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  • 1
    Electronic Resource
    Electronic Resource
    As desorption from GaAs and AlAs surfaces studied by improved high-energy electron reflectivity measurements (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1753-1759 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The desorption of As from GaAs (001), (111)B, and AlAs(001) is studied in detail by measuring the electron-beam current reflected from these surfaces. When the As supply to the surface was terminated, the electron specular reflectivity decreases exponentially with time due to the As desorption. The decay rate was much smaller for AlAs (001) than for GaAs (001) and (111)B, which indicates stronger atomic bonding for AlAs than for GaAs. For the GaAs (001) surface, the decay rate and the activation energy for the decay in specular reflectivity change discontinuously at the transition between (2×4) and (3×1) reconstructions. This shows the As desorption process is sensitive to the transition of surface reconstruction. The dependence of the As desorption rate on the thickness of the top GaAs layer in GaAs/AlAs heterostructures indicates an abrupt change of bond strength near the interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351209
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  • 2
    Electronic Resource
    Electronic Resource
    Replacement of group-III atoms on the growing surface during migration-enhanced epitaxy (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1610-1615 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An InAs monolayer is grown between GaAs layers using migration-enhanced epitaxy. The surface chemical characteristics during growth are investigated by reflection high-energy electron diffraction. With low As4 pressure and with a substrate temperature of 500 °C, the oscillation amplitude of the reflected electron beam after growth of one monolayer of InAs vanishes during the growth of GaAs over more than 20 atomic layers. High-resolution secondary-ion-mass spectroscopic analysis and photoluminescence characteristics of fabricated structures indicate an anomalous distribution of In atoms with a gradual slope toward the growth direction only when the substrate temperature is 500 °C. Numerical calculation shows that the experimental results are explained by the In atoms in the InAs monolayer being replaced by subsequently deposited Ga atoms. The comparison between experimental results and calculated ones indicates that replacement occurs with a probability of 98% at 500 °C. An InGaAs layer was also grown on an InP substrate using migration-enhanced epitaxy with the deposition of two monolayer metallic atoms per one cycle. X-ray diffraction analysis shows that the composition is modulated with a period of two monolayers in the grown InGaAs layer. This phenomenon is also explained in terms of metallic atom replacement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346640
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of indium replacement by gallium on the energy gaps of InAs/GaAs thin-layer structures (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7697-7702 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Energy gaps of InAs/GaAs thin-layer structures are calculated using a modified finite square well model, which takes into account In-Ga replacement during growth. We compare the calculated results with the experimental energy gaps of structures grown by flow-rate modulation epitaxy, which is based on an alternate supply of gaseous sources, and molecular-beam epitaxy. The results indicate that In-Ga replacement is rare in flow-rate modulation epitaxy, but about 90% of the surface In atoms are replaced with the Ga atoms in molecular-beam epitaxy. Arsenic has a low sticking coefficient on the In surface, so it is difficult to achieve high As coverages on the In surface in molecular-beam epitaxy. In flow-rate modulation epitaxy and metalorganic chemical vapor deposition, the dangling bonds of the surface As atoms are probably terminated by hydrogen atoms. The surface As atoms are stabilized by establishing stable sp3 orbitals and prevent In-Ga replacement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347542
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  • 4
    Electronic Resource
    Electronic Resource
    Multiphonon-assisted energy transfer between Yb 4f shell and InP host (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7288-7295 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The energy transfer mechanism between an Yb 4f shell and an InP host was investigated, assuming that a nonradiative multiphonon process assists the energy transfer. The values of the energy involved in the energy transfer were determined from the results of optical and electrical experiments. Rate equations were solved to obtain the temperature dependence of the Yb intra-4f-shell luminescence decay time. The calculated results and the experimentally obtained temperature dependence agree well. The calculated temperature dependence of the Yb intra-4f-shell luminescence intensity also agrees with the experimental measurements. These results strongly suggest that phonon absorption and emission compensate the energy mismatch in the energy transfer processes. The calculations also indicate that the thermal quenching phenomenon is mainly determined by the energy mismatch between the recombination energy of an electron and a hole and the Yb 4f-shell energy between the excited and ground states. On the basis of the above formulation, the Yb intra-4f-shell luminescence intensity under hydrostatic pressure was also investigated theoretically and compared with experimental results. The 4f-shell luminescence recovery at elevated temperature under hydrostatic pressure was qualitatively explained in the framework of the present model. The characteristic behavior of the thermal quenching in other rare-earth doped semiconductors could also be explained qualitatively assuming that the energy transfer mechanism is similar to the one for InP:Yb. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358014
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  • 5
    Electronic Resource
    Electronic Resource
    Epitaxial growth of AlAs/CoAl/AlAs(001) heterostructures by controlling the metal surface (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6013-6026 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial growth of CoAl films on AlAs(001) films was examined for films with Co contents of 47–58 at. %. The surface terminations of CoAl films were characterized, and the dependance of surface terminations and surface reconstructions on the Co/Al composition was examined. When AlAs/CoAl/AlAs heterostructures were fabricated by growing AlAs overlayers on CoAl films whose surface terminations were well defined, a mixture of AlAs(001) and AlAs(111) phases grew on the Al-terminated surface, whereas only the AlAs(001) phase grew on the Co-terminated surface. The Co-terminated CoAl surface thus is suitable for the overgrowth of AlAs. A high-quality epitaxial GaAs/AlAs/CoAl/AlAs/GaAs heterostructure was grown by combining the control of metal surface terminations with low-temperature migration-enhanced epitaxial growth of AlAs overlayers. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360608
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  • 6
    Electronic Resource
    Electronic Resource
    Study of photoconductivity in AlxGa1−xAs/GaAs modulation-doped heterostructures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3592-3596 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature-dependent Hall effect measurements under different illumination conditions are performed on AlxGa1−xAs/GaAs heterostructures doped with both Si and Sn. For a Sn-doped AlxGa1−xAs/GaAs heterostructure with x=0.35, two distinct DX center levels are observed directly without exposure to light. The two-dimensional electron gas concentration measured under illumination decreases from the value due to persistent photoconductivity to a value less than that measured in the dark when the excitation photon energy is larger than the band gap of the AlGaAs barrier. This decrease occurs only at temperatures below 90 K. This negative photoconductivity is explained by taking into account the partial freeze-out of electrons into the shallow DX centers and the transfer of holes photogenerated in the barrier into the channel region. No such phenomena are observed in Sn-doped heterostructures with x 〈0.35 or in the Si-doped heterostructures. The reasons for this are also investigated. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361412
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  • 7
    Electronic Resource
    Electronic Resource
    High-field magneto-optical study of type-II GaAs/AlAs short-period superlattices (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 96-98 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetoabsorption and magnetophotoluminescence spectra of type-II (GaAs)m/(AlAs)n superlattices with (m,n)=(3,5) and (5,6) have been measured in pulsed high magnetic fields up to about 40 T. Large dependence of the diamagnetic shift of the excitons on the field direction was observed in magneto-photoluminescence spectra, strongly suggesting XZ character of the conduction band minima for these values of m and n. Oscillatory structures related to the higher lying Γ-like conduction band are also resolved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105535
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  • 8
    Electronic Resource
    Electronic Resource
    Direct comparison of GaAs surface morphology between migration enhanced epitaxy and molecular beam epitaxy using in situ scanning electron microscopy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 63-65 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used scanning electron microscopy (SEM) for real-time-observation to compare the surface evolution during the early stage growth of GaAs with molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE), at the substrate temperature of 500 °C. Surface roughness during MEE growth is about 1 ML and much smaller than during MBE growth. Immediately after growth termination, monolayer steps can be seen and the surface recovers to initial smoothness in MEE, while islands do not disappear without higher temperature annealing in MBE. Present results confirm high surface atom mobility in MEE growth. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116758
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  • 9
    Electronic Resource
    Electronic Resource
    Modulation of quantized levels of GaAs/AlGaAs quantum wells by InAs monomolecular plane insertion (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1555-1557 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs/AlGaAs quantum well structures with InAs monomolecular planes are fabricated by flow-rate modulation epitaxy. Photocurrent spectra of these structures are measured to investigate the effect of the InAs planes on the quantized levels. The InAs monomolecular plane inserted at the center of the well shifts the transition peak between the lowest levels (n=1 heavy hole and electron), but does not shift the transition peak between n=2 levels. The amplitude of the wave function for the electrons and holes on the n=2 levels is zero at the center of the well. Therefore, an InAs plane at the center does not modify the distribution of the n=2 carriers. When two InAs planes are inserted in a well and the distance between the two planes is varied, both n=1 and n=2 transition peaks are shifted. Measured spectra are well explained by a finite square well model calculation using the band parameters of GaAs and strained InAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103172
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  • 10
    Electronic Resource
    Electronic Resource
    Low-frequency resonant Raman scattering in AlAs-GaAs atomic-layer superlattices (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1614-1616 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: New Raman lines are observed at the lowest ever frequencies in (AlAs)1(GaAs)n (n=1,2,3) atomic-layer superlattices under band-gap resonant excitation at low temperature. These lines appear in the 30–60 cm−1 region and their intensity is resonantly enhanced as the excitation photon energy approaches the photoluminescence peak energy. Analyses using the elastic continuum model indicate that these lines could be attributed to folded transverse acoustic phonons near the Brillouin-zone edge of the superlattices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99928
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