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  • 1
    Electronic Resource
    Electronic Resource
    Impurity effects on both the creation and the migration of Ga vacancies in GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 674-684 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of impurities, such as Si and Be, on both the creation and the migration of Ga vacancies in annealing of GaAs were investigated by a slow positron beam technique. The results show that vacancies diffuse from the surface during the annealing and one of the dominant types is a monovacancy of Ga, VGa, in Be-doped GaAs and/or Si-doped GaAs, while the other is a divacancy of VGa-VAs in undoped GaAs. In annealing the bilayer structures composed of the Si-doped layer grown on the Be-doped layer, it was found that VGa is a major type of defect rather than VGa-VAs if the Si concentration is higher or lower than the Be one in GaAs, but VGa-VAs is dominant if the concentrations of the impurities are similar. This proposes that the interaction between Si and Be is stronger than that of VAs-BeGa and/or VGa-SiGa. The Ga interstitial IGa is created in the Be-doped layer where IGa interacts with VGa created from the surface and suppresses the migration of VGa. This supports the validity of the kick-out mechanism involving a column-III interstitial rather than the Longini mechanism for Be diffusion in GaAs. In Si-doped GaAs, VGa is created from the surface and the diffusion constant of VGa decreases with the increase of Si doping concentration. This implies that VGa forms a complex of SiGa-VGa and the interaction time of VGa at the Si donor by making a complex of SiGa-VGa is a rate-limiting step in the diffusion of VGa in GaAs. The present results propose the creation of IGa and VGa in the Be-diffused GaAs and in Si-diffused GaAs, respectively. This is consistent with the Fermi-level effect of the impurities on the creation of those defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349647
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of vacancy-type defects in Se-implanted GaAs by means of a slow positron beam (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1405-1409 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Variable-energy (0–30 keV) positron beam studies have been carried out on 200 keV Se-implanted GaAs specimens before and after annealing for the electrical activation. From the measurements of Doppler broadened profiles of the positron annihilation as a function of the incident positron energy, it was found that vacancy clusters with high concentration were introduced especially in the annealed specimens after Se implantation. From the parallel measurement of electric characteristics, the higher activation efficiency was found to be obtained for the higher concentration of vacancy clusters. This fact implies that electrons supplied by the activation of Se also convert the charge state of As vacancies from positive to negative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351753
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  • 3
    Electronic Resource
    Electronic Resource
    Be diffusion mechanism in GaAs investigated by slow positron beam (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6364-6368 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The slow positron beam technique was applied on undoped and Be-doped GaAs to study the effects of Be impurities on both creation and migration of Ga vacancies, VGa, during annealing. It is observed that a monovacancy of VGa is created in Be-doped GaAs to result in enhanced Coulombic interaction between As vacancy, VAs, and Be acceptor, BeGa. In undoped GaAs, the formation of divacancies, VGa-VAs, is dominant. The migration depth of vacancies is shorter in Be-doped GaAs than in undoped GaAs. This suggests the existence of Ga interstitials, IGa, in the Be diffused layer which interact with VGa introduced from the surface. Based on these observations, we suggest the kick-out mechanism for Be diffusion in GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348971
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of (NH4)2Sx treatment on the passivation of GaP surface (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2877-2879 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We applied slow positrons to both as-etched GaP and (NH4)2Sx-treated GaP. The results show that the surface of as-etched GaP is active for the adsorption of oxygen atoms when the etched surface was exposed to air for several minutes before the measurement. On the other hand, the monolayer of chemisorbed sulfur in (NH4)2Sx-treated GaP is effective to protect the clean surface from the adsorption of the oxygen atoms. The mean diffusion length of positrons in the etched GaP is shorter than that in (NH4)2Sx-treated GaP. This suggests that the centers for the positron trapping, such as Ga vacancies VGa and/or VGa-related complexes, are created by the adsorption of oxygen atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349354
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  • 5
    Electronic Resource
    Electronic Resource
    Impurity effect on the creation of Ga vacancies in a Si-doped layer grown on Be-doped GaAs by molecular-beam epitaxy (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5571-5575 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The impurity effects on the creation of Ga vacancies in Si-doped GaAs grown on a Be-doped epilayer by molecular-beam epitaxy were investigated through slow positron beam measurements. Doping of Si impurities enhances the creation of Ga vacancies in GaAs. The experimental results support the theoretical prediction of the creation of Ga vacancies in terms of the change in the Fermi-level position by the Si doping into GaAs, and also suggest that a Si atom diffuses in GaAs as a neutral complex of SiGa-VGa rather than that of SiGa-SiAs. The change in the S parameter distribution at the interface between Si and Be-doped regions is explained by the Be carryforward phenomenon which occurs during the growth of Si-doped GaAs on a Be-doped epilayer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346992
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  • 6
    Electronic Resource
    Electronic Resource
    Defects in p+-gate metal–oxide–semiconductor structures probed by monoenergetic positron beams (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5385-5391 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Defects in p+-gate metal–oxide–semiconductor structures were probed using monoenergetic positron beams. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured for BF2+- or B+-implanted polycrystalline-Si(300 nm)/SiO2(4 nm)/Si specimens. The line-shape parameter, S, corresponding to the annihilation of positrons near SiO2 films was decreased by annealing treatments performed after ion implantation. This fact was attributed to the trapping of positrons by vacancy-oxygen complexes introduced by the boron diffusion in the SiO2 film. The introduction of such complexes was enhanced by incorporation of fluorine, but suppressed by doping of phosphorus into polycrystalline films. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371535
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  • 7
    Electronic Resource
    Electronic Resource
    Oxygen-related defects in O+-implanted 6H–SiC studied by a monoenergetic positron beam (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5392-5398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Vacancy-type defects and their annealing properties for O+- or N2+-implanted 6H–SiC were studied using a monoenergetic positron beam. For ion-implanted specimens with a dose of 1×1013 cm2, the mean size of open volume of defects was estimated to be close to the size of divacancies. Annealing processes of the damage were identified to be agglomerations of vacancy-type defects due to migrations of carbon vacancies (100–400 °C), silicon vacancies (400–800 °C), and vacancy complexes such as divacancies (800–1000 °C), and the annealing out of the open spaces adjacent to extended defects (1000–1400 °C). From a comparison between the annealing behaviors of defects for the O+-and the N2+-implanted specimens, the migration and the agglomeration of vacancy-type defects were found to be suppressed in the O+-implanted specimen. This fact was attributed to the formation of complexes between vacancy-type defects and oxygen. For ion-implanted specimens with a dose of 1×1015 cm2, annealing behaviors of amorphous regions were also studied. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371536
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  • 8
    Electronic Resource
    Electronic Resource
    Crystallization of an amorphous layer in P+-implanted 6H-SiC studied by monoenergetic positron beams (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4119-4125 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Depth distributions and species of defects were determined from measurements of Doppler broadening spectra of annihilation radiation and lifetime spectra of positrons for 6H-SiC implanted with 200 keV P+ at a dose of 1×1015 cm−2. The annealing behavior of an amorphous layer was divided into four stages. Stages I (100–500 °C) and II (500–1100 °C) were identified as the relaxation of amorphous networks and the agglomeration of open spaces owing to rearrangements of atoms, respectively. In states III (1100–1500 °C) and IV (1500–1700 °C), corresponding to the recrystallization of the amorphous layer, the mean size of the open volume of defects decreased with increasing annealing temperature; these defects were identified as open spaces adjacent to extended defects. Vacancy-type defects were found in the subsurface region (〈100 nm) at high concentration even subsequent to an annealing at 1700 °C. The annealing behavior of defects in the specimens irradiated at elevated temperatures is also discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373039
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  • 9
    Electronic Resource
    Electronic Resource
    Evidence for the passivation effect in (NH4)2Sx-treated GaAs observed by slow positrons (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1167-1169 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We applied slow positrons to the as-etched GaAs and/or the (NH4)2Sx-treated GaAs. The results show that a thin oxide film is easily formed on the surface of as-etched GaAs as soon as the etched surface is exposed to air for several minutes before the measurement. On the other hand, the monolayer of chemisorbed sulfur atoms in the (NH4)2 Sx-treated GaAs is effective in protecting the clean surface from the adsorption of oxygen atoms. The mean diffusion length of positrons is not affected by the conditions of the surface treatment. This implies that the centers for the trapping of a positron are not created below the free surface by those treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104353
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of impurities Si and Be on the creation of Ga vacancies and Ga interstitials in GaAs grown by molecular beam epitaxy (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1524-1526 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two type of top layers, namely, undoped and Si-doped GaAs layers, were grown, respectively, on a Be-doped epilayer by molecular beam epitaxy, and the effects of impurities of Be and Si on the creation of Ga interstitials IGa and Ga vacancies VGa during the annealing of the specimens were investigated by a slow positron beam. The concentration of VGa created from the surface of the undoped GaAs during the annealing decreases drastically when the annealed GaAs was kept at room temperature for one month. This implies that the Be atoms diffusing to the undoped GaAs during the growth and/or the annealing cause the creation of IGa in the undoped layer and it makes the recombination with VGa. On the other hand, no decrease in the concentration of VGa was observed in the Si-doped GaAs. These support the creation of IGa and of VGa, respectively, in the Be-diffused GaAs and in Si-diffused GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105166
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