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  • 1
    Electronic Resource
    Electronic Resource
    The relation of active nitrogen species to high-temperature limitations for (0001¯) GaN growth by radio-frequency-plasma-assisted molecular beam epitaxy (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3836-3838 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A reduced growth rate for plasma-assisted molecular beam epitaxy of GaN often limits growth to temperatures less than 750 °C. The growth rate reduction can be significantly larger than expected based on thermal decomposition. Conditions producing a flux consisting predominantly of either atomic nitrogen or nitrogen metastables have been established using various radio-frequency sources. The use of atomic nitrogen, possibly coupled with the presence of low-energy ions, is associated with the premature decrease in growth rate. When the active nitrogen flux consists primarily of nitrogen metastables, the temperature dependence of the decrease is more consistent with decomposition rates. A significant improvement in electrical properties is observed for growth with molecular nitrogen metastables. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124196
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  • 2
    Electronic Resource
    Electronic Resource
    Controlled oxygen doping of GaN using plasma assisted molecular-beam epitaxy (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2740-2742 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-quality (0001) and (0001¯)-GaN films were grown by plasma-assisted molecular-beam epitaxy to study the dependence of oxygen incorporation on polarity and oxygen partial pressure. Oxygen incorporates at a rate ten times faster on nitrogen-polar GaN than on the Ga polarity. Oxygen doping is controllable, reproducible, and produces low compensation material up to concentrations of at least 1018 cm−3 with higher levels showing significant compensation. Layers containing oxygen at levels above 1022 cm−3 exhibit severe cracking while oxygen concentrations less than 1021 cm−3 do not introduce significant strain. The oxygen incorporation rate has a weak dependence on Ga overpressure during Ga-stable growth but dramatically increases for conditions approaching N-stable growth. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1403276
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  • 3
    Electronic Resource
    Electronic Resource
    Incorporation-related structural issues for beryllium doping during growth of GaN by rf-plasma molecular-beam epitaxy (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4524-4526 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Beryllium incorporation was studied for both Ga-polarity and N-polarity GaN using a series of Be step-doped epitaxial layers. Dopant concentration profiles indicated that surface polarity-related incorporation differences are not pronounced for Be. Significant surface accumulation of Be occurs during growth with surface accumulations approaching a monolayer for heavier doping levels. Transmission electron microscopy studies indicate the surface layer of Be has a significant effect on the microstructure, particularly for near monolayer coverage. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1429290
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  • 4
    Electronic Resource
    Electronic Resource
    Magnesium incorporation in GaN grown by molecular-beam epitaxy (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 285-287 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A pronounced dependence of Mg incorporation on surface polarity was observed in a series of Mg step-doped epitaxial GaN layers grown by rf-plasma-assisted molecular-beam epitaxy. Incorporation was studied for both (0001), or Ga-polarity and (0001¯) or N-polarity orientations. Up to a factor of 30 times more Mg was incorporated in Ga-polarity layers under certain conditions, as determined by secondary ion mass spectrometry. Measurements indicate surface accumulation of Mg occurs during growth, with stable accumulations of close to a monolayer of Mg on the Ga-polarity surface. The presence of atomic hydrogen during growth significantly increased incorporation of Mg without also incorporating potentially compensating hydrogen. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1339255
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  • 5
    Electronic Resource
    Electronic Resource
    BBXRT observations of supernova remnants
    Amsterdam : Elsevier
    Advances in Space Research 13 (1993), S. 57-66 
    Details
    ISSN: 0273-1177
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0273-1177(93)90097-U
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  • 6
    Electronic Resource
    Electronic Resource
    Interactions of Chlorophyll and Polypeptide Mixture with Bacterial Reaction Centres (2000)
    Springer
    Photosynthetica 38 (2000), S. 1-6 
    Details
    ISSN: 1573-9058
    Keywords: absorption spectra ; fluorescence spectra ; photoacoustic spectra ; Rhodobacter sphaeroides ; thermal deactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In aqueous solutions of chlorophyll (Chl) a with synthesized polypeptides, at high ratios of Chl to polypeptides (about 75–150 µM to 500 µM) clusters of polypeptides and pigment molecules were formed. The main absorption maxima of more than one formed cluster were located at about 500 nm (Soret band) and in the region of 720–806 nm (red band). The formation of these clusters was fairly slow (some hours) at room temperature and even slower at 4 °C. The rate of cluster formation increased with the increase in Chl concentration. The addition of the even low amount of reaction centres (RCs), separated from the purple bacteria Rhodobacter sphaeroides, to the sample of Chl with polypeptides caused a very strong decrease in the efficiency of cluster formation, and a change in concentration ratios of various pigment-polypeptide aggregates. It was probably a competition between the interaction of Chl with polypeptides and with the RCs. The yield of thermal deactivation of the clusters was high, much higher than that for the RCs alone and it was different for various types of cluster. The clusters absorbing at 725–750 nm were fluorescent with maximum of emission at about 770 nm, whereas clusters absorbing at about 800 nm were nonfluorescent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026723303078
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