bluuebunny/crossref_metadata_2025_split huggingface dataset:
Behavior of Dopant-Related Defects in AlGaAs Superlattices
Authors: Theodore N.D. , Mei P. , Schwarz S.A. , Carter C.B. , Palmstrom C. , Harbison J.P. , Florez L.T. 
Published: March 2011

AbstractDuring the course of investigation of the mixing of highly silicon-doped GaAs/AlAs superlattices, defects such as dislocation loops and Si-rich precipitates were found to form in the specimens. These defects formed at particular doping levels upon annealing of the samples. The presence of the defects can be related to changes in mixing behavior. In the present study, transmission electron microscopy has been used to characterize the defects. Superlattices with varying silicon doping levels were annealed at different temperatures for varying time-periods, to observe the temperature-time behavior of the dislocation loops. The defects aggregate preferentially in the GaAs as opposed to the AlAs in the superlattice. A number of the dislocation-loops were investigated using high-resolution TEM. All the loops observed were interstitial in nature.
The DX Center: Evidence for Charge Capture Via an Excited Intermediate State
Authors: Theis Thomas N. , Mooney Patricia M. 
Published: March 2011

AbstractWe review three important experimental results which suggest that electron capture and emission by the DX center in AlxGa1-xAs proceeds via an excited intermediate state: the very different dependencies of the thermal capture and emission rates on alloy composition, the exponential dependence of the thermal capture rate on the quasi-equilibrium Fermi energy, and the thermal activation of the hot electron capture rate. None of these results is readily explained by a conventional lattice relaxation model, in which an electron is captured directly from the lowest lying band edge, but each can be simply explained if the dominant channel for multiphonon capture is via a transition state which lies well above the band edge. This picture is consistent with recent pseudopotential calculations which predict that the lattice relaxed state (the DX state) is stabilized by capture of more than one electron, since such a model naturally admits the possibility of an intermediate one-electron state.
Theory of DX Centers in AlxGa1-x Alloys
Authors: Chadi D. J. , Zhang S. B. 
Published: March 2011

AbstractA theoretical model for DX centers which explains their unusual electronic properties in terms of two distinct bonding configurations for donor impurities in AlxGa1-x As alloys is examined. The results of our ab initio self-consistent pseudo-potential calculations show that for x > ≃20%, the normal fourfold coordinated substitutional site becomes unstable with respect to a large lattice distortion. The model explains the large difference between the thermal and optical ionization energies of DX centers.
A Photocapture Test of DX-Center Models
Authors: Hjalmarson Harold P. , Kurtz S. R. , Brennan T. M. 
Published: March 2011

AbstractThe DX-center model is widely used to explain data for the persistent photoconductivity (PPC) effect. An analysis of the DX-center model suggests a new experiment to test its correctness. In this experiment, photons near the threshold energy of the photoionization cross-section for the DX-center induce transitions from the partially occupied conduction band to empty DX-centers. This mechanism, which we call photocapture, competes with the usual photoionization which empties the DX-centers. The photocapture cross-section is estimated and an experimental attempt is made to detect photocapture. The significance of the null result is discussed.
Electronic and Optical Properties of Deep Donors in Hydrogenated AlxGa1-xAs:Si.
Authors: Mostefaoui R. , Legros R. , Chevallier J. , Tu C.W. , Kopf R.F. 
Published: March 2011

Abstract:Transient conductivity and photoconductivity experiments have been performed on hydrogenated Al0.37Ga0.63As:Si epilayers. The recapture kinetics of free electrons on the remaining deep donors is significantly affected under hydrogena-tion. The energy barrier height for capture on the deep donors drops from 210mev in the reference sample to 40mev in the hydrogenated sample. We also note a shift toward higher energies of the photoionization cross section versus photon energy curve. Different models are proposed for explaining the data.
EL-2 Defect Formation and Carbon Incorporation in GaAs grown by Organometallic Vapor Phase Epitaxy
Authors: Venkatasubramanian R. , Borrego J.M. , Ghandhi S.K. 
Published: March 2011

AbstractThe anti-site defect AsGa, EL-2, is used to understand the nature of arsenic surface species during the Organometallic Vapor Phase Epitaxy(OMVPE) of GaAs. The concentration of EL-2 in unintentionally doped n-GaAs, measured by Deep Level Transient Spectroscopy, is presented as a function of AsH3 partial pressure, TMGa partial pressure and the growth temperature. Based on this data, a model for EL-2 incorporation in OMVPE GaAs is developed in which all surface species As-H, are converted to As2 at around 765 ° C. Under the same set of growth conditions, relative carbon levels measured by 4K Photoluminescence, suggest that the increase in carbon levels with growth temperature is due to the gas-phase loss of H radical from the As-H species.
Effects of Si Incorporation and Electrical Activation on Intersubband Optical Absorption in MBE-grown GaAs/AlGaAs Multiple Quantum Well Structures
Authors: Ralston J.D. , Ennen H. , Maier M. , Ramsteiner M. , Dischler B. , Koidl P. , Hiesinger P. 
Published: March 2011

AbstractUsing SIMS profiling, temperature-dependent Hall measurements, electronic Raman scattering, and infra-red absorption, a detailed study is presented examining the effects of Si dopant behaviour on intersubband absorption in GaAs/Al .32Ga .68As MQW’s. The samples were grown by molecular beam epitaxy at substrate temperatures ranging from 520 to 680°C with Si doping in the GaAs quantum wells only. SIMS profiling reveals that, with increasing substrate temperature, substantial Si migration into the Al .32Ga.68 As barrier layers occurs during epitaxial growth. Hall measurements indicate that both at elevated growth temperatures and under reduced incident As4 beam fluxes, the electron sheet concentration is reduced in the QW’s. In both cases, loss of free carriers is attributed to enhanced Si compensation. Shifts in the absolute frequency of the infra-red absorption resonance, determined by electronic Raman scattering, as well as variations in the integrated absorption intensity, are both shown to directly reflect the growth-induced variations in the free-carrier concentration in the quantum wells.
Atomic Ordering and Alloy Clustering in MBE-Grown InAsy Sb1-y Epitaxial Layers
Authors: Seong Tae-Yeon , Norman A.G. , Booker G.R. , Droopad R. , Williams R.L. , Parker S.D. , Wang P.D. , Stradling R.A. 
Published: March 2011

AbstractMBE InASySb1-y layers were grown at 370°C across the full composition range. TEM/TED examinations directly showed that separation into two phases had taken place for compositions 0.4<y<0.8 with plates 20 to 200nm thick occurring approximately parallel to the layer surface. The two phases in the individual specimens were tetragonally distorted and their compositions were deduced from the TED results. CuPt-type atomic ordering occurred and was most pronounced in the middle of the composition range. Alloy clustering was also present. Hall measurements showed that the carrier concentration was a maximum, and the mobility was a minimum, for the middle of the composition range.
Rapid Thermal Process-Induced Defects : Gettering of Internal Contaminants
Authors: Hartiti Bouchaib , Eichhammer Wolfgang , Muller Jean-Claude , Siffert Paul 
Published: March 2011

AbstractWe show in this study that RTP-induced defects analysed by Deep Level Transient Spectroscopy (DLTS) are related to residual impurities present in as-grown silicon wafers. For one particular material an activation of a specific residual metallic impurity was observed in the temperature range 800 - 1000°C. This impurity can be returned to an electrically inactive precipitated form by classical thermal annealing (CTA) with a slow cooling rate or neutralized by means of low-energy hydrogen ion implantation.
A Hvem Study of the Electron Irradiated Defects in Nitrogen Doped FZ-Si Single Crystal
Authors: Yuzun Gao , Takeyama T. 
Published: March 2011

AbstractHigh voltage transmission electron microscope (JEM-1000) has been used to investigate the electron irradiated defects in in p-type FZ-Si and nitrogen doped p-type FZ-Si. It was found that when the irradiated conditions were the saie ,the irradiated defects were easier to be produced in the FZ-Si than in nitrogen doped FZ-Si in the temperature range 573-773 K. The defect density was higher in the foraer. The migration energy of the vacancies in the temperature range 573-773 K was 0.34 and 0.58 eV for FZ-Si and nitrogen doped FZ-Si respectively. It seems to indicate that there was some interaction between vacancies and nitrogen atoms in the nitrogen doped FZ-Si. The results proved that the nitrogen doped FZ-Si has excellent property against electron irradiation.
Radiative Recombination and Carrier Lifetimes in Surface-Free GaAs Homostructures
Authors: Smith L. M. , Wolford D. J. , Venkatasubramanian R. , Ghandhi S.K. 
Published: March 2011

AbstractWe show that the radiative efficiencies and lifetimes of photoexcited carriers in epitaxial GaAs may be enhanced by 3 to 4 orders-of-magnitude by the preparation of n+, doped layers at surface and substrate interfaces. Samples were prepared by Organo-Metallic Vapor Phase Epitaxy (OMVPE), with n-region thicknesses of 3–10 µm, and narrow layers Si-doped to n+ concentrations of 5×1018 cm-3. Time-resolved luminescence in such structures, under both surface and bulk (near-band-edge) excitation conditions, reveal near-edge-excitonic or band-to-band-dominated recombination spectra, with carrier lifetimes ranging from 1.5 nsec at 1.5 K to nearly 1 µsec at room temperature. This is in contrast to the sub-nanosecond lifetimes typical in conventionally prepared bulk GaAs, but is comparable to the best reported for high-purity LPE-prepared GaAs/AlxGa1-xAs double heterostructures. The spatial distributions of photoexcited carriers in these structures are observed to expand by over an order of magnitude during their 1 µsec room temperature lifetime. The expansion is diffusive, with a measured diffusion constant of 14 cm2/sec at 300 K. This corresponds to a room temperature mobility of 525 cm2/Vsec, comparable to previously measured hole mobilities in bulk p-type GaAs of similar purity. These results are clear evidence that the narrow, heavily doped layers effectively “shield” minority carriers from the interfaces, thereby reducing interface recombination.
Pd/Au:Be Ohmic Contacts to p-Type GaAs
Authors: Schmitz K.M. , Jiao K.L. , Sharama R. , Anderson W.A. , Rajeswaran G. , Zheng L.R. , Cole M.W. , Lareau R.T 
Published: March 2011

AbstractStable, low resistance ohmic contacts to p-type GaAs were studied for use in semiconductor laser applications. Comparison was made between Cr/Au, Au:Be and Pd/Au:Be metallizations. Regions of P+ were formed in N-type GaAs by a spin-on source which was rapid diffused at 950°C for 6s. Surface doping of 2×1020/cm3 and junction depth of 0.4 μm were determined by SIMS, groove and stain, and electrochemical profile. Metallizations were accomplished by thermal evaporation with a base pressure of 3×10-6 Torr. Sintering of the metallizations was done by furnace or RTA at 350°C. This sintering temperature was selected after RBS studies predicted an absence of significant interdiffusion. Pd/Au:Be yielded the best result of 0.3 μΩ-cm2 based upon transmission line, cross-bridge Kelvin and van der Pauw studies. A layer of BeO was revealed on the surface of Au:Be contacts by Auger studies. Cross-section TEM studies on Pd/Au:Be revealed a uniform layer of alloyed Ga-Au with an absence of spiking.
The Preparation and Properties of A New Family of Amorphous Fluoropolymers: Teflon® Af
Authors: Resnick Paul R. 
Published: March 2011

AbstractTeflon® AF is a family of amorphous fluoropolymers with glass transition temperatures as high as 300° based on bis-2,2-trfluoromethyl-4,5-difluoro-1,3-dioxole, (I), which has unusual properties [1–3] (Figure 1). The family retains the superior electrical, chemical resistance and thermal properties associated with fluoropolymers. In addition the polymers have high optical clarity, limited solubility in some commercially available perfluorinated ethers such as Fluorinert® FC-75 and improved physical properties below their glass transition temperatures (Figure 2). Teflon® AF polymers may be either solution cast into clear micron thin films or melt processed into a variety of forms.
Ceramic Fiber Composites for Electronic Packaging: Thermal Transport Properties
Authors: Zhang Hongmei , Onn David G. , Bolt Ohn D. 
Published: March 2011

AbstractThe thermal diffusivities and specific heats of several polymer matrix composites containing ceramic Fiber FP [1] and AIN fibers were measured between 20 K and 300 K. The anisotropic thermal conductivities inferred are related to specific fiber geometries and the thermal conductivities of the composite components. The high in-plane conductivities at 125K suggest possible applications for high-Tc, superconductor electronic packaging.
Low Temperature Die Attach Material
Authors: Blocker Mark A. , Herrington Tom L. , Nguyen My N. 
Published: March 2011

AbstractA new silver lead phosphovanadate glass die attach material is discussed. Its sintering characteristics are examined by dilatometry and the organic system by thermo gravimetric analysis. Sintering is found to occur at lower temperature than conventional silver glass systems. This is caused by reaction between silver and one of the glass components during heat treatment. The vehicle is found to evaporate faster allowing void free processing for large area dice.The new glass combined with a more volatile organic system has produced a single pass die attach material which can be fired as low as 360°C.
Aluminum Nitride: A Review of the Knowledge Base for Physical Property Development
Authors: Prohaska G. W. , Miller G. R. 
Published: March 2011

AbstractThe status of the publicly available knowledge base for aluminum nitride and its processing has been briefly reviewed in an attempt to clarify future research needs. Driving forces for the development of a scientific understanding of the property/process relationships have thus far been focused on thermal conductivity. Future developments may well be aimed at (1) retention of presently available properties while attempting to lower ceramic processing temperatures and (2) understanding metal-ALN and polymer-ALN interfaces. Progress has thus far been sufficient to define first generation ceramic powder requirements and sintering conditions to give adequate properties for packaged device evaluation. In addition, metal-ALN interfacial bonding, although not well developed, has shown sufficient promise to insure long-term interest in this material.
Temperature Dependence of Thermal Conductivity of Electronic Ceramics by an Improved Flash Diffusivity Technique
Authors: Enck R. C. , Harris R. D. 
Published: March 2011

AbstractThe thermal conductivity of ceramic materials used for IC substrates and packages has increased in importance as chip sizes have decreased and heat loads have risen. AIN which has a room temperature (RT) thermal conductivity (λ) greater than 200 W/m·K and BeO with λ(RT) ∼260 W/m·K are the major candidates for applications demanding high conductivity. Conflicting reports of the temperature dependences of λ for these materials over the range of interest for packaging use (≤200°C) have been published, with some reports suggesting a crossover in λ. These reported differences may be due to the reported problems in measuring λ in AIN using the flash diffusivity method. For the present experiments, we have used a new long wavelength laser flash diffusivity system which has been shown to determine thermal diffusivity to better than ± 3% for AIN with sample thicknesses ranging from 0.3 mm to 5 mm. No absorbinq coatings are required and no correction factors are needed to fit the data to theory. We report λ from room temperature to 400°C for AIN from a number of commercial sources, and for BeO and SiC. At room temperature, BeO has the highest thermal conductivity, but as the temperature is raised, the values for BeO and AIN approach one another, with crossover observed at about 350°C for the highest conductivity AIN sample studied. Recent steady state heat flow measurements agree with our thermal conductivity values rather than with previous literature values.
Temperature Dependence of the Thermal Conductivity of Materials for Microelectronic Packaging: Measuring and Modelling Effects of Microstructure and Impurities
Authors: Dinwiddie Ralph B. , Onn David G. 
Published: March 2011

AbstractThe materials studied in this research, having a wide range of thermal conductivities, permit a study of the mechanisms which affect their behavior. Data on the thermal conductivity of several substrate materials, over a wide temperature range, were analyzed using the Klemens model. Parameters in this model, which include crystallite size and impurity concentration, are determined through a nonlinear least squares fitting routine and related, where possible, to values obtained by other techniques. This analysis predicts an achievable upper limit of 290 W/m.K for very high purity sintered AlN with 5 micron crystallites.
Time-Resolved Luminescence of Oxygen Related Defects in Aluminum Nitride
Authors: Harris J. H. , Youngman R. A. 
Published: March 2011

AbtractA charged defect model for the formation of band-tail states, first proposed by Redfield et al. to understand the optical properties of Si doped GaAs [1], is applied to oxygen doped aluminum nitride (AIN) ceramics. In this case, oxygen substituting on a nitrogen site and (subsequently formed) aluminum vacancies comprise the charged centers. The results of optical absorption edge measurements as well as steady state and time-resolved luminescence between 10 and 300K are used to support this model. Finally, it is noted that the mixed covalent and ionic nature of bonding in AIN make it a model system for this charge defect picture, and thus explains the extremely large extent of the band-tail states in this material.
Real-Time Investigation of Solid and Liquid State Reactions In Au-Sn/Cu System
Authors: Oh Seyong , Khandros Igor Y. , Poetzinger Janet L. 
Published: March 2011

AbstractA real-time x-ray analysis technique has been developed and employed for in-situ investigation of solid and liquid state reactions in Au-Sn/Cu system as a function of temperature. Typically, 1 μm eutectic Au-Sn films were deposited on 1.5 μm Cu layers on Si wafers. Phase changes in Au-Sn films on Cu from ambient to above the eutectic temperature have been investigated. Cu diffusion into Au-Sn film above 250 °C resulted in a ternary Au-Sn-Cu compound and raised the melting temperature of the structure to about 325 °C. This affects joining characteristics of the Au-Sn metallization.
Polyimide-Ceramic Substrate for Supercomputer Packaging
Authors: Kimbara K. , Dohya A. , Watari T. 
Published: March 2011

AbstractThis paper introduces the Polylmide-Ceramic substrate for NEC SX Supercomputers. In case of high performance system such as supercomputers and top end machines in general purpose computer, sophisticated packaging technologies are essential to achieve fastest operations as well as to use highestspeed, highly integrated LSIs.Wiring substrate which mounts and interconnects LSIs is the key to back up LSI's higher logical-operations.The high speed interconnection wirings and high density LSI mounting are requested for substrate.The Polyimide-Ceramic substrate had been developed to meet these demands and have many features of high density thin film wiring, high power supply, high thermal conductivity and huge number of I/Os, in addition to high speed wiring.25μm wide 75μm center-to-center spacing, two signal layers, 6ns/m signal transmissions, 2.5W/cm2 high power density, 2177 I/Os on a 100mm square substrate have been achieved by using this super substrate technology.The packaging hierarchy, the first level packaging of TAB LSI, the second level of multi-chip packaging by using Polyimide-Ceramic substrate and liquid cooling module, and the third level of board assemblies are introduced.
Microstructure and Kinetics of the Interface Reaction Between Titanium Thin Films and (112) Sapphire Substrates
Authors: Selverian J.H. , Ohuchi F.S. , Notis M.R. 
Published: March 2011

AbstractWe studied the reactivity of titanium with the R-plane (112) surface of sapphire by transmission electron microscopy (TEM), x-ray diffraction (XRD), and Rutherford backscattering (RBS) techniques. Cross-section TEM specimens were prepared from 200–400 nm thick titanium films deposited on sapphire at 25, 525, 554, 562, 580, 630, and 663°C to observe the interfacial region. In samples deposited at 25°C, without further annealing, no reaction zone could be seen in the TEM. In all other samples titanium reduced the sapphire to form Ti0 6 7[O0 3 3] and Ti3Al[O], Ti and Ti3Al with oxygen in solid solution. An activation energy of 24.7 ± 6 kcal/deg-mole was determined for the growth of the Ti3Al[O] layer. Layer thickness measurements from the TEM and RBS studies were within 10–20% of one another.
In-Plane Residual Stresses in Filament-Evaporated Aluminum Films on Single Crystal Silicon Wafers
Authors: Park Hai-Woong , Danyluk Steven 
Published: March 2011

AbstractThe in-plane residual stresses of single crystal silicon wafers that were coated with filament-evaporated aluminum films have been obtained from measurements of strains produced by shadow Moir interferometry. The aluminum films were deposited as thin film layers over a 8.9cm diameter area on (100) p-type, 10.16cm diameter, 0.05cm thick single crystal silicon wafers, and the stresses were determined by an analysis that accounts for the finite dimensions of the samples. The aluminum film thicknesses varied from 70 to 78Onm. The aluminum films increased the inplane stresses of the wafers by 3 to 15MPa depending on the film thickness.
Material Development Challenges in High Density Pakaging of Advanced VLSI Memory Devices
Authors: Prough Steven D. , Pope D. Elaine 
Published: March 2011

AbstractAdvances in semiconductor memory storage technology are making possible the development of high density memory cards for hand held and portable product applications. This in turn is driving development of ever denser, ultra-thin component packages. Both materials and package design must be more robust in order for next generation packages to withstand surface mount reflow soldering stresses. Trade-offs among ercapsulant properties may be possible in view of new interconnect, die surface protection and leadframe design technologies which are being adopted for high density packaging. Materials and packaging engineers are challenged to capitalize on opportunities offered by these changes in order to optimize strength and moisture resistarnce in developing encapsulating materials for the new generation of packages.
Optical Interconnect Switch
Authors: Prucnal Paul R. , Perrier Philippe A. 
Published: March 2011

AbstractA novel photonic interconnect architecture is proposed which can provide extremely high dimensionality. The proposed architecture, which resembles a collapsed network, avoids the difficulties associated with the use of optical crosspoints. This is accomplished by providing a dedicated path for all input- and output-port connections on a common transmission medium. This eliminates the restrictions imposed by 2×2 switching elements in classical space-division switching architectures.