bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antimony on Diamond: A Comparison to Sb/Si and Sb/Ge
Authors: Wu J. , Richter M. , Cao R. , Terry J. , Pianetita P. , Lindau I. 
Published: March 2011

ABSTRACTDiamond is an important semiconductor which has great potential in high temperature, high power device applications. In the fabrication process of diamond electronic device, doping ofdiamond and understanding of diamond/metal interfaces are important. As a Column V element, Sb is a possible dopant for diamond. Early work reported that Sb is incorporated into diamond by ion implantaion [1]. In addition, Sb plays an important role in Si and Ge heteroepitaxial growth. On the Si or Ge surface one ordered monolayer of Sb occupies the epitaxial sites and saturates the surface dangling bonds, which leads to uniform epitaxial growth. While diamond has the same crystal structure as both silicon and germanium, it has a drastically smaller lattice and much stronger bond. This makes it very difficult to extrapolate antimony's behavior on diamond from its behavior on either silicon or germanium. In this work, we have studied the electronic and geometric structure of Sb on diamond surfaces using photoelectron spectroscopy and low energy electron diffraction. While the exact adsorption sites could not be determined, we find that antimony strongly bonds to the diamond surface. Further, antimony behaves very differently on the diamond(100) face as compared to the diamond(111) face. We also find that neither Sb/diamond system behaves like antimony on either silicon or germanium. We attribute these results to the drastically smaller diamond lattice and the stronger C-C bond.
Formation and Characterization of Ohmic Contacts on Diamond
Authors: Venkatesan V. , Malta D.M. , Das K. 
Published: March 2011

ABSTRACTLow resistance ohmic contacts have been fabricated on a naturally occurring lib diamond crystal and on polycrystalline diamond films by B ion-implantation and subsequent Ti/Au bilayer metallization. A high B concentration was obtained at the surface by ion implantation, a postimplant anneal and a subsequent chemical removal of the graphite layer. A bilayer metallization of Ti followed by Au, annealed at 850°C, yielded specific contact resistance values (as measured using a standard transmission line model (TLM) pattern) of the order of 10-5Ω cm2for chemical vapor deposition (CVD) grown polycrystalline films and the natural lib crystal. Specific contact resistance values have also been determined from circular TLM measurements on CVD films and the values compared to those from standard TLM measurements. These contacts were stable to a measurement temperature of ∼400°C and no degradation due to temperature cycling was observed.
Effect of Mechanical Stress on Polycrystalline Diamond Schottky Diode I-V Characteristics
Authors: Zhao G. , Charlson E. M. , Charlson E. J. , Stacy T. , Meese J. , Popovici G. , Prelas M. 
Published: March 2011

ABSTRACTSchottky diodes to be used for mechanical stress effect studies were fabricated using aluminum contacts to polycrystalline diamond thin films grown by a hot-filament assisted chemical vapor deposition process. Compressive stress was found to have a large effect on the forward biased current-voltage characteristics of the diode. At selected values of constant forward biased current, a linear relationship between voltage and stress, for stress less than 10 N was observed. The stress sensitivity of the diode was as high as 0.74 V/N at 1 mA forward bias. This study shows that polycrystalline diamond Schottky diodes are stress sensitive devices and have potential as mechanical sensors.
Electrical and Optical Properties of Heterostructures Made from Diamond-Like Carbon Layers on Crystalline Silicon
Authors: Hammerschmidt Albert , Mandel Th. , Helbig R. , Birkle S. , Kammermaier J. 
Published: March 2011

ABSTRACTThin films of amorphous, diamond-like carbon (DLC) were deposited on crystalline silicon substrates in a capacitively coupled RF-plasma discharge. The investigations concentrated on I-V and C-V measurements, on photoconductivity and on optical transmission between wavelengths of 2 and 50 microns of the heterostructure DLC/Si. The photoconductivity of the heterostructure is investigated for the first time; it depends on the band gap of the film, the thickness and the doping of the substrate. The DLC/Si heterostructure works like a MIS-photoelectric cell.
The Effect of Pyrolysis Temperature and Formulation on Pore Size Distribution and Surfacearea of Carbon Aerogels
Authors: Hulsey S.S. , Alviso C.T. , Kong F.M. , Pekala R.W. 
Published: March 2011

ABSTRACTRecently we reported the chemistry-structure-property relationships of organic aerogels, which are synthesized by the polycondensation of resorcinol and formaldehyde in a slightly basic medium, followed by supercritical drying. These materials can be pyrolyzed in an inert atmosphere to form vitreous carbon aerogels. As measured by gas adsorption techniques, the BET surface area and pore size distributions of micro and meso pores of the carbon aerogels are affected both by the pyrolysis temperature and the formulation. Definite trends are observed in our preliminary measurements; for example, the surface area decreases with increasing pyrolysis temperature until a plateau is reached at about 900°C. This paper explores the effects of pyrolysis temperature and aerogel density on the BET surface area and pore size distributions.
The Effect of Thermal Processing in Vacuum on the Water Adsorption Characteristics of Carbon Black
Authors: Schachner Kurt D. , Thoma Paul E. 
Published: March 2011

ABSTRACTCommercially available carbon black contains oxygen complexes on its surface that affect the surface properties of the carbon. Water adsorption on the surface of carbon black is influenced by the amount and type of oxygen complexes present. When carbon black is heated in vacuum at sufficiently high temperatures, removal of the oxygen complexes occurs and the surface of the carbon particles is modified. The amount of water adsorbed by the carbon is dependent on the vacuum heat treatment temperature. As the heat treatment temperature increases, water adsorption on the carbon decreases.Commercially available electrically conductive carbon black adsorbs from 1.25% to 2.50% water when exposed to 50% relative humidity for 24 hours at 25°C. This variation in water adsorption is due to a difference in the amount of oxygen complexes on the surface of the carbon. The carbon with more oxygen complexes adsorbs more water. However, when this carbon black is heat treated at 1200°C for 4 hours in a vacuum of 1 × 10−5 torr or better, the water adsorbed by the carbon is 0.4% when exposed to 50% relative humidity. Data showing the dependence of water adsorption on vacuum thermal processing are presented and discussed.
Surface Chemical Modification and Analysis of Carbon Fibers - The Key to Novel Composites
Authors: Sherwood Peter M.A. 
Published: March 2011

ABSTRACTCarbon fibers are finding increasing application in making various composites with special properties. It is found that such composites have properties that can be markedly effected by the carbon fiber surface. The effects of surface modification by electrochemical and plasma oxidation is discussed and the surface chemical changes described. The interaction of the matrix with the fiber surface is a subtle mixture of physical and chemical effects. The paper discusses work in the author's laboratory using surface studies with core and valence band X-ray photoelectron spectroscopy (XPS) and other techniques.
The Growth and Characterization of Germanium-Carbon Alloy Thin Films
Authors: Yuan Haojie , Williams R. Stanley 
Published: March 2011

ABSTRACTThin films of pure germanium-carbon alloys (GexC1−x with x ≈ 0.0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) have been grown on Si(100) and A12O3 (0001) substrates by pulsed laser ablation in a high vacuum chamber. The films were analyzed by x-ray θ-2θ diffraction (XRD), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), conductivity measurements and optical absorption spectroscopy. The analyses of these new materials showed that films of all compositions were amorphous, free of contamination and uniform in composition. By changing the film composition, the optical band gap of these semiconducting films was varied from 0.00eV to 0.85eV for x = 0.0 to 1.0 respectively. According to the AES results, the carbon atoms in the Ge-C alloy thin film samples has a bonding configuration that is a mixture of sp2 and sp3 hybridizations.
X-RAY Diagnostics of Large-Period Lattice-Matched InGaAs/InP Superlattices
Authors: Vandenberg J. M. , Rttter D. , Hamm R. A. , Chu S. N. G. , Panish M. B. 
Published: March 2011

ABSTRACTThe interfacial structure of InGaAs/InP superlattices grown on (100) InP by metalorganic molecular beam epitaxy has been studied by fully dynamical simulations of high-resolution x-ray diffraction curves of the (200) and (400) reflectjon. The superlattice under investigation is lattice-matched and has a long period of ∼630Å. This kind of structure creates a very symmetrical x-ray pattern enveloping a large number of closely spaced satellite intensities with pronounced maxima and minima. It appears in the dynamical analysis that the position and shape of these maxima and minima is extremely sensitive to the number N of monolayers and atomic spacing d of the InGaAs and InP layer, as well as the presence of interfacial layers and impurities.
Xafs Study on Interfaces in III-V Semiconductor Heterostructures
Authors: Ogata Kiyoshi , Kazufumisuenaga  , Nakano Asao , Mozume Teruo 
Published: March 2011

ABSTRACTInterfaces in InGaAs/InP heterostructures were investigated by XAFS analysis using synchrotron radiation. Two types of InGaAs/InP heterostructures were made by MEE using Ga, In, AsH3 and PH3 as sources. These InGaAs layers were terminated by (a) InGa and (b) As. The local structures around P were investigated by fluorescent XAFS analysis. It shows that the nearest neighbor around P is Ga and In in the InGa (a) sample and mainly In in the As (b) sample.
The Influence of Lattice Mismatch on Indium Phosphide Based High Electron Mobility Transistor (HEMT) Structures Observed in High Resolution Monochromatic Synchrotron X-Radiation Diffraction Imaging
Authors: Steiner Bruce , Comas James , Tseng Wen , Laor Uri 
Published: March 2011

ABSTRACTThe formation of mismatch dislocations in layered semiconductor structures was found recently in high resolution monochromatic synchrotron x-radiation diffraction images to be correlated with characteristics of the substrate as well as with the layer thickness and degree of lattice mismatch of non pseudomorphic layers.1,2We have now extended these studies to examine the accommodation to strain as a function of lattice mismatch in a series of high electron mobility transistor (HEMT) structures grown by molecular beam epitaxy (MBE) on indium phosphide substrates.Five distinct types of irregularity are observed: 1) lattice warping, 2) the formation of a nonpseudomorphic layer, 3) the formation of extended arrays of linear mismatch dislocations at the interface between the substrate and a nonpseudomorphic layer, 4) the formation of oval regions of tweed-like local lattice variation imbedded among these arrays, and 5) extended tweed-like local lattice variation over large peripheral areas in which the formation of straight mismatch dislocation arrays is not observed.Warping of the lattice is found in nearly all layered structures. A distinct layer with a different lattice parameter but without visible misfit dislocations is formed with a mismatch of 0.27 %. With increase of the mismatch to 0.5 %, the other three forms of accommodation appear in distinct regions of the structure: arrays of <011> mismatch dislocations; oval regions of tweed-like irregularity, oriented in the [011] direction; and peripheral regions of extended tweed-like local lattice variation.
The Use of Strain to Optimize Quantum Well Device Performance
Authors: Koteles Emil S. 
Published: March 2011

ABSTRACTRecently, conventional wisdom has reversed its view on the disadvantages of strain in active semiconductor devices. Now lattice-mismatch-induced biaxial strain is being actively studied as a technique for optimizing bulk and quantum well (QW) device performance. It has been realized that, in addition to permitting once inaccessible energy ranges to be reached, strain has the potential of altering the properties of energy bands in a precise and advantageous manner provided that care is taken that the strain remain pseudomorphic (i.e., that the critical thickness, beyond which the layer relaxes with detrimental effects on quality, not be exceeded).This paper reviews progress in this field including techniques for determining the magnitude of pseudomorphic strain in single QWs, and recent theory and experiments detailing the advantages which strain, both compressive and tensile, can bring to QW laser diodes. The use of strain to balance the polarization anisotropy inherent in QW structures is also discussed. Finally, a novel use of biaxial tensile strain in the barriers of QW devices to minimize polarization sensitivity is introduced. The idea is to create a structure in which the light and heavy hole valence bands are degenerate, as in bulk material, but which still retains the advantages of QWs (higher quantum and differential quantum efficiency, etc.).
Interfacial Quality of Strained-Layer InGaAs/GaAs Quantum Well Lasers Grown by Gas-Source Molecular Beam Epitaxy
Authors: Zhang G. , Ovtchinnikov A. , Pessa M. 
Published: March 2011

ABSTRACTWe report a study of interfacial quality of strained-layer InGaAs/GaAs quantum well lasers grown by gas-source molecular beam epitaxy. It was found that the growth temperature (Tgr) of the InGaAs layer plays an important role in the interfacial quality. For Tgr < 515 °C, a large amount of non-radiative recombination centers is likely to exist in the InGaAs/GaAs quantum well, which can be attributed to the presence of vacancies and atom clusters and lattice misfit defects. For Tgr > 515 °C, the InGaAs/GaAs interfaces show significant roughness due to In segregation. Rapid thermal annealing grades the InGaAs/GaAs interface because of interdiffusion of group-III atoms at the interface, and removes most of the non-radiative recombination centers from the low Tgr (<515 °C) samples. In addition, we observed that the interfacial quality of the InGaAs/GaAs quantum well shows no strong dependence on (100) vicinal orientations of GaAs substrate.
Characterization of AlGaAs/InGaAs/GaAs Heteroepitaxial Layers by Transmission Electron Microscopy and Energy Dispersive Spectroscopy
Authors: Rai R. S. , Tartaglia J. M. , Quinn W. E. , Martel D. C. 
Published: March 2011

ABSTRACTAlGaAs/InGaAs/GaAs heteroepitaxial layers grown by molecular beam epitaxy were studied by cross-sectional transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The presence of waviness/roughness, fine periodic striation contrast due to Al composition oscillations, and defects were observed by TEM in selected samples. EDS on the TEM was of limited utility in determining the composition of thin epitaxial layers and in comparing the composition near and away from a defect. Arguments are presented to rationalize these results.
The Influence of the Real Structure on the Deformations in Layer Systems
Authors: Jenichen B. , Kohler R. 
Published: March 2011

ABSTRACTThe relaxation of thermal stresses during the Czochralsky growth leads to frozen in deformations in the boules. These deformations lead to a nonintentional inhomogeneous miscut of the wafers. From the X-ray double crystal measurement of frozen in deformations in GaAs bulk crystals a nonintentional miscut of about 10−4 may be estimated. The measurement of the misorientation distribution over a LEC GaAs wafer yielded even higher inhomogeneities which are believed to be due to local curvature of the lcm2 samples. The relaxation of GaAs/AlAs Braggreflectors of 3μm overall thickness depends on the density of threading dislocations i.e. of the type of substrate (LEC or HB). The inhomogeneous strain field of misfit dislocations in InGaAs/GaAs multilayer systems and their inhomogeneous distribution leads to deformations in epitaxial layers limiting the dimensions of coherently scattering domains. The resulting mosaic spread in the epitaxial layer systems has been obtained using triple crystal measurements. The experimentally determined mosaic spread has to be taken into account to simulate the the diffraction pattern more correctly.
Manifestation of the DX Centre in Heavily δ-Doped GaAs(Si)
Authors: Arscott S. , Missous M. , Dobaczewski L. , Harness P. C. , Maude D. K. , Portal J. C. 
Published: March 2011

ABSTRACTShubnikov-de Haas and Hall measurements have been performed on singly delta doped GaAs(Si) structures, grown by molecular beam epitaxy, enabling us to study the effects of illumination and temperature upon bulk and individual subband, mobilities and carrier concentrations. In a highly doped sample, where the peak 3D electron concentration approaches 2×1019cm−3, we have observed novel changes in subband transport characteristics, not observed in the lower doped samples, which we attribute to the presence of DX centre phenomena. This paper explains the variations in individual subband transport properties due to a possible shift of the electronic wave functions contained in the potential well. This shift occurs due to a recombination-autoionization(R-A) process involving filled DX centres and free holes upon sample illumination at low temperatures.
Electronic Structure of GaAs/GaInP Strained Layer Quantum Wells
Authors: Rerbal K. , Zitouni K. , Kadri A. 
Published: March 2011

ABSTRACTThis work reports on the calculations of the electronic structure of GaAs/GaxIn1−x P strained layer quantum wells. The calculations are based on the multiband envelope function approach, considering the valence band offset value that has been recently proposed. The effect of strain due to the lattice-mismatch is studied. The calculated results are compared with the data obtained from photoreflectance measurements. Satisfactory agreement is obtained.
Graded Buffer Layers for Molecular Beam Epitaxial Growth of High in Content InGaAs on GaAs for Optoelectronics
Authors: Lord S. M. , Pezeshki B. , Marshall A. F. , Harris J. S. , Fernandez R. , Harwit A. 
Published: March 2011

ABSTRACTLinearly-graded buffer layers are used to achieve exciton resonances in InGaAs/GaAs at the 1.3 μm dispersion minimum of optical fibers. We investigate the effect of various gradients in the linearly-graded InGaAs buffer layer of a p-i-n structure designed as an optical modulator. Samples were grown by molecular beam epitaxy on GaAs substrates at 450°C. Each consisted of an n-type graded buffer region followed by thirty In0.5Ga0.5 As quantum wells with Alo.35Ga0.65As barriers, and 5000 Å of ρ-type InGaAs. Gradients of 7.5%, 15%, and 30% In/μm, or 0.5%, 1%, and 2% misfit/μm were used to grade the In concentration from 0% to 35%. Room temperature absorption measurements reveal well-defined zero-field excitonic features near 1.3 μm for all samples. The exciton resonance becomes sharper as the gradient decreases. Analyses of these samples by TEM and double crystal X-ray diffraction confirm the trend that a slower grading yields better quality material.
Materials and Structures for Advanced III-HBTs
Authors: Asbeck P. M. , Tu C. W. , Ho M. C. , Fu S. L. , Gee R. C. , Chin T. P. 
Published: March 2011

ABSTRACTThis paper reviews the present status of heterojunction bipolar transistor (HBT) technology based on GaAlAs/GaAs and InP/InGaAs materials, and discusses a variety of approaches for device improvement. Among the possibilities presented are novel structures to reduce base-collector capacitance, and novel materials to increase breakdown voltage and reduce base-emitter turn-on voltage.
Delta Doping for Deep Level Analysis in Semiconductors
Authors: Piprek J. , Krispin P. , Kostial H. , BÖer K. W. 
Published: March 2011

ABSTRACTThe occupation of deep-level defects in semiconductors is investigated by delta-doping such impurities at a specified distance from the metallurgical boundary within Schottky diodes. Capacitance-voltage characteristics are analyzed using ID device simulation software. These characteristics change significantly depending on the deep-level energy and the sheet position. This new approach to deep-level analysis is applied to Schottky diodes on MBE-grown n-GaAs with a planar titanium doped sheet. At moderate Ti concentrations the well-known Ti acceptor level near Ec-0.2 eV governs the electrical properties. In addition, two other types of Ti defects are found.
Materials and Device Characteristics of InAlAs/InGaAs HEMTs
Authors: Ho Pin , Kao M. Y. , Chao P. C. , Duh K. H. G. , Smith P. M. , Martin P. A. , Liu S. M. J. , Hwang K. C. , Ballingall J. M. , Yu T. , Swanson A. W. 
Published: March 2011

ABSTRACTHigh electron mobility transistors (HEMTs) based on the InAlAs/InGaAs heterostructure have been grown on InP by molecular beam epitaxy. At room temperature, typical sheet charge densities of 2.1–3.0×1012 cm−2 and Hall electron mobilities over 10000 cm2 /V-s are obtained. An electron mobility as high as 13000 cm2 /V-s is achieved with a pseudomorphic Iny Ga1−y As channel and a y value of 0.70.HEMTs with a T- or Γ-shaped gate and with gate lengths ranging from 0.1–0.25 urn have been fabricated. A record low noise figure of 0.7 dB with an associated gain of 8.6 dB at 62 GHz has been achieved with 0.1 μm Γ-gate devices, while T-gate devices exhibit a minimum noise figure of 1.2 dB with 7.2 dB associated gain at 94 GHz. Separately, a record fmax value of 455 GHz was determined by extrapolating at -6 dB/octave from the measured gain of 13.6 dB at 95 GHz.Power HEMTs using a double heterojunction structure exhibit a record peak power-added efficiency (P.A.E.) of 49% with 8.6 dB power gain and 0.30 W/mm power density measured at 60 GHz. When biased and tuned for maximum output power, our best 60 GHz output power density to date is 0.52 W/mm with 33% P.A.E. and 5.9 dB power gain using a single heterojunction HEMT scheme with pseudomorphic channel. A similar device also yields peak P.A.E. of 26% with 0.20 W/mm power density and 4.9 dB gain at 94 GHz. These results represent the highest P.A.E.S and power gains ever reported for any transistor at these frequencies.
Characteristics and Growth of Strained-Layer InGaAs/GaInAsP/GaInP Quantum Well Lasers
Authors: Zhang G. , Ovtchinnikov A. , Näppi J. , Asonen H. 
Published: March 2011

ABSTRACTStrained-layer InGaAs/GalnAsP/GalnP separate-confinement-heterostructure quantum well lasers emitting at 980 nm have been developed. The lowest threshold current densities obtained for the single-quantum-well and three-quantum-well lasers are 72 and 150 A/cm2, respectively. The internal quantum efficiency is as high as 94 %, and the internal waveguide loss 5.4 cm−1. The transparency current density and gain coefficient are 33 A/cm2 per well and 0.091 μm A−1, respectively. High characteristic temperatures ranging from 220 to 280 K was obtained. The vertical and lateral full-width at half-maximum of the far-field pattern of the ridge waveguide laser are 47° and 13°, respectively. The results are comparable with the best values reported for the InGaAs/AlGaAs lasers.