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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1398-1402 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: AlGaAs/GaAs heterostructure emitter bipolar transistors were grown with emitter thicknesses varied from 300 to 900 A(ring) and the emitter thickness effects on the current gain and offset voltage were studied. It was found that both the current gain and offset voltage are strongly dependent on the emitter thickness. The current gain decreases with increasing emitter thickness. For an emitter thickness smaller than 500 A(ring), the offset voltage decreases with increasing emitter thickness, but for an emitter thickness larger than 500 A(ring), the offset voltage stays at a nearly constant value. Offset voltage as low as 55 mV was obtained for an emitter thickness of 700 A(ring). This low offset voltage, mostly contributed by the geometric effect, indicates that the base-emitter junction is a homojunction. From the current gain and offset voltage considerations, the optimal emitter thickness was found to be about 300–500 A(ring).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4706-4708 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new ridge waveguide laser array with stable fundamental mode operation has been fabricated. By introducing absorption regions in all the laser stripes except for the central one, the electric field distribution of the laser arrays and the modal gains of the array supermodes are changed, resulting in fundamental mode operation. The threshold current of an array with five elements is typically 40 mA and the maximum output power is higher than 150 mW. The single-lobed far-field pattern centered at 0° with full width at half maximum of 2° is obtained at 1.5 times of the threshold current (Ith).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4302-4306 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Compositional disordering of GaAs/AlGaAs quantum wells due to the presence of low-temperature grown GaAs (by molecular beam epitaxy) was studied. Ga vacancy enhanced interdiffusion was found to be the mechanism underlying the observed intermixing. Diffusion equations were solved numerically to obtain the band profile after intermixing. The transition energies in the quantum wells under various annealing conditions were solved and agree very well with the observed photoluminescence emission peaks. The diffusivity of Ga vacancies and that of induced Al-Ga interdiffusion were obtained. The vacancy induced interdiffusion diffusivity was found to have an activation energy of 4.08 eV, which is smaller than the activation energy of interdiffusion diffusivity of normal temperature grown GaAs/AlGaAs heterostructures. This is a clear indication of enhanced interdiffusion due to the presence of low-temperature grown GaAs. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 274-277 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of oxygen on the performance of GaAs/AlGaAs quantum well infrared photodetectors (QWIP) has been studied. Photoluminescence and secondary ion mass spectroscopy were used to examine the relationship between the quality of AlGaAs and the oxygen content that were then correlated to the performance of QWIPs. It was found that oxygen is the dominant impurity in the GaAs/AlGaAs superlattice. Because oxygen atoms behave likes electron traps, which effectively reduce the carrier concentration in the material, both of the responsivity and the dark current of QWIP are reduced. The detectivities of QWIPs with lower oxygen concentrations are better than those with higher oxygen concentrations.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2720-2722 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Four n-i-n GaAs/AlGaAs diodes have been used to demonstrate that at room temperature the carrier blocking is influenced by the X-valley superlattice in a multiquantum barrier. The diode with a Γ-X crossover multiquantum barrier has a current at least three orders lower than the corresponding diode with only a bulk barrier. However, diodes without Γ-X crossover barriers have resistance as low as 10 Ω in spite of whether a multiquantum barrier exists or not. This indicates that the X-valley superlattice plays an important role in blocking the current flowing across/through a multiquantum barrier. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2436-2438 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Asymmetric dark current versus voltage characteristics in quantum well infrared photodetectors have been studied. A model based on asymmetrical potential barriers was proposed. The asymmetrical potential barriers, which are most likely due to the accumulation of oxygen impurities at one of the interfaces, cause the asymmetrical I-V characteristics. The height of the potential spike is found to increase with the Al content in the AlGaAs barriers. Calculations based on our model agree well with experimental results.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 3504-3506 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-color infrared detector using GaAs/AlGaAs and strained InGaAs/AlGaAs multiquantum wells is demonstrated. The response peak of the GaAs/AlGaAs quantum well is at 8 μm, and that of the InGaAs/AlGaAs quantum well is at 5.3 μm. The responsivity of the detector is 1 A/W at 8 μm and 0.27 A/W at 5.3 μm; these are the best values reported for a two-color quantum well infrared detectors (QWIPs) with peak sensitivities in the spectral regions of 3–5.3 μm and 7.5–14 μm. Single-colored 5.3 and 8 μm QWIPs were also fabricated to study the bias dependent behavior. This behavior can be explained using the concept of current continuity. Because of a higher electrical resistance, a high electric field domain is always formed first in the shorter wavelength quantum well stack.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4882-4885 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of indium doping in the graded-index regions of the InGaAs/GaAs/AlGaAs graded-index separated confinement heterostructure quantum well laser has been studied. It was found that the threshold current density can be greatly reduced by a proper amount of In doping in the graded AlGaAs region. This result is attributed to an improvement in material quality due to a reduction in group III vacancies. The effect of thermal treatment on laser performance has also been studied. Although high temperature annealing can significantly improve non-In-doped lasers, it has little effect on In-doped lasers.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of oral pathology & medicine 24 (1995), S. 0 
    ISSN: 1600-0714
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Over a 10-year period (1982–1991), a total of 150 patients divided into two groups with varying degrees of oral submucous fibrosis (OSF) were treated by either medical or surgical therapies. Medical treatment involved (a) conservative oral administration of vitamin B-complex, buflomedial hydrochloride and topical triamcinolone acetonide 0.1%, or (b) conventional submucosal injections of a combination of dexamethasone and hyaluronidase, or (c) a combination of both (a) and (b). The surgical group was treated by the excision of fibrotic tissues and covering the defect with split-thickness skin, fresh human amnion, or buccal fat pad (BFP) grafts. Treatment was chosen according to the stage of clinical progression to gain maximal interincisal distance (ID). The cases were followed up by monthly examinations for at least two years, or when possible even longer. A combination of (a) and (b) medical treatment was satisfactory in cases of mild impairment (ID 〉 20 mm) but in the long term it led to symptomatic relief only. Surgical therapy, on the other hand, when accepted by the patients, led to a significant improvement of trismus in cases of severe limitation (ID 〈 20 mm). Following this strategy, an additional ID increase was observed in all patients. BFP grafting was particularly successful in diminishing scarring after two years as compared with the other two grafts. Together with a cessation of the betel quid chewing habit before and after therapy, these treatment regimens combined with daily mouth opening exercises were found to be necessary to manage OSF cases in early and advanced stages of progression.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 53 (2004), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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