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  • 1
    Electronic Resource
    Electronic Resource
    DX-center-related features by capacitance measurements in AlGaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 215-220 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of quasistatic C-V measurements in investigating DX-center-related features in AlGaAs (x=0.25, 0.30, and 0.35) Schottky barriers has been reconsidered under different experimental conditions. The vanishing of the electron-capture rate by the DX center, at low temperature, is responsible for a frozen-step-like density profile of positively charged DX centers near the metal-semiconductor interface. This causes a knee-shaped 1/C2-vs-V plot and gives rise to an apparent built-in potential. The low-temperature freezing in of the free-electron density in the flatband region has been demonstrated through specific experiments of thermally stimulated capacitance and low-temperature C-V measurements performed on the sample cooled at different cooling rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350313
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  • 2
    Electronic Resource
    Electronic Resource
    X-ray diffuse scattering by composition waves in GaAlAs (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4533-4538 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The possibility of using x-ray diffuse scattering experiments to investigate the atomic arrangement within the substituted sublattice in III-V solid solutions has been demonstrated. The Icw scattering by static composition waves has been separated from Compton and phonon scattering along the 100 direction in reciprocal space for a thick Ga1−xAlxAs (x=0.32) layer grown by liquid-phase epitaxy. The dependence of Icw on the scattering angle has given a detailed experimental proof that the Ga and Al atoms are distributed in a random way within the cation sublattice. An exception to this behavior, which is related to a slight (13%) increase of Icw at the 100 point, is discussed in the light of the pseudochalcopyrite model for the local bonding in III-V alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335354
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of the occupancy level of the DX center resonant with the conduction band in Te-doped AlGaSb (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 3015-3020 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The analysis of the amplitude of the deep level transient spectroscopy signal due to DX centers is exploited to determine the EDX occupancy level of the DX center in Te-doped AlxGa1−xSb in the range of low values of x where EDX is resonant with the conduction band. We take advantage of a small but still detectable change in the occupancy factor of the DX level induced by the filling pulse. It is shown that EDX is very close to the L conduction band edge for x≤0.20. This behavior is different from the one at x≥0.30 where EDX lies in the forbidden energy gap and exhibits an x dependence similar to the X edge. These results are discussed at the light of different atomic configuration for DX centers at an anion-substitutional impurity. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1445495
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  • 4
    Electronic Resource
    Electronic Resource
    In-plane electrical transport in n-type selectively doped GaSb/AlGaSb multiquantum wells (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5166-5170 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results are reported regarding in-plane electrical transport in n-type selectively doped GaSb/AlGaSb multiquantum wells. In the samples, which were grown by molecular beam epitaxy, only the central regions of the Al0.40Ga0.60Sb barriers were Te doped. Low-field, low-temperature Hall measurements in the dark demonstrated the presence in the GaSb wells of a degenerate electron gas with nonzero occupancy only for the lowest miniband. A positive persistent photoconductivity effect, related to the DX character of the Te impurity, was also observed. This behavior enabled the μ electron mobility to be measured at T=10 K as a function of the nS sheet carrier density. Since the experimental data were consistent with a dominant role of the interface roughness scattering in the limiting of μ, the height, Δ, and the lateral size, Λ, of the interface roughness were determined from the analysis of the μ=μ(nS) dependence. Acceptable values of Δ were obtained, consistent with results of structural investigations in single quantum well samples of GaSb/Al0.40Ga0.60Sb [E. Kh. Mukhamedzhanov, C. Bocchi, S. Franchi, A. Baraldi, R. Magnanini, and L. Nasi, J. Appl. Phys. 87, 4234 (2000)]. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1407310
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  • 5
    Electronic Resource
    Electronic Resource
    Hole injection in AlGaAs Schottky barriers: Influence on the DX center occupation (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5072-5078 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown that current instabilities, which are frequently observed at low temperatures in forward biased Schottky barriers on n-type AlGaAs, result from changes in the distribution of negatively charged donors (DX centers) near the metal contact. These changes cannot be ascribed to sample-heating effects, but they originate from hole injection in the barrier during forward biasing. The dominant mechanisms which are expected to induce the observed distortions in the DX center profile are (i) direct capture of the injected holes by the DX center and (ii) radiative electron-hole recombination resulting in DX center photoionization. The role of the two mechanisms is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355750
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  • 6
    Electronic Resource
    Electronic Resource
    Photoionization cross-section of the DX center in Te-doped AlxGa1−xSb (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 491-496 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoionization of DX centers in Te-doped AlxGa1−xSb layers grown by molecular beam epitaxy is investigated by measuring the increase of the Hall free electron density after illumination by monochromatic light in the temperature range typical of the persistent photoconductivity (PPC) effect. The investigated samples have AlSb molar fractions in the 0.3≤x≤0.5 range and n-type doping in the 1017−1018 cm−3 range. An accurate investigation of the isothermal photoionization transients is performed to evidence features in the curve not directly related to the phenomenology of the DX center, the free electron density being influenced by the possible occupancy of other impurity levels. The transients show, in particular, an initial nonexponential behavior which is demonstrated as due to localization of a fraction of the photoexcited electrons into a nonmetastable impurity state which is responsible for the semiconductor-to-metal transition observed under the PPC regime. When this effect is accounted for, the dependence of the photoionization cross section of the DX center on the photon energy was obtained from the analysis of the linear part of the transients and analyzed through a model given in the literature. The analysis gives values of the optical ionization energy and of the Frank-Condon shift varying in the ranges of 0.84–0.95 and 0.70–0.74 eV, respectively, depending on the alloy composition. This confirms a large lattice relaxation for the DX center related to the Te-impurity in AlxGa1−xSb. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366720
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  • 7
    Electronic Resource
    Electronic Resource
    Use of spatially dependent electron capture to profile deep-level densities in Schottky barriers (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 1285-1291 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new procedure to profile deep-level densities within the space-charge region of Schottky barriers is presented. The method takes advantage of the spatial dependence of the time constant for the free-electron capture by deep-donor traps. The amplitude of the slow component of the capture capacitance transient following a negative reverse voltage pulse is simply related to the trap density at the point where the Fermi level crosses the trap level itself. The density profile of a given trap can be achieved by measuring the slow-component transient signal as a function of the reverse voltage at a suitably chosen constant temperature. The estimated spatial resolution of the method was near 50 A(ring) in a practical case. Experimental density profiles for EL14, EL8, EL3, and the EC−ET =0.37 eV level in Cr/GaAs and Al/GaAs Schottky barriers are presented and discussed. The procedure is expected to be also applicable to the case of trap densities comparable with the shallow-donor density without introducing large errors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336096
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  • 8
    Electronic Resource
    Electronic Resource
    Occupancy level of the DX center in Te-doped AlxGa1−xSb (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 256-263 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hall effect measurements were performed in Te-doped AlxGa1−xSb layers grown by molecular beam epitaxy to investigate the composition dependence of the DX center occupancy level. The investigated samples have AlSb molar fractions in the 0.25≤x≤0.50 range and n-type doping of about 1018 cm−3. A family of x(approximate)0.40 samples of different doping (5×1015–1018 cm−3) were also studied. The Hall electron density data versus temperature were analyzed at high temperatures (T≥150 K) where the DX center is at equilibrium, by assuming the negative-U model for the DX level and by taking into account the multivalley conduction effects. The DX level, degenerate in energy with the conduction band at low x values, enters the forbidden gap at x(approximate)0.25 and then it becomes deeper with increasing x. In lightly doped samples, the introduction of a second level of the same Te impurity is required to fit the data; such level can be identified with the nonmetastable level which controls the low temperature electrical properties of the material. A critical discussion on the choice of the conduction band parameters for the fitting is reported. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369438
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  • 9
    Electronic Resource
    Electronic Resource
    Anharmonic contributions to the Debye–Waller factor for zinc (1976)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 32 (1976), S. 904-909 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Anharmonic contributions to the Debye-Waller factor of Zn for vibrations parallel to the c axis were obtained from the temperature dependence of integrated intensities for Bragg scattering at high temperatures. The Mössbauer technique was used to measure the purely elastic scattering. Both Gaussian and non-Gaussian contributions were found to be important. Their magnitude and sign were derived from the experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739476001812
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  • 10
    Electronic Resource
    Electronic Resource
    X-ray determination of the mean-square vibrational amplitudes of atoms in nearly perfect CdS crystals
    Amsterdam : Elsevier
    Journal of Physics and Chemistry of Solids 36 (1975), S. 421-426 
    Details
    ISSN: 0022-3697
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-3697(75)90068-2
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