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  • 1
    Electronic Resource
    Electronic Resource
    Influence of As incorporation on the deviation from Vegard's law in the AlxGa1−xSb/GaSb system (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4676-4678 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A possible unintentional incorporation of As in AlxGa1−xSb/GaSb heterostructures grown by molecular beam epitaxy in a chamber where group-III arsenides are also prepared, was investigated by high resolution x-ray diffraction measurements. The incorporation was determined by measuring the lattice mismatch between GaSb substrates and the possibly As-contaminated GaSb buffer layers in several structures containing layers with different Al concentration. The largest As molar fraction value measured is 0.000 43. The effect of the As incorporation on the deviation from Vegard's law, as previously found in the AlGaSb epitaxial system, was considered. From this analysis it was possible to confirm the nonlinear variation of the lattice constant versus the Al content, as previously determined. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1357460
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  • 2
    Electronic Resource
    Electronic Resource
    Measurement of aluminum concentration in the Ga1−xAlxSb/GaSb epitaxial system (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1298-1305 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The composition of several Ga1−xAlxSb epitaxial layers of different thicknesses grown by molecular beam epitaxy on GaSb with x ranging between 0.1 and 0.8, has been obtained independently by high resolution x-ray diffraction, Rutherford backscattering spectrometry, and reflection high-energy electron diffraction. From the comparison between the results obtained by the different experimental methods, it has been possible to point out that the lattice constant of the layer increases nonlinearly with the Al content. A comparison with theoretical models has been done. A phenomenological equation has been derived for a correct analysis of the x-ray results. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370885
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Optical study of strained and relaxed epitaxial InxGa1−xAs on GaAs (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6745-6751 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance (PR) at different temperatures and spectroellipsometry (SE) at room temperature were used to study, in a systematic and complementary way, the optical response of a series of strained and relaxed InxGa1−xAs (x〈0.15) epilayers. All the samples were grown by molecular-beam epitaxy on GaAs, both with and without a GaAs cap layer, which in the thinnest samples determines a single-quantum-well configuration. The effects of the strain on the optical structures E0, E1, and E1+Δ1 observed in the 1.2–3.3 eV photon-energy range were analyzed by fitting standard critical points (CP) line shapes to the PR and SE spectra. The CP experimental energies versus x were compared with the relations obtained in the framework of the elastic strain theory and, in the quantum-well structures, of the envelope-function scheme. The excellent agreement between experiment and theory allowed us to determine, independently and only by optical techniques, the strain ε and the composition x values, which compare well with those measured by x-ray diffraction. Additional information concerning the critical thickness for the pseudomorphic growth and the residual strain in quasirelaxed layers was achieved. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360498
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of different processes with hydrogen on the photoluminescence of GaAlAs:Si grown by molecular beam epitaxy (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2797-2799 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a study on low-temperature photoluminescence (PL) of Si-doped Ga1−xAlxAs (n ∼ 1×1017 cm−3, 0.2≤x≤ 0.5) grown by molecular beam epitaxy (MBE) either in the presence and in the absence of a hydrogen backpressure and/or post-growth hydrogenated by exposure to a hydrogen plasma; we show that GaAlAs grown with hydrogen has a PL efficiency higher than that of material grown without hydrogen by a factor of up to 20; even more interestingly, the relative enhancement of transitions related to excitons and to shallow donors and acceptors is so large that the two kinds of PL spectra are qualitatively different. On the contrary, independently on whether material grown without hydrogen is post-growth hydrogenated, the spectral features of PL spectra are dominated by transitions involving relatively deep donors and/or acceptors. Our results suggest that the two treatments with hydrogen act on deep levels of different origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103790
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  • 6
    Electronic Resource
    Electronic Resource
    Thermally activated carrier transfer and luminescence line shape in self-organized InAs quantum dots (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3354-3356 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the temperature dependence (10–180 K) of the photoluminescence (PL) emission spectrum of self-organized InAs/GaAs quantum dots grown under different conditions. The temperature dependence of the PL intensity is determined by two thermally activated processes: (i) quenching due to the escape of carriers from the quantum dots and (ii) carrier transfer between dots via wetting layer states. The existence of different dot families is confirmed by the deconvolution of the spectra in gaussian components with full width half maxima of 20–30 meV. The transfer of excitation is responsible for the sigmoidal temperature dependence of the peak energies of undeconvoluted PL bands. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117304
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  • 7
    Electronic Resource
    Electronic Resource
    Deep levels in virtually unstrained InGaAs layers deposited on GaAs (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 2965-2967 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dislocation-related deep levels in InxGa1−xAs layers grown by molecular beam epitaxy on GaAs substrates have been investigated. Virtually unstrained InGaAs layers with mole fraction x of 0.10, 0.20, and 0.30 have been obtained by properly designing the In composition of linearly graded InxGa1−xAs buffers. Two electron traps, labeled as E2 and E3, whose activation energy scales well with the energy gap, have been found. Unlike E2, E3 shows: (i) a logarithmic dependence of the deep level transient spectroscopy amplitude on the filling pulse width and (ii) an increase of concentration as the buffer/InGaAs interface is approached. These findings, together with the observation that, in compressively strained In0.2Ga0.8As, the E3-related concentration is definitely higher than that of virtually unstrained In0.2Ga0.8As, indicate that this trap is likely originated by extended defects like threading dislocations. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368404
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  • 8
    Electronic Resource
    Electronic Resource
    Optical investigation of interface roughness and defect incorporation in GaAs/AlGaAs quantum wells grown with and without growth interruption (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2150-2152 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a comparative analysis of photoluminescence and photoluminescence excitation of GaAs/AlGaAs quantum well structures grown by molecular beam epitaxy with and without growth interruption, which clearly indicates the improvement of interface quality when interruptions are used during growth. Time resolved spectroscopy, together with the temperature dependence of the integrated radiative recombination intensity, are used as a sensitive probe of the defect incorporation, which is usually observed to increase as a consequence of growth interruptions. We find that a significant increase of both extrinsic photoluminescence and nonradiative processes is not a necessary consequence of growth interruptions, unlike recent reports in the literature. We conclude that growth interruptions are compatible with the growth of high quality quantum well structures with a very high radiative efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106109
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  • 9
    Electronic Resource
    Electronic Resource
    Deep levels in GaAs grown by atomic layer molecular beam epitaxy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2848-2850 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a study on deep levels in GaAs:Si grown by atomic layer molecular beam epitaxy (ALMBE). We show that in ALMBE GaAs grown at temperatures TS in the range 370–530 °C, the deep level concentrations: (i) are up to 3 orders of magnitude smaller than those of material grown by molecular beam epitaxy (MBE) at similar temperature ranges, and (ii) can be compared to those of GaAs grown by MBE at 600 °C. These features are independent whether Si is supplied during: (a) both the Ga and As subcycles, (b) the As subcycles, or (c) the Ga subcycles. Therefore, as for deep levels, ALMBE GaAs grown at 370≤TS≤530 °C can be related to GaAs prepared by MBE at conventional temperatures. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112512
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  • 10
    Electronic Resource
    Electronic Resource
    Lattice strain relaxation study in the Ga1−xAlxSb/GaSb system by high resolution x-ray diffraction (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1549-1551 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Lattice strain relaxation has been studied in the Ga1−xAlxSb/GaSb system by analyzing layers with thicknesses ranging between 0.1 and 6 μm and with Al concentration x=0.4. The samples have been grown by molecular beam epitaxy at 550 °C on (001) oriented undoped GaSb substrates. The heterostructures were investigated by a high resolution x-ray diffraction method. The experimental critical thickness for the strain relaxation has been found to be tc(approximate) 310 nm. The measured residual strain εres shows a t−0.47 dependence on the layer thickness t. This result is in agreement with the theoretical predictions based on the energy balance model, and cannot be described in the frame of the equilibrium theories which yield εres∝t−1. The values of εres have been corrected by the so-called thermal misfit (ΔT) for epitaxial systems with different thermal expansion coefficients. For the Ga0.6Al0.4Sb/GaSb epitaxial system grown at TG=550 °C, the value ΔT=−3.28×10−4 has been calculated from the literature data.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119962
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