bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Covalent and Metallic Radii in Covalent Metallic Superlattices and Two-Dimensional Isoelectronic Alloys
Authors: Tsu Raphael
Published: March 2011

Covalent metallic superlattices and isoelectronic alloys consist of ordered layers of, for example, Si/AlP, Ge/GaAs, and Si/Sb,etc. Depending on design, wide range of electrical properties can result. The covalent, metallic and ionic radii play a crucial role in the stoichiometry of epitaxial systems.
A Tem Study of Rhodium on Gaas; Reactions and Morphology
Authors: Packer Stacy L , Gronsky Ronald
Published: March 2011

Reaction between Rhodium films and n-type GaAs in the temperature range of 300° to 700°C has been examined using the TEM to look at the interface and phases present. The reaction between Rh and GaAs produces a layered structure of Rh/RhGa/RhAs2/GaAs based on RBS and TEM. Above 300°C, the RhGa phase has an orientation relationship of [011]RhGa // [100]GaAs. In cross-section, an interpenetrated layered structure was observed with equiaxed RhGa above columnar grains of RhAs2. Rhodium is the moving species as suggested by voids at the Rh/reacted layer interface. The interface between the reacted layer and GaAs was smooth at 450° and 20 minutes of annealing but showed 10 nm periodic penetrations when annealed at 400° for 90 minutes. Interface roughness may influence the low barrier height reported for the Rh Schottky diode annealed at 400°.
Characterization of Si MBE Layers Doped in Situ by As Ion Beams
Authors: Swanson Max L. , Parikh N.R. , Jackman T.E. , Houghton D.C. , Denhoff M.W.
Published: March 2011

To achieve high concentrations and electrical activation of As in Si without subsequent annealing, 500-3000 eV As + ions were implanted during MBE growth of Si at 450-840°C. The epitaxial layers were characterized by Rutherford backscattering/channeling, transmission electron microscopy, secondary ion mald spectroscopy, and electrical measurements. Samples containing 1.2×1020 As cm-3 grown at 700°C showed little damage, high As substitutionality and high electrical activation. However, similarly doped layers grown at 460°C showed lower As activation and varying amounts of structural damage. In one case, a band of damage near the Si substrate was observed which persisted even after rapid thermal annealing at 1120°C (10 s); the damage was characterized by a dechanneling step, non-substitutional As atoms and dislocation loops. A sample grown at 460°C with a high implantation energy (3 keV) was highly defected.
Epitaxial Films of Germanium by MOCVD
Authors: Khan Altaf H. , Santiago Jorge J.
Published: March 2011

A simple and easily expandable atmospheric pressure MOCVD (metal organic chemical vapor deposition) reactor for the growth of germanium films is proposed and implemented. It employs a resistively heated horizontal quartz reaction chamber. The organometallic compound tetramethylgermanium (TMGe) is used as the germanium source, and hydrogen as the carrier gas. Using this reactor, epitaxial films of germanium on <111> germanium substrates were grown at 550-650°C. The growth rate was found to increase with temperature. The single crystallinity of these films was evaluated by x-ray rocking curves, and the interface strain between the film and substrate was found to be less than 1%. These Ge/Ge samples have the same morphology as the bare substrate and their sheet resistance is 30% higher than the bare substrate value.
Nickel Silicide Structures on Single-Crystal Silicon Membranes
Authors: Hren P. , Fernandez A. , Silcox J.
Published: March 2011

Nickel structures have been deposited on large (300 μm diameter), thin (1400 to 3000Å) single crystal (111) silicon membranes. On annealing, the nickel-silicon reaction generates strain which can be partially accommodated through buckling of the membrane, a mode of strain relief not available on bulk wafers. Examples of such buckling are presented in this paper. Features of the silicide structures observed include thin epitaxial Ni2 Si that grows on clean surfaces during deposition, vertical and lateral growth of NiSi2 into the membrane from nickel dots, and the absence of interfacial dislocations between NiSi2 and silicon, probably due to the stress relief.
Electron Beam Source Molecular Beam Epitaxy of AlxGa1−Xas Graded Band Gap Device Structures
Authors: Malik R. J. , Levi A. F. J. , Levine B. F. , Miller R. C. , Lang D. V. , Hopkins L. C. , Ryan R. W.
Published: March 2011

A new method has been developed for the growth of graded band-gap AlxGal-xAs alloys by molecular beam epitaxy which is based upon electron beam evaporation of the Group III elements. The metal evaporation rates are measured real-time and feedback controlled using beam flux sensors. The system is computer controlled which allows precise programming of the Ga and Al evaporation rates. The large dynamic response of the metal sources enables for the first time the synthesis of variable band-gap AlxGal-.xAs with arbitrary composition profiles. This new technique has been demonstrated in the growth of unipolar hot electron transistors, graded base bipolar transistors, and Mshaped barrier superlattices.
OMVPE Growth of GalnAs/InP Quantum Well Structures
Authors: Stringfellow G. B.
Published: March 2011

InP/GalnAs/InP quantum well structures have been grown using atmospheric pressure organometallic vapor phase epitaxy (AP-OMVPE). The optimum conditions for growth of extremely abrupt interfaces were studied. The optimum orientation was exactly (100). The growth had to be interrupted for 40 seconds at the first interface and 2 minutes at the 2nd interface to obtain the most abrupt interfaces. The narrowest photoluminescence half widths were obtained at the lowest values (31) of V/III ratio in the input vapor phase. These growth conditions allow the growth of wells as thin as <10Å with photoluminescence (PL) spectra consisting of doublets or triplets. The extremely narrow peaks correspond to regions of the quantum well differing in thickness by a single monolayer. The energy separations of the neighboring peaks are found to increase with decreasing well width until, at a thickness of approximately 12 Å, the separation begins to decrease rapidly with decreasing well width. The exciton binding energies in the quantum wells have also been measured using thermally modulated PL. The binding energy is found to increase with decreasing well width until a maximum value of approximately 17 meV is measured for a nominal well width of approximately 13 Å. For thinner wells the exciton binding energy is found to decrease with decreasing well width.
Dislocation Detection by MeV Ion Channelling
Authors: Wielunski Leszek S.
Published: March 2011

MeV H+ and He+ ion channelling has been used to characterise the post annealing, residual ion implantation damage in silicon. The observed energy dependence of direct scattering peaks agrees with theoretical predictions for direct scattering on dislocations. Similar peaks are observed in the channelling spectrum from the hetero-epitaxial structure In0.3Ga0.7 As on GaAs and are also interpreted as direct scattering on interfacial dislocations. The sensitivity for dislocation detection by this technique is about 1×105 cm−1 therefore, when high dislocation densities are expected, it is suggested that direct scattering on dislocations should be included in the analysis of channelling data.
Energy Loss Rates for Light Holes in Ingaas/GaAs Strained-Layer Single Quantum Wells
Authors: Smith M. C. , Jones E. D. , Fritz I. J. , Drummond T. J. , Zipperian T. E. , Schirber J. E.
Published: March 2011

Energy relaxation rates for light holes in InGaAs/GaAs strained layer quantum wells are measured. Two techniques were used to measure light hole temperatures as a function of power dissipated in the hole gas. For Th < 20K, Shubnikov-de Haas oscillations were used and for Th> 20K, a photoluminescence technique was employed.
Photoluminescence Characterization of Heteroepitaxial ZnSe/GaAs and ZnSe/AlAs Grown By MBE
Authors: Skromme B. J. , Tamargo M. C. , De Miguel J. L. , Nahory R. E.
Published: March 2011

Heteroepitaxial ZnSe grown by molecular beam epitaxy (MBE) has been characterized using low temperature photoluminescence (PL) and reflectance. Excitonic PL linewidths of thick (relaxed) ZnSe layers are>1.4 meV, and depend little on the type of substrate or buffer layer used (e.g. GaAs or AlAs). In contrast, thin (pseudomorphic) ZnSe layers on AlAs buffer layers of moderate thickness are found to exhibit by far the sharpest (FWHM=0.22-0.37 meV) excitonic features ever observed for heteroepitaxial ZnSe grown by any technique. A tentative explanation for this result is that step-grading the lattice constant (by the AlAs buffer layer) has eliminated the crystal defects which produce localized strain fields that inhomogeneously broaden the peaks in ZnSe/GaAs. Acceptor-related PL peaks are discussed, and the first discrete donor-acceptor pair line spectrum in heteroepitaxial ZnSe is reported.
Study of Diffusion Length and Alloy Segregation in MOCVD AlGaAs
Authors: Bradshaw J. L. , Choyke W. J. , Feng Z. C. , Meier D. L. , Messham R. L.
Published: March 2011

Various thicknesses of AlGaAs are grown on GaAs substrates by MOCVD. Low temperature photoluminescence of the substrate is observed even for layers of AlGaAs 24μm thick. Direct excitation by the 488.0 nm pumping radiation and excitation by reradiation from the AlGaAs are eliminated as causes. From photoluminescence and EBIC studies, evidence is given to show that the substrate luminescence is caused by a much larger than expected electron diffusion length. A small trace of GaAs luminescence may be due to alloy segregation in the AlGaAs films themselves.
High Quality n-Cd0.2 Hg0.8 Te Grown by Liquid Phase Epitaxy
Authors: Yasumura K. , Kimura H. , Komine Y. , Sato K.
Published: March 2011

Influential factors to the detectivity of n-CMT grown by liquid phase epitaxy on CdTe(111)B substrate are investigated. The factors are such as qualities of the substratesdopants and electrical parameters by which photoconductivity in CMT is governed.

We show that the doping with small amounts of In is an appropriate mean not only to raise the mobility but also to make reproductivity better. The In- doped epitagia�r after annealed has the highest mobility among tested in 3×10 cm5 /Vsec, and the photoconductive lifetime in 0.54 μsec at 77K.The resultant detectivity of an infrared device is 3×1010 cmHz1/2 w−1.
The Mechanisms of Relaxation in Strained Layer GeSi/Si Superlattices: Diffusion Vs. Dislocation Formation
Authors: LeGoues F. K. , Iyer S. S. , Tu K. N. , Delage S. L.
Published: March 2011

SixGe1−x strained layer superlattices are known to be metastable in that they can be grown fully commensurate with layer thickness higher than the equilibrium, calculated Tc at which dislocation formation becomes energetically favorable. In this paper, we describe the mechanism of relaxation in such multilayers. Both plane-view and cross-sectional transmission electron microscopy (TEM) were used to examine the formation of dislocation at the different interfaces. RBS was used to follow interdiffusion. We found two competing mechanisms for relaxation: The preferred mode for relaxation is the creation of dislocation networks at each of the interfaces. This process can be stopped or considerably inhibited by the difficulty of forming new dislocations in samples which are perfectly commensurate after growth; Some dislocations appear necessary in order to generate more dislocations during annealing. When this is not the case, the only possible way to attain relaxation is through diffusion. In such a case, stress-enhanced diffusion is observed, with a diffusion coefficient 200 times higher than expected.
Relaxation of Metastable Semiconductor Strained-Layer Structures by Plastic Flow
Authors: Dodson Brian W. , Tsao Jeffrey Y.
Published: March 2011

The relaxation of misfit strain in metastable structures by plastic flow is described using a continuum model based on Haasen's picture of plastic flow in bulk diamond-phase semiconductors and the concept of excess stress. This model provides a unified explanation of the equilibrium critical thickness, the relaxation behavior of metastable strained-layer structures, and the “metastable” critical thicknesses reported in many semiconductor strained-layer geometries.
Crystallization and Melting in Multilayered Structures
Authors: Sevenhans W. , Vanderstraeten H. , Locquet J. P. , Bruynseraede Y. , Homma H. , Scihuller Ivan K.
Published: March 2011

The stability of Pb/Ge and Pb/C multilayers has been studied over a broad temperature range by x-ray diffraction experiments. In the Pb/Ge system an amorphous to microcrystalline phase transformation of the Ge-layers was already observed at ≃ 100 °C. This transition destroys the modulation structure and improves the Pb(111) texture. In the Pb/C multilayers, the layered structure was still present at temperatures higher than the melting temperature of Pb. Contrary to recent publications, no depression of the melting temperature of the two-dimensional Pb layers could be observed.
Superconducting Superlattice Structures
Authors: Makous John L. , Leavitt John A. , Mcintyre Laurence C. , Maritato Luigi , Vaglio Ruggero , Cucolo Annamaria , Falco Charles M.
Published: March 2011

Superlattice superconductors exhibit behavior different from other “homogeneous” superconductors because of their layered structures. Sputtering has proved to be an excellent technique for producing such multilayered systems. Also, systems naturally having layered structures, such as the new high-Tc materials, can be fabricated by sputtering. Here we describe the preparation of superconducting superlattices by dc triode sputtering and techniques useful for characterizing them. In particular, we discuss Mo/Ta superconducting superlattices and high Tc thin films of YBa2Cu3O7-x.
The Sputter Deposition of Metal Multilayers
Authors: Somekh R. E. , Highmore R. J. , Page K. , Home R. J. , Barber Z. H.
Published: March 2011

We describe the strategy that we are using to make precision metal multilayers. Differential scanning calorimetry has been used with the Ni/Zr system to study the abruptness of the interface as a function of the sputtering pressure. For 10nm period multilayers there is a monotonic increase in the width of the interface with increasing sputtering pressure. W/Si multilayers have been studied as a function of both the sputtering pressure and the relative thicknesses of tungsten and silicon. At reasonably low sputtering pressures a well textured (110) tungsten X-ray peak is seen which is compatible with the expected thickness of the tungsten layers.

Finally, we report some preliminary work on sputtering from tungsten and silicon targets which are at different distances from the substrate so that the degrees of bombardment on the growing layers of the film can be independently varied.
Critical Field Measurements on Superconducting Graphite-KHG Multilayers
Authors: Chaiken A. , Tedrow P. M. , Dresselhaus G.
Published: March 2011

Upper critical fields of graphite-KHg multilayers with 10Å periodicity were measured as a function of angle and temperature. The Hc2 (θ, T) data were compared to the anisotropic Ginzburg-Landau model and were found to be in qualitative agreement, except at the lowest reduced temperatures, where significant deviations are found. The primary deviations from the anisotropic GL model are first, that the values of the critical field at the lowest temperatures are found to be higher than that predicted by the model, and secondly, the critical field anistropy ratio is found to be temperaturedependent. These deviations are discussed in light of more detailed models of anisotropic superconductivity.
Thin Film Growth
Authors: Vook R. W.
Published: March 2011

A review of the experimental and theoretical results describing thin film growth modes is presented. Thermodynamic criteria for determining which growth mode might be expected to occur in a particular case along with some kinetic considerations are given. The characteristics of each of the three principal growth modes, namely Frank and van der Merwe (layer), Stranski-Krastanov (layer plus island), and Volmer-Weber (island), are discussed. Lastly, the requirements favoring the growth of epitaxial multilayers are briefly considered.
Elastic Properties of Artificially Layered Thin Films
Authors: Cammarata Robert C.
Published: March 2011

Enhancements in the elastic moduli by factors of two or more in compositionally modulated metallic thin films have been observed for a certain range of composition modulation wavelengths. The experimental and theoretical understanding of this phenomenon, known as the supermodulus effect, is reviewed. Also, the mechanical properties of other artificially layered and composite materials are discussed and compared with the behavior of metallic superlattice thin films.
Growth and Structure of Tungsten Carbide-Transition Metal Superlattices
Authors: Moustakas T. D. , Koo J. Y. , Ozekcin A.
Published: March 2011

Superlattices between ceramic materials, such as tungsten carbide, and transition metals have been synthesized for the first time. The growth and structure of these superlattices were investigated by low angle X-ray diffraction and TEM lattice imaging and microdiffraction. The data show that the low temperature process of forming these two dimensional composites leads to unique crystal structures and morphology in the nanoscale range.
Phenomenological Approach to Multilayer Growth and Stability
Authors: Zangwill Andrew
Published: March 2011

I review recent theoretical studies designed to examine the effect of strain, facetting and growth conditions on multilayer stability. A phenomenological approach is used to investigate both morphological and crystal structural phase stability.
Atomic Level Investigations of W-Si Multilayers by High Resolution Tem and X Ray Scattering
Authors: Nutt S. R , Keem J. E.
Published: March 2011

We have prepared multilayer films of W-Si with bilayer repeat spacing from approximately 1.5 nm to 9 nm and performed high resolution electron microscopy and low angle x-ray scattering on them. Average composition estimates as inferred from deposition conditions, x ray scattering and electron microscopy are compared. Determinations of the individual layer thickness ratios by electron microscopy and x ray scattering vary significantly from expectations as the bilayer thickness approaches 1.5 nm. Layer intermixing to increase as the bilayer thickness decreases. Composition profiles as inferred from the Cuk x ray profile are compared to those inferred from the high resolution electron micrographs. Visual observations from melectron microscopy are presented indicating that the interface roughness is rapidly damped in the W-Si multilayer system. Estimates of the layer uniformity are made from the high resolution images.
Vacancy-Type Defects in Ion-Implanted Si Studied By Slow Positron Beam
Authors: Hautojdärvi P. , Huttunen P. , Mäkinen J. , Punkka E. , Vehanen A.
Published: March 2011

Variable-energy positron beam studies have been made on ion implanted silicon. After 35, 60 and 100 keV H+ implantation a clear separation between vacancy and H atom distributions was found. In 100 keV As+ and P+ implanted Si the damaged layer extends to 300 and 400 nm, respectively, far beyond the the range of implanted atoms and the amorphous layer. Effect of thermal and laser annealing is also discussed.
Electrical Characterization of Silicon With Buried Defects
Authors: Honeycutt J. , Radzimski Z. , Kola R. R. , Salih A. S. M. , Rozgonyi G. A.
Published: March 2011

Depth-dependent electrical characterization of epitaxial silicon extrinsically gettered with intentionally introduced misfit dislocations is described. To study the effect of buried defects on minority carrier lifetime, a modified Zerbst analysis of the MOS capacitance vs. time response was used to determine generation lifetime as a function of space charge region width. In addition, SEMEBIC imaging at different electron beam energies and EBIC imaging of cross-sections were used to investigate the depth-dependent electrical behavior of these materials.
Depth-Dependent Character of Extended Defects in Ion-Implanted and RTA'd Si
Authors: Herring Rodney A.
Published: March 2011

The character of extended defects formed in high-energy S-ion implanted and rapid thermal annealed (RTA'd) Si has been found by transmission electron microscopy (TEM) to be dependent on the depth at which the defects have formed in the ion-implanted regions. Si implanted with 6 MeV S-ions and RTA'd at 1000°C for 10 s showed a buried layer of extended defects with unfaulted loops towards the top and faulted loops towards the bottom. At higher S fluences, all the loops were unfaulted, some loops coalesced to form a dislocation network, and SiS precipitates were formed. At higher RTA temperatures, all the loops were unfaulted. A few possibilities that could explain the difference in defect character will be discussed.
Gold-Silicon Interfaces: High Resolution Electron Microscopy Reactions. Precipitation and Subsurface Gettering
Authors: Carpenter R. W. , Kim M. J.
Published: March 2011

Deposition of Au on exsitu cleaned (100) Si wafers resulted in the formation of a discontinuous polvcrvstalline Au layer containing lattice defects. On parts of the interface Au and Si were separated by a thin oxide layer, but elsewhere were in direct contact, with no evidence of metastable phase formation. Post deposition heating to 1000°C. well above the 370°C eutectic temperature of the system, caused formation of a reaction zone at the interface, and disappearance of the thin oxide layer. No amorphous phases formed during cooling. Quenching produced small Au precipitates in Si-rich regions. If the wafer contained dislocations. Au precipitation was observed on subboundaries directly connected to the Au/Si interface, but not on dislocations remote from the interface.
On the Diffusion of Oxygen Dimer in a Silicon Crystal
Authors: Snyder Lawrence C. , Corbett James W. , Deák Peter , Wu Rongzhi
Published: March 2011

We have made MINDO/3 calculations on a 47 silicon atom molecular cluster to model the diffusion of oxygen in silicon crystal. For interstitial oxygen (O1), we compute an activation energy for diffusion of 2.49 ev. We compute a binding energy of 0.1 ev. when two isolated interstitial oxygen atoms bond to a common silicon atom of the lattice. This complex (O2) is computed to move through the lattice with an activation energy of 1.36 ev. The diffusion path is through a four-member ring intermediate structure. We conclude that the diffusion constant for (O2) is eight orders of magnitude greater than that of (O1).
Nitrogen-Oxygen Complexes in Silicon
Authors: Suezawa Masashi , Sumino Koji
Published: March 2011

Several series of optical absorption lines are found in the wavenumber range 190–270 1/cm in as-grown crytals of n-type Si involving oxygen and nitrogen simultaneously. They are related to the electronic transitions associated with five kinds of shallow donors each consisting of nitrogen and oxygen atoms (N-O complex). The analysis of the generation kinetics shows that the complex of the main type consists of one oxygen atom and two or three pairs of nitrogen atoms.
Effect of Rapid Thermal Processing on Oxygen Precipitation in Silicon
Authors: Hawkins G. A. , Lavine J. P.
Published: March 2011

The precipitation of oxygen in silicon can be initiated by both homogeneous and heterogeneous nucleation mechanisms. Homogeneous nucleation has been studied in much greater detail; however, in some cases, superior contaminant gettering has been reported for precipitation processes believed to be based on heterogeneous nucleation. In this study, we use rapid thermal annealing (RTA) to demonstrate conclusively that the nucleation mechanism for one such process is, in fact, heterogeneous. We also investigate the sensitivity of precipitation to slight alterations in thermal process steps. We interpret our results in terms of point-defect-induced changes in the critical radius (Rc) for precipitate growth.
Theory of Hydrogen Reactions in Silicon
Authors: Walle Chris G. Van De , Bar-Yam Y. , Pantelides S. T.
Published: March 2011

We report first-principles total-energy calculations for H atoms in a Si lattice. Our results for single H atoms are presented in the form of total-energy surfaces, providing immediate insight in stable positions and migration paths. We examine the stability of different charge states (H+, H0, H−) as a function of Fermi-level position, and its impli-cations for H diffusion in p-type vs. n-type material. The results are used to scrutinize and supplement existing understanding of experimental observations. We also study the co-operative interactions of several H atoms, and propose a novel mechanism for H-induced damage.
The Structure of the Boron-Hydrogen Complex in Silicon
Authors: Marwick A. D. , Oehrlein G. S. , Barrett J. H. , Johnson N. M
Published: March 2011

Channeling and lattice location has been used to investigate the structure of the boron-hydrogen complex in crystalline silicon. The positions of both the boron and hydrogen atoms have been determined. The results are compared with Monte-Carlo simulations. The boron atom in the B-H pair is found to be displaced from a substitutional site by 0.28±0.03Å, while the hydrogen atom is predominantly at a bond-center site, with a small proportion in a back-bonded position.
Hydrogen Neutralization of Shallow-Donor Impurities in Single-Crystal Silicon
Authors: Johnson N. M. , Herring C.
Published: March 2011

New data are presented that considerably strengthen the conclusion, reported previously, that hydrogen can passivate shallow donors in silicon by associating with them to form neutral complexes. Effects of inhomogeneity of doping with depth have been eliminated in the new experiments; the observed increase of the effective Hall mobility after hydrogenation requires neutralization of ionizeddonor scattering centers.
Passivation of N-Type Silicon by Hydrogen
Authors: Bergman K. , Stavola Michael , Pearton S. J. , Lopata J.
Published: March 2011

Infrared spectroscopy has been used to study hydrogen passivation of P, As, and Sb donors in Si. The spectra show several new absorption bands due to donor-H complexes. By comparing spectra after different heat treatments it is shown directly that the passivation is due to complex formation.
Interactions Between Hydrogen and Silicon Acceptors in p-Type GaAs:Si
Authors: Chevallier J. , Pajot B. , Jalil A. , Mostefaoui R. , Rahbi R. , Bolssy M. C.
Published: March 2011

We show that silicon acceptors can be neutralized in p-type GaAs: Si. SIMS analysis shows that the deuterium concentration closely follows the net acceptor concentration. Infrared absorption spectroscopy reveals lines at 2094.7cm-1 and 1514.5cm-1 in hydrogenated and deuterated samples respectively. The ratio r of the two frequencies is 1.383 indicating that the lines are related to hydrogen isotopes. The reduction of the intensity of the local vibrational mode (LVM) of SiAs after neutralization is consistent with the formation of SiAs-H bonds. From SIMS data, it is concluded that most of the hydrogen present in the passivated material is complexed with silicon. A microscopic model of the Si-H complex is proposed.
Evidence for Complexes of Hydrogen with Impurities or Defects in Bulk III-V Materials
Authors: Clerjaud B. , Côte D. , Krause M. , Naud C.
Published: March 2011

Series of sharp optical absorption lines around 2200 cm-1 in GaP, 2000 cm-1 in GaAs, and 2300 cm-1 in InP are observed in bulk materials. They are shown to be due to stretching local modes of vibration of P-H or As-H bonds, the hydrogen sitting nearby an impurity or defect. The origin of the hydrogen contamination of the bulk materials is discussed.
A Determination of the Symmetry of EL2 Using Ballistic Phonon Transmission
Authors: Culbertson J. C. , Strom U. , Wolf S. A.
Published: March 2011

We have measured the time resolved transmission of short pulses of ballistic phonons in a GaAs crystal known to contain the intrinsic defect EL2. These measurements were performed for phonons propagating along several high symmetry directions at 2K. Measurements were made both before and after the crystal was irradiated with 1.06 μm light to convert EL2 from its ground state to its metastable state. The changes in phonon transmission measured for the different phonon polarizations and propagation directions lead us to associate a trigonal symmetry with the defect whose phonon scattering has changed. The identification of this defect as EL2 is discussed below.
On the Origin of EL2 Intracenter Absorption Band in GaAs
Authors: Skowronski M.
Published: March 2011

An alternative interpretation of optical absorption spectra due to intracenter transition within EL2 defect in GaAs is provided. The arguments are presented that states originating from the L-valley of the conduction band can account for the presence of the wide absorption band, the no-phonon line and the observed uniaxial stress splittings. Using the analogy to the DX center, this model presents an explanation for the existence of the metastable state of EL2.
Point Defects, Dislocations in GaAs and Material Homogeneity
Authors: Bourgoin J. C. , Bardeleben H. J. von , Lin H. , Stievenard D.
Published: March 2011

Combined positron annihilation and differential thermal analysis have shown that, in bulk GaAs materials, dislocations are decorated with vacancy related defects which recombine with As interstitials originating from As clusters. The role of these dislocations, the role of As source of these clusters are described and the consequences on the material homogeneity discussed.
Positron Annihilation Spectroscopy of As Vacancies in As-Grown GaAs
Authors: Corbel C. , Stucky M. , Hautojärvi P. , Saarinen K. , Moser P.
Published: March 2011

Positron lifetime measurements give direct evidence on positron trapping in monovacancy defects in n-type, but not in p-type nor in semi-insulating LEC-grown GaAs. The defects are identified as As vacancies. Two Fermi level controlled transitions have been found in positron lifetime spectra at 0.03±0.01 eV and at 0.10±0.01 eV below the conduction band. We attribute them to the 2-/- and - / 0 ionisation levels of the As vacancy.
Fermi Level Stabilization in Semiconductors: Implications for Implant Activation Efficiency
Authors: Walukiewicz W.
Published: March 2011

We propose the existence of a Fermi level stabilization energy in III-V semiconductors which provides a reference level for the electronic part of defect annihilation energies. It is shown that the position of the stabilization energy with respect to the band edges determines the maximum free carrier concentration which can be obtained through doping. The proposed model accounts for previously unexplained trends in implant activation efficiency in III-V semiconductors.
DX Center Analysis in Sn DOPED AlGaAs Layer of Double Heterostructures
Authors: Kaniewska M. , Kaniewski J.
Published: March 2011

Capacitance as well as photovoltage response methods have been used to analyse DX centers in the N–type AlGaAs:Sn layer of double heterostructures. DLTS spectra have revealed two deep traps. The first center (ΔE1 = 0.20eV) has been interpreted as the DX center related to Sn. In this paper, it is suggested that the second trap, with thermal activation energy equal to ΔE2 = 0.33eV, is also a DX center due to Sn, connected with another final state (the L minimum) of thermal processes. C-T characteristics and DLTS spectra have been compared with photovoltage spectra to find a correlation between the trap populations and Al content. The binding energy of the trap 2, as well as the temperature dependence of the electron capture cross-section, have been determined from measurements of the transition region width. Photoionization measurements confirm that there is large lattice relaxation when an electron is captured at the trap.
Enhanced Interdiffusion Effects in Compound Semiconductors
Authors: Petroff P. M.
Published: March 2011

This paper reviews the principal processes involved in the enhanced interdiffusion of elements across interfaces between two III-V compound semiconductors. Implantation enhanced interdiffusion effects in GaAs-Gal−xAlxAs are compared for single Quantum Well structures and Superlattice structures. Measurements indicate a marked difference in the annealing and enhanced interdiffusion kinetics between these 2 types of structures.
Metastable Phases and the Molecular Beam Epitaxy of Metal Silicides
Authors: Gibson J. M.
Published: March 2011

The growth of the epitaxial silicides NiSi2 and CoSi2 on Si is discussed from observations made by in-situ transmission electron microscopy. In particular, we observe the occurrence of epitaxial metastable phases which arise from the dominance of interface energy in extremely thin films. Such phases relate to the thickness dependence of the microstructure in these silicides and may be expected to occur in many binary and more complex thin film systems.
Kinetics of Silicon Oxide Thin Film Deposition From Silane and Disilane with Nitrous Oxide.
Authors: Chapple-Sokol Jonathan D. , Giunta Carmen J. , Gordon Roy G.
Published: March 2011

A mechanistic study of the deposition of silicon oxide films (SiOx, 0 < x ≤2) from silanes with nitrous oxide was performed. The depositions of non-stoichiometric films from silane and stoichiometric silicon dioxide from disilane were dominated by SiH2 generation from the decomposition of the silicon-containing reactant. The depositions of stoichiometric films from silane were found to follow chain reaction kinetics initiated by the homogeneous decomposition of N2O.
Radiation Response of Thin Oxides Grown By Rapid Thermal Oxidation and Rapid Thermal Annealing Techniques
Authors: Schubert W. K. , Seager C. H.
Published: March 2011

High quality, 20 to 30 nm thick SiO2 films were grown using rapid thermal oxidation techniques. Metal-oxide-semiconductor (MOS) capacitors formed with these oxides were characterized electrically using low and high frequency capacitance measurements. The effects of post oxidation annealing (POA) ambient, temperature and duration on the initial oxide properties and the radiation response of the MOS capacitors were determined. The addition of a small amount of O2 to the POA ambient significantly reduced the radiation induced hole trapping and interface state creation, particularly for the higher POA temperatures. In addition, annealing and reirradiation experiments were carried out and showed that both the trapped charge and interface state buildup were completely reversible after anneals at 400°C. This repeatability argues against interface state creation models which involve irreversible changes in the atomic arrangements near the interface.
Photo-Oxidation of Silicon: Reaction Mechanisms and Film Structure
Authors: Boyd Ian W.
Published: March 2011

The use of intense photon beams to initiate silicon oxidation is reviewed. In particular, recent experiments involving visible photons are discussed, which confirm a thermal domination and a clear photon enhancement. With equal powers of 488 and 514 nm radiation, the latter initiates faster reaction rates. Structural studies of the films are also reported using IR spectrometry, where we find broad similarities and intriguing differences the between laser and furnace grown films.
Analysis of composition changes across the Si/SiOx interface using fresnel fringe contrast analysis
Authors: Ross Frances M. , Stobbs W. M.
Published: March 2011

Fresnel fringe contrast analysis and high resolution electron microscopy are used in conjunction to measure compositional and structural changes across the Si/SiOx interface with atomic resolution.
Charge-Transfer Dipoles at the Si-SiO2 Interface and the Metal-Semiconductor Worfunction Difference In Mos Devices.
Authors: Massoud Hisham Z.
Published: March 2011

The magnitude of the dipole moment at the Si-SiO2 interface resulting from partial charge transfer that takes place upon the formation of interface bonds has been calculated. The charge transfer occurs because of the difference in electronegativity between silicon atoms and SiO2 molecules which are present across the interface. Results obtained for (100) and (111) silicon substrates indicate that the magnitude of the interface dipole moment is dependent on substrate orientation and the interface chemistry. Dipole moments at the Si-SiO2 and gate-SiO2 interfaces should be included in the definition of the flatband voltage VFB of MOS structures. CV-based measurements of the metal-semiconductor workfunction difference φms on (100) and (111) silicon oxidized in dry oxygen and metallized with Al agree with the predictions of this model. Other types of interface dipoles and their processing dependence are briefly discussed.
Structure of Sol-Gel Silic
Authors: Brinker C. J. , Brow R. K. , Tallant D. R. , Kirkpatrick R. J.
Published: March 2011

Combined Raman, 29Si NMR and reactivity studies of silica gels indicate that dehydroxylation of the silica surface results in cyclotrisiloxane species with reduced Si-O-Si bond angles and altered acid/base characteristics. XPS experiments indicate that the expected 0.35 eV shifts in Si2p and O1s binding energies due to the reduced bond angles are hidden within broad peaks due to the remaining hydroxyls. Additional Si2P, OlS, and ClS peaks are also observed and are postulated to result from preferential adsorption of extrinsic C-containing species on sites with enhanced acid/base properties.
Process Dependent Morphology of the Si/SiO2 Interface Measured with Scanning Tunneling Microscopy
Authors: Hecht Michael H. , Bell L. D. , Grunthaner F. J. , Kaiser W. J.
Published: March 2011

A new experimental technique to determine Si/SiO2 interface morphology is described. Thermal oxides of silicon are chemically removed, and the resulting surface topography is measured with scanning tunneling microscopy. Interfaces prepared by oxidation of Si (100) and (111) surfaces, followed by post oxidation anneal (POA) at different temperatures, have been characterized. Correlations between interface structure, chemistry, and electrical characteristics are described.
The Mechanism of Oxidation of SiGe.
Authors: LeGoues F. K. , Rosenberg R. , Nguyen T. , Meyerson B. S.
Published: March 2011

We have studied the oxidation mechanism of SiGe alloys, prepared by UHV/CVD. Ge is found to be completely rejected from the oxide and to pile up at the oxide/substrate interface. In the case of thick SiGe layers, this can give rise to very heavily concentrated layers of SiGe (up to 80% Ge) several hundreds of angstroms thick between the oxide and the substrate. The oxidation of Si then proceeds by Si diffusing though the Ge-rich layer. When only a thin layer of Ge is present on top of Si at the start, it acts as a marker, moving, unchanged, with the SiO2/Si interface. The rate of oxidation is enhanced in this case. The atomic motion and chemical reactions involved in the process are discussed and possible mechanisms are described to explain the data. Oxidation of a SiGeB sample is also discussed and compared with the previous case.
Low Temperature Plasma Enhanced CVD of ‘Device Quality’ Silicon Dioxide.
Authors: Batey J. , Tierney E. , Nguyen T. N. , Stasiak J. W. , Li J.
Published: March 2011

As silicon-based technologies move towards submicron dimensions, vertical and three dimensional structures, the need for reduced thermal processing becomes more evident than ever. Currently, insulator (usually SiO2) growth and deposition contribute significantly to the total thermal budget, and it is clear that this will have to be reduced in future processes. In addition, many other applications require the deposition of high quality dielectrics at very low substrate temperatures, typically ≳ 350°C. Plasma-enhanced chemical vapor deposition (PECVD) is a technique which can be used to deposit insulators at suitably low temperatures, although it tends to produce SiO2 which exhibits poor electrical and physical properties and which forms poor interfaces with semiconductor substrates. Direct exposure to the high energy environment of the plasma is generally thought to be the main reason for this.
Conduction and Injection in Off-Stoichiometry Oxides
Authors: Chang K.-T. , Lam C. , Rose K.
Published: March 2011

Slightly silicon rich oxides or off-stoichiometry oxides (OSO) have been prepared by LPCVD. When R, the nitrous oxide/silane ratio, equals or exceeds 30 these films have the refractive index and CV characteristics of stoichiometric CVD oxide. Injection into these oxides by oxides richer in silicon has been compared with injection into thermal oxides. We find that silicon rich oxides with higher silicon content having the same Research-article values provide the same enhancement of electron injection into thermal oxides and off-stoichiometry oxides. Conduction in off-stoichiometry oxides depends on preparation, but can be accounted for by tunneling between islands.
Microstructural Control through Diffusion-Induced Grain Boundary Migration
Authors: Handwerker Carol A. , Cahn John W.
Published: March 2011

Diffusion-induced grain boundary migration (DIGM) is a common, but only recently discovered low temperature phenomenon that results in high rates of both chemical mixing (or unmixing) and grain boundary migration. DIGM is found in many situations where chemical heterogeneities lead to diffusion. For example, DIGM is observed during diffusion and compound formation in polycrystalline multilayer contact systems produced by low temperature deposition techniques. The diffusional mixing along the moving grain boundary is high, localized, and results in a distinctive composition profile behind the moving interface. Theory has indicated, and experiments have confirmed, which conditions lead to DIGM and which conditions suppress it. The microstructural changes can result in either a grain refinement as seen in many metallic systems or in enhanced grain growth as seen in polysilicon. In either case these microstructural and compositional changes are controllable in a way that may allow fabrication of unique devices.
A TEM Study of the Structure of Polycrystalline Si Films on (111) Si Substrates Grown by Low Pressure Chemical Vapor Deposition
Authors: Piette Scott A. , Kiely Chris J. , Eden J. Gary
Published: March 2011

A systematic series of films have been deposited on Si (111) wafers by the pyrolytic decomposition of disilane in a low pressure CVD reactor at temperatures below 765°C, at a variety of Si2H6 partial pressures. Usually, large columnar Si grains nucleate with the [110] fiber axis parallel to the [111] substrate normal, and exhibit a random arrangement of azimuthal orientations about this axis. Fine scale microtwinning and sub-grain boundaries which are often seen within individual columnar grains have been characterized by HREM. The facetted boundaries between individual columnar grains have also been characterized. The correlation between typical grain size, defect densities and Si2 H6 partial pressure is presented and the effect of changing partial pressure during growth is shown to be detrimental to film quality. Finally it is noted that randomly oriented polycrystalline Si films can be formed under certain growth conditions.
Low Temperature Oxidation of PTSI on As-Doped Si
Authors: Gambino J. P. , Cunningham B. , Turene F. E. , Shepard J. F.
Published: March 2011

PtSi on As-doped polysilicon oxidizes rapidly at temperatures as low as 500 °C. The resulting SiO2-PtSi and PtSi-polysilicon interfaces are very rough. Silicide inclusions are present in the oxide, probably due to differences in oxidation rate between different PtSi grains. The presence of some inclusions near the SiO2 surface suggests that PtSi dissociates during oxidation. Rapid oxidation does not occur for PtSi on B or P-doped polysilicon, or for As concentrations of 1×1020 cm−3 or less.
Sb-Doped Polycrystalline Si Obtained by Means of Sb and Si Thin-Film Reactions
Authors: Gong S. F. , Robertsson A. E. , Hörnström S.-E. , Radnoczi G. , Hentzell H. T. G.
Published: March 2011

We have grown Sb-doped poly-Si by thin-film reactions between Sb and amorphous Si (a-Si). The reactions and microstructures of the films were investigated by transmission electron microscopy (TEM) during in situ annealing and Auger electron spectroscopy (AES). The reactions either resulted in an amorphous Sb-Si (a-Sb-Si) alloy or caused crystallization of a-Si at low temperatures, depending on the film thickness of the a-Si layer as well as the heating rate. The electrical properties of the as-deposited and the annealed thin multi-layers deposited on SiO2 layer were determined using Hall measurements. After annealing at 1375 K for 60 minutes, Sb-doped poly-Si with a resistivity of 1.4×10−2 ohm-cm was obtained. A p-n junction was formed in a p-type Si substrate by using an a-Si/Sb/a-Si multi-layer as a diffusion source. The doping concentration in the Si substrate was obtained using secondary ion mass spectrometry (SIMS).
Investigation of Impurity Neutralization and Defect Passivation in Polycrystalline Silicon Solar Cells
Authors: Kazmerski Lawrence L.
Published: March 2011

The passivation of grain boundaries and the neutralization of impurities in polycrystalline silicon, important processes for the improvement of performance of devices fabricated from this material, are discussed. The incorporation of hydrogen into grain boundaries is investigated using surface analysis methods. Volume-mapping techniques are used to identify the bonding mechanisms of the hydrogen in oxygen-free and oxygen-rich intergrain regions. Interactions between shallow acceptors (B, Al, Ga and In) and hydrogen in polycrystalline Si are studied. The bonding mechanisms involved in the acceptor neutralization process at the grain boundaries are evaluated using microanalytical techniques. Differences in the incorporation of molecular and atomic hydrogen, and corresponding variation in electrical passivation of grain boundaries, are observed. Volume-indexed AES and Auger difference spectroscopy data are complemented by scanning tunneling microscope images to confirm the direct hydrogen-silicon bonding in boron-doped grain boundaries.
The Polysilicon-Silicon Interface
Authors: Keyes Robert W.
Published: March 2011

Polycrystalline silicon is frequently deposited on single crystal silicon as a part of devices. The poly is used as both a dopant source and a low resistance contact in a modern method of fabricating high gain bipolar transistors. The randomness of polysilicon and its interface with the single crystal is an inherent source of differences among nominally identical transistors, however, and is a marked departure from the trend towards more and more perfect crystals that characterizes the rest of silicon technology.
Microstructures of Polysilicon
Authors: Sinclair R. , Carim A. H. , Morgiel J. , Bravman J. C.
Published: March 2011

Some typical microstructural studies of polycrystalline silicon using transmission electron microscopy (TEM) are described, including the application of this material for assisting TEM investigations themselves. Examples include oxidation and realignment of polysilicon thin films, the structure of polysilicon in EEPROM devices, polysilicon in trench capacitors and measurement of SiO2 layer thicknesses with polysilicon overlayers. It is also shown tha grain growth in heavily phosphorus doped polysilicon films can be followed by in situ heating in the TEM.
Characteristics of Arsenic Doped Polycrystalline Silicon-Gate Capacitors After Rapid Thermal Processing
Authors: Angelucci R. , Wong C. Y. , Sun J. Y.-C. , Scilla G. , McFarland P. A. , Megdanis A. C. , Landi E.
Published: March 2011

The feasibility and advantages of using rapid thermal annealing to achieve a proper n+ polysilicon work function are demonstrated. Our data shows that RTA can be used to activate arsenic in the polysilicon gate after a regular furnace anneal or to diffuse and activate arsenic without any prior furnace anneal. Interface states and fixed charges due to RTA can be annealed out at 500°C for 30 min in forming gas. New insights into the diffusion, segregation, and activation of As in polysilicon during furnace and/or rapid thermal annealing have been obtained.