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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1454-1462 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical and optical properties of liquid encapsulated Czochralski grown, Ga-rich (melt composed of 55% Ga and 45% As), p-type GaAs were studied by the Hall effect, capacitance-voltage measurements, magnetic circular dichroism, optically detected electron spin resonance, deep level transient spectroscopy (DLTS), and Raman spectroscopy. Two levels with ionization energies of 78 and 203 meV above the valence band edge were examined and fitted to the singly and doubly charged ground states of a double acceptor which is designated an EK2 center. The Raman scattering cross sections for electronic excitations were determined from the defect concentrations measured by DLTS. The EK2 center is electrically passivated via a remote microwave hydrogen plasma technique. It can be reactivated by heat treatments with an activation energy of Ea=1.4 eV. The concentrations of the two levels were equal to each other in four as-grown samples, in samples following passivation, and at all stages during the subsequent reactivation. The observations are inconsistent with previous suggestions that the levels are due to two separate defects.
    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. 740-748 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of diffusion of monatomic hydrogen and deuterium in InGaAs/AlGaAs quantum wells were studied using photoluminescence (PL) and secondary-ion-mass spectroscopy. The multiquantum-well structures were grown by molecular-beam epitaxy and hydrogenated with a remote plasma. A significant increase in 77 K PL integrated intensity of bound excitons was observed after hydrogenation. This is attributed to the passivation of nonradiative recombination centers within InGaAs/AlGaAs quantum wells. A series of studies demonstrating the increase in passivation efficiency with increasing Al concentration in the barriers, the stability of the hydrogenation upon annealing to temperatures of up to and above 450 °C, the ratio of the deuterium concentration for samples with different barrier thicknesses, and the comparison of strained versus relaxed quantum wells, all strongly suggest that the passivated nonradiative recombination centers are interface defects. The stability of this hydrogen passivation at temperatures commonly used in device processing is particularly promising for device applications.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2914-2916 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated hydrogen and deuterium passivation of two copper-related deep levels at EV+0.13 eV and EV+0.40 eV in GaAs with deep level transient spectroscopy (DLTS). The DLTS signals of the two copper-related acceptor levels disappear after exposing the samples to a remote hydrogen or deuterium plasma at 300 °C for 1/2 h. Both copper-related levels can be reactivated by thermal annealing. The copper-related donor–accepter pair luminescence at 1.36 eV is correlated with the DLTS signal of the copper-related acceptor level at EV+0.13 eV.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1040-1042 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A significant reduction in lasing threshold is achieved by rapid thermal annealing (RTA) for strained InGaAs/GaAs single quantum well lasers grown by molecular beam epitaxy under standard conditions (the growth temperature is 620 °C or less), not especially optimized for lasers. When RTA at 900 °C for 10 s is applied twice to the wafer after the growth, the room-temperature photoluminescence efficiency of the active layer increases by about 80 times and the threshold current decreases by a factor of 5 to 7. We suggest that this enhancement is due to improvement of the quality of the InGaAs quantum well rather than that of the AlGaAs cladding layers.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2276-2278 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of diffusion of monatomic hydrogen on photoluminescence (PL) in the InGaAs/AlGaAs system has been studied. A significant increase in 77 K PL integrated intensity for In0.2Ga0.8As/AlxGa1−xAs quantum wells grown by molecular beam epitaxy is observed after hydrogenation. A 50% increase is observed for InGaAs/GaAs and the effect increases as the Al concentration increases from 0% to 33%. For 33%, the increase is approximately a factor of 9. This enhancement of the PL may be ascribed to hydrogen passivation of defects at the heterointerface or within the layers.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 461-463 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal dissociation kinetics of the hydrogen-donor complex in n-type GaAs:Si were determined from bias-temperature anneals on hydrogenated Schottky-barrier diodes. The anneal kinetics are approximately first order and yield a thermal dissociation energy for the Si-H complex of 1.2±0.1 eV. Depth redistribution of the Si-H complexes both within the depletion layer of biased diodes and in the field-free region of unbiased diodes suggests that hydrogen in n-type GaAs can migrate as a negatively charged species.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 1897-1902 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogen passivation of chalcogen impurities (S, Se, and Te) in n- and p-type silicon was studied by deep-level transient spectroscopy (DLTS). After exposure to monatomic hydrogen from a remote microwave plasma, the chalcogen-related double-donor defects were completely neutralized near the exposed surface of the silicon samples (at 150 °C). Vacuum anneals of hydrogenated specimens revealed that the two donor levels of each chalcogen complex recover simultaneously. Reactivation of the double donors was quantitatively examined with DLTS measurements of hydrogenated specimens after isothermal anneals. The activation energies for reactivation of the neutralized chalcogen-impurity complexes are as follows: For isolated substitutional sulfur, selenium, and tellurium, the energies are 1.61±0.21 eV, 1.39±0.17 eV, 1.39±0.18 eV, respectively, and for the pure pairs of sulfur and selenium, they are 1.56±0.2 eV and 1.41±0.18 eV, respectively. The experimental results are discussed with regard to available calculations for hydrogen passivation of the sulfur impurity in silicon.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of oral pathology & medicine 23 (1994), S. 0 
    ISSN: 1600-0714
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In a comparison of flow cytometric DNA measurements on fresh and para (Tin-embedded material from primary squamous cell carcinomas of the head and neck region, we discovered that previously undetected aneuploid clones could he detected by dual parameter analysis of cytokeratin and DNA applied to disintegrated cells from paraffin sections. Using this new approach the correlation coefficient between DNA-indices from fresh and paraffin-embedded material increased from 0.42.1 to 0.904.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1530-0358
    Keywords: Jejunoileal bypass ; Colorectal cancer ; Dysplasia ; DNA analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Jejunoileal bypass (JIB) has been a widespread operation for treatment of morbid obesity. Bile acids are regarded as cofactors in the carcinogenesis of the colon, and, since intestinal bypass involves increased exposure of bile acids to the large intestinal mucosa, JIB has been postulated to increase the risk for colorectal carcinoma. In experimental studies on animals, the results have indicated an increased frequency of induced carcinomas, but in clinical series only one patient with colon carcinoma has been reported. Thirty women, operated on with JIB 11 to 17 years earlier, were examined by colonoscopy with multiple biopsies, systematically taken for histologic evaluation and flow cytometric DNA analysis. In only one patient, low-grade dysplasia was detected in an initial adenomatous lesion but was not visible macroscopically. No DNA aneuploidy was found. In a control group of 11 patients examined for non-neoplastic disease, neither dysplasia nor aneuploidy was diagnosed. Within 17 years postoperatively, we have, by these methods, not been able to verify any colorectal malignant transformation in patients operated on with JIB. However, since carcinogenesis is a long process, further surveillance will be demanded before an increased risk for colorectal carcinoma can be excluded.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 38-41 (Jan. 1991), p. 951-956 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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