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Träfflista för sökning "WFRF:(Wernersson Lars Erik) ;pers:(Seifert Werner)"

Sökning: WFRF:(Wernersson Lars Erik) > Seifert Werner

  • Resultat 1-10 av 23
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1.
  • Wernersson, Lars-Erik, et al. (författare)
  • Attractive potential around a buried metallic gate in a Schottky Collector Hot Electron Transistor
  • 2002
  • Ingår i: Institute of Physics Conference Series. - 0951-3248. ; 170, s. 81-85
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the formation of an attractive potential around buried metal wires in a novel design for the Hot Electron Transistor (HET). In this device, the doped base layer in the HET is replaced by an embedded metal grating, which is forward biased beyond flat band conditions in order to efficiently extract carriers from the emitter into the active region. These carriers are collected in a Schottky Collector contact. By tuning the gate and collector voltages, the potential profile around the wires can be repulsive as well as attractive. This is a key result for the realisation of a Biprism device.
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2.
  • Wernersson, Lars-Erik, et al. (författare)
  • Epitaxially overgrown, stable W-GaAs Schottky contacts with sizes down to 50 nm
  • 2002
  • Ingår i: Journal of Vacuum Science and Technology B. - : American Vacuum Society. - 1520-8567. ; 20:2, s. 580-589
  • Tidskriftsartikel (refereegranskat)abstract
    • A processing scheme for the fabrication of embedded W-GaAs contacts has been established and the resulting contact characteristics have been evaluated. The main advantage of these contacts is that they are stable during high-temperature epitaxial overgrowth. The fabrication scheme is based on a liftoff process with electron beam evaporation of tungsten and subsequent epitaxial overgrowth using metalorganic vapor phase epitaxy. Various methods were used to characterize the buried contacts. First, the structural properties of GaAs surrounding embedded W features, with widths down to 50 nm, were characterized by high-resolution transmission electron microscopy. Measurements of the conductivity in individual, buried wires were performed in order to study the influence of the overgrowth process on the properties of the tungsten. We also evaluated the current-voltage characteristics for macroscopic contacts, which revealed a clear dependence on processing parameters. Optimized processing conditions could thus be established under which limited contact degradation occurred during overgrowth. Finally, we used the overgrowth technique to perform a detailed investigation of the electrical and optical properties of floating-potential embedded nano-Schottky contacts by space-charge spectroscopy.
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3.
  • Wernersson, Lars-Erik, et al. (författare)
  • Metalorganic vapor phase epitaxy-grown GaP/GaAs/GaP and GaAsP/GaAs/GaAsP n-type resonant tunnelling diodes
  • 2002
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:10, s. 1841-1843
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied GaP/GaAs/GaP and GaAsxP1-x/GaAs/GaAsxP1-x double-barrier resonant tunnelling diodes grown by metalorganic vapor phase epitaxy. We find that GaP tensile strained barriers in GaP/GaAs/GaP diodes may be grown with a barrier thickness below the critical thickness of about 12 monolayers. However, a corrugation of the strained barrier is observed by transmission electron microscopy. This variation may explain the low peak-to-valley ratio of the diodes (about 2). In contrast, GaAsxP1-x/GaAs/GaAsxP1-x resonant tunnelling diodes have been grown with a homogeneous thickness of the barriers, consequently showing a substantially improved electrical performance compared to the GaP diodes with peak-to-valley ratios >5.
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4.
  • Aberg, I, et al. (författare)
  • Nanoscale tungsten aerosol particles embedded in GaAs
  • 2002
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:16, s. 2976-2978
  • Tidskriftsartikel (refereegranskat)abstract
    • GaAs containing buried nanoscale tungsten particles has been characterized electrically. The particles were produced using a special aerosol process and were embedded in GaAs by epitaxial overgrowth. Two different particle sizes were investigated separately. When the particle concentration was increased, a conductance drop of about 500 times was observed. A simulation model, based on a random distribution of the particles, was developed and used to support our findings. The major advantage of our method is the simplicity and low processing cost.
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5.
  • Borgström, Magnus, et al. (författare)
  • Site control of InAs quantum dots on a patterned InP surface: As/P exchange reactions
  • 2003
  • Ingår i: Journal of Crystal Growth. - 0022-0248. ; 248, s. 310-316
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper. we present the effect of annealing temperature and annealing time on InAs site-controlled quantum dot growth. Individual InAs quantum dots formed by self-assembling have been positioned into holes, created by partial overgrowth of electron beam induced nano-carbon deposits by metal organic vapor phase epitaxy. As/P exchange reactions produce material sufficient for selective dot nucleation in the holes. Results. showing that As/P exchange reactions occur even when capping the dots with InP are presented. (C) 2002 Elsevier Science B.V. All rights reserved.
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6.
  • Borgström, Magnus, et al. (författare)
  • Site-control of InAs quantum dots on a patterned InP surface: As/P exchange reactions
  • 2002
  • Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
  • Konferensbidrag (refereegranskat)abstract
    • We present the effect of annealing temperature and annealing time on InAs/InP site-controlled quantum dot growth. Electron beam pre-patterning forms carbon nano-deposits at the InP surface, which then can be used as growth masks to form nano-holes at the surface. By only annealing of the patterned InP surface under an arsine ambient, As/P exchange reactions produce material sufficient for selective dot nucleation in the holes at the surface
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7.
  • Bryllert, Tomas, et al. (författare)
  • Designed emitter states in resonant tunneling through quantum dots
  • 2002
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:15, s. 2681-2683
  • Tidskriftsartikel (refereegranskat)abstract
    • Resonant tunneling through a single layer of self-assembled quantum dots (QDs) is compared to tunneling through two layers of vertically aligned (stacked) dots. The difference can be viewed as going from a two-dimensional emitter to a zero-dimensional emitter. The temperature dependence of current peaks originating in tunneling through individual QDs and individual stacks is used to clarify this point. In addition, we show that the statistical size distribution of self-assembled quantum dots causing the inhomogeneous broadening in luminescence experiments can be analyzed in a resonant tunneling experiment. (C) 2002 American Institute of Physics.
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8.
  • Bryllert, Tomas, et al. (författare)
  • Resonant tunneling through coupled self-assembled quantum dots and the influence of inhomogeneous broadening
  • 2002
  • Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science.
  • Konferensbidrag (refereegranskat)abstract
    • Resonant tunneling through a single layer of self-assembled quantum dots (QDs) as well as tunneling through two layers of vertically aligned (stacked) dots is investigated. The difference between single and double layers of QDs can be viewed as going from a two-dimensional emitter to a zero-dimensional emitter. By fabricating small-area devices we are able to probe single stacks of quantum dots, revealing details of the coupling between the stacked dots. Very sharp resonances, with peak-to-valley ratios of several hundred, have been measured in the current-voltage characteristics. We also show that the statistical size distribution of self-assembled quantum dots causing the inhomogeneous broadening in luminescence experiments can be analysed in a resonant tunneling experiment
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9.
  • Bryllert, Tomas, et al. (författare)
  • Transport through an isolated artificial molecule formed from stacked self-assembled quantum dots
  • 2003
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:16, s. 2655-2657
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate resonant tunneling through two coupled self-assembled quantum dots. The strong confinement and the high crystalline quality provided by the self-assembled dots, in combination with the tunneling coupling between the dots, create a system that may be thought of as an artificial molecule. We are able to isolate one single artificial molecule and detailed investigations of the electrical properties are performed. Peak-to-valley ratios above 1000 and full width half maximum of a few millivolts are measured at 4 K. By changing the temperature we also observe Coulomb blockade effects in a different way. (C) 2003 American Institute of Physics.
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10.
  • Gustafson, Boel, et al. (författare)
  • Coupling between lateral modes in a vertical resonant tunneling structure
  • 2002
  • Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - 1386-9477. ; 13:2-4, s. 950-953
  • Tidskriftsartikel (refereegranskat)abstract
    • We present experimental results and theoretical calculations of the vertical electron transport through a laterally constricted resonant tunneling transistor. Current-voltage measurements at 4.2 K show numerous current peaks that exhibit a complex dependence on the applied gate voltage. A scattering-matrix approach combined with the Landauer formalism was used to perform quantum mechanical calculations of the electron transport through a quantum dot structure with laterally confined emitter and collector regions. The simulations qualitatively reproduce the measured data, suggesting a strong coupling between the lateral modes in the quantum dot and the collector
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  • Resultat 1-10 av 23

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