivasan
    KTH, Superseded Departments, Electronics.
    Marz, R.
    Forchel, A. W.
    Photonic crystal waveguide based dispersion compensators2006In: Proc SPIE Int Soc Opt Eng, 2006Conference paper (Refereed)
    Abstract [en]

    We have investigated the dispersion properties of photonic crystal waveguide resonators. A passive InGaAsP/InP slab waveguide structure was used for the fabrication of the samples. The PhC waveguide resonators were defined by the omission of several rows of holes along the ΓK or ΓM direction of a triangular photonic crystal lattice. In addition, mirrors with a thickness of 1 to 4 rows of holes were inserted into the waveguide. An optimized dry etch process was used to etch the patterns to a depth of 3.5 μm through the waveguide layer. The group delay of the PhC devices was measured using the phase shift technique. The signal of a tunable laser was modulated at 3 GHz using a LiNbO 3 Mach-Zehnder modulator and detected with a high-frequency lightwave receiver. A phase sensitive detection with a network analyer measured the phase shift of the transmitted signal, which is proportional to the group delay. Close to the center of the resonances, the chromatic dispersion reaches values of -250 ps/nm and 250 ps/nm. This corresponds to the chromatic dispersion of 15 km standard fiber.

  • 34.
    Kjebon, Olle
    KTH, Superseded Departments, Electronics.
    Design, fabrication and analysis of high speed semiconductor lasers for optical communication1997Doctoral thesis, comprehensive summary (Other scientific)
  • 35.
    Kjebon, Olle
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Nilsson, Stefan
    KTH, Superseded Departments, Electronics.
    Stålnacke, Björn
    KTH, Superseded Departments, Electronics.
    Modulation response measurements and evaluation of MQW InGaAsP lasers of various designs1996In: Proc. SPIE, Vol. 2684, 1996, p. 138-152Conference paper (Other academic)
    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.

  • 36.
    Kjebon, Olle
    et al.
    KTH, Superseded Departments, Electronics.
    Schatz, Richard
    KTH, Superseded Departments, Electronics.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Electronics.
    Nilsson, Stefan
    KTH, Superseded Departments, Electronics.
    Stålnacke, Björn
    KTH, Superseded Departments, Electronics.
    Bäckbom, Lena
    KTH, Superseded Departments, Electronics.
    30GHz direct modulation bandwidth indetuned loaded InGaAsP DBR lasers at1.55 μm wavelength1997In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 33, p. 488-489Article in journal (Refereed)
    Abstract [en]

    An increased resonance frequency and reduced damping of theresonance peak leading to a record high modulation bandwidth of30GHz were observed in 1.55 mm InGaAsP DBR lasers. Theseresults are attributed to the mechanism of detuned loading.

  • 37.
    Kjebon, Olle
    et al.
    KTH, Superseded Departments, Electronics.
    Öhlander, U
    KTH, Superseded Departments, Electronics.
    Lourdudoss, Sebastian
    KTH, Superseded Departments, Electronics.
    Wallin, J
    KTH, Superseded Departments, Electronics.
    Streubel, K
    KTH, Superseded Departments, Electronics.
    Nilsson, S
    KTH, Superseded Departments, Electronics.
    Klinga, T
    KTH, Superseded Departments, Electronics.
    Multi quantum well 1.55 μm DFB lasers with low threshold current, high resonance frequency and bandwidth at low current injection1994In:  Semiconductor Laser Conference, 1994: 14th IEEE International, 1994, p. 221-222Conference paper (Other academic)
    Abstract [en]

    Summary form only given. Multi quantum well GaInAsP DFB buried heterostructure lasers with low threshold, 3.4 mA, large slope of resonance frequency versus square root of current above threshold, 2.6 GHz/mA1/2 and high maximum bandwidth, 21.7 GHz, have been fabricated

  • 38. Lewen, R.
    et al.
    Westergren, Urban
    KTH, Superseded Departments, Electronics. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Berglind, Eilert
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Design of inductive p-i-n diode matching for optical receivers with increased bit-rate operation2001In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 19, no 12, p. 1956-1963Article in journal (Refereed)
    Abstract [en]

    We have studied matching of a p-i-n photodiode (PD) with a single serial inductive element for broadband operation. The bit rate and rise time may be significantly improved, compared to a device without inductor for nonreturn-to-zero (NRZ) modulation. The matched device offers improved pulse equalization leading to increased receiver sensitivity, and reduces the need for an additional pulse-equalizing filter. The material is presented so that it can serve as a guideline of how the inductor can be included when choosing the thickness of the absorption layer and/or area for a p-i-n PD design, and ends with typical design examples.

  • 39.
    Lewén, Robert
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Irmscher, Stefan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Westergren, Urban
    KTH, Superseded Departments, Electronics.
    Thylén, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Eriksson, U.
    Segmented transmission-line electroabsorption modulators2004In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 22, no 1, p. 172-179Article in journal (Refereed)
    Abstract [en]

    We present segmented transmission-line (TML) electroabsorption modulators (EAMs) with characteristic impedance close to 50 M The segmented TML approach allows us to design a traveling-wave EAM with 50 Omega impedance and very high band width. The devices show low return loss (< -15 dB) and excellent frequency response up to 50 GHz, and exhibit a maximum model extrapolated 3 dBe bandwidth (BW) of 9,0 GHz. An effective modeling tool based on Bloch-wave analysis is derived. Design considerations and TML properties for periodic TML-EAMs are discussed.

  • 40.
    Lindgren, Stefan
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Åhlfeldt, Henrik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Bäcklin, Lennart
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Forssén, Lili
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Vieider, Christian
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Elderstig, Håkan
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Svensson, Magnus
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Granlund, Lennart
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Andersson, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kerzar, Boris
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Broberg, Björn
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Kjebon, Olle
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Forzelius, Elisabeth
    KTH, Superseded Departments, Electronics.
    Nilsson, Stefan
    KTH, Superseded Departments, Electronics.
    24-GHz modulation bandwidth and passive alignment of flip-chip mounted DFB laser diodes1997In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 9, no 3, p. 306-308Article in journal (Refereed)
  • 41.
    Linnarsson, Margareta K.
    KTH, Superseded Departments, Electronics.
    Compound semiconductors: defects and relocation of atoms during growth sputtering and diffusion1997Doctoral thesis, comprehensive summary (Other scientific)
  • 42.
    Linnarsson, Margareta K.
    et al.
    KTH, Superseded Departments, Electronics.
    Doyle, J. P.
    Svensson, B. G.
    KTH, Superseded Departments, Electronics.
    Diffusion of hydrogen in 6H silicon carbide1996In: III-nitride, SiC and diamond materials for electronic devices: Proceedings of the Symposium, San Francisco, CA; UNITED STATES; 8-12 Apr. 1996., 1996, p. 625-630Conference paper (Other academic)
    Abstract [en]

    6H polytype silicon carbide (SiC) samples of n-type have been implanted with 50-keV H(+) ions and subsequently annealed at temperatures between 200 and 1150 C. Using depth profiling by secondary ion mass spectrometry, the motion of hydrogen is observed in the implanted region for temperatures above 700 C. A diffusion coefficient of about 10 exp -14 sq cm/s is extracted at 800 C with an approximate activation energy of about 3.5 eV. Hydrogen displays strong interaction with the implantation-induced defects, and stable hydrogen-defect complexes are formed. These complexes anneal out at temperatures in excess of 900 C, and are tentatively identified as carbon-hydrogen centers at a Si vacancy.

  • 43.
    Linnarsson, Margareta K.
    et al.
    KTH, Superseded Departments, Electronics.
    Svensson, B. G.
    KTH, Superseded Departments, Electronics.
    Cascade mixing in AlxGa1-xAs/GaAs during sputter profiling by noble-gas ions1999In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 60, no 20, p. 14302-14310Article in journal (Refereed)
    Abstract [en]

    The effect of cascade mixing on profile broadening during secondary-ion mass spectrometry (SIMS) analysis has been thoroughly investigated for AlxGa1-xAs/GaAs structures of five different compositions (x=0.1, 0.3, 0.5, 0.73, or 1) and layers with varying thicknesses (from one monolayer to 1000 Å). The SIMS analyses were performed using primary sputtering ions of 20Ne+, 40Ar+, 84Kr+, and 136Xe+ with an impact energy (E) ranging from 1.8 to 13.2 keV and an angle of incidence, with respect to the surface normal (θ), from 62° to 35°. Within the experimental accuracy, the decay length of the trailing edge was found to be proportional to E1/2cosθ where the proportionality constant displays a relatively weak dependence on primary ion mass. However, the leading edge is strongly affected by the extension of the collision cascade as demonstrated by a comparison of the results for the different ions at a given energy. As long as the cascade is fully developed before reaching an interface no dependence on the sample depth is obtained for the profile broadening. Furthermore, the decay length for the trailing edges is extracted in the dilute limit and no effect of the marker thickness or the x value is revealed. A numerical treatment of the profile broadening within a diffusional model, where the diffusion coefficient is assumed to be proportional to the energy deposited in elastic collisions, gives a surprisingly good agreement with the experimental data.

  • 44.
    Linnarsson, Margareta K.
    et al.
    KTH, Superseded Departments, Electronics.
    Svensson, B. G.
    KTH, Superseded Departments, Electronics.
    Andersson, T. G.
    Wang, S. M.
    Paska, Z. F.
    Sputter profiling of AlGaAs/GaAs superlattice structures using oxygen and argon ions1993In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 70-71, no 1, p. 40-43Article in journal (Refereed)
    Abstract [en]

    Broadening of Al sputter profiles in AlxGa1-xAs/GaAs structures has been investigated using secondary ion mass spectrometry. The depth profiling was carried out with 32O+2 ions and 40Ar+ ions using net primary energies of 1.8, 2.2, 3.2 and 5.7 keV. The decay lengths of the Al profiles show a pronounced increase with increasing sputtering ion energy caused by ballistic mixing. Moreover, in the O+2 case the λ-values degrade with eroded depth, indicating that beam-induced surface roughening takes place during profiling and in particular, this holds for high x-values. The results are discussed in terms of a semi-empirical model for ion-beam-induced broadening developed by Zalm and Vriezema.

  • 45.
    Linnarsson, Margareta K.
    et al.
    KTH, Superseded Departments, Electronics.
    Svensson, B. G.
    KTH, Superseded Departments, Electronics.
    Paska, Z. F.
    Borglind, J.
    Influence of layer thickness and primary ion on profile broadening during sputtering of Al0.5Ga0.5As/GaAs structures1994In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, Vol. 85, no 1-4, p. 395-398Article in journal (Refereed)
    Abstract [en]

    Broadening of secondary ion mass spectrometry depth profiles for Al in Al0.5Ga0.5As/GaAs structures, where the layer thicknesses vary from two monolayers to 1000 Å, is investigated. The experiments were performed in the net primary energy range 1.8–13.2 keV with 40Ar+ ions and 84Kr+ ions. The broadening is mainly determined by ballistic mixing, and no dependence on the Al0.5Ga0.5As layer thickness is revealed. Good agreement is found with a semi-empirical mixing model published recently by Zalm and Vriezema and [Nucl. Instr. and Meth. B 67 (1992) 467] although a small contribution from surface roughness occurs. The surface roughness develops initially but saturates already after the first Al0.5Ga0.5As layer.

  • 46.
    Ljunggren, Daniel
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Bourennane, Mohamed
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Karlsson, Anders
    KTH, Superseded Departments, Electronics.
    Authority-based user authentication in quantum key distribution2000In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 62, no 2, p. 022305-Article in journal (Refereed)
    Abstract [en]

     We propose secure protocols for user authenticated quantum key distribution on jammable public channels between two parties, Alice and Bob. Via an arbitrator, Trent, these protocols provide data integrity and mutual identification of the messenger and recipient. The first three are based on single-photon generation and detection. The first and second require (initially) an unjammable channel between the arbitrator and each party. The third requires one broadcast from the arbitrator, disclosing what type of deterministic modification of the states sent through the quantum channel was done by him. The fourth and fifth protocols are based on two-particle entanglement with a preselection of nonorthogonal superpositions of Bell states. These two protocols also require one broadcast from the arbitrator disclosing the type of entangled state in each sending.

  • 47.
    Lourdudoss, Sebastian
    et al.
    KTH, Superseded Departments, Electronics.
    Kjebon, Olle
    KTH, Superseded Departments, Electronics.
    Hydride vapor phase epitaxy revisited1997In: IEEE Journal of Selected Topics in Quantum Electronics, ISSN 1077-260X, E-ISSN 1558-4542, Vol. 3, no 3, p. 749-767Article in journal (Refereed)
  • 48.
    Lourdudoss, Sebastian
    et al.
    KTH, Superseded Departments, Electronics.
    Rodríguez Messmer, E.
    KTH, Superseded Departments, Electronics.
    Kjebon, Olle
    KTH, Superseded Departments, Electronics.
    Landgren, Gunnar
    KTH, Superseded Departments, Electronics.
    Temporally resolved selective regrowth of InP around [110] and [110] mesas1996In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 25, no 3, p. 389-394Article in journal (Refereed)
    Abstract [en]

    Temporally resolved selective regrowth of InP around reactive ion etched [110] and [110] directional mesas is studied by hydride vapor phase epitaxy at the growth temperatures of 600, 650, 685, and 700°C. The regrowth profiles are strikingly different depending upon the mesa orientation. The results are interpreted by invoking the difference in the bonding configurations of these mesas as well as the growth facility in a direction leading to the largest reduction of dangling bonds under the growth conditions. Various emerging planes during regrowth are identified and are {hhl} planes with initial values of l/h ≤ 3 but ≥ 3 as the planarization is approached. Initial lateral growth defined as the growth away from the mesa at half of its height in the very first minute is a decreasing function of temperature when plotted as Arrhenius curves. Such a behavior is attributed to the exothermicity of the reaction and to an enhanced pyrolysis of PH3 to P2. The lateral growth rate is much larger than that on the planar substrate. This should be taken into account when regrowth of a doped layer (e.g. InP:Fe or InP:Zn) is carried out to fabricate a buried heterostructure device since the dopant concentration can be very much lower than the one optimized on the planar substrates.

  • 49. Nordell, N.
    et al.
    Schöner, A.
    Linnarsson, Margareta K.
    KTH, Superseded Departments, Electronics.
    Control of Al and B doping transients in 6H and 4H SiC grown by vapor phase epitaxy1997In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 26, no 3, p. 187-192Article in journal (Refereed)
    Abstract [en]

    The atomic concentration profiles in 4H and 6H SiC created by Al and B doping turn-on and turn-off during vapor phase epitaxy (VPE) was investigated by secondary ion mass spectrometry (SIMS). It was found that dopant traces were adsorbed to the reactor walls and re-evaporated after the dopant precursor flow was switched off. This adsorption/re-evaporation process limits the doping dynamic range to about three orders of magnitude for Al, and two orders of magnitude for B. An order of magnitude in doping dynamics could be gained by simultaneously switching the gases and changing the C:Si precursor ratio. By adding a 10 min growth interruption with an H or HC1 etch at the doping turn-off, the background doping tail could be considerably suppressed. In total, a doping dynamics for Al of almost five orders of magnitude can be controlled within a 30 nm layer. For B, the dynamic range is more than three orders of magnitude, and the abruptness is most probably diffusion limited. Abackground doping level of 2 × 1015 cm−3 for Al and 2 × 1016 cm−3 for B was obtained. For Al, the background doping is most probably due to the adsorption/re-evaporation of dopants at the reactor walls; while for B, the background doping may in addition be limited by diffusion.

  • 50. Paskova, T.
    et al.
    Paskov, P. P.
    Goldys, E. M.
    Valcheva, E.
    Darakchieva, V.
    Södervall, U.
    Godlewski, M.
    Zielinski, M.
    Hautakangas, S.
    Saarinen, K.
    Carlström, Carl-Fredrik
    KTH, Superseded Departments, Electronics.
    Wahab, Q.
    Monemar, B.
    Characterization of mass-transport grown GaN by hydride vapour-phase epitaxy2004In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 273, no 1-2, p. 118-128Article in journal (Refereed)
    Abstract [en]

    A comprehensive study of the morphological, optical and microstructural properties of mass-transport (MT) and conventionally grown GaN by hydride vapour-phase epitaxy is presented. Spatially resolved techniques have been utilized to reveal in a comparative way, the characteristics of the material grown either in predominant vertical or lateral growth modes. A strong donor-acceptor pair (DAP) emission is observed from the MT regions with a distinctive intensity contrast between the exciton and DAP emission bands from MT and nontransport regions. Secondary ion mass spectroscopy and imaging were employed to investigate the impurity incorporation into different regions. An increase of residual oxygen and aluminium impurity concentrations was found in the MT areas. In addition, positron annihilation spectroscopy showed a strong signal of Ga vacancy clusters in the MT grown material. The increase of the point defect concentrations of both Ga vacancy and oxygen impurity, most likely forming defect complexes, is related to the enhancement of the DAP emission.

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