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  • 1
    Electronic Resource
    Electronic Resource
    Self-organized InGaAs quantum dots on GaAs (311)B studied by conductive atomic force microscope tip (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 192-196 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used conductive atomic force microscope (AFM) tips in order to probe the local electronic properties of InGaAs quantum dots (QDs) grown on GaAs (311)B and (001) substrates by atomic H-assisted molecular beam epitaxy. Highly doped Si and Si3N4 AFM tips coated with a metal such as Au and Ti which warrant electrical conductivity were used to measure the current–voltage (I–V) characteristics of QDs of varying sizes and of any other arbitrary positions on the surface such as the wetting layer. In the case of QDs formed on (001) substrates, it was found that the local surface potentials of larger QDs were lower than the small QDs due to the effect of surface states. On the other hand, noticeable differences were not observed for the QDs formed on (311)B substrates. The local surface potential was similar on each QD and in fact over the whole (311)B surface, and a complex phase separation and strain-relief mechanism were thought to be responsible the observed QDs assembly on (311)B. Last, a resonant tunneling characteristics through the quantized energy levels was studied with a small QD with ∼45 nm in diameter and ∼4 nm in height. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1377302
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  • 2
    Electronic Resource
    Electronic Resource
    Highly packed InGaAs quantum dots on GaAs(311)B (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3411-3413 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated highly packed and ordered In0.4Ga0.6As quantum dots (QDs) array on GaAs(311)B substrate without coalescence of QDs. Reflection high-energy electron diffraction and Auger spectra suggest the inhomogeneous distribution of In and Ga in QD. In concentration near the surface of QD is larger than that of the inside, and the inhomogeneous distribution of In and Ga in QDs prevents QDs from merging. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122781
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  • 3
    Electronic Resource
    Electronic Resource
    Low dislocation density GaAs on Si heteroepitaxy with atomic hydrogen irradiation for optoelectronic integration (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7376-7384 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Basic experimental results obtained for the low-temperature molecular beam epitaxy with atomic hydrogen have been presented. GaAs films grown at different substrate temperatures have exhibited different values of dislocation densities and the average dislocation density as low as 3×104 cm−2 has been successfully obtained for the films grown at a low-temperature of 330 °C with atomic hydrogen irradiation. These are among the lowest dislocation values reported to date. The surface cleaning effects and reconstruction of vicinal Si(100) surfaces during the atomic hydrogen irradiation, and also the electrical properties of epitaxial films have been investigated and analyzed. Physics behind the drastic dislocation density reduction has been investigated in detail based on the results of cross-sectional and plan-view transmission electron microscope observations and analysis of the growth kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354029
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  • 4
    Electronic Resource
    Electronic Resource
    Be diffusion mechanism in GaAs investigated by slow positron beam (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6364-6368 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The slow positron beam technique was applied on undoped and Be-doped GaAs to study the effects of Be impurities on both creation and migration of Ga vacancies, VGa, during annealing. It is observed that a monovacancy of VGa is created in Be-doped GaAs to result in enhanced Coulombic interaction between As vacancy, VAs, and Be acceptor, BeGa. In undoped GaAs, the formation of divacancies, VGa-VAs, is dominant. The migration depth of vacancies is shorter in Be-doped GaAs than in undoped GaAs. This suggests the existence of Ga interstitials, IGa, in the Be diffused layer which interact with VGa introduced from the surface. Based on these observations, we suggest the kick-out mechanism for Be diffusion in GaAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348971
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  • 5
    Electronic Resource
    Electronic Resource
    Impurity effects on both the creation and the migration of Ga vacancies in GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 674-684 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of impurities, such as Si and Be, on both the creation and the migration of Ga vacancies in annealing of GaAs were investigated by a slow positron beam technique. The results show that vacancies diffuse from the surface during the annealing and one of the dominant types is a monovacancy of Ga, VGa, in Be-doped GaAs and/or Si-doped GaAs, while the other is a divacancy of VGa-VAs in undoped GaAs. In annealing the bilayer structures composed of the Si-doped layer grown on the Be-doped layer, it was found that VGa is a major type of defect rather than VGa-VAs if the Si concentration is higher or lower than the Be one in GaAs, but VGa-VAs is dominant if the concentrations of the impurities are similar. This proposes that the interaction between Si and Be is stronger than that of VAs-BeGa and/or VGa-SiGa. The Ga interstitial IGa is created in the Be-doped layer where IGa interacts with VGa created from the surface and suppresses the migration of VGa. This supports the validity of the kick-out mechanism involving a column-III interstitial rather than the Longini mechanism for Be diffusion in GaAs. In Si-doped GaAs, VGa is created from the surface and the diffusion constant of VGa decreases with the increase of Si doping concentration. This implies that VGa forms a complex of SiGa-VGa and the interaction time of VGa at the Si donor by making a complex of SiGa-VGa is a rate-limiting step in the diffusion of VGa in GaAs. The present results propose the creation of IGa and VGa in the Be-diffused GaAs and in Si-diffused GaAs, respectively. This is consistent with the Fermi-level effect of the impurities on the creation of those defects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349647
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  • 6
    Electronic Resource
    Electronic Resource
    Formation of extended states in disordered two-dimensional In0.4Ga0.6As/GaAs(311)B quantum dot superlattices (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 227-235 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Formation of extended states or minibands in two-dimensional (2D) In0.4Ga0.6As/GaAs(311)B quantum dot superlattices (QDSLs) is directly demonstrated in time-resolved photoluminescence measurements. At a low excitation density of 1 W/cm2, photoluminescence transients with ∼15 ps rise time and ∼25 ps decay time are observed. Both rise and decay times are found to increase with increasing excitation density. The excitons in 2D QDSLs exhibit different relaxation and recombination behaviors as compared to those in quantum wells and quantum dots. A physical model treating 2D QDSLs as disordered systems containing localized and extended states can successfully interpret all of the experimental observations. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373706
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  • 7
    Electronic Resource
    Electronic Resource
    Scanning probe microscope tip-induced oxidation of GaAs using modulated tip bias (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8754-8758 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the basic mechanisms that determine the lateral resolution limits in the tip-induced nano-oxidation process of n+-GaAs(100) substrates. For this purpose, a set of systematic experiments and measurements were conducted. First, the cross-sectional profiles of GaAs oxide nanodots were investigated upon which the relationship between the measured profiles and oxidation parameters were studied. The current that flows during oxidation was monitored and analyzed. It is shown that the fundamental mechanism that governs the lateral resolution would be a finite electrical conductance of an adsorbed thin water film existing between the substrate and the tip, which then acts to defocus the electric field required for the oxidation. Second, the use of a modulated or pulsed bias with a short voltage duration in the range of 10–100 ms upon oxidation was proposed in order to improve the lithographic performance. The lateral resolution and aspect ratio were significantly improved with the modulated/pulsed tip bias scheme. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373606
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  • 8
    Electronic Resource
    Electronic Resource
    Atomic hydrogen-assisted molecular beam epitaxy for the fabrication of multi-quantum-well solar cells (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5858-5861 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The atomic hydrogen-assisted molecular beam epitaxy (H-MBE) technique has been applied to fabricate multi-quantum-well (MQW) based compound semiconductor solar cells. A number of different InGaAs/GaAs MQW structures were inserted within the photon absorption region of a p–i–n GaAs junction diode. The spectral response characteristics of each device with varying number, thickness, and In composition of MQWs were measured and analyzed to investigate the effects of atomic H on the device performance. In the photon wavelength region of 800–1000 nm, the spectral response of H-MBE-grown cells was increased by 〉25% for the GaAs homojunction control cell, and by as much as ∼35% for a 10-period MQW cell (In0.07Ga0.93As: GaAs=50 nm:50 nm) as compared to the conventionally MBE-grown cells with identical layer structures. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371603
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  • 9
    Electronic Resource
    Electronic Resource
    Basic properties of GaAs oxide generated by scanning probe microscope tip-induced nano-oxidation process (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1136-1140 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The basic properties of GaAs oxide generated by atomic force microscope (AFM) tip-induced nano-oxidation process have been investigated. The chemical analysis of the AFM tip-generated GaAs oxide was performed by using scanning microprobe x-ray photoelectron spectroscopy, and the main constituents of GaAs anodic oxide were determined to be Ga2O3 and As2O3. The electrical characterization showed that the electron transport across a GaAs oxide nanodot of ∼5.7 nm thickness, from a doped n+-Si tip into the n+-GaAs substrate follows the Fowler–Nordheim tunneling mechanism over a range of applied bias. Further, the tip-generated GaAs oxide nanodots were found to withstand moderate thermal treatments, but some volume reduction was observed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373788
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  • 10
    Electronic Resource
    Electronic Resource
    Impurity effect on the creation of Ga vacancies in a Si-doped layer grown on Be-doped GaAs by molecular-beam epitaxy (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5571-5575 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The impurity effects on the creation of Ga vacancies in Si-doped GaAs grown on a Be-doped epilayer by molecular-beam epitaxy were investigated through slow positron beam measurements. Doping of Si impurities enhances the creation of Ga vacancies in GaAs. The experimental results support the theoretical prediction of the creation of Ga vacancies in terms of the change in the Fermi-level position by the Si doping into GaAs, and also suggest that a Si atom diffuses in GaAs as a neutral complex of SiGa-VGa rather than that of SiGa-SiAs. The change in the S parameter distribution at the interface between Si and Be-doped regions is explained by the Be carryforward phenomenon which occurs during the growth of Si-doped GaAs on a Be-doped epilayer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346992
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