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  • 1
    Electronic Resource
    Electronic Resource
    Structural and Optical Properties of GaN Layers Directly Grown on 6H-SiC(0001) by Plasma-Assisted Molecular Beam Epitaxy (1998)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 264-268 (Feb. 1998), p. 1235-1238 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/03/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.264-268.1235.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Investigation of epitaxial lateral overgrowth by x-ray topography (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 405-409 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial lateral overgrowth by liquid phase epitaxy of silicon over SiO2 has been investigated by x-ray double crystal topography. A large number of lamellae was free of crystallographic defects, but all of the lamellae showed growth striations. For the lamellae grown from indium solutions growth striations with indium concentration differences of about 1016–2 × 1017 cm−3 were detected. A considerable part of the indium impurities in the lamellae seemed to be electrically inactive. The tilt of the defect free lamellae against the substrate is of the order of 10−6. Some of the lamellae showed single dislocations parallel to the sample surface. These dislocations originated at the edges of the seeding windows and ended in reentrant corners at the outer edge of the lamellae. In most of the defective lamellae the dislocations formed a dense network.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351868
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  • 3
    Electronic Resource
    Electronic Resource
    Depth-resolved measurement of lattice relaxation in Ga1−xInxAs/GaAs strained layer superlattices by means of grazing-incidence x-ray diffraction (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2381-2387 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The state of relaxation in two different superlattices (SLs) of a system with large lattice mismatch, Ga0.8In0.2As/GaAs grown on GaAs [001] by molecular beam epitaxy, has been investigated by surface-sensitive grazing-incidence diffraction (GID). The SL is squeezed between the substrate and a thick GaAs top layer. The thickness of individual GaInAs layers ta (active layer) is the same in both samples, while the GaAs barrier thickness tb is different. We have studied the influence of the thickness ratio tb/ta on the state of relaxation for different distances from the sample surface. We find that for thick barriers the whole SL remains coherently strained and for the thinner barrier thickness the SL is partially relaxed against the the GaAs top layer. The GID technique was applied for the first time to obtain depth resolution of the lateral lattice parameter in a SL. It is demonstrated to be especially well suited for SL systems with a small difference of the average electron density between the sublayers. The scattering contrast is improved by measuring the intensity as a function of the exit angle ("rod scans'') from the "weak'' (200) Bragg reflection. Comparing computer simulations with the measured variation of the scattering contrast between GaAs and GaInAs layers obtained from different "information depths'' and at different angular positions of the in-plane rocking curves, the state of relaxation can quantitatively be evaluated. On the basis of these results we propose two models for the partial relaxation of the SL into the state of strain-reduced domains. We believe that the partial relaxation is due to the elastic field interaction between the GaInAs layers accross the GaAs barriers, if tb is small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354724
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  • 4
    Electronic Resource
    Electronic Resource
    Structural properties of GaN layers on Si(001) grown by plasma-assisted molecular beam epitaxy (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 3800-3806 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the growth and microstructure of GaN films deposited on Si(001) substrates by plasma-assisted molecular beam epitaxy. GaN films grown directly on Si(001) are found to be phase mixtured, containing both cubic (β) and hexagonal (α) modifications. The origin of this phase mixture is identified to be due to the formation of amorphous SixNy at the GaN/Si interface during the nucleation stage. Therefore, a GaAs buffer layer is employed to prevent the formation of SixNy. GaN films grown on this GaAs/Si(001) structure are in fact predominantly cubic and exhibit the characteristic band-edge photoluminescence (PL) of β-GaN up to room temperature. However, the PL efficiency from these samples is low compared to that of β-GaN layers directly grown on GaAs(001). We explain the lower PL efficiency by the presence of additional structural defects, which are observed in the GaN/GaAs/Si(001) heterostructure by transmission electron microscopy. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367144
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  • 5
    Electronic Resource
    Electronic Resource
    Cubic (In,Ga)N layers grown on GaAs(001) by dc plasma-assisted molecular beam epitaxy (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1918-1920 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cubic (In,Ga)N layers with In contents up to 11% are grown on GaAs(001) by dc plasma-assisted molecular beam epitaxy. Comparatively high substrate temperatures are used to desorb In accumulated on the growth front by the massive In segregation in this material system. We report the observation of band-edge photoluminescence and the dependence of the emission energy on In composition for the (In,Ga)N layers. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365999
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  • 6
    Electronic Resource
    Electronic Resource
    Interface roughness of InAs/AlSb superlattices investigated by x-ray scattering (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 120-124 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InAs/AlSb short period superlattices grown either with AlAs-like or with InSb-like interfaces are investigated by grazing incidence x-ray scattering and high resolution diffractometry. The superlattices are grown on a relaxed AlSb buffer layer. It is shown that the two possible stackings of layers in the superlattices resulting in a different degree of lattice relaxation lead also to a different height of interface roughness. The lateral and vertical correlation lengths of the roughness decrease with increasing relaxation of the superlattice. The vertical correlation length corresponds to an almost complete correlation of different interfaces in the case of the nearly perfect superlattice with InSb-like interfaces. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360918
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of the interface composition of InAs/AlSb superlattices on their optical and structural properties (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 811-820 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of five short-period (InAs)6/(AlSb)6 superlattices, grown either with AlAs-like, InSb-like, or alternating interfaces, were studied by means of x-ray diffraction, high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, photoluminescence and ellipsometry. The combination of these techniques allows us to explain the pronounced differences in the optical and structural properties of both types of interfaces. In samples with an AlAs-like bottom interface x-ray, HRTEM and Raman results demonstrate the differing structural quality to be related to inhomogeneous strain relaxation and As intermixing. The energies of the critical points E0, E1 and E1+Δ1 of the samples with pure AlAs-like interfaces are shifted by more than 100 meV to higher energies with respect to those of the samples with InSb-like interfaces. These differences can be understood on the basis of the different interfacial atomic structure and strain in the samples. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359004
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  • 8
    Electronic Resource
    Electronic Resource
    Investigation of GaAs/AlAs multilayer systems for optical Bragg reflectors using x-ray double crystal techniques (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2220-2224 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Layer systems for optical Bragg reflectors (grown by molecular beam epitaxy) were studied using double crystal topography and diffractometry. The initiation of stress relaxation was detected topographically in the substrate reflection and in different satellite reflections for undoped and slightly silicon doped layers (up to a doping level of 3×1017 cm−3). Higher silicon doping (1018 cm−3) prevented misfit dislocations. When using Czochralsky substrates it was observed that half-loops were formed by misfit dislocations between pairs of threading dislocations. Misfit dislocations were shown to be situated on different levels of the layer stack. Satellite reflection topography is suggested as a new tool for directly observing strains in multilayer systems since the signal originates in the layer stack. Even for very small layer thicknesses good defect contrasts can be expected for high-quality layers, as shown by simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353125
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  • 9
    Electronic Resource
    Electronic Resource
    Deformations in (Al,Ga)As epitaxial layers wafer bonded on dissimilar substrates (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2173-2178 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deformations in heteroepitaxial layer stacks of AlGaAs/GaAs grown on GaAs are measured by triple crystal diffractometry before epitaxial liftoff and after subsequent wafer bonding on various substrates (GaAs, glass, Si, and LiNbO3). The tetragonal deformation present in the as-grown layer stack partially relaxes during epitaxial liftoff. The roughness of the as-grown layer stack gives rise to a bending of the atomic planes after wafer bonding. The widths of the x-ray diffraction peaks are used to estimate the misorientation of the lattice planes and compared with the atomic force microscopy measurements of the surface roughness. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1342804
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  • 10
    Electronic Resource
    Electronic Resource
    Interference effects in x-ray double-crystal rocking curves of Ga1−xAlxAs/GaAs laser structures and superlattices (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 499-501 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interference effects in the x-ray double-crystal rocking curves of Ga1−xAlxAs/GaAs laser structures and superlattices have been discussed in the framework of a reliable simulation model based on the Takagi–Taupin dynamical theory. It has been found that in the laser structures the presence of the active GaAs layer between the Ga1−xAlxAs confining layers causes a splitting of the confining layer Bragg peak in subpeaks of comparable intensity; in a similar way, the presence of GaAs layers inside a superlattice is able to split each satellite peak in subpeaks. Interference effects have been experimentally revealed in an AlAs/GaAs heterostructure made of three identical superlattices separated by thin GaAs layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350258
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