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  • 1
    Electronic Resource
    Electronic Resource
    Growth optimization of n-type GaAs on GaAs(201) substrates (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 612-614 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the growth by molecular-beam epitaxy of Si-doped n -type GaAs on the GaAs(201) surface is presented. The motivation for attempting growth on this particular plane, apart from fundamental considerations, is in connection with an investigation of off-axis transport in GaAs. The effects of growth temperature and doping on GaAs(201) and GaAs(100) samples have been compared using the Hall effect, low-temperature photoluminescence (PL), and Nomarski interference contrast microscopy. These studies showed that the PL, onset of conduction, and mobility behavior were very similar for both orientations. It was possible to dope n-GaAs/GaAs(201) reliably from NSi∼4×1014 to 6×1018 cm−3, the highest mobility of 96 000 cm2 V−1 s−1 measured at 77 K, being obtained for a sample doped at NSi∼4×1014 cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357056
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  • 2
    Electronic Resource
    Electronic Resource
    Strain, alloy composition, and lattice relaxation measured by optical-absorption spectroscopy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3393-3398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The validity of optical absorption (OA) as a technique for the measurement of strain e11, alloy composition x, and relaxation in InxGa1−xAs epilayers on InP has been examined by comparison with similar measurements by double-crystal x-ray diffraction (DCXD). Provided that the strain arising from differences in the thermal contraction of the substrate and epilayer are taken into account, measurements of strain by OA show good agreement with DCXD results, with a dispersion of Δe11=±0.27×10−3. Comparison of alloy compositions given by the two techniques shows similarly good agreement, with a dispersion in the values of x of less than Δx=±0.7%. OA may also be used to determine lattice relaxation. The degree of uncertainty in the measurement of this parameter increases as lattice match is approached and decreases as the lattice relaxes. Our studies indicate that OA may be used as an independent technique to evaluate strain, alloy composition, and the degree of lattice relaxation in InxGa1−xAs epilayers. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358629
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  • 3
    Electronic Resource
    Electronic Resource
    Investigation of silicon delta-doped gallium arsenide using the Shubnikov–de Haas effect and theoretical modeling (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3583-3588 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a detailed study of electron sub-band occupancies and saturation effects in silicon delta-doped gallium arsenide samples, using Hall and Shubnikov–de Haas (SdH) measurements in conjunction with numerical modeling. This study extends previous work in two respects. First, the samples, produced by molecular beam epitaxy with a nominal delta doping density of 1×1013 cm−2, were examined over a wide range of growth temperature (395–710 °C) to allow the influence of broadening of the doping profile to be examined. Second, the numerical modeling method, based on a self-consistent solution of Poisson's and Schrödinger's equations, included directly the influence of DX-like donor levels, located at 200 meV above the conduction band edge. Excellent agreement with the individual sub-band occupancies determined by SdH was found for all samples up to a growth temperature of 605 °C, with the total silicon doping density kept constant and dopant broadening as the only adjustable parameter in the fit. Despite the evidence for inclusion of DX-like donor levels based on our modeling, all samples showed only a weak persistent photoconductivity effect. This is in contrast to uniformly doped bulk GaAs, indicating the different nature of the DX level in two and three dimensional doping. Above 605 °C it was not possible to model sub-band occupancies using a constant total doping density, showing that another deactivation mechanism such as autocompensation becomes important.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357418
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  • 4
    Electronic Resource
    Electronic Resource
    Optical and electrical properties of selectively delta-doped strained InxGa1−xAs/GaAs quantum wells (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2627-2632 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report here an investigation of selectively delta-doped strained InGaAs/GaAs quantum wells. Electronic structures of the systems were calculated by self-consistently solving the Schrödinger and Poisson equations and the calculations revealed a systematic variation of the band structure as the delta sheet moved away from the center of the well to the edge and finally to the barrier. The results were found to be in agreement with our photoluminescence (PL) measurements. For center-doped samples, band-gap renormalization was found to be strong from the PL data, and our realistic random-phase approximation calculation for the heavily doped sample is in excellent agreement with the PL data. The radiative lifetimes were measured to be around 450 ps for all the samples, and surprisingly they vary very little from sample to sample although the wave-function overlap was considerably different for some samples. We also report Shubnikov–de Haas (SdH) measurements on the two barrier doped cases. For the heavily doped sample (A12132), two oscillation signals were detected and they were identified as two upper subbands. The measured electron densities were in very good agreement with the self-consistent calculation. Illumination did not make any difference to the measured densities. For the low-doped sample (A12025), however, the measured electron density before illumination is much smaller than the calculated, and illumination was found to make a large difference. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361133
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  • 5
    Electronic Resource
    Electronic Resource
    In situ reflectance anisotropy studies of AlxGa1−xAs layers grown on GaAs(001) by molecular beam epitaxy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3115-3120 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reflectance anisotropy spectroscopy was used to examine the surfaces of AlxGa1−xAs layers grown on GaAs(001) by molecular beam epitaxy, where the Al mole fraction was varied across the whole composition range x=(0.0,0.25,0.50,0.75,1.0). All surfaces were also independently characterized using reflection high-energy electron diffraction, and were found to exhibit a c(4×4) reconstruction. After initial changes in the spectra were observed on depositing very thin layers (≤20 monolayers), in the intermediate thickness range a regime was entered in which strong optical interference effects appeared. These effects are accurately accounted for using a four-media model. For thicker layers (≥8000 monolayers), interference effects were seen to diminish and spectra representative of the surfaces of bulk AlxGa1−xAs were obtained. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358663
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  • 6
    Electronic Resource
    Electronic Resource
    State-of-the-art AlGaAs alloys by antimony doping (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1300-1305 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Historically GaAlAs alloys grown by molecular-beam epitaxy have high deep level concentrations (〉1016 cm−3), low luminescent efficiency with broad peaks, and are difficult to dope controllably below mid 1016 cm−3. We report the effect that the low incident antimony molecule fluxes during growth appear to help reduce the density of deep levels below 1014 cm−3, which then allows reproducible doping control in the low 1015 cm−3 range. Exciton-dominated photoluminescence with half widths ∼4.0 meV are now routinely achieved using this technique. Further evidence for the quality improvement of AlGaAs by heavy atom (Sb) doping comes from high 4 K two-dimensional electron gas mobilities for low sheet electron densities, e.g., 1.3×106 cm2/V s for n=2×1011 cm−2. SIMS profiles of antimony content are presented and estimates of incorporated concentrations are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337300
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  • 7
    Electronic Resource
    Electronic Resource
    Residual strain measurements in thick InxGa1−xAs layers grown on GaAs (100) by molecular beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 1187-1192 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The final stages of strain relief in the lattice mismatched InxGa1−xAs/GaAs(100) system are addressed by the examination of the residual strain in thick films (∼3 μm), grown by molecular beam epitaxy, across the entire compositional range. These results are compared with the observed variations in both the growth mode and material quality, and related to available theories. It is found that measurements are not consistent with a degradation of material quality that is simply misfit dependent, or to an abrupt change from two-dimensional (2-D) to three-dimensional (3-D) growth in the relaxation stage. Instead, the results seem to be more consistent with a continuous change from 2-D to 3-D growth between x=0 and x=0.4 (it is wholly 3-D above x=0.4). In addition, the large residual strains observed around x=0.5 are related to the poor material quality (possibly through work hardening) at this composition, which is in turn due to problems peculiar to the growth of mismatched alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354040
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  • 8
    Electronic Resource
    Electronic Resource
    The molecular beam epitaxial growth of GaAs/GaAs(111)B: doping and growth temperature studies (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4908-4915 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of investigations are presented which address various aspects of the growth, by molecular beam epitaxy, of n-type (Si doped) on-axis GaAs/GaAs(111)B. In situ characterization by reflection high-energy electron diffraction has identified four surface phases on the static (zero growth rate) surface, and three reconstructions which occur, depending upon the substrate temperature, during growth. The n-type doping properties of GaAs/GaAs(111)B epilayers have been compared with n-GaAs/GaAs(100) structures. Hall effect and low-temperature photoluminescence measurements have demonstrated that it is possible to dope GaAs/GaAs(111)B with Si in the 6×1014 to 1018 cm−3 range. A variable growth temperature study is also presented which examines the surface structural, electrical, optical, and surface morphological properties of n-GaAs/GaAs(111)B grown in the 400 to 650 °C temperature range. The onset of electrical conduction, and optically active material, was found to be directly related to changes in the dynamic surface structure. The variable growth temperature study also revealed a temperature regime within which it was possible to significantly improve the surface morphology of on-axis GaAs/GaAs(111)B structures whilst retaining good electrical and optical properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350638
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  • 9
    Electronic Resource
    Electronic Resource
    Photoluminescence measurements for GaAs grown on Si(100) and Si(111) by molecular beam epitaxy (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 628-630 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence measurements have been used to characterize Si-doped GaAs layers, ranging in thickness from 1.1–8.1 μm, grown on Si(111) and misorientated Si(100) substrates by molecular beam epitaxy. 4.2 K PL spectra for GaAs/Si (100) show a strain-induced splitting between the heavy and light hole valence bands which corresponds to a biaxial tensile stress of 2.8± 0.15 kbar acting on the GaAs layer. Similar measurements for GaAs/Si(111) indicate that the GaAs layer is subject to a biaxial tensile stress of 3.9±0.15 kbar at 4.2 K. Furthermore, the intensity and line shape of luminescence features for GaAs/Si(111) for the first time indicate a crystalline quality comparable with the best GaAs/Si(100) material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104550
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of mismatch on the defects in relaxed epitaxial InGaAs/GaAs(100) films grown by molecular beam epitaxy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1731-1735 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thick (∼3 μm) films of InxGa1−xAs grown on GaAs(100) substrates, across the whole composition range, have been examined by transmission electron microscopy and double-crystal x-ray diffraction. The results were compared with the observed growth mode of the material determined by in situ reflection high-energy electron diffraction in the molecular beam epitaxy growth system. The quality of the material degraded noticeably for compositions up to x∼0.5 associated with an increased density of dislocations and stacking faults. In contrast, improvements in quality as x approached 1.0 were correlated with the introduction of an increasingly more regular array of edge dislocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354827
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