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  • 1
    Electronic Resource
    Electronic Resource
    High resolution x-ray analysis of pseudomorphic InGaN/GaN multiple quantum wells: Influence of Si doping concentration (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3006-3008 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the structural properties of InGaN/GaN/AlGaN multiple quantum wells (MQWs) by means of two-dimensional reciprocal space mapping (RSM) of high resolution x-ray diffraction. The influence of Si doping in GaN barriers on the characteristics has been studied for 12-period MQWs grown by metalorganic chemical vapor deposition, which have different Si doping concentrations in the GaN barriers ranging from 1×1017 to 3×1019 cm−3. Information on the structural quality of these MQWs was extracted from the linewidth broadening of the higher-order superlattice satellite peaks, as well as from the presence of Pendellösung oscillations. The measured diffraction curves were modeled using kinematic diffraction theory. From the symmetric and asymmetric RSMs around (0002), (0004) and (112¯4) reflections, we found that the InGaN/GaN/AlGaN MQWs are grown coherently on the GaN base layer. Better interface properties are achieved with Si doping. Our results indicate that Si doping in the GaN barriers affects the interface quality of the InGaN/GaN MQW systems, and thus, also influences the optical properties. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369620
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  • 2
    Electronic Resource
    Electronic Resource
    Anisotropic phonon scattering in γ-irradiated LiF (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 1417-1419 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A heat-pulse technique was used to study phonon scattering in γ-irradiated LiF as a function of polarization, input power, and propagation direction. The results provide direct experimental evidence of a strong, anisotropic, polarization-dependent scattering by γ-induced defects with a frequency-dependent absorption of transverse phonons for propagation in the [111] direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334502
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of substrate temperature and V/III flux ratio on In incorporation for InGaN/GaN heterostructures grown by plasma-assisted molecular-beam epitaxy (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2280-2282 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reflection high-energy electron diffraction (RHEED) and laterally spatially resolved high resolution x-ray diffraction (HRXRD) have been used to identify and characterize rf plasma-assisted molecular-beam epitaxial growth factors which strongly affect the efficiency of In incorporation into InxGa1−xN epitaxial materials. HRXRD results for InxGa1−xN/GaN superlattices reveal a particularly strong dependence of average alloy composition x¯ upon both substrate growth temperature and incident V/III flux ratio. For fixed flux ratio, results reveal a strong thermally activated behavior, with over an order-of-magnitude decrease in x¯ with increasing growth temperature within the narrow range 590–670 °C. Within this same range, a further strong dependence upon V/III flux ratio is observed. The decreased In incorporation at elevated substrate temperatures is tentatively attributed to In surface-segregation and desorption processes. RHEED observations support this segregation/desorption interpretation to account for In loss. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124990
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  • 4
    Electronic Resource
    Electronic Resource
    Pressure-dependent photoluminescence study of wurtzite GaN (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3492-3494 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature photoluminescence (PL) in single-crystal GaN films grown on sapphire substrates by metalorganic chemical vapor deposition has been studied as a function of applied hydrostatic pressure using the diamond-anvil-cell technique. The PL spectra of the GaN at atmospheric pressure were dominated by two sharp, strong, near-band-edge exciton luminescence lines and a broad emission band in the yellow spectral region. The exciton emission lines were found to shift almost linearly toward higher energy with increasing pressure. While the yellow emission band showed a similar blue shift behavior under applied pressure, a relatively strong sublinear pressure dependence was observed. By examining the pressure dependence of the exciton emission structures, the pressure coefficient of the direct Γ band gap in the wurtzite GaN was determined. The value of the hydrostatic deformation potential of the band gap has also been deduced from the experimental results. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113774
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  • 5
    Electronic Resource
    Electronic Resource
    Schottky-based band lineups for refractory semiconductors (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1974-1976 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An overview is presented of band alignments for small-lattice parameter, refractory semiconductors. The band alignments are estimated empirically through the use of available Schottky barrier height data, and are compared to theoretically predicted values. Results for tetrahedrally bonded semiconductors with lattice constant values in the range from C through ZnSe are presented. Based on the estimated band alignments and the recently demonstrated p-type dopability of GaN, we propose three novel heterojunction schemes which seek to address inherent difficulties in doping or electrical contact to wide-gap semiconductors such as ZnO, ZnSe, and ZnS. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113295
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  • 6
    Electronic Resource
    Electronic Resource
    Dependence of critical thickness on growth temperature in GexSi1−x/Si superlattices (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 916-918 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present direct evidence for the dependence of critical thickness on growth temperature in a lattice-mismatched epitaxial system. Ge0.5Si0.5/Si strained-layer superlattices have been grown by molecular beam epitaxy on (100) Si substrates at temperatures between 330 and 530 °C. The extent to which lattice mismatch is accommodated by elastic strain has been determined through x-ray diffraction, channeled Rutherford backscattering spectroscopy, and transmission electron microscopy. Lattice mismatch is found to be accommodated purely elastically in a structure grown at 365 °C. Samples grown at higher temperatures are seen to display increasingly high densities of misfit-accommodating dislocations. This growth-temperature dependence may account for apparent inconsistencies in critical thickness data reported in the literature. Our results clearly demonstrate the need to account adequately for the kinetics of defect formation in the prediction of critical thicknesses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99272
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  • 7
    Electronic Resource
    Electronic Resource
    Growth of superconducting V3Si on Si by molecular beam epitaxial techniques (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 514-516 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting thin films (500–1000 A(ring) in thickness) of A15 V3Si have been grown on (111)Si substrates through molecular beam epitaxial techniques. V and Si are codeposited in a feedback-stabilized, 3:1 flux ratio from dual e-beam evaporators onto clean, heated Si substrates in an ultrahigh vacuum chamber. For the first time, the superconducting A15 V3Si phase is metastably fabricated directly on a crystalline Si substrate without the formation of thermodynamically favored Si-rich VxSiy phases. Our films exhibit superconductivity only within a narrow range of intermediate growth temperatures (centered near 400 °C), with an optimum Tc of 12.5 K. X-ray diffraction shows the superconducting films to be polycrystalline A15 V3Si. For slightly higher growth temperatures (≈530 °C), Auger profile, x-ray, and transmission electron microscopy measurements indicate the appearance of an intermediate layer of roughly 1:1 V:Si composition. Our observations demonstrate that a growth temperature near 400 °C results in successful nucleation of the superconducting A15 phase while minimizing solid phase reaction with the substrate during V3Si growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100621
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  • 8
    Electronic Resource
    Electronic Resource
    Intrinsic exciton transitions in GaN (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 455-461 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Intrinsic excitonic transitions in GaN have been studied using a variety of spectroscopic measurements. Sharp spectral structures associated with intrinsic free excitons could be observed in photoluminescence, reflection, and absorption spectra. The energy positions of excitonic transitions in GaN epitaxial layers were found to be influenced by the residual strain resulting from lattice-parameter and thermal-expansion mismatches between the epilayers and the substrates. The values of the four principal deformation potentials of wurtzite GaN were derived by using the strain tensor components determined by x-ray measurements. The observation of spectral features involving the emission of LO phonons in absorption and photoluminescence excitation spectra at energies above exciton resonances indicate that a phonon-assisted indirect excitation process, which simultaneously generates a free exciton and a LO phonon, is a very significant and efficient process in GaN. The lifetime of the free excitons is found to be longer than the relaxation time of LO-phonon emission but much shorter than that of acoustic-phonon emission. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366660
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  • 9
    Electronic Resource
    Electronic Resource
    Kinetic modeling of microscopic processes during electron cyclotron resonance microwave plasma-assisted molecular beam epitaxial growth of GaN/GaAs-based heterostructures (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1510-1512 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microscopic growth processes associated with GaN/GaAs molecular beam epitaxy (MBE) are examined through the introduction of a first-order kinetic model. The model is applied to the electron cyclotron resonance microwave plasma-assisted MBE (ECR-MBE) growth of a set of δ-GaNyAs1−y/GaAs strained-layer superlattices that consist of nitrided GaAs monolayers separated by GaAs spacers, and that exhibit a strong decrease of y with increasing T over the range 540–580 °C. This y(T) dependence is quantitatively explained in terms of microscopic anion exchange, and thermally activated N surface-desorption and surface-segregation processes. N surface segregation is found to be significant during GaAs overgrowth of GaNyAs1−y layers at typical GaN ECR-MBE growth temperatures, with an estimated activation energy Es∼0.9 eV. The observed y(T) dependence is shown to result from a combination of N surface segregation/desorption processes. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115682
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  • 10
    Electronic Resource
    Electronic Resource
    Reflection high energy electron diffraction study of nitrogen plasma interactions with a GaAs (100) surface (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2861-2863 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Effect of a nitrogen electron-cyclotron-resonance (ECR) microwave plasma on near-surface composition, crystal structure, and morphology of the As-stabilized GaAs (100) surface is investigated with the use of digitally image-processed in situ reflection high energy electron diffraction. Nitridation is performed on molecular beam epitaxially (MBE) grown GaAs surfaces near 600 °C under typical conditions for ECR microwave plasma-assisted MBE growth of GaN films on GaAs. Brief plasma exposures (≈3–5 s) are shown to result in a specular, coherently strained, relatively stable, GaN film approximately one monolayer in thickness, which can be commensurately overgrown with GaAs while longer exposures (up to 1 min) result in incommensurate zincblende epitaxial GaN island structures. Specular and nonspecular film formations are explained in terms of N-for-As surface and subsurface anion exchange reactions, respectively. Commensurate growth of ultrathin buried GaN layers in GaAs is achieved. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113454
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