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  • 1
    Electronic Resource
    Electronic Resource
    Gain enhancement in InAlAs/InGaAs heterojunction bipolar transistors using an emitter ledge (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1954-1955 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Improved gain was observed at low currents when a thin emitter ledge was incorporated into npn In0.52Al0.48As/In0.53Ga0.47As heterojunction bipolar transistors. A 40-nm-thick n-In0.52Al0.48As emitter ledge resulted in over four times higher gain at low biases due to reduced surface recombination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357654
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Refinements in the method of moments for analysis of multiexponential capacitance transients in deep-level transient spectroscopy (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 182-190 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The analysis of multiexponential capacitance transients that arise in deep-level transient spectroscopy has been examined. The method of moments, a technique that provides a reliable method for resolution of a multiexponential capacitance transient into its exponential components, has been adapted and enhanced by incorporating an initial fast Fourier transform to extract the base-line offset, and a refinement in the cutoff correction to the moments integrals which improves convergence and accuracy. In addition, the mean displaced ratio smoothing algorithm has been incorporated and shown to improve the method's accuracy in the presence of noise. For the case where the response is not significantly convoluted with the excitation, a simplified form of the method of moments technique provides a simple and more direct determination of the exponential components. Examples of results for simulated data are provided illustrating application of the analysis. The limitations of the technique in determining the number of exponential components, their amplitudes and emission rates, and the applicability of the smoothing algorithm are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338852
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    GaAs/AlGaAs multiquantum well resonant photorefractive devices fabricated using epitaxial lift-off (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2244-2246 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This letter deals with resonant photorefractive devices fabricated from multiquantum wells of GaAs/Al0.3Ga0.7As and operated in a quantum-confined Stark effect geometry. Details of the processing are presented. Epitaxial lift-off was used to remove the active device from the substrate. Low-temperature Al0.3Ga.07As was used as an insulator to form metal-insulator-semiconductor structures on both sides of the multiquantum wells. Proton implant damage was used to improve the fringe visibility. Photorefractive wave mixing with a diffraction efficiency of ∼0.03% was demonstrated. The incorporation of a nitride layer between the top electrode and the low-temperature AlGaAs increased the efficiency to 0.5%. The improvement is attributed to a reduction in the conduction of carriers across the low-temperature layer into the electrode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111658
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  • 4
    Electronic Resource
    Electronic Resource
    Interface states in regrown GaAs p-n junctions by selective molecular beam epitaxy (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 297-299 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first evaluation of interface states present in GaAs p-n junctions regrown on a SiO2 masked substrate by selective molecular beam epitaxy. A constant-capacitance deep-level transient spectroscopy (CC-DLTS) method is extended to the regrown p-n junction case, and a technique to distinguish the DLTS signal emerging from bulk and interface states is employed. The extracted interface state density is in good agreement with predictions based on the unified disorder-induced gap state model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107917
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    High-resolution spatial light modulators using GaAs/AlGaAs multiple quantum wells (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 956-958 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report improved performance in semi-insulating GaAs/AlGaAs quantum well based spatial light modulators grown by molecular beam epitaxy. The optically addressed modulator reported here are of a new design and have significantly higher spatial resolution than previously reported devices. Strong diffraction efficiencies are described for spatial periods as fine as 2.6 μm at framing rate as high as 600 kHz. Two modulators are characterized, one with x=0.1 and the other with x=0.3 for the AlxGa1−xAs quantum barriers of the superlattices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112160
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  • 6
    Electronic Resource
    Electronic Resource
    MODELLING OF WAVE PROPAGATION IN THE NEARSHORE REGION USING THE MILD SLOPE EQUATION WITH GMRES-BASED ITERATIVE SOLVERS (1996)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 23 (1996), S. 397-411 
    Details
    ISSN: 0271-2091
    Keywords: GMRES ; mild slope equation ; iterative solvers ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The mild slope equation in its linear and non-linear forms is used for the modelling of nearshore wave propagation. The finite difference method is used to descretize the governing elliptic equations and the resulting system of equations is solved using GMRES-based iterative method. The original GMRES solution technique of Saad and Schultz is not directly applicable to the present case owing to the complex coefficient matrix. The simpler GMRES algorithm of Walker and Zhou is used as the core solver, making the upper Hessenberg factorization unneccessary when solving the least squares problem. Several preconditioning-based acceleration strategies are tested and the results show that the GMRES-based iteration scheme performs very well and leads to monotonic convergence for all the test-cases considered.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 7
    Electronic Resource
    Electronic Resource
    Solution of the 2D shallow water equations using the finite volume method on unstructured triangular meshes (1997)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 24 (1997), S. 1225-1245 
    Details
    ISSN: 0271-2091
    Keywords: free surface flow ; unstructured triangular mesh ; Roe's matrix ; upwind finite volume method ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A 2D, depth-integrated, free surface flow solver for the shallow water equations is developed and tested. The solver is implemented on unstructured triangular meshes and the solution methodology is based upon a Godunov-type second-order upwind finite volume formulation, whereby the inviscid fluxes of the system of equations are obtained using Roe's flux function. The eigensystem of the 2D shallow water equations is derived and is used for the construction of Roe's matrix on an unstructured mesh. The viscous terms of the shallow water equations are computed using a finite volume formulation which is second-order-accurate. Verification of the solution technique for the inviscid form of the governing equations as well as for the full system of equations is carried out by comparing the model output with documented published results and very good agreement is obtained. A numerical experiment is also conducted in order to evaluate the performance of the solution technique as applied to linear convection problems. The presented results show that the solution technique is robust. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 8
    Electronic Resource
    Electronic Resource
    AN AUTOMATIC TETRAHEDRAL MESH GENERATION SCHEME BY THE ADVANCING FRONT METHOD (1997)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 13 (1997), S. 33-46 
    Details
    ISSN: 1069-8299
    Keywords: advancing front ; tetrahedrization ; inverse-power interpolation ; triangular Bezier patches ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper deals with the discretization of any given multi-connected volume into a set of tetrahedral elements. A simple but robust tetrahedrization scheme based on a two-stage advancing front technique is presented. The method evolves from the triangulated domain bounding surfaces for which geometry representations are derived from triangular Bezier patches. Tetrahedral elements are then generated which fill the domain volume based on the set of distributed interior nodes. A new and efficient procedure is introduced for the distribution of the mesh interior nodes which uses an inverse-power interpolation technique. The proposed scheme is robust in that it is capable of tetrahedrizing a given arbitrary domain of any degree of irregularity, and allows the distribution of its interior nodes to be specified by the user. Results are presented typical of those which might be encountered in hydrodynamics modelling involving flows with a free surface. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Automatic triangular mesh generation scheme for curved surfaces (1996)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 12 (1996), S. 197-208 
    Details
    ISSN: 1069-8299
    Keywords: curved surface ; triangular mesh ; automatic generation ; Bézier patches ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper deals with the discretization of any given multi-connected curved surface into triangular elements with straight sides. The method evolves from an initial rough triangular mesh generated from a set of input points which describe the geometry of the problem domain. Interior nodes are distributed according to user-established node-spacing functions of pre-specified spacing control parameters, and they are linked using the advancing front technique. Particular attention is paid to obtaining good distribution of interior nodes in the vicinity of the domain limits. Surface geometry representation is established using triangular Bézier patches with G1 continuity. This approach ensures a geometrically well-defined working platform for the subsequent discretization of the problem domain. The proposed method requires minimum input from the user and allows mesh gradation and remeshing to be carried out in a straightforward manner. Furthermore, problems associated with variations in the domain geometry as a result of local remeshing are eliminated with the aid of the geometrically pre-defined discretization platform. Results are presented for a range of both curved and planar surfaces, typical of those which might be encountered in hydrodynamics modelling involving flows with a free surface. The presented results demonstrate the flexibility and power of the technique.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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