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  • Digitale Medien  (23)
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  • Digitale Medien  (23)
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  • 1
    Digitale Medien
    Digitale Medien
    Lattice constants and thermal expansion of AlxGa1−xAs:Te (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6994-6998 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An influence of Te doping on the lattice parameter and the thermal expansion of AlxGa1−xAs epitaxial layers was examined by high-resolution x-ray diffractometry over a temperature range 77–673 K. For doped AlxGa1−xAs layers the thermal expansion coefficients were found to be larger relative to undoped samples of the same Al content. This phenomenon is attributed to the change of anharmonic part of lattice vibrations by free electrons and/or ionized tellurium atoms. An increase of thermal expansion caused by doping is a factor which should be taken into account in lattice constant measurements at 295 K. We propose an interpretation of the lattice expansion (examined at room temperature by other authors and by us) of GaAs caused by Te doping in terms of three factors: (i) "size'' effect (bigger Te atoms with respect to As), (ii) free electrons via the deformation potential of the conduction-band minimum occupied by these electrons, (iii) increase of the thermal expansion. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360467
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  • 2
    Digitale Medien
    Digitale Medien
    Thermal expansion of gallium nitride (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4909-4911 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Lattice constants of gallium nitride (wurzite structure) have been measured at temperatures 294–753 K. The measurements were performed by using x-ray diffractometry. Two kinds of samples were used: (1) bulk monocrystal grown at pressure of 15 kbar, (2) epitaxial layer grown on a sapphire substrate. The latter had a smaller lattice constant in a direction parallel to the interface plane by about 0.03%. This difference was induced by a higher thermal expansion of the sapphire with respect to the GaN layer. However, this thermal strain was created mainly at temperatures below 500–600 K. Above these temperatures the lattice mismatch in parallel direction diminished to zero at a temperature of about 800 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357273
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  • 3
    Digitale Medien
    Digitale Medien
    Influence of redistribution of electrons in the conduction band on the lattice parameters of AlxGa1−xAs (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3366-3368 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Lattice parameters of GaAs layers were measured using the Bond method. For samples heavily doped with S and Se, we observed an increase of lattice parameters with respect to the undoped samples. The results are compared with those observed for AlxGa1−xAs:S (Wagner et al.) and both are explained by the influence of free electrons and their redistribution in the conduction band. For Al0.39Ga0.61As, the following values of deformation potentials of the conduction-band minima were obtained: DΓ=−6.7 eV, DL=1.4 eV, and DX=1 eV. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.117308
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  • 4
    Digitale Medien
    Digitale Medien
    Optical activation and diffusivity of ion-implanted Zn acceptors in GaN under high-pressure, high-temperature annealing (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1155-1157 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Optical activation of Zn ions implanted to an epitaxial film of GaN was performed by means of sample annealing at N2 overpressure up to 1.6 GPa. By applying pressure we avoided GaN decomposition and could increase the annealing temperature up to 1550 °C versus a limit of 1000–1100 °C at ambient pressure. The Zn-acceptor-related photoluminescence (PL) intensity in implanted samples is maximized by annealing above 1350 °C after which the Zn PL intensity exceeds epitaxially doped GaN:Zn with comparable Zn concentration by factor 15. High-pressure annealing causes a significant diffusion of implanted Zn atoms in GaN films. It is also possible to diffuse Zn from the external source into the implanted/unimplanted layers. High dislocation densities strongly accelarate the Zn diffusion. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.368118
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  • 5
    Digitale Medien
    Digitale Medien
    Thermal expansion of GaAs:Te and AlGaAs:Te at low temperatures (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4678-4680 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We studied the influence of free electrons on the lattice parameters, thermal expansion, and negative thermal expansion of GaAs:Te and AlGaAs:Te. The samples were examined at temperatures in the range of 10–295 K. Dylatometry and high-resolution x-ray diffraction were used as experimental techniques. Additionally, for the doped layer of Al0.32Ga0.68As, the free-electron concentration was changed in situ by illumination and emptying the metastable DX centers. These results were compared with those for GaAs bulk crystals examined using dylatometry. It was confirmed that n-type doping increases thermal expansion at temperatures higher than about 120 K. At lower temperatures, a phenomenon of the negative thermal expansion becomes much more pronounced for the doped GaAs sample. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.366207
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  • 6
    Digitale Medien
    Digitale Medien
    Thermal expansion of gallium arsenide layers grown by molecular beam epitaxy at low temperatures (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1484-1486 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The thermal expansion of low-temperature (190–220 °C) MBE grown gallium arsenide (LT GaAs) was measured using x-ray diffraction methods. The experiment was performed in order to observe the influence of high nonstoichiometric excess (about 1%) of arsenic on the thermal expansion of gallium arsenide. The diffraction measurements enabled the simultaneous monitoring of the lattice constants of the LT GaAs layers and their semi-insulating GaAs substrates. Their lattice mismatch was only slightly temperature dependent and decreased by about 5% with a temperature rise from 77 K (in dark) up to 550 K. This means that the value of the thermal expansion coefficient of as-grown LT GaAs was lower only by about 0.05×10−6 K−1 than that of the semi-insulating GaAs substrate. Reduction of arsenic excess by air annealing at 420 °C resulted in the decrease of lattice mismatch and the difference in the thermal expansion. This means that both are related to such point defects as arsenic antisites and interstitials. The experimental results are compared with the previously published data for variously doped gallium arsenide samples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.108666
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  • 7
    Digitale Medien
    Digitale Medien
    Detection of the EL2 metastability by x-ray rocking-curve measurements at low temperatures (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2561-2563 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: X-ray experiments are usually seen as a tool for studying large lattice imperfections. We present for the first time experimental evidence obtained from x-ray measurements that metastable behavior of the EL2 defect in semi-insulating GaAs can be connected with crystal lattice relaxation. New unexpected results showing change of the lattice state while cooling semi-insulating GaAs samples in darkness are also reported.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105953
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  • 8
    Digitale Medien
    Digitale Medien
    Lattice dilation by free electrons in heavily doped GaAs:Si (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 539-541 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Lattice constants of GaAs layers grown by molecular beam epitaxy were examined by using the high resolution x-ray diffractometer. For highly doped samples (up to 9×1018 cm−3 of free-electron concentration) we observed an increase of the lattice constant with respect to the undoped layers. Since substitutional silicon atoms decrease the lattice constant of GaAs, the results are explained by the influence of free-electrons via the deformation potential of the Γ minimum of the conduction band. The best fit to our diffractometric data was obtained for the band-gap deformation potential equal to −8.5 eV. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.115181
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  • 9
    Digitale Medien
    Digitale Medien
    Mechanism of yellow luminescence in GaN (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2188-2190 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We investigated the pressure behavior of yellow luminescence in bulk crystals and epitaxial layers of GaN. This photoluminescence band exhibits a blueshift of 30±2 meV/GPa for pressures up to about 20 GPa. For higher pressure we observe the saturation of the position of this luminescence. Both effects are consistent with the mechanism of yellow luminescence caused by electron recombination between the shallow donor (or conduction band) and a deep gap state of donor or acceptor character. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.115098
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  • 10
    Digitale Medien
    Digitale Medien
    Erratum: "Evidence for localized Si-donor state and its DX-like properties in AlGaN" [Appl. Phys. Lett. 74, 3833 (1999)] (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3225-3225 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.125286
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