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  • Articles  (2)
  • 1990-1994  (2)
  • Computer Science  (1)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (1)
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  • Articles  (2)
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  • 1
    ISSN: 1432-0630
    Keywords: 6855 ; 7280E ; 7340L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Modulation doped Al0.3Ga0.7As/In x Ga1−x As/GaAs high electron mobility transistor structures for device application have been grown using molecular beam epitaxy. Initially the critical layer thickness for InAs mole fractions up to 0.5 was investigated. For InAs mole fractions up to 0.35 good agreement with theoretical considerations was observed. For higher InAs mole fractions disagreement occurred due to a strong decrease of the critical layer thickness. The carrier concentration for Al0.3Ga0.7As/In x Ga1−x As/GaAs high electron mobility transistor structures with a constant In x Ga1−x As quantum well width was investigated as a function of InAs mole fraction. If the In x Ga1−x As quantum well width is grown at the critical layer thickness the maximum carrier concentration is obtained for an InAs mole fraction of 0.37. A considerable higher carrier concentration in comparison to single-sided δ-doped structures was obtained for the structures with δ-doping on both sides of the In x Ga1−x As quantum well. Al0.3Ga0.7As/In x Ga1−x As/GaAs high electron mobility transistor structures with InAs mole fractions in the range 0–0.35 were fabricated for device application. For the presented field effect transistors best device performance was obtained for InAs mole fractions in the range 0.25–0.3. For the field effect transistors with an InAs mole fraction of 0.25 and a gate length of 0.15 μm a f T of 115 GHz was measured.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Acta informatica 28 (1991), S. 365-407 
    ISSN: 1432-0525
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Summary Temporal integrity constraints describe long-term data dependencies in databases to be satisfied by each correct database evolution. They can be formulated in a temporal logic. For a runtime monitoring of temporal integrity the problem arises to handle the historical information necessary to monitor the long-term dependencies. This paper extends the already known techniques for minimizing the stored information for a single substitution of the free constraint variables using transition graph construction. Our extension allows to decrease also the amount of handled substitutions for constraint monitoring. For this purpose, the notion of substitution descriptions is formally introduced allowing to monitor simultaneously whole substitution sets. The notions of formula validity and of stepwise monitoring potential validity of temporal constraints are redefined for descriptions. Based on these notions an algorithm for monitoring temporal integrity by handling descriptions is presented.
    Type of Medium: Electronic Resource
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