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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3760-3762 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we report magneto-photoluminescence measurements on stacked self-assembled InAs quantum dots. By applying a magnetic field parallel to the growth direction, we determined the exciton reduced mass and exciton radius from the photoluminescence (PL) peak energy. We observed an asymmetric increase of the full width at half maximum of the quantum dots PL peak to the high-energy side that we associate to the size selectivity of the oscillator strength of the ground state transitions. The observed increase of the integrated intensity of the quantum dots line is explained in terms of the reabsorption of the photons emitted by the GaAs substrate and the InAs wetting layer. These effects are related to the multilayer structure of the sample. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3283-3287 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photo Hall concentration and mobility were measured for two molecular beam epitaxy-grown samples having a silicon planar-doped structure in the GaAs layer of a GaAs/AlGaAs heterojunction. The nominal silicon concentration for both samples was 1.5×1013 cm−2 and the distance between the ideal localization of the doped plane and the interface was adjusted to be 15 A(ring). The difference between the two samples is the growth direction. The Hall measurements were carried out at 77 K both in darkness and under illumination using an infrared light emitting diode as light source. Photoexcited effects indicate the presence of silicon atoms inside the undoped AlGaAs layer and that the silicon profile spreads mainly in the growth direction. Self-consistent electronic structure calculations, in the effective-mass approximations, were performed assuming doping profiles that simulate both samples. The calculations show that parallel conduction occurs when the growth direction is from GaAs to AlGaAs. This is consistent with the Hall measurements. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 8051-8054 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The optical properties of a Si-doped Al0.3Ga0.7As alloy are studied as a function of the Si dopant concentration by means of photoluminescence measurements. The photoluminescence spectra show peaks due to electron Si acceptors and Si-related complex-defects transitions, which we tentatively attribute to Si acceptor coupled to an As vacancy (SiAs-VAs) and Si donor coupled to a Ga(Al) vacancy (SiIII-VIII). We show that the importance of each of these defects to the alloy optical properties is strongly dependent on the growing parameters. Spectrum for a planar-doped sample also showing peaks related to Si complex defects is presented. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 820-823 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the current density as a function of the applied bias have been performed to study the electronic properties of the Al:n-GaAs(100) interface. The samples were grown by molecular beam epitaxy. A Si planar doping was placed in GaAs(100) at different depths underneath the metal-semiconductor interface and the charge transport across this interface has been investigated. An increasing tunneling contribution to the net current through the Schottky barrier has been observed by decreasing the planar doping depth. For sufficiently small depths, the tunneling current dominated. Planar doping near the metal-semiconductor interface was found to be equivalent, concerning charge transport properties, to a bulk semiconductor doped well beyond the currently achievable limit.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2659-2665 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoconductivity, photo-Hall free carrier concentrations and mobilities were measured on molecular beam epitaxy-grown silicon planar-doped GaAs samples, with silicon concentrations between 1.4×1012 and 8.8×1013 cm−2, as functions of temperature. In all samples, the planar-doped region is placed 0.2 μm below a n+-doped cap layer at the surface. We perform a systematic investigation of the persistent as well as nonpersistent photoconductivity effects which are present in all samples. A phenomenological analysis shows the presence of two distinct conduction channels, one with n characteristics and the other with p characteristics. These channels can present either bulk or two-dimensional characteristics, depending on the light intensity and on the temperature. A model based on spatial separation between electrons and holes is proposed to account for the persistence of the photoconductivity effect. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6541-6544 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have carried out the time, temperature, and illumination dependencies of the current density in a semi-insulating GaAs sample grown at 300 °C under strong electric field. Standard ohmic behavior was observed at room temperature. A negative differential behavior as a function of the applied electric field was observed by lowering the temperature and increasing the photon flux, and this phenomenon was associated to the field-enhanced trapping effect. We have fit our data with a model for enhanced capture by a multiple-phonon emission capture process assisted by the applied electrical field. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 3764-3769 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using thermally stimulated current (TSC) spectroscopy we have identified the presence of several deep traps in low temperature grown (LTG) nonintentionally doped bulk molecular beam epitaxy (MBE)-GaAs and silicon planar-doped MBE-GaAs samples. The experiments of TSC spectroscopy were carried out on a LTG MBE-GaAs epilayer grown at 300 °C and the planar-doped layer with a nominal silicon concentration of 3.4×1012 cm−2. The LTG nonintentionally doped bulk MBE-GaAs sample shows three peaks in the TSC spectra but the planar-doped MBE-GaAs sample shows spectra similar to those of bulk samples grown by the liquid-encapsulated Czochralski and vertical gradient freeze methods. The main achievement is the experimental evidence that the potential well present in the planar-doped sample is effective in detecting the presence of different deep traps previously not seen in LTG bulk MBE-GaAs epilayers due to a shorter carrier lifetime (about 10−12 s) in the conduction band which occurs due to EL2-like deep traps recombination. This fact is evidenced by a strong hopping conduction in LTG bulk MBE-GaAs samples at temperatures lower than 300 K, but not in planar-doped MBE-GaAs samples because the two-dimensional electron gas has a higher mobility than lateral LTG bulk MBE-GaAs epilayers. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, grazing incidence x-ray scattering is employed as a method to identify relaxed islands in an ensemble of partially coherent self-assembled InAs quantum dots. A simple model of strained pyramidal islands enables the association of the local lattice parameter of an island to its lateral size. A comparison between the island side length and its strain state allows the identification of coherent and incoherent nanostructures, revealing the size–strain interplay during growth. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3400-3402 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on experiments aimed at producing three-dimensional self-organization in InAs quantum-dot multilayers embedded in GaAs. These InAs/GaAs quantum-dot multilayers have been grown by molecular beam epitaxy. Employing atomic force microscopy, we have analyzed the island density in samples with different number of periods of InAs/GaAs bilayers The results reveals a decrease and a tendency to saturation of the island density with an increase in the number of periods, as a three-dimensional self-organization characteristic of these samples. Optical properties of the samples are examined via photoluminescence spectroscopy. The evolution of the quantum-dot photoluminescence peak position indicates an increment in the mean size of the buried islands and a relative homogenization in size of the quantum dots, as the number of periods increases. The results of the optical measurements agree with the morphological data, and characterize a spatial process of self-organization, related to the increment of the number of periods in the multilayers. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1056-1058 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The degree of vertical alignment of InAs quantum dots in InAs/GaAs(001) multilayers was studied using grazing incidence x-ray scattering. We show that it is necessary to access one of the weak (200) x-ray reflections to observe the modulation of the GaAs lattice periodicity produced by the stacking of the InAs dots. The degree of alignment of the dots was assessed by fitting the x-ray diffuse scattering profiles near a GaAs (200) reciprocal lattice point. By using a model of gaussian lateral displacement of the dots, we show that we can determine the average value of the mistake in stacking positions of the islands from one bilayer to the next. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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