bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Residual Stresses on the Rupture Properties of Film/Substrate Samples
Authors: Ignat M. , Chouaf A. , Bernard C. , Terriez J.M.
Published: March 2011

The residual stresses of two different film/substrate systems were calculated. Besides, several micromechanical tests were performed. Joining the calculated residual stresses to the analysis of the experimental results, some insight on the interfacial adhesion of film/substrate systems is presented.
Residual Stress Analysis of A Multi-Layer Thin Film Structure by Destructive (Curvature) and Non-Destructive (X-Ray) Methods
Authors: Chen P.C. , Oshida Yoshiki
Published: March 2011

Multi-layer thin film which has structure of Cu/Cr/K/Cr/Cu prepared by sputtering process was analyzed for interfacial stresses for as-deposited conditions. This structure was also annealed at 150°C, 250°C, and 350°C for around 15 min. in a vacuum and cooled slowly down for stress analyses.

Equations derived by Osgood [1] for residual stress estimations for homogeneous material system using layer removal technique (stress relief) is now applied for inhomogeneous system (multilayer structure). The results are compared with the data obtained from x-ray diffraction technique by using sin2Ψ-2θ method, for Cu layer.

From the present analyses, the data obatined using layer removal seem to be qualitatively consistent with but not quantitatively in agreement with x-ray method. Data obtained using the layer removal method have some overlaps with those obtained from x-ray technique. However, in details, data from the curvature method present different scattering band from the x-ray method. It is suggested that the layer removal method is more practical to be used to estimate the average residual stress of the multi-layer system not only because the layer removal method estimates the bulk behavior but also when the metal film is thin (e.g., 200A for Cr layer), x-ray technique becomes impractical. By annealing the sputtered structure up to 250°C, the residual stresses, in particularly Cu layer, decreased on both sides in x- and y-directions.

From the main results drawn from the present studies, the layer removal sequence for the curvature method shows significant affects on the obtained results of residual stresses. Minimizing influences caused by layer removal sequences as well as removing duration and temperature provides the most accurate results on residual stress measurements.
Study of Contact Angles of Metals and Alloys on the Superconducting YBa2Cu3O7-x
Authors: Chan Siu-Wai , Bader W. G. , Yeung N. S. , Hull G. W.
Published: March 2011

Wettability and contactibility of selected metals and alloys on superconducting YBa2Cu3O7-x were studied. Droplets of metals and alloys were formed by melting short segments of wires on pellets of YBa2Cu3O7-x The wires were melted in a rapid thermal annealer with an oxygen atmosphere to lessen the oxygen loss from the YBa2Cu3O7-x surface. The contact angles of the solidified droplets on the pellets were measured from the micrographs taken with a scanning electron microscope. Contact angles less than 90° were obtained with Pb and Ag, while angles greater than 90° were obtained with Bi metal, 40Pb/60Sn, and 99Pb/lSb alloys. Pb alloyed with either Sn or Sb increased the wetting angles. The contact angles provided a direct measurement of wetting characteristics and were used to relate various surface energies and the work of adhesion between tested metallic systems and YBa2Cu3O7-x.
Mechanical Damping and Dynamic Modulus Measurements in Continuous Fiber-Reinforced Composite Materials: Al/Al2O3 and Al/W
Authors: Wolfenden Alan , Wolla Jeffrey M.
Published: March 2011

Measurements of mechanical damping, or internal friction (Q−1), and dynamic Young's modulus (E) have been made near 80 kHz and at strain amplitudes (ε) in the range of 10−8 to 10−4 on small specimens of the following two continuous fiber-reinforced metal matrix composites (MMCs): 6061 aluminum reinforced with alumina (Al/A12O3) and 6061 aluminum reinforced with tungsten (AI/W). Baseline experiments were also performed on 99.999% aluminum (pure Al) for comparison puposes. The temperature (T) dependence of modulus up to 475°C was determined for AI/A12O3 and pure Al. The rate of modulus decrease with increasing temperature for AI/A12O3 and Al was the same, that is, dE/dT was essentially the same for both materials. Thus, the reduction in modulus observed for the Al/Al2O3 was attributed to the reduction in modulus of the Al matrix and not that of the Al2O3 fibers. The strain amplitude dependence of damping was examined for all three materials. The pure Al exhibited classical dislocation damping behavior with strain amplitude dependent damping starting at a strain of 2 × 10−5. The Al/Al2O3 specimens showed only mild dependence of damping on strain amplitude starting at strains near 10−5. The AI/W exhibited significant amplitude dependence of damping starting at strains of 2 × 10−6 with the fiber diameter being a major factor in determining the damping behavior. The Q−1 versus ε data for Al/Al2O3, when analyzed in terms of the Granato-Lücke (GL) theory for dislocation damping, yielded minor pinning lengths of dislocations near 10−8 m and mobile dislocation densities near 1011 m−2. The same analysis for the Al/W data gave values near 10−8 m for the minor pinning lengths and 1012 M−2 for the dislocation density. Relative to the results for pure Al, the minor pinning lengths for Al/Al2O3 and AL/W are comparable (10−8 m for pure Al), but the dislocation densities are much higher (109 m−2 found in the pure Al). The relatively high dislocation densities calculated for these aluminum matrix MMCs agree with previous findings of other researchers and may be associated with the fiber/matrix interface.
An Atomistic Study of the Nickel-Alumina Interfacial Reactions
Authors: Zhong Q. , Ohuchi F. S.
Published: March 2011

The initial stage of formation of the Ni/A12O3 interface under different conditions was studied by various surface science techniques. Nickel was deposited in situ in a UHV system onto the basal plane of a sapphire substrate at various temperatures and oxygen partial pressures. The interfacial reaction processes were simultaneously monitored by XPS. When Ni was deposited at elevated temperatures and in the presence of sufficient oxygen, the NiAl204 spinel was formed epitaxially on the Al2O3 substrate, as confirmed by LEED. While under UHV conditions (<4×10−11 torr) and at elevated temperatures (<800°C), the Al2O3 was partially reduced by Ni, and the evidence of Ni-Al intermetallic alloy formation was observed. Further efforts include the construction of a UHV system capable of preparing interfaces suitable for interfacial structure and adhesion studies.
Interfacial Reactions in the Al/Si3N4/Si and Au/Si3N4/Si Systems
Authors: Edelman F. , Gutmanas E. , Brener R.
Published: March 2011

The interface chemistry and structure of thin Al and Au films deposited on Si3N4 have been studied. In the case of Al/Si3N4 system, an interfacial AIN like layer was observed in the as-deposited state. The thickness of this layer was found to increase with increasing the temperature up to 600°C. This thin AlN layer acts as a diffusion barrier which prevents Al to diffuse into Si3N4 Furthermore, Si released in the reaction between Al and Si3N4 appears to crystallize into small islands dispersed in the interfacial region. In contrast to Al, no reaction between Au and Si3N4 was observed in the as-deposited state. However, after heat treatment at temperatures higher than 400°C gold silicides (Au5Si2,Au2Si,Au3Si) with a very thin Si layer accumulated on the Au surface were observed.
Electrical and Material Characterization of the Stability of ALGaAs and GaAs Planar Doped Structures
Authors: Sadwick Larry P. , Streit Dwight C.
Published: March 2011

In this work we have studied the effects of silicon planar doping on the electrical and optical properties of GaAs, and the effects of rapid thermal annealing on AIGaAs planar-doped structures. MBE-grown GaAs epilayers with multiple planar-doped layers displayed a 1.2 eV photoluminescence peak, presumably due to gallium vacancy - donor complexes, for samples with nominal silicon sheet densities much greater than measured charge densities. The Hall mobilities of these samples were also reduced compared to both uniformly-doped and planar-doped structures whose silicon areal densities were more nearly equal to measured sheet charge densities, although X-Ray rocking curves were nearly identical in all cases. Planar-doped AIGaAs Schottky diodes had nearly ideal electrical characteristics. Rapid thermal annealing of the planar-doped structures before fabrication increased the diode ideality factor from n=1.06 to n=1.60, seriously degraded the saturation current and breakdown voltage, and increased the doping profile FWHM from 60Å to 170Å.
Photoluminescence Studies of Impurities and Defects in Mercuric Iodide
Authors: Bao X.J. , Schlesinger T.E. , James R.B. , Cheng A.Y. , Ortale C.
Published: March 2011

We have studied the effects of chemical etching in potassium iodide(KI) aqueous solution, vacuum exposure and bulk heating on the photoluminescence(PL) spectra of mercuric i0dide(HgI2). Different contact materials deposited onto HgI2 were also investigated, such as Pd, Cu, Al, Ni, Sn, In, Ag and Ta. These processing steps and the choice of a suitable electrode material are very important in the manufacturing of high-quality mercuric iodide nuclear detectors. Comparisons are made between the front surface photoluminescence and transmission photoluminescence spectra.
Electrical and Photoluminescence Properties of Mg+ and C+ Implanted Acceptors in InP.
Authors: Beye A.C. , Yamada A. , Shimizu A. , Shibata H. , Tanoue H. , Mayer K.M. , Sugiyama H. , Kamijoh K. , Oda T. , Arriga O. , Akiyama I. , Kutsuwada N. , Matsumori T. , Uekusa S. , Makita Y.
Published: March 2011

Implantation of Mg+ and C+ ions is carried out in bulk InP substrates using single or several energies up to 400 keV. The net carrier concentration profile at 300K is measured by capacitance-voltage (C-V) method. The ground and excited states binding energies of Mg and C acceptors are determined by low-temperature selective excitation of photoluminescence (PL). Additional sharp exciton-Iike emissions are detected after annealing of the samples. Their intensity is found to decrease with increasing Mg+ or C+ dose. Annealing-induced activation and/or formation of complex defect are the likely candidate mechanisms for the involved defect.
Optically Detected Magnetic Resonance of Sulfur Doped Gallium Phosphide
Authors: Brower K. L.
Published: March 2011

An isotropic optically detected magnetic resonance (ODMR) having a Lorentzian lineshape at g - 2.050 ± 0.003 and linewidth (FWHM) of 67.3 mT is observed in GaP doped with 6 - 9 × 1017 S/cm3. The ODMR at g - 2.050 is believed to arise from free electrons (or holes) in the conduction (valence) band. This ODMR is completely quenched due to non-radiative recombination in the vicinity of g - 1.99.
Infrared Absorption Study of Zinc-Doped Silicon.
Authors: Merk E. , Heyman J. , Haller E. E.
Published: March 2011

We report high resolution infrared absorption spectra associated with the deep zinc acceptor in silicon. The optical transitions between ground and bound excited “p-like” states of the neutral helium-like double acceptor Zn0 center have been observed for the first time. The absorption cross section for the hole transition is found to be very small, of the order of 10-17 cm2. Energy spacings of the P3/2 Rydberg series are very similar to the spacings of the group-III acceptors, suggesting that, in spite of the large ground state binding energy, effective mass approximation still applies to the bound excited states. This represents one more case where the strong central cell potential does not significantly disturb the neutral helium-like bound excited states. Similar observations have been made for the less deep neutral double acceptor Be, and for the chalcogens donors S, Se and Te.

The optical ionization energy of Zn0/- has been determined to be 2575 cm-1 (319 meV).

Two additional sets of absorption lines related to zinc have been observed at 2130 cm-1 and 2758 cm-1. Their origin will be discussed.
Correlation of the 0.8 eV Emission Band with the EL6 Center in GaAs
Authors: Alaya S. , Zaidi M. A. , Marrakchi G. , Maaref H. , Von Bardeleben H. J. , Bourgoin J. C.
Published: March 2011

Combined photoluminescence and DLTS investigations of semi-insulating and n-type GaAs before and after a 15min, 850°C heat treatment under AsH3 reveal that the treatment which anneals the EL6 center leads also to a disappearence of the O.8eV PL band. The suggested correlation between EL6 and the O.8eV PL is confirmed by the determination of the electron capture barrier of EL6 and the Franck-Condon shift deduced from the temperature dependence of the PL band leading to a consistant Configuration Coordinate diagram of this defect.
The Electronic Structure of the “0.15 eV” Cu Acceptor Level in GaAs
Authors: Janzén E. , Linnarsson M. , Monemar B. , Kleverman M.
Published: March 2011

Cu diffused GaAs samples have been investigated using different kinds of FΠR techniques and photoluminescence. The results suggest that tne “0.15 eV” level originates from the ioruzation of a neutral, nearly substitutional Cu acceptor at a Ga site. Furthermore, the results indicate a distortion in the [100] direction. The ground state binding energy obtained from the effective-mass-like excited states is 157.8 meV at 6K.
The Deep 0.11eV Manganese Acceptor Level in GaAs
Authors: Kleverman M. , Janzén E. , Linnarsson M. , Monemar B.
Published: March 2011

The 0.11 eV Mn acceptor has been investigated using different kinds of FΠR techniques, Zeeman spectroscopy, and photoluminescence. The results clearly fits into the Зd5+ shallow hole model for Mn° and show that the 0.11 eV level originates from the io-nization of a neutral, substitutional Mn acceptor at a Ga-site. The ground state binding energy obtained from the effective-mass like excited states is 112.4 meV.
Optical Properties of Novel Vibronic Bands in Electron-Irradiated Tin Doped Silicon
Authors: Svensson J. H. , Monemar B. , Svensson B. G.
Published: March 2011

The optical absorption of two new electronic transitions in silicon doped with tin has been investigated. At low temperatures two no-phonon lines are observed at 2755.3 and 4112.2 cm-1, each with strong coupling to a single quasi-localized vibration in the excited electronic state. These vibrations have quantum energies of 69.6 and 70.2 cm-1, respectively. At higher temperatures coupling to thermally excited vibrational states in the ground electronic states is observed for both lines. The transition with the no-phonon line at 4112.2 cm-1 has been studied in detail and is found to be well described using the adiabatic and Condon approximations. The optical properties of the two transitions are found to be quite similar. Moreover the relative intensities of the two lines are found to be dependent on the optical excitation conditions.
A New Metastable Defect in Silicon, Optical Properties and an Investigation of the Mechanism Causing the Configurational Change
Authors: Svensson J. H. , Monemar B.
Published: March 2011

A new optical transition with a no-phonon energy of 0.615 eV discovered in electron-irradiated silicon grown by the Czochralski technique is investigated, revealing metastable properties of the related defect. The investigation is focused on the optical properties of the transition and its associated structure and on the mechanism governing the change of defect configuration. The transformation of the defect to the metastable state is suggested to be induced by excitonic Auger recombination. A pseudo-donor model is presented as an explanation of the optical spectrum.
Uniaxial Stress and Zeeman Measurements on the 943 meV Luminescence Band in Silicon
Authors: Carmo M.C. , Mcguigan K.G. , Henry M.O. , Davies G. , Lightowlers E.C.
Published: March 2011

The photoluminescence from silicon lightly doped with copper and rapidly quenched from ~ 1100° C is dominated by a vibronic band with zero--phonon lines (ZPL) in the region of 943 meV. We have studied the effect of external fields on the electronic properties of this band and the results are consistent with the luminescence occurring at a defect with Td symmetry. The Zeeman measurements indicate that the luminescence is due to the recombination of excitons in J = 1, J = 2 states with the normal ordering of these levels reversed. This reversal is explained by the different response of these states to hydrostatic strains, and it is also argued that strain at the defect provides the binding potential for the exciton.
Defect-Formation Dependence on Group V-Dopant Atoms in Electron-Irradiated Silicon
Authors: Awadelkarim O.O. , Henry A. , Monemar B. , Lindström J.L.
Published: March 2011

The defect states introduced in P-, As- and Sb-doped silicon upon room-temperature electron-irradiation are studied by deep-level transient spectroscopy (DLTS). Evidence is provided for the involvement of the P-atom and the vacancy in the defect complex giving rise to the prominent electron trap commonly observed at ≈ EC-0.4 eV (EC being the edge of the conduction band). This electron trap together with another at EC-0.30 eV, apparently phosphorus related, exhibit configurationally metastable behaviour. Other electron traps observed at EC-0.27 eV and Ec-0.51 eV in Sb-doped material and EC-0.34 eV in As-doped material are attributed to complexes involving Sb and As atoms, respectively.
Hydrogen in Crystalline and Amorphous Silicon
Authors: Chiarotti Guido L. , Buda F. , Car R. , Parrinello M.
Published: March 2011

We investigate static and dynamic properties of hydrogen in crystalline and amorphous silicon by means of ab initio molecular dynamics simulations. In the crystalline case we focus mainly on the diffusion process of an isolated positively charged hydrogen impurity at high temperature. In the amorphous case we analyze the local order and the dynamical properties corresponding to an atomic hydrogen concentration of ~ 11%, typical of a device quality material. In both crystalline and amorphous cases, our results are in good agreement with available experimental data and give unique insight into the microscopic details of hydrogen incorporation in silicon.
Dissociation Kinetics of Shallow-Acceptor-Hydrogen Pairs in Silicon
Authors: Zundel T. , Weber J.
Published: March 2011

Annealing of hydrogenated p-type silicon with a reverse bias applied to a Schottky diode allows us to precisely determine the dissociation frequency vA of shallow acceptor-hydrogen pairs (AH with A = B, Al, Ga, and In). The temperature dependent values of vA satisfy the relation vA = voAexp (-EA/kT), with voB = 2.8 . 1014 s-1, voAl = 3.1 . 1013 s-1, VoGa = 6.9 . 1013 s-1, and voIn = 8.4 · 1013 s-1. The dissociation energies EA depend only weakly on the acceptors: EB = (1.28±0.03)eV, EAl = (1.44±0.02) eV, EGa = (1.40±0.03) eV, and EIn = (1.42±0.05) eV. The dissociation frequency of BH pairs shifts to a lower value when H is replaced by the deuterium isotope.
Passivation of Zn-Acceptors in InGaAs During Rie with CHF3/H2 and CH4/H2
Authors: Möhrle Martin
Published: March 2011

Reactive ion etching of highly Zn-doped InGaAs with hydrogen-containing gases such as CHF3/H2, CH4/H2 and CH4/He leads to a drastical reduction of the concentration of electrically active acceptors in a near-surface layer. Ti/Pt/Au contacts applied on as-treated p++-InGaAs layers show non-ohmic I/V-characteristics due to this passivation effect. Annealing at moderate temperatures (330°C, 20 minutes) was found to restore full electrical activity.
Surface Protection during Plasma Hydrogenation for Acceptor Passivation in InP
Authors: Lopata J. , Dautremont-Smith W. C. , Pearton S. J. , Lee J. W. , Ha N. T. , Luftman H. S.
Published: March 2011

Various dielectric and metallic films were examined as H-permeable surface protection layers on InP during H2 or D2 plasma exposure for passivation of acceptors in the InP. Plasma deposited SiNx, SiO2, and a-Si(H) films ranging in thickness from 85 to 225 Å were used to protect p-InP during D2 plasma exposure at 250°C. Optimum protective layer thicknesses were determined by a trade-off between the effectiveness of the layer to prevent P loss from the wafer surface and the ability to diffuse atomic H or D at a rate greater than or equal to that in the underlying InP. SIMS and capacitance-voltage depth profiling were used to determine the extent of D in-diffusion and acceptor passivation respectively. Sputter deposited W and e-beam evaporated Ti films ~100 Å thick were also evaluated. The W coated sample yielded similar results to those with dielectric films in that acceptors in p-InP were passivated to a similar depth for the same plasma exposure. The 100 Å Ti film, however, did not allow the D to diffuse into the InP substrate. It is surmised that the Ti film trapped the D, thus preventing diffusion into the substrate.
Determination of Diffusion Parameters for Arsenic
Authors: Heinrich Michael , Budil Matthias , Pötzl Hans W.
Published: March 2011

This paper deals with an analysis of the oxynitridation and direct nitridation experiments of Fahey et al.(1984[1]). The inconsistencies in the evaluation of the fiactional component of diffusion for aisenic are discussed. Using a recently developed diffusion model an explanation for the diffusion data for arsenic is given. The standard equation for analyzing diffusion under nonequilibrium conditions is shown to lead to erroneous results. A consistent treatment must account for the concentrations of arsenic, point defects and arsenic point defect pairs. Pair formation kinetics must be included. Values are presented for the diffusion constants DIAs, DVAS, and the reaction constants kIAs, kVAs depending on the fractional interstitial component of diffusion .
Measurements of Enhanced Oxygen Diffusion in Silicon During Thermal Donor Formation: New Evidence for Possible Mechanisms
Authors: Brown A.R. , Murray R. , Newman R.C. , Tucker J.H.
Published: March 2011

Czochralski silicon has been heated in a H-plasma at temperatures in the range 300-450°C, and compared with furnace annealed material. Plasma treatments produce enhanced rates of oxygen diffusion jumps, loss of oxygen from solution and formation of thermal donor centres. The available evidence indicates that atomic hydrogen catalyses the enhancements via the oxygen diffusion rate. Donor concentrations greater than 1017cm-3 have been observed in samples heated in a plasma at 350°C. Doubts have been raised about dimer formation being the primary mechanism for oxygen loss in furnace anneals at 350°C, but invoking enhanced diffusion leads to a conflict with stress dichroism data.
Anomalous Transient Tail Diffusion of Boron in Silicon: Kinetic Modeling of Diffusion and Cluster Formation
Authors: Cowern N.E.B. , Jos H.F.F. , Janssen K.T.F. , Wachters A.J.H.
Published: March 2011

A kinetic modeling approach is used together with experimental studies to gain insight into the processes taking place during anomalous transient diffusion. A physical process analogous to B clustering is found to play an important role, even at B concentrations well below the solid solubility limit.
Failure of the “Kick-Out” Model for the Diffusion of Au into Si when Tested by Monte Carlo Simulation
Authors: Schmid U. , Van Vechtent J. A. , Myers N. C. , Koch U.
Published: March 2011

We have performed large scale computer simulations on the controversial issue of Au diffusion into Si at T = 1095° C. Using a Monte Carlo algorithm and a conveniently parametrized set of parameters, our computer program is capable of working out the macroscopic consequences of a variety of models, i.e. atom level assumptions, in an unbiased way and without the approximations introduced in analytic calculations.

When applied to the “kick-out” hypothesis, our results are dramatically at odds with the properties claimed by its proponents. Neither the profile of the Au substitutionals, nor the Au-interstitial profiles are in agreement with the analytically obtained results. The discrepancy becomes most pronounced when comparing the variation with time of the Au concentration in the center of the sample, which we find to be linear at all times, in contrast to the alleged t1/2 behavior. Moreover, the Au profile of a one-sided diffusion never becomes U-shaped, as experimentally observed.
Diffusion of Au in Amorphous Si Measured by the Artificial Multilayer Technique
Authors: Nygren E. , Park B. , Goldman L.M. , Wu D.T. , Wagner A.V. , Spaepen F.
Published: March 2011

The diffusivity of Au in amorphous Si (a-Si) has been determined in the temperature range 200-260°C using and Ar-ion sputter deposited artificial multilayered films of a-Si and a-Si(0.7at%Au) with repeat lengths between 44 and 48 Å. Diffusion on lengths scales of the order of interatomic spacings have been investigated. The Au diffusivity exhibits an Arrhenius temperature dependence with an activation enthalpy of 1.2eV and shows good agreement with extrapolations of higher temperature Au diffusion data obtained by Rutherford backscattering spectrometry (RBS) in ion-implanted, CVD, and sputter deposited a-Si. The measured Au diffusivity also shows a significant time dependence.
Photoluminescence Excitation Spectroscopy of MOCVD-Grown: GaAs:V
Authors: Kao Y.J. , Haegel N.M. , Hobson W.S.
Published: March 2011

Photoluminescence excitation spectra have been obtained at 4.2 K for the characteristic V3+ intra-center emission (0.65 – 0.75 eV) of MOCVD-grown GaAs:V. Oscillatory structure of the PLE spectrum with above-band-edge excitation has been observed in GaAs:V for the first time. The oscillatory period is found to be 41.3 ± 0.5 meV, corresponding to , and is due to energy relaxation of conduction band electrons through LO phonon emission. Our results suggest capture by a shallow donor as an intermediate step in the luminescence from the V center.
Atomic Layer Epitaxy of GaAs on Ge Substrates
Authors: Ramdani J. , Mcdermott B.T. , Bedair S.M.
Published: March 2011

We report on the low temperature growth of GaAs on Ge substrates using Atomic Layer Epitaxy. Low temperature deposition has resulted in substantial reduction of the outdiffusion of Ge into the GaAs epilayer as being indicated from SIMS. The I-V characteristics of the GaAs/Ge heterojunction were thyristor like or near abrupt depending on the growth temperature. We also report on the use of the Atomic Layer Epitaxy self-limiting adsorption process of TMGa to control the diffusion of Ga into Ge substrates at the monolayer level.
An Examination of the Mechanisms of Si Diffusion in GaAs
Authors: Yu Shaofeng , Gosele Ulrich M. , Tan Teh Y.
Published: March 2011

An examination of the three available quantitative models of Si diffusion in GaAs has led to the conclusion that the Fermi-level effect mechanism plays the most essential role. In some experimental results a point defect concentration transient is involved which should be incoorporated in future models.
Mechanism for the Diffusion of Zinc in Gallium Arsenide
Authors: KAHEN K. B.
Published: March 2011

The anomalous shape of the Zn diffusion profile in GaAs has been quantitatively explained. The interchange between interstitial Zn and substitutional Zn is assumed to occur via the Ga vacancies. These vacancies are proposed to be either neutral or singly ionized, depending on the position of the Fermi level. In addition, two physical phenomena are proposed. Substitutional Zn thermally generates interstitial Zn-Ga vacancy pairs and there is pairing between the donor, interstitial Zn and the acceptor, substitutional Zn. This pairing leads to the interstitial Zn diffusivity being a decreasing function of the substitutional Zn concentration. The model is found to be in good agreement with the experimental data.
Diffusion of Ion-Implanted Tin in Gallium Arsenide
Authors: Allen E.L. , Deal M.D. , Plummer J.D.
Published: March 2011

The diffusion of ion-implanted tin in gallium arsenide was investigated as a function of temperature, dose and background doping. The chemical depth profiles were determined using SIMS and the carrier profiles were determined by CV Etch Profiling. The data was fit using a numerical process simulator, SUPREM 3.5. Sn diffusivity was found to depend on the square of the electron concentration. Sn and Ge were found to have relatively high diffusivities when implanted, while Si diffused very little.
Impurity-Induced Layer Disordering: Current Understanding and Areas for Future Investigation
Authors: Guido L.J. , Holonyak Nick
Published: March 2011

The purpose of this work is to give an overview of the current phenomenological understanding of impurity-induced layer disordering (IILD). First, we identify key experimental findings such as the influence of the crystal surface-ambient interaction, the Fermi-level effect, and the impurity concentration on Al-Ga interdiffusion. Second, we review the strengths and weaknesses of existing IILD models in consideration of the above mentioned experimental data. Finally, we discuss the pitfalls involved in generalizing the results of individual Al-Ga interdiffusion experiments in order to explain a broader collection of IILD data.
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

During 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

We 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

A 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

The 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

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

The 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

Using 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

MBE 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

We 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

High 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

We 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

Stable, 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

Teflon® 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.
Characterization of Dielectrics Over Broad Electrical Bandwidths
Authors: Arjavalingam G. , Pastol Y. , Halbout J.-M. , Kopcsay G. V.
Published: March 2011

There is considerable recent interest in the dielectric properties of materials measured over broad electrical bandwidths. This follows from advances made in the performance of electronic devices which now produce pulses with risetimes in the order of 5 picoseconds. It is essential to know the dielectric constants and loss properties of the materials used in fabricating these devices and their interconnection structures, up to frequencies of about 100 GHz. Moreover, such information will be invaluable for the effective use of microwaves in materials processing [1]. The curing of polymers and the sintering of ceramics are two examples. Here, we discuss the recently developed coherent microwave transient spectroscopy (COMITS) technique which measures the complex dielectric constants of materials, from 10 GHz to about 125 GHz, in a single experiment [2,3].
Ceramic Fiber Composites for Electronic Packaging: Thermal Transport Properties
Authors: Zhang Hongmei , Onn David G. , Bolt Ohn D.
Published: March 2011

The 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

A 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

The 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

The 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

The 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.