bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strain in Epitaxial GaAs on Si and CaF2/Si
Authors: Schowalter L. J. , Hashimoto Shin , Smith G. A. , Gibson W. M. , Lewis N. , Hall E. L. , Sullivan P. W. 
Published: March 2011

ABSTRACTIn this paper, ion channeling techniques are used to show that epitaxial GaAs layers grown on vicinal Si(001) wafers do not have their [001] axis precisely aligned with that of the Si substrate. Instead, the [001] axis of the GaAs layer is found to be tilted toward the surface normal of the Si substrate. This tilt was found to be ∼0.2° on vicinal Si(001) substrates which have their [001] axis tilted 4° toward the [110] azimuth. It is speculated that this misalignment is reponsible for the residual density of threading dislocations in the GaAs on Si layer. An approach described here, which can be used to avoid strain in the GaAs layer, is to grow a CaF2 buffer layer between the Si substrate and the epitaxial GaAs layer. High quality epitaxial GaAs layers have been obtained on both CaF 2 /Si(001) and CaF 2 /Si(111) substrates. Strain measurements of the epitaxial GaAs on the CaF 2 buffer layers indicate that these layers have strains below our detection limits.
Heteronucleation onto Si Surfaces
Authors: Hull R. , Bean J. C. , Chand N. , Leibenguth R. E. , Bahnck D. , Koch S. M. , Harris J. S. 
Published: March 2011

ABSTRACTSurface structure and heteronucleation of GaAs, In(Ga)As and Ge onto Si surfaces by Molecular Beam Epitaxy are studied by transmission electron microscopy as functions of substrate orientation and cleaning. We find that Shiraki cleaning of vicinal ( 4 degree misorientation ) (100) Si surfaces can produce significant surface facetting at temperatures ∼ 900°C. Subsequent nucleation of GaAs is then influenced by the facet distribution. Nucleation of InAs onto vicinal (100) Si surfaces exhibits a highly bimodal distribution of nuclei dimensions and anomalously high surface diffusion lengths. Sputter and annealing of Si surfaces produces microroughness of an amplitude a few monolayers high on (211) and vicinal and exact (100) surfaces. Subsequent growth of Si buffer layers increases the surface roughness amplitude slightly on the exact (100) and (211) surfaces and significantly on the vicinal (100) surface. Nucleation densities and surface diffusion lengths of Ge on the Si buffer layers surfaces correlate to the surface roughness amplitude. We also describe techniques for experimental quantification of surface roughness amplitudes and periodicities from electron microscope lattice structure images.
Chemical Beam Epitaxy of III-V Semiconductor Heterostructures
Authors: Tsang W. T. 
Published: March 2011

ABSTRACTThis paper reviews briefly some of the recent progress in chemical beam epitaxy (CBE) for the preparation of GaInAs(P)/InP and GaAs/AlGaAs quantum wells, superlattices, and heterostructure devices. Chemical beam epitaxy can be viewed as a chemical vapor deposition process but with the pressure inside the growth chamber sufficient, ow (< 10-4 torr) so that the transport of the gaseous reactants becomes molecular beam instead of via viscous flow. This not only eliminates the complicated gas phase reactions and the stagnant boundary layer above the substrate through which the reactants have to diffuse, but also allows for quick transitions of material compositions and dopings as those achievable by molecular beam epitaxy (MBE). For the growth of HI-V semiconductors, the group Inl elements are derived by the pyrolysis of organometallics (or inorganometallics such as dopant gases) on the heated substrate surface, while the group V elements are derived by the thermal decomposition of hydrides using a high temperature cracker. For the growth of group IV semiconductors, beams of inorganometallic compounds are used. Thus, both organometallic and inorganometallic compounds can be used as starting sources. There are two other alternatives: the gas source MBE (GSMBE), which uses group III elements evaporated from solid sources as in MBE and thermally decomposed hydrides, and the metalorganic MBE (MOMBE), which uses metalorganics as group III sources and group V elements evaporated from solid sources as in MBE. These other processes will not be reviewed here. Introd
Characterization of MBE Grown GaAs With Isoelectronic Doping of Indium or Antimony
Authors: Li A.Z. , Kim H.K. , Jeong J. , Zhao J. , Schlesinger T.E. , Milnes A.G. 
Published: March 2011

ABSTRACTThe effects of In and Sb on the concentration of electron traps in MBE grown n-type GaAs are investigated. Two traps, labeled M3 and M6, dominate the DLTS spectrum. It is observed that at growth temperatures of 500 and 550° C their concentrations can be reduced by up to two orders of magnitude by the introduction of a few atomic percent of either In or Sb. The percent In or Sb producing the lowest trap concentrations decreases with increasing substrate temperature and thus for a substrate growth temperature of 600° C no additional improvement in the deep trap concentration is observed.
Liquid Phase Epitaxial Growth of Semi-Insulating Aigalnas by Fe Doping
Authors: Tanahashi T. , Okuda S. , Kondo M. , Sugawara M. , Isozumi S. , Nakajima K. 
Published: March 2011

ABSTRACTFe-doped semi-insulating AlGalnAs grown by liquid phase epitaxy has been studied and compared to Fe-doped GalnAsP. It has been found that semiinsulating AlGalnAs is easier to obtain than semi-insulating GalnAsP, because of its high iron distribution coeficient. The high resistivity of 1×109 ohm-cm has been obtained for Al0.481n0.52 As grown at 750°C. The activation energy of the Fe acceptor level in the AlGalnAs system has also been studied.
Phonon Shifts and Strains in Strained-Layer (Ga1−xInx)As
Authors: Burns Gerald , Wie C. R. , Dacol F. H. , Pettit G. D. , Woodall J. M. 
Published: March 2011

ABSTRACTFor thin (Ga1−xInx)As films on GaAs (100) substrates we have measured the phonon frequencies (Raninn technique) and the strains (x-ray rocking curve technique). The films range from perfect epitaxial (the thinner films) to those that have relaxed by different amounts (thicker films). Using the measured strains and the phonon deformation constants, the strain-induced frequency shift was calculated for each sample. From the measurements and calculation, we find that the frequency shifts due to strain give equivalent bulk phonon frequencies that are in good agreement with each other. This indicates that the Raman technique can be used for in-situ monitoring of the growth process.
Band Offsets at Strained-Layer Interfaces
Authors: Van De Walle Chris G. 
Published: March 2011

ABSTRACTStrained-layer heterojunctions and superlattices have recently shown tremendous potential for device applications because of their flexibility for tailoring the electronic band structure. We present a theoretical model to predict the band offsets at both lattice-matched and pseudomorphic strained-layer interfaces. The theory is based on the local-density- functional pseudopotential formalism, and the “model solid approach” of Van de Walle and Martin. The results can be most simply expressed in terms of an “absolute” energy level for each semiconductor, and deformation potentials that describe the effects of strain on the electronic bands. The model predicts reliable values for the experimentally observed lineups in Si/Ge, GaAs/InAs, and ZnSe/ZnS systems, and can be used to ex-plore which combinations of materials and configurations of the strains will lead to the desired electronic properties.
Effect of Electric Fields in Coupled Double Quantum Wells
Authors: Chen Y. J. , Koteles Emil S. , Elman B. , Armiento C. A. 
Published: March 2011

ABSTRACTWe present a detailed experimental study of the influence of electric fields on exciton states in a GaAs/AlGaAs coupled double quantum well structure and discuss the advantages of using this novel structure. The coupling of electronic states in the two quantum wells, due to the narrowness of the barrier between them, leads to an enhancement of the quantum-confined Stark effect (by as much as five times that of the single quantum well case). From the measured energies of the exciton transitions, splittings of the levels in a coupled double quantum well structure were derived without recourse to a theoretical model.
Substitutionally Doped II–VI Semiconductor Films and Layered Structures
Authors: Schetzina J. F. , Harper R. L. , Han J. , Hwang S. , Giles N. C. , Lansari Y. , Cook J. W. 
Published: March 2011

ABSTRACTPhotoassisted molecular beam epitaxy (PAMBE), in which the substrate is illuminated during film growth, is being employed in a new approach to controlled substitutional doping of II–VI compound semiconductors. Substitutional doping of these materials has been a long standing problem which has severely limited their applications potential. The PAMBE technique gives rise to dramatic changes in the electrical properties of as-grown epilayers. In particular, highly conducting n-type and p-type CdTe films have been grown using indium and antimony as n-type and p-type dopants, respectively. Double-crystal x-ray rocking curve data indicate that the doped epilayers are of high structural quality. Successful n-type doping of CdMnTe, a dilute magnetic semiconductor, with indium has also been achieved. Most recently, the photoassisted growth technique has been employed to prepare doped CdMnTe-CdTe quantum well structures and superlattices. In addition, HgCdTe films which exhibit excellent optical and electrical properties as well as exceptional structural perfection have been grown by the PAMBE technique.
Stability and Metastability in Semiconductor Strained-Layer Structures
Authors: Dodson Brian W. , Fritz I. J. , Picraux S. Thomas , Tsao Jeffrey Y. 
Published: March 2011

ABSTRACTThe physics governing stability properties and relaxation of mismatch strain in semiconductor strained-layer structures is reviewed. Experimental data on stability and rates of strain relaxation are examined. We conclude that essentially all observations on structural relaxation of semiconductor strained-layer structures can be explained by standard models of plastic deformation adapted to the special conditions controlling dislocation dynamics in these structures.
Electronic and Mechanical Properties of DC Sputtered Compositionally Modulated Metal Films
Authors: Drewery J. S. , Greer A. L. 
Published: March 2011

ABSTRACTWe describe a recently constructed apparatus for the measurement of the Young's modulus and Poisson's ratio of free-standing sputtered multilayer films. In comparison with more conventional methods, this is expected to permit both measurement with lower uncertainties and interpretation which is more straightforward. A separate apparatus for the accurate measurement of the conductivity, magnetoresistance, and Hall coefficient of such systems has been prepared which will enable the contribution of Fermi surface-Brillouin zone interactions to the behaviour of these materials to be assessed.
“Magnetic Exchange Interactions in Fe/TbFe Bilayers”
Authors: Marinero E. E. , Sprokel G. S. , Notarys H. 
Published: March 2011

ABSTRACTWe report on magnetic exchange coupling phenomena between Fe and TbFe thin films. The structures are grown utilizing D.C. magnetron sputtering from separate Tb and Fe targets and their magnetic characteristics are measured utilizing VSM and Longitudinal Kerr Rotation. In addition, Auger depth profiling and x-ray diffraction studies were conducted to study film composition and structure.Uniaxial alignment of the Fe moment in the plane of the substrate is revealed by the longitudinal Kerr measurements. The coercivity of the Fe layer varies from 19 Oe to 130 Oe depending on the azimuthal angle between the normal to the plane of the bilayer and the direction of the external field. The hysterisis loops vary in shape from rectangular in the alignment direction to S-shape in the direction orthogonal to this direction.These effects are discussed in terms of magnetic exchange coupling interactions between the ferromagnetic layer and the ferrimagnetic alloy.
Ellipsometric Characterization for Multilayers Containing Magneto-Optic TbFeCo Films
Authors: Ruane M. , Jain A. 
Published: March 2011

ABSTRACTMultilayered structures containing sputter-deposited films of amorphous TbFeCo can exhibit magneto-optical Kerr rotation and are leading candidates for erasable optical storage media. Ellipsometric characterization of optically active multilayered media is desirable during media development, testing and production, but traditional ellipsometry does not account for the presence of optical activity. A novel ellipsometer is described that can characterize both the dielectric overcoat and the optically active layers. Reflectivity measurements are collected for different incident angles and polarizations using a differential detector while the magnetic reversibility of the active film layer is exploited to enhance the magneto-optical signal from the TbFeCo. A multilayer film model is used to process observations and estimate media characteristics. The model explicitly accounts for the optical activity of the TbFeCo layer, and is parameterized in terms of the index of refraction and thickness of the overcoat, and the real and imaginary parts of the elements of the dielectric tensor of the active layer.A series of TbFeCo films with varying composition, rf-sputter deposited on quartz substrates with Al2O3 dielectric protective overcoats, is characterized. Both Tb-rich and Fe-rich samples were deposited, with room temperature coercivities ranging from 1.6kOe to about 4kOe, and film-side Kerr rotations between 21 minutes and 28 minutes. Reflectivity data versus angle of incidence, and estimated dielectric tensor elements for the TbFeCo layers are presented. A standard figure of merit, based on the off-diagonal tensor elements, is used to compare competing media in terms of their optimal performance in a multilayered structure.
Interdiffusion in Short-Wavelength Modulated Materials Studied by Monte-Carlo Simulations
Authors: Atzmon M. 
Published: March 2011

ABSTRACTInterdiffusion in a two-dimensional compositionally modulated lattice has been studied by Monte-Carlo simulations. In the initial stages, the interdiffusion coefficient has been observed to change with time due to the development of short-range order simultaneously with the interdiffusion process. When the short-range order parameter approached its limiting value, the diffusion coefficient approached a constant value. The dependence of the interdiffusion coefficient on the modulation wavelength does not agree with the prediction of one-dimensional theories. For ordering alloy systems, the effective interdiffusion coefficient is positive, i.e., an initially present modulation decays in time, for all wavelengths.
Characterization of Multilayers as X-Ray Dispersion Devices
Authors: Gilfrich John V. , Brown Dennis B. , Rosen David L. , Freitag Ralph K. 
Published: March 2011

ABSTRACTThe appropriate application of multilayers as x-ray dispersion devices requires that their diffraction characteristics be understood. Conventional models, based on perfect-crystal and mosaic-crystal theories, predict diffraction efficiencies (integral reflection coefficients) significantly larger than values measured experimentally. It has been shown that introduction of surface roughness effects into the model can promote agreement between experimental and theoretical values, while the presence of other types of defects produce changes too small in magnitude to explain the discrepancy. Because it is reasonably well agreed that the resolving power of multilayers is only moderate, compared to the more conventional “crystal” dispersing devices, it is important to be able to predict or measure that parameter in order to assess the usefulness for a particular application. Experimental measurements and theoretical calculations have been carried out on multilayers (almost exclusively tungsten/carbon) prepared to have 2d-spacings from 50 to 140A. The experimental work used both singlecrystal and double-crystal spectrometers; the calculations used the crystal diffraction model, as modified to include surface roughness.
Exploring the Relation between Interface Structure & Mechanical Properties in Multilayer Materials
Authors: Jankowski A. F. , Makowiecki D. M. , Mckernan M. A. , Nutt S. R. , Green K. 
Published: March 2011

ABSTRACTThe relationship between microstructure and physical behavior is especially pronounced in synthetic multilayer materials. Insight to the mechanisms responsible for changes in the mechanical properties can be investigated through a careful examination of the multilayer microstructure. A dominant feature of the nultilayer structure is the interface. The population of interlayer boundaries, that is interfaces, is directly proportional to the multilayer period for any given film thickness. In this paper, we will evaluate “TEM” images of multilayer systems. The interface structure will be viewed in cross-section and a range of layer thicknesses will be considered. Variation in the elastic modulus, yield stress, and microhardness have been observed for noble-transition metal systems over a wide range of multilayer periods, from less than 1 nm to greater than 1000 nm. In epitaxial systems, the extent of superlattice perfection (coherency effects) is closely tied with changes in physical behavior. Emphasis will thus be placed on the str'ucture and strain distribution from the interface, and its role in determining the mechanical properties of multilayers.
Tungsten-Carbon Multiiayer System Studied with X-Ray Scattering
Authors: Kortright J. B. , Denlinger J. D. 
Published: March 2011

ABSTRACTThe tungsten-carbon multilayer system has been studied using x-ray scattering techniques as a function of multilayer period and annealing. Grazing incidence x-ray scattering shows that interatomic arrangements in the W-rich layers depend strongly on their proximity to the interface with the C-rich layers. Amorphous interface layers are stabilized by intermixing of W and C during deposition into local structures similar to those in the tungsten carbides. Further intermixing and structural relaxation in the amorphous state occurs on annealing these structures. This interatomic structural interpretation is consistent with trends in the observed x-ray optical properties.
Breathing Mode Lattice Relaxation Associated With Carrier Emission and Capture by Deep Electronic Levels in Silicon
Authors: Samara G. A. 
Published: March 2011

ABSTRACTThe breathing mode (volume) lattice relaxations associated with carrier emission and capture are evaluated for a variety of deep levels in silicon using a recently proposed method based on high pressure measurements of the emission rates and capture cross sections. Included are 1) the vacancy-like acceptor levels associated with the oxygen-vacancy pair (or A-center) and the gold, platinum and palladium impurities, 2) the chalcogenide donors in their singly- and doubly-charged states and 3) a number of 3d transition metal donors. The signs and magnitudes (which range from -O to 5A 3/emitted carrier) of these relaxations are discussed in terms of models for the impurities and defects responsible for the associated levels. The results on the chalcogenides are compared with recent theoretical calculations.
Hexagonal Silicon, a Stress-Induced Martesitic Transformation
Authors: Pirouz P. , Chaim R. , Dahmen U. 
Published: March 2011

ABSTRACTIt is shown that indentation-induced formation of hexagonal silicon at the temperature range 400–700°C is fully consistent with its occurence via a martensitic transformation. After presenting HREM images of hexagonal ribbons in a diamond cubic matrix, a crystallographic analysis of the phase transformation is given, and a dislocation mechanism responsible for the transformation is discussed.
The Structure of Thermal Donors (NL8) in Silicon: a Model Derived From 17O and 29SI Endor Experiments
Authors: Michel Jürgen , Nikias J. R. , Spaeth J.-M. 
Published: March 2011

ABSTRACTResults of new electron nuclear double resonance (ENDOR) experiments on the thermal donors (NL8) in silicon are presented. Hyperfine interactions (hf) with 17O were observed. Two types of oxygen were found, of each type there are at least two oxygen atoms. The size and tensor orientations of their hf interactions are consistent with the presence of four oxygen atoms with approx. <111>-symmetry in the core of the thermal donors.
Complex Defect Formation in Heat Treated Aluminium Doped Cz Silicon
Authors: Drakeford Andrew C. T. , Lightowlers Edward C. 
Published: March 2011

ABSTRACTResistivity and photoluminescence measurements have been made on Al-doped CZ Si, with high and with low C concentrations, heat treated at 450°C. The results are compared with those obtained from nominally undoped CZ Si with a low residual B concentration. It is shown that Al acceptors are completely lost, presumably by the removal of Al from substitutional sites by exchange with Si self interstitials generated during oxygen aggregation. Luminescence features observed are tentatively identified with electronic transitions at neutral Al-C and Al-thermal donor complexes.
Raman Studies of Hydrogen Passivation in Silicon
Authors: Stutzmann M. , Herrero C. P. 
Published: March 2011

ABSTRACTWe have studied the hydrogen passivation of boron acceptors in bulk crystalline silicon with Raman scattering. Upon hydro-genation, distinct changes in the optical phonon lineshape and the localized vibrational modes of boron are observed. The hy-drogen in the passivated region gives rise to a specific Raman-active mode, whose vibrational frequency depends strongly on temperature and uniaxial stress. Implications of these results on possible structural models are discussed.
The Effects of High and Low Dose Hydrogen Ion Implantations on Al/n-Si Schottky Diodes
Authors: Yapsir A. S. , Hadizad P. , Lu T. -M. , Corelli J. C. , Corbett J. W. , Lanford W. A. , Bakhru H. 
Published: March 2011

ABSTRACTHydrogen ion implantation was performed on Al/n-Si Schottky diodes at doses ranging from 1014 H cm2 to 1016 H cm−2. The effects of ion bombardment and subsequent heat treatments on the diodes were studied using the current-voltage, capacitance-voltage and deep level transient spectroscopy techniques. To explore the stability of hydrogen in silicon, the 1H(15N,aγ)12C nuclear resonance reaction was used. The different effects observed in the low and high dose implantation will be presented.
Diffusion and Subsurface Bonding of Hydrogen in Silicon
Authors: Jaworowski A. E. , Wielunski L. S. 
Published: March 2011

ABSTRACTThe hydrogen depth profiling in the near-surface region in silicon reveals the existence of a subsurface hydrogen layer. This layer acts as a barrier to diffusion. The observed subsurface hydrogen profile rises and then drops off sharply with increasing depth and is stable up to 770 K. Our annealing data indicate a rather complex motion of monatomic and molecular hydrogen in the near-surface region (<1500 A) in the temperature range 300 – 800 K. The subsurface molecule formation represents the dominant hydrogen trapping process in silicon.
Optical Detection of Magnetic Resonance (ODMR) Studies of the Electronic Structure of Complex Defects in GaP
Authors: Chen W. M. , Godlewski M. , Monemar B. , Gislason H. P. 
Published: March 2011

ABSTRACTOptical detection of magnetic resonance (ODMR) is applied to studies of neutral (“isoelectronic”) complex defects in GaP, via monitoring recombination of the excited bound exciton (BE) state associated with these defects. With examples of isoelectronic complex defects in GaP associated with C, Cu, Li and the PGa -antisite, it is shown how the ODMR data reveal the magnetic properties of both electrons and holes bound at such defects. The procedures to conclude on defect symmetry, structure and identity are also elucidated.