bluuebunny/crossref_metadata_2025 huggingface dataset:
Metal Organic Chemical Vapour Deposition Growth of Epitaxial ZnSe/ZnS Multiple Layered Structures
Authors: Yates Heather M , Williams John O
Published: March 2011

ZnSe-ZnS multilayers have been prepared by atmospheric. pressure metal organic chemical vapour deposition (M0CVD) using dimethylzinc, hydrogen sulphide and hydrogen selenide. Layer thicknesses down to 500Å have been obtained and the interfaces, as measured by secondary ion mass spectroscopy (SIMS) and electron microscopy, are regular. A notable improvement in interface abruptness was observed with better control of experimental procedures and more especially with the growth of a ZnSe buffer layer between the GaAs(100) substrate and multilayers.
Effect of Strain on Bound Excitons in High-Purity ZnSe Bulk and MOCVD Homoepitaxially-Grown ZnSe Layer
Authors: Asao Yoshiaki , Hayamizu Shunichi , Yamada Yoichi , Taguchi Tsunemasa , Hiraki Akio
Published: March 2011

Back-doping experiments with intentional donors (Al, Cl, Ga and In) and acceptor (Na) species have been conducted in the recrystallization travelling-heater-method (THM)-grown ZnSe single crystals. Sharp bound-exciton lines and associated two-electron or two-hole transitions appear clearly and their bind-ing energies can be accurately estimated using central cell corrections. Uni-axial stress measurements on the l1d line at 2.783 eV and on the l2In line at 2.7968eV confirm that the spatial symmetry of the localized centers which bind excitons is Td. Utilizing the present THM ZnSe crystal as a substrate for ZnSe layer with good optical-quality was homoepitxially grown by metalorganic-chemical- vapor-deposition and exhibited a strong donor-bound exciton line locating at 2.7964 eV, probably Al. Low-resistive n-type layer with 0.1ω·cm was achieved by doping with Al from trimethylaluminum source.
Formation of a New Blue-Shift Emission in Highly Be-Doped GaAs Grown by Molecular Beam Epitaxy
Authors: Makita Yunosuke , Mori Masahiko , Ohnishi Nobukazu , Phelan Paul , Taguchi Takashi , Sugiyama Yoshinobu , Tacano Munecazu
Published: March 2011

Photoluminescence measurements of Be-doped GaAs, grown by molecular beam epitaxy, were carried out at low temperature as a function of acceptor concentration. Results revealed that besides the well-defined emission, [g-g], which is exclusively relevant to acceptor impurities, an additional specific emission, temporarily denoted by [g-g]α is formed near the band-edge, when the concentration of acceptors exceeds 1×1019 cm−3:. From the viewpoint of application it was suggested that also in case of acceptors, photoluminescence spectra can be practically used for the precise determina-tion the acceptor concentration.
Comparison of Low Temperature Photoluminescence of Bulk MBE Grown AlGaAs and GaAs Using a Graphite Generated Dimerb Versus a Standard Tetramer Arsenic Group-V Source
Authors: Brennan Thomas M. , Hammons B. E. , Smith M. C. , Jones E. D.
Published: March 2011

The carbon concentrations in GaAs and AIGaAs grown by Molecular Beam Epitaxy (MBE) have been studied when a graphite generated dimeric arsenic species and a standard tetramer arsenic species are used as the group-V source. Photoluminescence and Van der Pauw-Hall measurements have been made to examine the material quality in reference to which arsenic species is used for film growth. Results indicate that a graphite crucible arrangement for the thermal cracking of As4 produces significant carbon contamination and is unacceptable for the MBE growth of GaAs and AlGaAs.
Magnetoreflectivity Study of Excitons in MBE Grown Zn1−xFex Se Crystals
Authors: Liu X. , Petrou A. , Prinz G. A. , Jonke B. T. , Krebs J. J. , Warnock J.
Published: March 2011

We present a magnetoreflectivity study of the excitons in MBE grown Zn1−xFexSe crystals for x=0.017, 0.027 and 0.043. The excitonic spinsplitting was studied as function of magnetic field in both the Faraday and Voigt geometries. The exchange integrals were determined from the conduction and valence band spin-splittings. The exciton spin-splitting was also studied as function of temperature. This study yielded the value of the energy spacing of the Fe++ states and also verified that Zn1−xFexSe is a Van Vleck paramagnet.
Nucleation and Growth of Ultrathin Epitaxial Metal Silicides on Silicon
Authors: Batstone J. L. , Tung R. T. , Phillips Julia M. , Gibson J. M.
Published: March 2011

Growth of epitaxial single crystal nickel and cobalt disilicide films on silicon is performed under UHV conditions by deposition of Co or Ni on silicon followed by a high temperature reaction to form the silicide. The uniformity and perfection of ultrathin epitaxial layers has been studied using transmission electron microscopy. Mechanisms controlling island growth are discussed. Island nucleation observed in pseudomorphic films of NiSi2 /Si(100) (∼60Å thick) is shown to be the result of the difference in symmetry between the NiSi2 and Si. Islands related by a translation vector a/4<111> show an equilibrium island separation of 15±1.5Å. The boundary between islands is described as a coreless defect. In comparison,, pseudomorphic layers of CoSi2 /Si(111) are observed up to thicknesses ∼30Å. Pinholes are commonly observed in CoSi2 /Si(111) thin films. Finite contact angles (∼50) between substrate and deposit suggest a desire for three-dimensional growth under equilibrium conditions.
Reduction of Defect Levels in Si and Si/Ce Layers Grown by MBE
Authors: Gibbings C.J. , Tuppen D C.G.
Published: March 2011

The dislocation density in undoped Si-MBE layers grown on wafers without any chemical pre-cleaning has been studied. The oxide layer was removed using a low silicon flux. Factors influencing the dislocation density have been studied, including substrate type, growth temperature and the temperature at which oxide is removed. Dislocation densities below 10-3 cm-2 have been obtained. The defect density in p-type silicon doped with boron oxide has also been studied. The influence of boron oxide on dislocation density has been found to be negligible, even though incorporation of oxygen is large at growth temperatures ≤650°C. Boron oxide doped Si.88Ge.12 layers have also been grown and a similar level of dislocations has been found.
Epitaxial Growth of Copper, Silver and Gold on a Semiconducting Layered Material: Tungsten Disulfide
Authors: Doering D. L. , Ohuchi F. S. , Jaegermann W. , Parkinson B. A.
Published: March 2011

The growth of copper, silver and gold thin films on tungsten disulfide has been examined as a model of metal contacts on a layered semiconductor. All three metals were found to grow epitaxially on the WS2. However, Cu appears to form a discontinuous film while Au and Ag grow layer by layer. Such epitaxial growth is somewhat surprising since there is a large lattice mismatch between the metals and the WS2.
Theory of Optical Transitions in SinGen(001) Strained Layer Superlattices
Authors: Hybertsen Mark S. , Schlüter Michael
Published: March 2011

Systematic trends for the minimum gap and low-lying direct optical transitions for superlattices alternating 2, 4 or 6 atomic layers of Si and Ge grown on Si(001) and Ge(001) substrates are calculated using the local density functional approach. Results of a many-body self energy calculation for the optical transition energies of the Si4Ge4/Si(001) case are compared to photocurrent and electroreflectance data. Emphasis is placed on the narrow type II heterostructure formed by the Si4Ge4 region between the Si(001) substrate and cap layer.
Properties of SiGe Alloys Grown on Si Substrates by Liquid Phase Epitaxy
Authors: Alonso M.I. , Trah H.-P. , Bauser E. , Cerva H. , Strunki H.P.
Published: March 2011

Si1−zGez single crystal layers were grown on Si(iii) by liquid phase epitaxy (LPE) over the entire composition range (0 ≤ x ( 1). Using Sn as solvent all compositions were produced; alloys with compositions 0 ≤ x ≤ 0.75 were obtained using In as solvent; the range 0.75 ≤ x ≤ 1 was covered with Bi solvent. The solvents used, the composition of the solution, the saturation temperature, and the cooling rate, were found to strongly influence the growth morphology.
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

In 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

Surface 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

This 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

The 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

Fe-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

For 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

Strained-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

We 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

Photoassisted 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

The 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

We 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

We 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

Multilayered 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

Interdiffusion 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

The 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

The 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

The 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

The 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

It 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

Results 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

Resistivity 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

We 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

Hydrogen 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

The 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

Optical 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.
Influence of Structural and Electrical Characteristics of Extended Defects on GaAs Field Effect Transistors
Authors: Van Hove M. , De Raedt W. , De Potter M. , Van Rossum M. , Weyher J. L.
Published: March 2011

The paper presents a systematic study of grown-in and process-induced defects on LEC GaAs substrates. Defects have been revealed by photoetching the wafers with diluted Sirti-like solutions after various processing steps. MESFET arrays have been processed on the wafers and a systematic mapping of the I-V characteristics has been performed. A correlation between various defect configurations and the FET threshold voltage shifts has been established.
New Defect Related Phenomena in Semiconductor Heterolayers and Superlattices
Authors: Capasso Federico , Beltram Fabio
Published: March 2011

Recent work on defect related phenomena in heterojunctions and quantum well structures is reviewed. These include situations in which quantum wells behave as deep traps and the use of shallow and deep centers as new tools for band structure engineering. Among the latter tunable band discontinuities and the artificial tailoring of superlattice states via δ-doping techniques are discussed.
Evidence of a Radiation-Induced Defect Level in n-Type InSb
Authors: Kouimtzi S. D.
Published: March 2011

Capacitance bridge measurements of loss on irradiated n-type InSb specimens at low temperatures are reported. A peak in A.C. conductance at ?55K is seen after irradiation and it is attributed to a radiation induced level.
Characterization of Defects in GaP, GaAs and GaAsl-xPx Electroluminescent Diodes by Transmission Electron Microscope
Authors: Hirata Mitsuji , Takeda Seiji , Fujii Katsushi
Published: March 2011

Dislocations and some other lattice defects were observed in typical III-V semiconducting materials. The usefulness of electron microscopy is emphasized and some examples of characterizing the nature of lattice imperfections are presented here.
Spectroscopy of III–Vs Under Hydrostatic Pressure
Authors: Stradling R. A.
Published: March 2011

In GaAs and InSb common residual contaminants introduce both shallow donor states and other levels normally resonant with the conduction band but taking their predominant character from higher conduction band minima. These states can be made to emerge into the forbidden gap by applying hydrostatic pressure. Judged by the measured pressure coefficients two sets of levels are closely tied to the L- and X-conduction band minima. At low temperatures the X-associated states show local relaxation effects and metastability (i.e., D(X) behaviour). Pressure experiments have also been performed with spike-doped GaAs both in single layer and in superlattice form. Shubnikov-de Haas peaks can be observed above 3T. Fourier analysis of these shows that up to six sub-bands can be occupied. The application of hydrostatic pressure of up to 20kbar dramatically increases the mobility of the electrons in the lowest sub-band by as much as an order of magnitude with smaller increases occurring the higher sub-bands. The increases in mobility arise from the diffusion of the silicon donors during growth. Localised donor states associated with the L-conduction band drop below the Fermi energy in the centre of diffused distribution of donors on the application of pressure and become neutralised. This reduction of ionised scattering centres affects the most confined electron states and thus the mobility of the lowest sub-band increases very substantially.
Characterisation of Epitaxial MBE and MOCVD GaAs DOPED with Donors or Acceptors Using FTIR Spectroscopy
Authors: Murray R. , Newman R. C. , Nandhra P. S. , Beall R. B. , Harris J. J. , Wright P. J.
Published: March 2011

Epitaxial layers of GaAs grown by MBE or MOCVD and doped with silicon impurities have been studied using FTIR spectroscopy. Vibrational modes are observed for Si(Ga), Si(As), Si(Ga)-Si(As) and a defect labelled SI-X. This latter defect appears to be responsible for the compensation effects found in some highly doped material. The Si(Ga) mode is modified in AlGaAs but understood in terms of a simple statistical model. Epitaxial GaAs layers doped with silicon or beryllium are passivated by exposing the samples to an RF hydrogen plasma which leads to the formation of Si-H and Be-H close pairs.
DX Centers in GaAs and AlxGal-x.As: Properties and Influence on Material and Device Characteristics
Authors: Mooney P. M.
Published: March 2011

The DX center, the lowest energy state of the donor in AlGaAs with x > 0.22, is responsible for the reduced conductivity as well as the persistent photoconductivity observed in this material at low temperature. Extensive studies of the properties of this level and of its effects on the characteristics of some heterojunction devices are reviewed here. Recent measurements are presented showing that the characteristics of the DX center remain essentially unchanged when it is resonant with the conduction band (x < 0.22) and that, independent of other compensation mechanisms, the DX center therefore limits the free carrier concentration in GaAs to a maximum of about 2×1019 cm− 3.
Mechanisms of Doping-Enhanced Superlattice Disordering and of Gallium Self-Diffusion in GaAs
Authors: Tan T. Y. , Gösele U. , Marioton B. P. R.
Published: March 2011

Recently available Ga-Al interdiffusion results in GaAs/AlAs superlattices allow to conclude that Ga self-diffusion in GaAs is carried by triply-negatively charged Ga vacancies under intrinsic and n-doping conditions. The mechanism of the Si enhanced superlattice disordering is the Fermi-level effect which increases the concentrations of the charged point defect species. For the effect of the p-dopants Be and Zn, the Fermi-level effect has to be considered together with dopant diffusion induced Ga self-interstitial supersaturation or undersaturation. Self-diffusion of Ga in GaAs under heavy p-doping conditions is governed by positively charged Ga self-interstitials.
TEM Studies of Ordering in MOCVD-Grown (GaIn)P on GaAs
Authors: McKernan S. , Cooman B. C. De , Carter C. B. , Bour D. P. , Shealy J. R.
Published: March 2011

GaxIn(1−x)P epilayers grown on GaAs substrates by MOVPE, for different growth temperatures and values of x∼0.5, have been studied by electron microscopy. The results indicate that under certain conditions the ternary epilayer is ordered parallel to the (111) plane. Dark-field images obtained using the superlattice reflections reveal ordered domains of different orientations. High-resolution images have been obtained from the ordered domains. The structure of these domains is not perfect but contains many planar faults parallel to the growth surface.
Uniaxial Stress Studies of Optical Centres in Silicon
Authors: Davies Gordon
Published: March 2011

Uniaxial stress perturbations have provided considerable data on the properties of optical centres in silicon. This paper reviews their uses in determining atomic kinetics and the symmetry of optical centres. Examples are given of the different effects of stress-induced interactions between states, and of the thermalisation of stress-split states. Uniaxial stresses are shown to be useful in grouping together similar optical centres, and in understanding the defect-induced widths of zero phonon lines and the vibronic properties of centres. At some optical centres, “internal” stresses can be used to contruct bound states from perfect crystal states.
Effects of Pre-Gate Oxidation Intrinsic Gettering Upon Thin Gate Oxide Integrity In High Carbon Content CZ Si
Authors: Hahn S. , Tung C. Y. , Lee J. , Tuomi T. , Partanen J.
Published: March 2011

Effects of post-well drive intrinsic gettering (PWIG) upon the integrity of thin gate oxide in Cz Si wafers with carbon levels, Cs, ranged from 0.2 - ∼ 4 ppma were investigated. A 10 nm thick gate oxide capacitor was used to study its time-dependent breakdown characteristics and minority carrier lifetime. Our data have shown that PWIG cycles and/or carbon impurity affect both bulk oxygen precipitation and minority carrier lifetime, but not the oxide integrity.
Comparison of Low Temperature Methods for the Production of Silicon Dioxide Thin Films.
Authors: Baker Stephen D. , Milne W. I. , Taylor S.
Published: March 2011

In this paper we present a comparison of the physical and electrical properties of high quality insulating thin films of silicon dioxide produced at low temperatures by three methods; standard plasma enhanced CVD of silane/nitrous oxide, photo enhanced CVD of silane/nitrous oxide using a novel internal nitrogen discharge lamp, and oxygen plasma anodisation.

The electrical and interface properties of the films, obtained from current-voltage and capacitance-voltage measurements are compared. The physical properties and composition of the films have been investigated by standard methods such as ellipsometry and p-etch rate, and spectroscopic techniques such as Auger, XPS, LIMA and Infrared absorption. The results of these investigations are reported.

The effects of low temperature annealing on the film properties have been examined and the suitability of each of the fabrication techniques to a variety of applications is discussed.
The Role of Diatomic SiO in Dry Oxidation of Si
Authors: Raider Stanley I. , Walkup Robert E.
Published: March 2011

The interaction of O2(g) with clean Si(s) surfaces at high temperature and low pressure leads to an etching reaction, 1/2 O2(g) + Si(s) → SiO(g), which results in the evolution of SiO molecules from the surface. Above a critical O2 pressure, an oxide film SiO2(s) begins to grow. The evolution of diatomic SiO during the early stages of film growth may provide a mechanism to account for deviations from standard models of oxidation kinetics for thin oxides, and for the results of oxygen isotope tracer studies of oxide formation. In order to monitor the rate of SiO evolution, we have made in-situ measurements of the SiO concentration in the gas phase, using a laser-induced fluorescence technique. With this method, SiO(g) can be monitored in the furnace with good spatial resolution and a sensitivity limit of ˜ 106 molecules cm−3. Measurements of SiO evolution and the implications for oxide growth will be discussed.
The Oxygen Vacancy and The E1′ Center In SiO2
Authors: Bar-Yam Y. , Pantelides S. T. , Joannopoulos J. D. , Allan D. C. , Teter M. P.
Published: March 2011

We report parameter-free self-consistent calculations of structural properties for the oxygen vacancy in silicon-dioxide using new oxygen pseudopotentials and quantum molecular dynamics simulations. Results challenge the accepted identification of the oxygen vacancy with the paramagnetic E1′ center. Bonding of the adjacent silicon atoms occurs sufficiently strongly for all charge states to inhibit the asymmetric distortion which would be required for correspondence with the E1′ center.
Density Functional Based Studies of Oxygen Vacancies In Crystalline Silicon Dioxide
Authors: Pederson Mark R. , Harrison Joseph G. , Klein Barry M.
Published: March 2011

We have performed electronic structure studies on two neutral oxygen vacancies in crystalline silicon dioxide. The idealized beta-crystobalite structure has been used as a model for the host perfect crystal. The calculations have been carried out by representing the host-defect system as a large cluster of atoms which is properly. embedded into the host crystal, with a Gaussian orbital basis used to describe the electronic states of the host and defect systems. The local density approximation with and without the self-interaction correction has been used in these calculations.
Electrical Characteristics of Tisi2/n+-Polysilicon/Sio2/Si Mos Capacitors Stressed Under High Temperature Silicide Processing Conditions
Authors: Shenai K. , Piacente P. A. , Baliga B. J.
Published: March 2011

Detailed electrical characteristics of TiSi2/n+-polysilicon/SiO2/Si MOS capacitors stressed under a variety of high temperature processing conditions is reported. These devices have ˜2000Å TiSi2 formed by a two-step thermal anneal on heavily POCl3doped polysilicon with thicknesses of 6 kÅ and 8 kÅ. These structures were capped with 8 kÅ of SiO2 and stressed in nitrogen at process temperatures in the range of 700° C to 1100° C. The electrical performance was evaluated in terms of I-V, C-V, Fowler-Nordheim tunneling, and SiO2/Si interface characteristics of MOS structures. A systematic degradation of the SiO2/Si interface was observed due to process limitations of TiSi2 at high Lemperatures.
LPCVD of Silicon Nitride Films From Hexachlorodisilane and Ammonia
Authors: Taylor R. C. , Scot B. A.
Published: March 2011

Hexachlorodisilane (Si2Cl6) has been used as an alternative to dichlorosilane and silane for growth of silicon nitride films. The films were grown at a pressure of 0.7 Torr at temperatures between 450° and 850°C. Growth rate data indicates a kinetically controlled deposition with an activation energy of 29.3 kcal/mole. Growth rates are substantially higher than those obtained from SiH2Cl2 under similar conditions, and the physical properties of the films are essentially the same. At the higher growth temperatures stoichiometric Si3N4 films with no detectable chlorine can be obtained when a NH3/Si2Cl6 ratio of 60 or greater is used.
Control of Bonded SiH in Silicon Oxides Deposited by Remote Plasma Enhanced CVD
Authors: Tsu D. V. , Parsons G. N. , Lucovsky G. , Watkins M. W.
Published: March 2011

This paper describes Optical Emission Spectrocopy (OES) and Mass Spectrometry (MS) studies of the plasma region in the Remote Plasma Enhanced Chemical Vapor Deposition (PECVD) of amorphous hydrogenated silicon (a-Si:H) and silicon oxide thin films. In Remote PECVD, only the O2/He mixture is plasma excited, silane is introduced into the deposition chamber well below the plasma region. Deposition of films has been studied over a wide range of relative He and O2flows, between 100% He and 100% O2. The incorporation of SiH in the oxides derives from the same mechanism as the deposition of a-Si:H, i.e., a metastable He induced fragmentation of silane.
Degradation of Micron-Sized Silicide Lines on Polycrystalline Silicon
Authors: Phillips J. Randall , Zheng Lung-Ru , Mayer James W.
Published: March 2011

The thermal stability of silicide fine lines on undoped CVD polycrystalline silicon was investigated. Heat treatments were in vacuum at temperatures up to 950 ° C. We observed that fine silicide lines on undoped polysilicon degrade during vacuum annealing. Voids and hillocks are formed as silicon diffuses out from the fine grained poly-Si, undergoes long-range transport through the silicide, and recrystallizes into large grains. The phenomenon is similar to that seen previously in planar samples, but fine lines were found to degrade at lower temperatures and especially along line edges. Lines of two refractory metal silicides, TiSi2 and CrSi2, and one near-noble silicide, CoSi2 were examined.
Interactions of Polysilicon with Aluminum
Authors: Ottaviani G. , Tu K. N. , Nobili C.
Published: March 2011

In-situ resistivity measurements togheter with Auger electron spectroscopy, MeV 4He+ backscattering spectrometry, scanning electron microscope and x-ray diffraction have been used to investigate interactions between Al films and CVD polycristalline silicon layers deposited on thermally grown SiO2 on silicon. A sharp and well defined increase in resistivity around 450 °C has been associated to the erosion of the polysilicon and growth of Si crystallites in the metal film. The kinetic of the transformation has been studied by isothermal treatment over the 390–450 °C temperature range. An activation energy of 2.2 ± 0.2 eV has been measured. Similar results have been obtained by using treatments at constant heating rate. A critical analysis of the available data suggests that the rate limiting step is the nucleation of Si grains in the aluminum film. The driving force for the process can be identified to be the free energy difference between the initial and final states.
Modelling of the Dislocation Influence on Electrical Properties of Polycrystalline Silicon Cells
Authors: Ghitani H. El , Martinuzzi S.
Published: March 2011

The influence of the density Ndis and recombination activity Sd of dislocations on the photocurrent Jsc, the spectral variation of Jsc and electron diffusion length Ln are computed by means of the Green's function. Sd is the surface recombination velocity of the space charge cylinder surrounding a dislocation line, assumed to be perpendicular to the illuminated surface of the cells.

It is found that the value and the spectral variation in the near infrared of Jsc and that of Ln, are dependent on Ndis and Sd, specially when Ndis and Sd are higher than 104 cm−2 and 104 cm s−1 respectively. A reasonnable agreement is obtained with experimental results.