bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study of Microdeformation and Creep-Fatigue Damage using Acoustic Emission Technique
Authors: Liu Yunxu , Li Xingren
Published: March 2011

This paper deals with the relationship between the plastic deformation damage and microstructure by means of Acoustic Emmission. The plastic deformation behavior of AISI 4340 steel of various microstructures was investigated in both the tensile and creep-fatigue testings with a view to providing new insights into properties of high performance steel. Based on Theory of Damage Mechanics, a creep-fatigue law was derived and formulated. The reason of early failure and the service life prophecy of high strength steels was studied.

The damage micromechanism of four stages was studied by the optical microscope, scanning electron microscope, and microhardness tester. It seems that the nucleation and the growth of the voids at the martensiteferrite interface is the dominant mechanism of damage. The monitoring of Acoustic Emmission indicated that the plastic deformation did not appear in the circulating hardening stage. But in the circulating softening stage, the accumulation of the plastic deformation and the creep-fatigue damage become more and more severe. The total energy of Acoustic Emmission was successfully applied to measure the degree of the damage caused by the plastic deformation.
A Study of High Temperature Damage Processes Using Microradiography
Authors: Benci J. E. , Pope D. P.
Published: March 2011

Synchrotron radiation and microradiographic techniques were used to study the development of creep damage in notched tensile samples. The creep damage in these samples was recorded using microradiography. The density and distribution of creep damage was measured from the microradiographs using an image analysis system. The results from the image analysis can be compared to damage predictions from finite element models of the damage process to determine the quality of these models.

Notched tensile samples of copper, iron and a low alloy steel were subjected to slow strain rate tensile tests at 500°C or 700°C. The tests were interrupted after various fractions of the creep lives had been expended. 1 mm thick longitudinal sections were then removed from the center of each sample for microradiography using electro-discharge machining.

Creep damage in the copper alloy was concentrated in a fairly narrow band around the plane of minimum cross-section in the samples. This is in stark contrast to the results from iron and the low alloy steel. The creep damage in these materials developed at fairly sharp angles to the notch or crack plane. These results show that the damage process in iron and this steel is controlled by the equivalent stress while the formation of damage in copper is controlled by the maximum principal or hydrostatic stress.
Dynamic Cure and Diffusion Monitoring in Thin Encapsulant Films
Authors: Day David R , Shepard David D.
Published: March 2011

Recent developments in the area of microelectronics now enable the fabrication of microdielectric sensors that can follow the drying, curing, and diffusion phenomena in thin films. This paper first investigates the response of the rricrodielectric sensor to cure in a thin epoxy film. The multi-frequency loss factor data are reduced to a single “ion-viscosity” response curve representative of the change in ion mobility during the cure reaction. The dynanic dielectric data are compared to Tg as a function of time as determined by differential scanning calorimetry (DSC) on several partially cured samples. The dielectric response is shown to be extremely sensitive to the entire cure process. A similar epoxy film is exposed to alternately wet and dry environments while the dielectric response is monitored. The diffusion coefficient of water in the cured resin is estimated through the dynamic change in permittivity using a simple Fickian model and the results are shown to be in good agreement with the literature values. Finally, changes in dielectric properties of a photoresist during UV exposure are presented.
Ultrasonic Monitoring of Polymer Properties from the Melt to the Solid State: Influence of Chemical/Structural Details
Authors: Piché L. , Lessard G. , Massines F. , Hamel A.
Published: March 2011

An ultrasonic technique is described for the simultaneous measurement of specific volume, V, sound velocity, v, and attenuation, a, at frequencies between f = 0.5 and f = 15 MHz, in a wide range of temperature (- 150 to + 400°C) and pressure (up to 2 kbars). The results (V,v,a) are translated into a complex modulus, M* = M’ + iM” and analyzed in terms of the thermodynamic state of the material. Typical results for amorphous and semi-crystalline polymers are presented which show that the technique is a probe of the fundamental features of these materials (glass transition, crystallization, melting, molecular structure) which determine processability and end use properties. The method should prove of great interest for quality and process control.
Thermal Wave Characterization of Glass-Bonded Alumina
Authors: Inglehart Lorretta J. , Haber Richard A. , Wachtman John B.
Published: March 2011

We present the results of a study of glass-bonded Al2O3 with controlled composition and particle size using photoacoustic thermal wave nondestructive evaluation. Experimental results are related to particle size, density, porosity, and thermal properties of the materials.
Neutron Diffraction as a Tool for Non-Destructive Evaluation of Ceramics
Authors: Root John H. , Sullivan James D.
Published: March 2011

Neutron diffraction is a powerful probe of the properties of condensed matter. In recent years neutron diffraction has been applied to the non-destructive evaluation of mechanical characteristics of engineering components. This paper presents examples of applications to ceramic composites including the measurement of position dependence of residual strain, grain size and minority phase concentration. In addition, an example of volume-averaged crystallographic texture is presented.
Rapid Non-Destructive Testing of Ceramic Multilayer Capacitors by a Resonance Method
Authors: Boser O. , Kellawon P. , Geyer R.
Published: March 2011

A rapid non-destructive test method for ceramic multilayer capacitors made from piezoelectric materials such as barium titanate or lead containing materials is described and evaluated. The test method is based on the internal excitation of standing acoustic waves in the capacitors. The standing waves are severely dampened by defects such as delaminations and pores. An undampened resonance is a good indication of a defect free ceramic multilayer capacitor. This finding was used in a nondestructive test set-up to evaluate about 1,000 capacitors. The test set-up has the potential to test over 100,000 capacitors an hour. Through metallographic (cross section) examination a sorting accuracy of 2% false accepts and 8% false rejects was determined for the high speed test set-up.
Nondestructive Characterization of Beryllium Effects on Ni-Cr Dental Alloy Elastic Properties and Microstructure: Ultrasonics, X-Ray Diffractometry, Scanning Electron Microscopy and Wavelength Dispersive Spectrometry
Authors: Singh Surendra , Katz J. Lawrence , Rosenblatt B. S.
Published: March 2011

Knowledge of structure-properties relationship is a key factor in the development and improvement of new and existing metal alloys through manipulation in their chemical-compositions. In this study, the elastic properties and microstructure of cast Ni-Cr-Be and Ni-Cr dental alloys were studied. The elastic properties, i.e., Young's, shear and bulk moduli and Poisson's ratios, were determined using measurements on the ultrasonic velocities and densities. Both the shear and the longitudinal (dilatational) velocities were measured using an ultrasonic pulse-through-transmission method; density was measured using a buoyant force method. In microstructure, crystallinity, porosity, particle-size and quantitative elemental compositions were studied using x-ray diffractometry (XRD), scanning electron microscopy (SEM) and wavelength dispersive spectrometry (WDS) respectively. These results show that: (1) the addition of Be increased significantly the alloy's elastic moduli and Poisson's ratio; and (2) the presence of Be in Ni-Cr alloy also significantly modified its microstructure by producing a second binary phase, Ni-Be, in eutectic areas.
X-Ray Determination of Strain Distribution in Inconel Alloy 600 C-Ring
Authors: Lo C. F. , Kamide H. , Feng G. , Mayo W. E. , Weissmann S.
Published: March 2011

An Inconel Alloy 600 C-ring was subjected to various strain levels and the deformation process was monitored by a Computer Aided Rocking Curve Analyzer (CARCA). A large grain population was sampled, and the calibration curve of average rocking curve halfwidth of the individual grains relating to the nominal strain was established. The strain distribution as a function of the angular position along the peripheral surface layer and layers at different depth distance was obtained. Up to C-ring closure at the nominal strain of 3.3% at the apex, the induced plastic strains were confined to a surface layer of 30–40 gm in depth.The largest strain and strain gradients below the surface occurred at the apex and near apex region. The extent and the spread of microdeformation inhomogeneity increased with applied strain. At ring closure some grains exhibited large plastic strains while others exhibited only small plastic strains or were not affected by the deformation process at all. These experimental results were not in agreement with the current theoretical understanding of the deformation of C-ring since these theories did not take shape changes into account. When such changes were included, good agreement on the angular strain dependence for the apex and near apex region were achieved between experiment and theory. It was concluded that the CARCA X-ray method can be a useful research tool in aiding and guiding mathematical modeling of non-linear inelastic behavior of solids by disclosing important microstructural and micromechanical aspects.
Surface Roughness and Correlation Length Determined from X-Ray Diffraction Line Shape Analysis on Germanium (111)
Authors: Shen Q. , Blakely J. M. , Bedzyk M. J. , Finkelstein K. D.
Published: March 2011

In an x-ray diffraction experiment performed on a germanium (111) crystal, both the rod-like and the diffuse-like scattering from the surface have been observed on a nonspecular crystal truncation rod. These scattering contributions can be explained using existing theory on surface roughness. Two treatments to the Ge (111) surface have been used to provide examples with different roughness characteristics for this study. Quantitative analysis results in a surface roughness of 2.5+0.3Å for a clean surface passivated with iodine and 4.3+0.5Å for a Syton polished surface covered with a naturally grown oxide layer. A typical lateral scale of flat surface regions has also been obtained from the transverse width of the diffuse-like scattering peak, and found to be 200 A and 400 Å respectively.
Studies of an InAs/GaAs Heterojunction by Total-Electron-Yield
Authors: Krol A. , Sher C. J. , Storch D. R. , Woronick S. C. , Krebs L. , Kao Y. H. , Chang L. L.
Published: March 2011

Total electron yield (TEY) of an InAs/GaAs heterojunction due to soft x-ray excitation has been studied. This heterojunction was prepared by an overgrowth of a 600 Å InAs layer on a GaAs substrate using molecular beam epitaxy. Experimental data are compared with theoretical analysis based on a modified Fresnel formulation to calculate the wave field distribution in stratified media with interfacial roughness. The TEY angular profiles obtained at a given x-ray energy reveal information on the interfacial roughness, secondary electron escape length, attenuation length of elastically scattered photo-electrons, and optical constants of the epilayer in the xray regime.
Reflectivity of Soft X-Rays by Polymer Mixtures
Authors: Russell T. P. , Jark W. , Comelli G. , Stöhr J.
Published: March 2011

The specular reflectivty of soft x-rays has been used to investigate the surface behavior of mixtures of poly(vinylidene fluoride), PVF2, and poly(methyl methacrylate), PMMA. Mixtures where the concentration of PMMA is 0.8 where investigated as a function of the preparation and annealing conditions. It was found that mixtures prepared by rapidly casting from dimethylformamide, DMF, exhibited a gradient in the concentration of the two components. The gradient extended over large distances and was such that PMMA, the higher surface energy component was located preferentially at the surface. With annealing at 165°C, the width of the gradient diminished but the concentration of PMMA remained high at the surface. Films of the mixtures prepared under a slower solvent evaporation procedure produced a reflectivity profile characteristic of a phase separated mixture. The extent of phase separation was reduced with annealing. In all cases the roughness of the surface of the films was found to be 5.OÅ or less.
X-Ray Diffractometer for the Study of a Monomolecular Film Spread on a Liquid Substrate
Authors: Robinson Karl M. , Mann J. Adin
Published: March 2011

The study of ultrathin films spread on liquid substrates has been limited to macroscopic observations of general film behavior. Synchrotron radiation has provided the means of observing the two-dimensional crystalline properties of monolayers. Our recent experiments performed on NSLS X-23B beam line was the trial run of a new liquid surface diffractometer. Major emphasis has been placed on vibrational and environmental isolation of the film, in addition to 0.1 micron resolution in the control of beam positioning. The film is examined in a closed, ultraclean environment consisting of a fused silica trough, purified N2 atmosphere, 0.1°C temperature control and chromatography grade or better solvents and surfactants. Surface properties (surface tension, and visco-elastic moduli) are monitored by surface laser light scattering spectroscopy. The x-ray scattering pattern from the liquid surface contains the expected specular reflection as well as scattered peaks at small wave numbers. We believe these to be caused by high frequency surface ripple fields.
In Situ X-Ray Scattering of Monolayers Adsorbed at Electrochemical Interfaces.
Authors: Toney Michael F. , Melroy Owen. R
Published: March 2011

Surface x-ray scattering has been used to study in-situ the structure of Pb monolayers electrochemically adsorbed on Ag (111) electrodes. Pb forms an incommensurate, hexagonal two-dimensional (2D) solid, which is rotated approximately 4.5° from the substrate symmetry directions and compressed relative to bulk Pb. Between monolayer formation and bulk deposition, the Pb-Pb near neighbor distance decreases linearly with applied potential. Due to the chemical equilibrium between the Pb monolayer and the Pb in solution, the isothermal compressibility of the monolayer can be measured and is in good agreement with that calculated for a 2D non-interacting free electron gas model of the monolayer. It is observed that the intensity of surface diffraction from the Ag substrate (the Ag crystal truncation rod) decreases when the Pb monolayer is adsorbed, although the cause of this is not known.
Synchrotron Photoemission Studies of Surfaces and Overlayers
Authors: Chiang T.-C.
Published: March 2011

High-resolution core-level photoemission spectroscopy allows the distinction of atoms in different layers and in inequivalent sites by their binding energy shifts. By comparison with model structures and reference samples, the number of atoms in each distinct chemical configuration can be determined. The chemical shifts induced by adsorption can be correlated with the electronegativity difference between the substrate and the adsorbate atoms. These observations provide a quantitative description of the interaction and reaction between adsorbates and surfaces, and important information about the atomic structure and the electronic properties can be deduced. Results from several representative systems including the adsorption of In, Ag, and Sn on Si(100) will be discussed.
The Heteronucleation of and Defect Generation in MBE-Grown InAs Layers
Authors: AI-Jassim M. M. , Goral J. P. , Sheldon P. , Jones K. M.
Published: March 2011

Epitaxial InAs layers were grown by molecular beam epitaxy (MBE) on GaAs substrates. The initial stages of nucleation were studied by in situ reflection high energy electron diffraction (RHEED). Cross-sectional TEM examination was used to investigate the morphology of the growing layer, while plan-view examination revealed the generation of misfit dislocations. The growth mode was found to depend mainly on the conditions used to nucleate the epitaxial layer. In most cases, Stranski-Krastanov type of growth was observed.
Strain-Induced Lateral Confinement of Carriers in Semiconductor Quantum Wells
Authors: Kash K. , Bhat R. , Mahoney Derek D. , Worlock J.M. , Lin P.S.D. , Scherer A. , Van Der Gaag B.P. , Koza M. , Grabbe P.
Published: March 2011

We describe here an effort to provide lateral confinement of carriers within a continuous InGaAs quantum well by creating a pattern of strain in the well. A compressed InGaAsP layer overlying the quantum well and the InP barrier was patterned into submicron stressor wires by etching to within approximately 20 nm of the InP barrier. The relaxation of the compression at the edges of the quaternary stressors resulted in dilation of the quantum well material under their centers, thus lowering the band gap of the material, providing confinement for both electrons and holes there. We observed a red shift of the quantum well luminescence of 7 meV for 400 nm wide wires, evidence for the strain-induced lateral confinement. This is the first observation of a red-shifted band gap in submicron strain-confining structures.
Dislocations in GaAs/Si Interfaces
Authors: Zhu Jane G. , McKernan S. , Carter C. B. , Schaff W. J. , Eastman L. F.
Published: March 2011

Dislocations present at GaAs/Si interfaces have been characterized using transmission electron microscopy in plan-view. The GaAs was grown by molecular-beam epitaxy on Si (001) substrate tilted* towards the [110] direction. The dislocation network at the interface consists primarily of orthogonal edge dislocations with Burgers vectors of a/2[110] and a/2[110]. However, displacements of these dislocation lines at the interface are observed. These displacements can be attributed to the interaction of 60* dislocations with the network of orthogonal edge dislocations. The density of these 60* dislocations along [110] direction is different from that along [110] direction.
Heteroepitaxy of GaAs on Si and Ge by low-Energy ion Beam Deposition Using Alternating Beams
Authors: Haynes T. E. , Zuhr R. A. , Pennycook S. J.
Published: March 2011

In this paper, we demonstrate the growth of heteroepitaxial thin films of GaAs at low temperatures on Si(100) and Ge(100) substrates by direct deposition from controlled, low-energy (30-50 eV), mass-separated beams of 69Ga+ and 75As+ ions. This represents the first use of two fully ionized beams for the growth of compound semiconductor thin films. Mixing of the constituents was accomplished by periodically switching tile analyzing magnet to alternate between deposition of Ga and As at approximately monolayer intervals. Ion channeling and transmission electron microscopy show that GaAs films grown on Ge substrates at 400°C are free of the microtwins and stacking fault defects which emanate from the interface of GaAs similarly grown on Si. Single-crystal GaAs films with ion channeling minimum yields of around 6% have been grown on Ge(100) substrates at temperatures from 520°C down to as low as 320°C.
Material and Device Properties of 3” Diameter GaAs-on-Si with Buried P-type Layers
Authors: Pearton S. J. , Lee K. M. , Haegel N. M. , Huang C.-J. , Nakahara S. , Ren F. , Scarpelli V. , Short K. T. , Vernon S. M.
Published: March 2011

Two problems facing MOCVD grown GaAs-on-Si are firstly, scale up to 3” and greater wafer diameter with acceptably uniform layer thicknesses and electrical and optical properties, and secondly the achievement of adequate device isolation through the use of buffer layers of low doping density (≤1014 cm−3). We have investigated the thickness uniformity and 300K photoluminescence intensity of 3” Ø, MOCVD grown GaAs layers on Si substrates by whole wafer mapping of these parameters, and correlate the variations found with the gas flow direction during deposition of the GaAs. We have overcome the high background doping densities (n =5−20 × 1015 cm2) in the material by a buried Be implant (1−5 × 1012 at 120 keV) followed by 850°C, 3 sec annealing. This provides adequate isolation for MESFETS and we fabricated such devices with gm's of 160-175 mS mm−1 using our standard process. These values are similar to homoepitaxial MESFETS fabricated in the same way.
Low Temperature GaAs Growth on GaAs and Si with Metal-Organic Molecular Beam Epitaxy Assisted by Hydrogen Plasma
Authors: Suemune Ikuo , Kunitsugu Yasuhiro , Tanaka Yoshimitsu , Kan YAsuo , Yamanishi Masamichi
Published: March 2011

New low-temperature cleaning and growth processes are presented using hydrogen plasma. Cleaning of GaAs and Si surfaces are possible above 200°C and 300°C, respectively. Single-domain GaAs thin films are successfully grown on Si at 400°C using metal-organic compounds for both Ga and As. Selective growth of GaAs is demonstrated at 400°C on a Si surface partially covered withSiO2.
Ion Beam Processing of GaAs at Elevated Temperatures
Authors: Williams J. S. , Elliman R. G. , Johnson S. T. , Sengupta D. K. , Zemanski J. M.
Published: March 2011

Elevated temperature ion bombardment of GaAs has been examined to investigate the nature of residual damage and the interplay between bombardment-induced defect production and dynamic annealing. The nature of disorder is found to depend strongly on ion energy, species, dose, dose rate and substrate temperature. A temperature regime is identified in which dynamic annealing leads both to the efficient formation of band gap traps for carrier removal and to the low temperature crystallization of pre-existing amorphous layers.
Fabrication of GaAs/AlGaAs Quantum Well Lasers with MeV Oxygen Ion Implantation
Authors: Xiong Fulin , Tombrello T. A. , Wang H. , Chen T. R. , Chen H. Z. , Morkoc H. , Yariv A.
Published: March 2011

MeV oxygen ion implantation in GaAs/AlGaAs has been shown to provide a simple and very promising technique for quantum well laser fabrication. A l0μm stripe single quantum well (SQW) graded-index separation confinement heterostructure (GRINSCH) laser made in this way has achieved high performance with high quantum differential efficiency, low threshold current and good electrical isolation characteristics. MeV oxygen ion implantation with optimum thermal annealing produces a deep buried electrical isolation layer in n-type GaAs and reduces optical absorption in GaAs/AlGaAs quantum well structures. Ion implantation stimulated compositional disordering as well as implanted oxygen-related deep level traps may be considered as important effects for electrical and optical modification of interfaces in GaAs and AIGaAs.
Activation Uniformity Dependence of Undoped Semi-Insulating GaAs on Post-Implant Annealing Conditions
Authors: Lanzieri C. , Graffitti R. , Cetronio A.
Published: March 2011

In this article we will illustrate how by suitable furnace design, the radial thermal gradients generated on a GaAs substrate during the post-implant annealing cycle can be virtually eliminated, and how such a technique can result in appreciable improvement in on-wafer activation uniformity (standard deviation better than ± 2%), with virtually constant activation efficiency in going from seed to tail end wafer of a given ingot.
Arsine Ambient Rapid Thermal Annealing
Authors: Jackson T.N. , Degelormo J.F. , Pepper G.
Published: March 2011

We have constructed a multiple wafer arsine ambient rapid thermal anneal (RTA) system and have applied it to the fabrication of high-performance refractory-gate self-aligned GaAs MESFETs. This has allowed us to take advantage of some of the features of rapid thermal annealing for these devices (reduced dopant movement and gate-channel interaction) without the difficulties of capped RTA (decapping problems, cap thermal mismatch stress driven dopant movement and gate-channel interaction) or the uncertain As loss characteristics of uncapped or proximity RTA. The anneal system uses a cylindrical furnace with a graphite boat heated by tungsten lamps with a 60 KW maximum power input. This allows heating rates in excess of 100°C/sec for up to four, two-inch wafers per run with a controlled arsine ambient of 0–20 Torr in an inert gas carrier. Closed loop temperature control is accomplished using a 5 μm wavelength optical pyrometer. The system has been designed to collect the As cracked from AsH, in a downstream trap and essentially no As is deposited in the wafer load area.

Using arsine ambient RTA to anneal 15 KV 20Si+ self-aligning implants for GaAs MESFETs with MOCVD grown channels (30 nm, 1.7 × 1018/cm3), we have been able to fabricate enhancementmode self-aligned MESFETs with gm/gd > 20 and extrinsic k-factor as large as 765 mS/V-mm for 0.15 μm gate length.
Achieve of High-Quality GaAs N-Type Ion Implanted Layer
Authors: Jinsheng Luo , Tangsheng Chen
Published: March 2011

We have found that co-implantation of phosphorus (P) with Si into SI-GaAs caq improve the quality of ion implanted layer. Hall mobilities of 4600–4700 cm2/Vs and activation efficiencies of 75–85% are obtained. These results are better than those obtained from the samples without P co-implantation. Schottky-barrier technique measuerments show a better mobility profile for the samples with P co-implantation. DLTS measurements show that the number of deep levels and their concentrations decrease. We think that P atoms occupy As vacancies and enhance the activation efficiency and their uniformity. The damage produced under the Si-implanted layer by P co-implantation increases the average Hall mobility.
Implant Isolation Mechanisms in GaAs, AlGaAs, InP and InGaAs
Authors: Pearton S. J. , Abernathy C. R. , Hobson W. S. , Von Neida A. E.
Published: March 2011

We have investigated the thermal stability of high resistivity regions introduced by ion bombardment of GaAs, AlGaAs, InP and InGaAs. For low doses in which the ion species density is below that of the doping density in the target material, we obtain the usual damage-related compensation in which deep levels created by the bombardment trap the charge carriers. By this method one creates material with resistivities around 108 Ω/□ (n- or p-type GaAs and AlGaAs, p-type InP), around 106 Ω/□ (n-type InP) or around 105 Ω/□ (n-type InGaAs or p-type InGaAs), with a return of the initial resistivity after elevated temperature annealing (∼600°C for GaAs and AIGaAs, ∼500°C for InP and InGaAs). The more interesting case is the use of higher dose implants of species which create chemical deep levels. This occurs for O in n-type AlGaAs where O creates a deep acceptor (Ec-0.49 eV), and Fe in n-type InP and InGaAs, where it is also a deep acceptor. When the concentration of these species exceeds the doping density in the material, the bombarded regions retain their high resistivity even after high temperature annealing (> 1000°C for GaAs and AIGaAs, >850°C for InP and InGaAs). The case of O in GaAs appears to represent a third mechanism; it creates thermally stable material only in the case of Be-doped GaAs, suggesting an ion-pairing reaction.
Outdiffusion of Magnesium from Mg + implanted GaAs.
Authors: Baratte H. , Jackson T. N. , Sadana D. K. , Degelormo J. F. , Scilla G.J. , Cardone F.
Published: March 2011

Magnesium implanted at high doses (1×1014cm−2 for a 120keV implant energy) into GaAs diffuses out of the crystal upon annealing. The outdiffusion is reduced, but not eliminated, when rapid thermal annealing is employed rather than furnace annealing. We have investigated various mechanisms that may explain this large outdiffusion. The high vapor pressure of the magnesium is not responsible for the outdiffusion since beryllium, which has a low vapor pressure, also outdiffuses. The presence of oxygen in the anneal ambient mostly leads to significant GaAs surface etching. The etching is more pronounced in the case of shallow energy and high dose implants, which suggests some oxygen- magnesium interaction mechanism. A high level of damage at the GaAs surface in the case of shallow magnesium implantation at high dose may also favor rapid outdiffusion of interstitial magnesium.
Comparison of Low Vapor Pressure Organoarsenic Compounds for Movpe Growth of GaAs
Authors: Lum R.M. , Kiingert J.K.
Published: March 2011

We have investigated the use of various alkylarsine compounds as alternatives to arsine in the metalorganic vapor phase epitaxy (MOVPE) of GaAs. These As-precursors, which include homologues of methyl, ethyl and butyl-based compounds, are typically low vapor pressure liquids and thus much safer to handle than arsine, which is a toxic high pressure gas. To enable a direct comparison of the alkylarsine and arsine sources, measurement of their growth and thermal decomposition properties were obtained in the same reactor under identical conditions. The composition and purity of the precursor compound was observed to affect both the film growth rate and its electrical and optical properties.
Mechanism of Au-GaAs Reaction and Effects on Ohmic Formation
Authors: Yeh L. Lu-Min , Holloway P. H.
Published: March 2011

Reactions between Au and GaAs occurs during alloying of Au-based ohmic contacts on GaAs. The reaction and electrical properties of annealed Au/GaAs contacts have both been studied. The extent of the Au-GaAs reactions increased with annealing temperature, incorporated Ga and As into the Au film and left pits on the GaAs surface. The activation energy for these reactions was determined to be 17.6 kcal/mole. Analysis of size evolution of reaction pits on GaAs proved that GaAs regrows at long time annealing. A mixed GaAs dissolution-regrowth mechanism is proposed for annealing temperature and time similar to those used to form alloyed ohmic contacts. Increased surface carrier concentrations resulting from accumulation of dopants near the Au/GaAs interface is proposed to enhance ohmic contact formation.
Properties of WSix-Schottky Diodes on n-Type GaAs Sputtered under UHV Background Conditions
Authors: Pletschen W. , Kaufel G. , Maier M. , Olander E. , Wiegert J. , Bachem K. H. , Rupprecht H. S.
Published: March 2011

Multilayered WSix films for use as gates in a self-aligned refractory gate process of GaAs MESFETs have been RF sputtered onto GaAs wafers under UHV background conditions in order to study their structure and morphology as well as their contact electrical properties. Annealed films deposited at 300°C with single layer thickness of 6 and 3 nm for W and Si respectively have a smooth morphology free from cracks and blisters and show a good adhesion to the substrate. Schottky diodes prepared on n-GaAs exhibit an almost excellent I-V characteristics with a barrier height of 0.73 V and an ideality factor of 1.11. In addition E - and D-FETs fabricated on implanted s.i. wafers have good electrical parameters with transconductances of 200 mS/mm at 1 μm gate length.
Semiconductor Optoelectronic Device Fabrication Using Dry Etching
Authors: Carter Adam J. , Thomas Ben , Morgan David V. , Bhardwaj Jyoti K.
Published: March 2011

Plasma etching of GaAs and InP using a CH4/H2 process gas and AlxGa1−xAs using a SiCl4 plasma are reported. Particular attention to etching characteristics as a function of gas and material composition, r.f. power, pressure and temperature are shown. Etching of GaAs and InP highlight two separate etching mechanisms. Surface roughness data at the etched surface is presented and Cl and CH4/H2 process chemistries are compared which shows the latter to yield significant improvements in etch surface characteristics.
Buried-shallow-implant (Bsi) process for High Efficiency Microwave power Mesfets
Authors: Liu S. G. , Capewell D. R.
Published: March 2011

We present a hybrid implant epitaxy process that alleviates the inherent depth-width-dependent limitation of ion implantation. This technique allows shallow implants, which produce a thin active N layer with a controlled doping gradient, to be buried at an arbitrary depth below the less-critical, epitaxiallygrown surface layer. The formation and characteristics of GaAs buried shallow-implant (BSI) layers for microwave power FETs will be discussed.
Metal-Organic Chemical Vapor Deposition of InSb on Gaas and InSb in an Inverted Stagnation Point Flow Geometry
Authors: Hebner G. A. , Biefeld R. M. , Killeen K. P.
Published: March 2011

Several properties of InSb such as high mobility and narrow bandgap make it an attractive candidate for many unique devices. We have examined the metalorganic chemical vapor deposition (MOCVD) of InSb on GaAs and InSb substrates under a variety of conditions using trimethylindium and trimethylantimony sources. The absolute metal-organic partial pressures above the susceptor were monitored using in-situ Ultraviolet (UV) absorption spectroscopy. X-ray studies of the homoepitaxial growth of InSb on InSb substrates (100) indicate good crystalline epitaxial growth while the x-ray peak for the InSb grown on GaAs (100) is broadened due to defects. Room-temperature Hall mobility measurements performed on the heteroepitaxial InSb layer on GaAs substrates indicates that the mobility of the InSb increases with increasing layer thickness. Mobilities range from 12,000 cm2/V sec for 0.8 micron layers to 38,000 cm2/V sec for 7.4 micron layers. The carrier concentrations are relatively constant (2 to 4 × 1016 cm−3 ) for the n type InSb deposited layers.
The Influence of Sb Doping on the Growth and Electronic Properties of GaAs(100) and AIGaAs(100)
Authors: Bensaoula A. , Jamison K.D. , Chen H.C. , Ignatiev A.
Published: March 2011

The effect of the group V isoelectronic dopant antimony (Sb) on the optimum growth temperature for GaAs and AIGaAs MBE grown films is examined with the aim of producing heterostructures at the lowest possible temperatures. RHEED intensity oscillations have been used to quantify the incorporation rate of Ga, Al, and As for different growth temperatures. The electrical properties of the layers are characterized using photoluminescence spectroscopy (PL), Hall mobility measurements, and deep level transient spectroscopy (DLTS). Results show that isoelectronic Sb doping of GaAs and AIGaAs permits the growth of these materials at temperatures up to 800C lower than optimum, with deep level trap densities, photoluminescence quality, and Hall mobilities at least comparable or better than those films grown at optimal temperatures.
Growth of InGaAsP films in a Multi-Wafer high Speed Rotating Disk Reactor by Mocvd
Authors: Reinert Paul , Mckee Mark , Norris Peter E. , Stall Richard A.
Published: March 2011

As the demands for InP epitaxial materials grow, the need for larger throughput growth techniques becomes important. However, uniformity of thickness and particularly composition of InGaAs and InGaAsP films has proved troublesome. This has limited much of the InGaAsP growth work to single wafer machines. The purpose of this work is to demonstrate good film properties and uniformity on a multi-wafer machine that holds three, two-inch diameter wafers.
Non-Hydride Group V Sources for Omvpe
Authors: Stringfellow G.B.
Published: March 2011

A major limitation to the continuing development of organometallic vapor phase epitaxy (OMVPE) for the growth of II/V semiconductor materials is the hazard posed by the hydride sources, AsH3 and PH3, which are virtually universally used, in high pressure cylinders, as the group V source materials for the growth of the highest quality materials. The set of stringent requirements for an organometallic group V source, which includes a high vapor pressure (>50 Torr) and freedom from undesirable carbon contamination, eliminates most commonly available non-hydride group V sources. Recent research on newly developed sources has shown considerable promise. The entire area of group V sources, including the elemental sources, for OMVPE growth of II/V materials will be reviewed. The sources with no hydrogen atoms attached to the group V atom, the elemental, trimethyl-V, and triethyl-V, sources all appear to give unacceptably high carbon incorporation, as does dimethylarsine. Diethylarsine, which has one H attached to the As, produces high quality GaAs. Tertiarybutylarsine (TBAs) and tertiarybutylphosphine (TBP) appear to be promising source materials. TBP has a very low toxicity, a vapor pressure ideal for OMVPE growth, and the pyrolysis occurs at lower temperatures than for PH3. No carbon contamination can be attributed to the TBP. Control of the As/P ratio in OMVPE grown GaAsP is much improved for TBP as compared with PH3 due to the more rapid pyrolysis. TBAs has similar attributes including a favorable vapor pressure and lower pyrolysis temperature than AsH3. The substitution of TBAs for AsH3 results in no observable increase in carbon in the epitaxial GaAs. Phenylarsine is a similar source, with a phenyl radical substituted for a single H atom on AsH3. The vapor pressure of phenylarsine is quite low and the pyrolysis temperature is expected to be some what lower than that for AsH3. Limited results indicate that carbon incorporation in GaAs is acceptable only when TEGa is the group V source.
Gas Phase and Surface Reactions of Organometallic Arsenic Sources
Authors: Omstead T.R. , Brandon S. , Hoveland M. , Jensen K.F. , Bohling D.A. , Muhr G.T.
Published: March 2011

The chemical kinetics of two new organometallic arsenic substitutes, tris-trifluoromethylarsenic (As(CF3)3) and phenylarsine (PhAsH2), for use in the MOCVD of GaAs have been characterized through the use of microbalance gravimetry and molecular beam mass spectrometry. Both growth rate and gas-phase cracking studies demonstrate that phenylarsine interacts only slightly with the common gallium precursors, which may make it a useful alternative to arsine. Growth with tris-trifluoromethylarsenic is achieved only at low V/III ratios and with pressures above 250 Torr. The compound etches GaAs under most conditions.
GaAs Solar Cell Using an Alternate Arsenic Source
Authors: Sundaram V. S. , Avery J. E. , Girard G. R. , Hager H. E. , Thompson A. G. , Fraas L. M.
Published: March 2011

Using an alternate arsenic source, namely, Tertiary Butyl Arsine, a concentrator GaAs solar cell has been grown in a low pressure metal organic chemical vapor deposition reactor. Under 72 sun, air mass 1.5 illumination, the cell had an open circuit voltage of 1.1 V, a fill factor of 83% and an overall efficiency of 21%.
The Use of Group V Alkyls as Replacements for Arsine and Phosphine in Hot-Walled VPe Reactors
Authors: Buckley D. Noel
Published: March 2011

The replacement of arsine and phosphine in a hot-walled VPE reactor by Group V alkyls is described. Epitaxial layers of lnP and InGaAs were grown using trimethylarsenic and trimethylphosphorus respectively. The surface morphology obtained was equivalent to that of samples grown using arsine and phosphine. InGaAs samples with no intentional doping were n- type with a background carrier concentration of 6 × 1015 cm−3, about 3 times higher than that of comparison samples grown using arsine. Mobilities measured at 77 K and 300 K respectively were similar to those measured for corresponding samples grown using arsine, suggesting that no significant carbon incorporation occurred. InP was n-type with a background carrier concentration of 3-6 × 1017 cm−3, significantly higher than that of samples grown using phosphine. Preliminary SIMS measurements on the layers suggest that this is due to silicon-based impurities in the trimethylphosphorus. Results reported for MOCVD using arsenic and phosphorus alkyls are contrasted with present results for a hot-walled reactor.
Large-Area Deposition of GaAs by Mocvd
Authors: Daly James T. , Roberts Carson B.
Published: March 2011

A new, large-scale, barrel-type MOCVD reactor which is capable of pro- ducing seven 3-inch wafers or fourteen 2-inch wafers at a time has been developed. Experiments and computer modelling studies of this geometry have been performed. The physical and electronic properties of n-type GaAs as a function of growth conditions are presented. Through the use of experimental design methods, the growth process has been optimized to yield highly uniform growth rates. The demonstrated uniformity supports the use of this reactor for production environments requiring 3-inch wafers.
Growth and Characterization of Heteroepitaxial GaAs on Semiconductor-on-Insulator and Insulating Substrates
Authors: Humphreys T.P. , Das K. , Parikh N.R. , Posthill J.B. , Nemanich R.J. , Miner C.J. , Sukow C.A. , Summerville M.K. , Ross P.L. , Markunas R.J.
Published: March 2011

A systematic study pertaining to the molecular beam epitaxial growth and charac- terization of GaAs films on various crystallographic orientations of sapphire is presented. For integration with silicon circuitry, heteroepitaxial GaAs layers have also been grown on commercially-available chemical vapor deposited silicon-on-sapphire (SOS) and SOS substrates that have been upgraded by the double solid-phase epitaxy process.
Atomic Layer Epitaxy of GaAs on Si by Mocvd
Authors: Karam N.H. , Haven V.E. , Vernon S.M. , Tran J.C. , El-Masry N.A.
Published: March 2011

Epitaxial GaAs films have been deposited on Si substrates using Atomic Layer Epitaxy (ALE) for the first time. This has been achieved in a SPI-MO CVD™ 450 reactor especially modified foroALE. After an initial high temperature bakeout, a nucleation layer 100-300 Å thick was deposited by ALE. Film growth was then resumed by conventional MOCVD to achieve the desired film thickness. The surface morphologies of the deposited films were found to be comparable to current state of the art conventional GaAs on Si films deposited by the two-step growth process in the same reactor.

Selective area epitaxy of GaAs on Si has also been achieved on Si02-coated and patterned Si wafers. The standard two-step deposition technique resulted in epitaxial growth in the patterned windows and poly-GaAs on the oxide mask, while ALE growth resulted in deposition only in the etched windows with no poly-growth on the oxide mask. We will report on the potential of this new deposition technique in producing high quality GaAs-on-Si films.
Electronic Properties of Dislocations in Heavily Dislocated Quantum well Structures: Doping Effects
Authors: Liu T. Y. , Petroff P. M. , Kroemer H. , Gossard A. C.
Published: March 2011

In heavily dislocated GaAs (dislocation density of 108cm-2), the low-temperature cathodo- luminescence efficiency of quantum wells and superlattices is dramatically higher than that of a bulk-like layer. Furthermore, the luminescence efficiency can be further improved by doping the barriers of the GaAs/(Al,Ga)As multi-quantum well structures with beryllium (Be). Two quite different possible models for this observation are discussed: One assumes that the effect is due to the expulsion of dislocation kinks from the wells, the other that it is due to the effect of well width fluctuations.
Near Gap Photoluminescence of GaAs Grown Directly on InP
Authors: Schnoes M. Lamont , Harris T.D. , Hobson W.S. , Lum R. M. , Klingert J. K.
Published: March 2011

We present a detailed photoluminescence and photoluminescence excitation study of GaAs grown directly on InP substrates by MOCVD. Reliable peak assignments are determined. With these peak assignments, we measure strain and strain uniformity, identify impurities, and assess material quality. Most samples exhibit three distinct spectral features. The two highest energy features are the strain split valence band, the third feature is a carbon impurity. The observed splitting is in good agreement with the value predicted from the thermal expansion mismatch.
Transient Photoconductivity in GaAs Films Grown by Molecular Beam Epitaxy.
Authors: Werner A. , Moustakas T. D. , Kunst M.
Published: March 2011

Hahn-Meitner-Institut, D-1000 Berlin 39, W. Germany Abstract The transient photoconductivity, in MBE grown silicon doped GaAs films, was studied by a contactless microwave conductivity technique. The dark carrier concentration of the investigated films varies from 4 x 1014 cm-3 to 6 x 1017 cm-3. At least two decay channels can be distinguished. An initial fast decay process (t<20 ns), which is excitation intensity dependent, followed by a slower one. The fast decay is tentativly identified with a direct electron-hole recombination and is more pronounced at high excitation intensities and in low impurity materials. The slower decay component is characterized by effective electron lifetimes ranging from 2 µs for low impurity fims up to 100 µs for high impurity samples. It can be concluded that an increase of the Si-concentration leads to an increase in the concentration of hole traps, which quenches the initial electron-hole recombination and decreases the electron decay rate in the microsecond region.
Growth of AlGaAs/GaAs Modfet Structures by Gsmbe Using Triethylalkyls and Arsine
Authors: Houng Yu-Min , Pao Yi-Ching , Mcleodl Paul
Published: March 2011

We have grown high quality AlGaAs/GaAs heterostructures by GSMBE, using triethylalkyls and arsine, for MODFET device applications. Al.28Ga.72As/GaAs modulation-doped structures with moblilities as high as 7,200 and 47,000 cm2/V-s at 300 and 77K, respectively, were obtained for a spacer layer thickness of 30Å and a sheet carrier concentration of l×l012cm−2. These results are comparable to films of a similar structure grown by elemental source MBE or by OMVPE techniques. Quarter-micron gate length MODFETs fabricated from this material have fr greater than 38 GHz and exhibit a 1.7 dB noise figure with 10 dB associated gain at 18 GHz when operated at room temperature.
InGaAs/InP Multiquantum well Structures Grown by Trichloride Vapor Phase Epitaxy
Authors: Wang K. W. , Mattera V. D. , Tai K. , Chu S. N. G. , Roccasecca D. D. , Luther L. , Livescusecca G.
Published: March 2011

Long wavelength (l.3pm<X<l.551un) InGaAs/InP multiquantum well (MQW) PIN structures in which the quantum confined Stark effect can be observed, are of particular interest because of their potential for high modulation contrast ratios and high speed operation. The chemistry of trichloride VPE lends itself to the growth of high purity InGaAsP heterostructures which are essential for the realization of high performance optical modulators and switches. In this study, we investigate the application of multi-frit trichloride VPE for the highly uniform epitaxial growth of InGaAs/InP MQW structures on two-inch InP substrates for advanced photonic device applications. The growth of MQW structures with various well thicknesses was studied as was the effect of substrate orientation. The structures have been characterized by infrared absorption and photoluminescence spectroscopy, cross-sectional transmission electron microscopy and double crystal x-ray diffraction.
A Study on Film Precursors in SiH4 Thermal CVD by use of Trench Coverage Measurements
Authors: Yuuki Akimasa , Kawahara Takaaki , Matsui Yasuji , Tachibana Kunihide
Published: March 2011

The precursors of Si film in SiH4 low pressure thermal CVD are studied by use of the trench coverage analysis. The cross sectional profile of the film deposited in a trench is simulated by a direct Monte-Carlo method using the composition of the precursors and their sticking probabilities as adjustable parameters. A comparison with the experimental results[1] shows that the trench coverage profiles are well reproduced by the model where two kinds of precursors deposit independently with respective sticking probabilities of almost zero and unity. The former is silane molecule, and the latter is radicals produced by gas phase reactions. The deposition rate due to radicals can be estimated from the comparison. Considering the sticking probability and the SiH4 pyrolysis reactions, it is concluded that H3SiSiH is one of ate dominant film precursors in gas phase reaction products.