bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Characterization of High Porosity Si02 Xerogels for Low k Dielectrics
Authors: Colomer M. T. 
Published: April 2011

AbstractDue to its low dielectric constant, high porosity SiO2 is a potential intermetal dielectric (IMD) film for sub-half micron devices. High porosity SiO2 xerogels with a low dielectric constant were prepared by a sol-gel method. Basic and mixtures of SiO2 sols (acid/base) aqueous particulate suspensions were employed using TEOS as a precursor.Porosity values up to 55% could be obtained for the silica xerogels calcined at 250°C. The porosity values were estimated by means of nitrogen adsorption (BET). The dielectric constant was directly measured using an impedance analyzer and also calculated from the nitrogen adsorption measurements. Both techniques were in good agreement and resulted in a dielectric constant value of 2.32 for xerogels having the highest porosity.
A Novel Air-Bridge Type Gate-Data Line Inter-Crossing to Reduce Signal delay for Large size AMLCD
Authors: Park C-M , Kang J-H , Han M-K 
Published: April 2011

AbstractA new TFT-LCD panel with an air-bridge type gate to data line inter-crossing has been proposed and its characteristics have been measured. The proposed structure has air-gap between gate and data line intercrossing. This air-bridge TFT-LCD panel has very small amount of capacitance between gate and data line. The new panel structure achieves 9 times faster signal delay compared with conventional panel, which enables to have enough design margin of over 20-inch diagonal size UXGA panel. We have examined thermal and mechanical durability of new panel to verify capability for commercial AMLCD application.
Atomic Structure Impacts on Dielectric and Mechanical Properties of Hydrogen-Silsesquioxane During Thermal Processing
Authors: Liu Youfan , Dall Fred 
Published: April 2011

AbstractAtomic structure impacts on the dielectric and mechanical properties of hydrogen-silsesquioxane (HSQ) were investigated to determine the sensitivity of HSQ to Si-H bond degradation during thermal processing. It was demonstrated that the dielectric properties of HSQ films are not sensitive to Si-H bond degradation up to 50 % if polar silanol or water species are not induced during thermal processing at a temperature of ≤ 450 °C. However, as the Si-H bond density is reduced, the mechanical properties are changed due to the increasingly formed Si-O-Si networks. This provides an opportunity for tuning mechanical properties per application requirements by process optimization.
Newly Developed Low-Density Methylsiloxane Spin-On-Glass Films
Authors: Yamada Noriko , Takahashi Toru 
Published: April 2011

AbstractSpin-on-glass (SOG) solution has been prepared from methyltriethoxysilane and dimethoxymethyl-3,3,3-trifluoropropylsilane. Trifluoropropyl groups attached to silicon are thermally decomposed by curing at 450°C in nitrogen. Since the overall methylsiloxane network is maintained without a significant shrinkage upon the thermal decomposition of trifluoropropyl groups, vacant spaces whose sizes are comparable to those of trifluoropropyl groups are introduced into the methylsiloxane network, leading to the low-density film with the Brunauer, Emmet and Teller (BET) surface area of 270 m2/g. The film shows the dielectric constant of 2.3, heat stability, low moisture uptake, good planarization property and no corrosion toward aluminum conducting lines.
In Situ Plasma Analysis, Fluorine Incorporation, Thermostability, Stress, and Hardness Comparison of Fluorinated Amorphous Carbon and Hydrogenated Amorphous Carbon Thin Films Deposited on Si by Plasma Enhanced Chemical Vapor Deposition
Authors: Glew A. D. , Cappelli M. A. , Touzelbaev M. N. , Hu Y. 
Published: April 2011

AbstractIn situ observation of the plasma properties during deposition of fluorinated amorphous hydrogenated carbon (FLAC) and unfluorinated amorphous hydrogenated carbon are performed. The relationship between film properties and impinging ion energy and incident ion momentum is discussed within the framework of existing models of diamond-like carbon (DLC) formation. The DLC films are deposited in a low pressure radio frequency discharge operating at 13.57 MHz with methane and carbon tetra-fluoride as the source gases. Thermostability, stress, and mechanical properties are investigated. The films are elevated to 400 degrees C in order to investigate thermostability. Thin film stress and nano-hardness are also studied. The film density is investigated by gravimetric methods. The fluorinated film stoichiometry is explored with x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.
The Use of Electron Channeling Patterns for Process Optimization of Low-Temperature Epitaxial Silicon Using Hot-Wire Chemical Vapor Deposition
Authors: Matson R. , Thiesen J. , Jones K.M. , Crandall R. , Iwaniczko E. , Mahan H. 
Published: April 2011

ABSTRACTWe demonstrate the first reported use of electron channeling patterns (ECPs) as a response for a statistical design of experiments process-optimization for epitaxial silicon. In an effort to fully characterize the new hot-wire chemical vapor deposition (HWCVD) method of epitaxial growth recently discovered at NREL, a large number of parameters with widely varying values needed to be considered. To accomplish this, we used the statistical design of experiments method. This technique allows one to limit the number of sample points necessary to evaluate a given parameter space. In this work we demonstrate how ECPs can effectively be used to optimize the process space as well as to quickly and economically provide the process engineer with absolutely key information.
Epitaxial Lateral Overgrowth of Gallium Arsenide Studied by Synchrotron Topography
Authors: Rantamäki R. , Tuomi T. , Zytkiewicz Z. R. , Dobosz D. , Mcnally P. J. , Danilewsky A. N. 
Published: April 2011

ABSTRACTSynchrotron x-ray topographs of GaAs epitaxial lateral overgrowth (ELO) samples are made both in transmission and reflection geometries. The topographs show that the bending of the ELO layers is visible in most geometries. A simulation of the topographic images is implemented taking into account only the orientational contrast. Simulated back reflection section topographs are in good agreement with the experimental ones. The shape of the lattice planes in an ELO layer is calculated using the simulation data and compared to the measured surface profile of the same ELO stripe.
The nature of ripples and islands in strained SiGe/Si heteroepitaxy: nucleation vs. instability phenomena
Authors: Christiansen S.H. , Albrecht M. , Becker M. , Strunk H.P. , Wawra H. 
Published: April 2011

ABSTRACTUsing liquid phase epitaxy from Bi solution in the temperature range 550°–700°C at low growth rates we study the formation of ripples and islands and their interdependence. As main results we find from the dependencies on growth time and temperature that ripples are an instability phenomenon and that islands nucleate thermally activated. Island nucleation on a ripple template (that is, as an instability phenomenon, highly ordered) has huge impact on the achievable order of the islands.
Cluster ‘Contact Epitaxy’- Direct Evidence for Novel Particle: Substrate Interactions
Authors: Yeadon M. , Yang J.C. , Ghaly M. , Averback R.S. , Gibson J.M. 
Published: April 2011

ABSTRACTIn this paper we describe observations of novel interactions between clusters of Ag deposited on the clean (001) Cu surface. The experiments are analogous to those performed by Gleiter and co-workers in the 1970's, where grain boundary orientations in particles of Cu and Ag supported on single crystal metal substrates were studied. Upon annealing close to the melting point, these particles (∼10–100μm in diameter) were found to rotate on the surface, forming low-energy grain boundary configurations with the substrate. The particles studied in our experiments are ∼104 times smaller, and show rather different behavior. In the case of Ag nanoparticles we have observed a novel phenomenon, which we call ‘contact epitaxy’, involving the formation of several monolayers of epitaxially oriented Ag at the Cu surface upon contact between this surface and the Ag cluster. The phenomenon may be understood from molecular dynamics simulations of the ‘soft impact’ between the nanoparticle and surface, which indicate that the ordered layers form within picoseconds of contact. We will discuss the mechanisms by which ‘contact epitaxy’ is believed to occur.
Heteroepitaxial Growth of Zinc Oxide Single Crystal Thin Films on (111) Plane YSZ by Pulsed Laser Deposition
Authors: Ohta Hiromichi , Tanji Hiroaki , Orita Masahiro , Hosono Hideo , Kawazoe Hiroshi 
Published: April 2011

ABSTRACTHeteroepitaxial ZnO films were grown on (111) surface of yttria stabilized zirconia (YSZ) and (0001) surface of sapphire by PLD method, using KrF eximer laser (248nm) in an ultra-high-vacuum chamber. ZnO grown on YSZ (111) at the substrate temperature of 800°C had an epitaxial relationship at the ZnO/YSZ interface of ZnO [1120]//YSZ [110]. Hexagonalshaped grains were observed whose surfaces were atomically flat. The grain size of ZnO increased and the Hall mobility rose toward 1400nm and 75cm2/Vs. respectively as film thickness increased from 10 nm to 800 nm.
The Role of the Lattice Step in Epitaxial Growth
Authors: Fu Tsu-Yi , Tsong Tien T. 
Published: April 2011

ABSTRACTSolid surfaces have many lattice steps. In epitaxy, aggregation of deposited atoms into islands or clusters during their diffusing can create many additional atomic steps. We study the effects of lattice steps on epitaxial growth in two aspects: 1. Movement of atoms across the step edge: a series of field ion microscope experiments reveal the importance of reflective and trapping properties of steps, and provide quantitative information that helps explain various growth modes observed in homoepitaxial growth. 2. Diffusion along the step edge: a number of field ion microscope experiments are done to determine diffusion parameters of a ledge atom along the step edge, and to derive the potential-energy diagram along different diffusion paths that helps explain the growth morphology. During growth, an atom undergoes a number of elementary atomic processes. Each process is characterized by a few energy parameters in bonding and diffusion. The integrated effect of all of these processes determines the growth process. We provide reliable experimental data and find the temperature ranges where various atomic processes are important
Optical Characterization of SiC Wafers
Authors: Burton J. C. , Pophristic M. , Long F. H. , Ferguson I. 
Published: April 2011

ABSTRACTRaman spectroscopy has been used to investigate wafers of both 4H-SiC and 6H-SiC. The two-phonon Raman spectra from both 4H- and 6H-SiC have been measured and found to be polytype dependent, consistent with changes in the vibrational density of states. We have observed electronic Raman scattering from nitrogen defect levels in both 4H- and 6H-SiC at room temperature. We have found that electronic Raman scattering from the nitrogen defect levels is significantly enhanced with excitation by red or near IR laser light. These results demonstrate that the laser wavelength is a key parameter in the characterization of SiC by Raman scattering. These results suggest that Raman spectroscopy can be used as a noninvasive, in situ diagnostic for SiC wafer production and substrate evaluation. We also present results on time-resolved photoluminescence spectra of n-type SiC wafers.
Growth and Characterization of 2″ 6H-Silicon Carbide
Authors: Schmitt Erwin , Eckstein Robert , Kölbl Martin , Weber Amd-Dietrich 
Published: April 2011

ABSTRACTFor the growth of 2″ 6H-SiC a sublimation growth process was developed. By different means of characterization crystal quality was evaluated. Higher defect densities, mainly in the periphery of the crystals were found to be correlated to unfavourable process conditions. Improvement of thermal boundary conditions lead to a decreased defect density and better homogeneity over the wafer area.
Epitaxial Growth of GaN Thin Films Using a Hybrid Pulsed Laser Deposition System
Authors: Mérel Philippe , Chaker Mohamed , Pépin Henri , Tabbal Malek 
Published: April 2011

ABSTRACTA hybrid Pulsed Laser Deposition system was developed to perform epitaxial growth of GaN on sapphire(0001). This system combines the laser ablation of a cooled Ga target with a well-characterized atomic nitrogen source. Taking advantage of the flexibility of this unique deposition system, high quality GaN thin films were deposited by optimizing both the laser intensity and the nitrogen flux. To date, our best GaN films show a FWHM of the GaN(0002) rocking curve peak equal to 480 arcsec. This result has been obtained at a laser intensity of I = 7×107 W/cm2, a substrate temperature of 800°C and under Ga-rich growth conditions.
Current-Voltage Characteristics of Ungated AlGaN/GaN Heterostructures
Authors: Albrecht J. D. , Rudento P. P. , Binari S. C. , Ikossi-Anastasiou K. , Ancona M. G. , Henry R. L. , Koleske D. D. , Wickenden A. E. 
Published: April 2011

ABSTRACTResults of a systematic study of the current vs. voltage characteristics of ungated AIGaN/GaN heterostructures grown on sapphire substrates are presented. It is experimentally observed that the saturation current nearly doubles as the source-to-drain channel lengths decrease from 11.8 to 1.7μm. The average electric field at which current saturation occurs is 10 to 30kV/cm, i.e. much less than the electron velocity saturation field. The experimental data is interpreted in the framework of a new model that takes into account the non-uniformity of the electron density in the channel, electron velocity saturation, and thermal effects. The temperature dependent electron transport characteristics of the model are based on Monte Carlo simulations of electron transport in GaN. It is shown that appreciable contact resistance, which leads to partial channel depletion near the source, and significant self-heating of the devices under high drain-to-source bias are the main reasons for the observed current saturation. The effective ambient temperature in the channel of the devices is calculated from a two-dimensional thermal model of heat dissipation through the sapphire substrate. Equilibrium channel carrier concentrations and low-field mobilities are determined from Hall effect data. The ungated structures are demonstrated to provide much useful materials and process characterization data for the development of AIGaN/GaN heterostructure field effect transistors.
Hydrostatic and uniaxial stress dependence and photo induced effects on the channel conductance of n-A1GaN/GaN heterostructures grown on sapphire substrates
Authors: Fung A. K. , Cai C. , Ruden P. P. , Nathan M. I. , Chen M. Y. , McDermott B. T. , Sullivan G. J. , Hove J. M. Van , Boutros K. , Redwing J. , Yange J. W. , Chene Q. , Khane M. A. , Schaff W. , Murphy M. 
Published: April 2011

ABSTRACTWe measure the hydrostatic stress, uniaxial stress, and photo induced dependence of the channel conductance of two-dimensional electron gas AlGaN/GaN heterostructures grown on c-axis sapphire. The structures examined are grown by nitrogen-plasma molecular beam epitaxy and metal organic chemical vapor deposition. Electrical conductance measurements are made with four point probes on Hall bar samples. Both, hydrostatic stress and uniaxial stress result in changes in the conductance. Moreover, these changes in conductance have long settling times after the stress is applied and may be due to deep level defects, the energy levels of which change with stress. Stress coefficients extracted from the samples are partially attributed to deep level defects and to the piezoelectric effect resulting from different piezoelectric coefficients of GaN and AlN. Photo induced changes of the two-dimensional electron gas are also observed. We find that pulsed illumination produces long transient times in the conductance. These transients are reduced by thermal heating in some samples. However, they can still be present at 153°C.
Piezoelectric Scattering in Large-Bandgap Semiconductors and Low-Dimensional Heterostructures
Authors: Ridley B. K. , Zakhleniuk N. A. , Bennett C. R. , Babiker M. , Anderson D. R. 
Published: April 2011

ABSTRACTWe develop a rigorous theory of piezoacoustic phonon limited electron transport in bulk GaN and GaN-based heterostructures. Within the Boltzmann equation approach we derive a new expression for the momentum relaxation rate and show that the Pauli principle restrictions are comparable in importance to a screening effect at temperatures up to 150 K provided that the electron density is large. This is of particular importance for electrons in GaN/AlN-based quantum wells where very high electron densities initiated by the piezoelectric effect have recently been reported. Variations of the piezoacoustic phonon limited electron mobility with the lattice temperature and with the electron density for a zinc-blende and wurtzite GaN are presented.
Correlation of Drain Current Pulsed Response with Microwave Power Output in AlGaN/GaN HEMTs
Authors: Binari S. C. , Ikossi-Anastasiou K. , Kruppa W. , Dietrich H. B. , Kelner G. , Henry R. L. , Koleske D. D. , Wickenden A. E. 
Published: April 2011

ABSTRACTThe drain-current response to short (<1μs) gate pulses has been measured for a series of GaN HEMT wafers that have similar dc and small-signal characteristics. This response has been found to correlate well with the measured microwave power output. For example, for devices where the pulsed drain current is greater than 70% of the dc value, output power densities of up to 2.3 W/mm are attained. This is in contrast with 0.5 W/mm measured for devices with low pulse response (less than 20% of the dc value). These results, which can be explained by the presence of traps in the device structure, provide a convenient test which is predictive of power performance.
High Voltage Schottky Barrier Diodes on P-Type SiC using Metal-Overlap on a Thick Oxide Layer as Edge Termination
Authors: Zhang Q. , Madangarli V. , Soloviev S. , Sudarshan T. S. 
Published: April 2011

ABSTRACTP-type 6H SiC Schottky barrier diodes with good rectifying characteristics upto breakdown voltage as high as 1000V have been successfully fabricated using metal-overlap over a thick oxide layer (∼ 6000 Å) as edge termination and Al as the barrier metal. The influence of the oxide layer edge termination in improving the reverse breakdown voltage as well as the forward current – voltage characteristics is presented. The terminated Schottky diodes indicate a factor of two higher breakdown voltage and 2–3 times larger forward current densities than those without edge termination. The specific series resistance of the unterminated diodes was ∼228 mΩ-cm2, while that of the terminated diodes was ∼84 mΩ-cm2.
A Study of Semiconductor Quantum Structures by Microwave Modulated Photolumenescence
Authors: Guliamov R. , Lifshitz E. , Cohen E. , Ron A. , Shtrikman H. 
Published: April 2011

ABSTRACTMixed types I - type II multiple quantum wells (QW) structures consist of alternating narrow- and wide GaAs wells, separated by AlAs barriers. Transfer of electrons from the narrow- to the wide well results in the formation of a two-dimensional electron gas (2DEG) in the wide wells and a hole gas (2DHG) in the narrow ones. The present study investigated the effect of these gases on the various photoluminescence (PL) bands. The study utilized two modulations techniques: double beam PL and microwave modulated PL (MMPL), offering high-resolution spectroscopy, control of the 2DEG density and effective temperature. The results showed that the formation of a low density 2DEG in the wide wells cause the formation of trions. However, a large density of excess electrons makes mutual collisions with other photo-generated species, causing the dissociation of the trions and excitons. In addition, electrons transfer through the barrier gives rise to barrier-well indirect recombination emission.
Energy Band Offsets at a Ga2O3(Gd2O3)-GaAs Interface
Authors: Lay T. S. , Hong M. , Kwo J. , Mannaerts J. P. , Hung W. H. , Huang D. J. 
Published: April 2011

ABSTRACTWe report the energy band offsets at a Ga2O3(Gd2O3)-GaAs interface. The valence-band offset (ΔEv) is ∼ 2.6 eV, measured by soft x-ray photoemission spectroscopy. Analysis of the current-voltage characteristics of a Pt-Ga2O3(Gd2O3)-GaAs MOS (metal-oxide-semiconductor) structure, which are dominated by Fowler-Nordheim tunneling, reveals a conduction-band offset (ΔEC) ∼ 1.4 eV at the Ga2O3(Gd2O3)-GaAs interface and an electron effective mass (m*) ∼ 0.29 me of the Ga2O3(Gd2O3) film.
Oxidation and Carbon Contamination in GaAs (100) Wet Treatments
Authors: Elbahnasawy R. F. , McInerney J. G. , Hughes G. 
Published: April 2011

ABSTRACTOxidation and carbon contamination of n-type GaAs (100) surfaces have been investigated by x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and secondary ion mass spectroscopy (SIMS) for a variety of cleaning and etching pretreatment procedures prior to immersion in either (NH4)2S, Na2S aqueous solutions or S2Cl2 solution in dichloromethane. The study has shown that sulfur passivation removes surface oxide and minimize carbon contamination for surfaces treated in (NH4)2S and S2Cl2 solutions. A significant oxygen and carbon contamination in the anodic passivation of GaAs (100) in (NH4)2Sx aqueous solution have been quantitatively measured. In addition, pretreatment in basic solutions have shown minimal oxygen and carbon level in comparison with the acidic solutions. Surface pretreatment carried out ex-situ has shown a higher risk of surface contamination prior to sulfur passivation.
Wet Oxidation of High-Al-Content III–V Semiconductors: Important Materials Considerations for Device Applications
Authors: Ashby Carol I. H. 
Published: April 2011

ABSTRACTWet oxidation of high-Al-content AIGaAs semiconductor layers in vertical cavity surface emitting lasers (VCSELs) has produced devices with record low threshold currents and voltages and with wall-plug efficiencies greater than 50%. Wet oxidation of buried AlGaAs layers has been employed to reduce the problems associated with substrate current leakage in GaAs-on-insulator (GOL) MESFETs. Wet oxidation has also been considered as a route to the long-sought goal of a III-V MIS technology. To continue improving device designs for even higher performance and to establish a truly manufacturable technology based on wet oxidation, the effect of oxidation of a given layer on the properties of the entire device structure must be understood. The oxidation of a given layer can strongly affect the electrical and chemical properties of adjacent layers. Many of these effects are derived from the production of large amounts of elemental As during the oxidation reaction, the resultant generation of point defects, and the diffusion of these defects into adjacent regions. This can modify the chemical and electrical properties of these regions in ways that can impact device design, fabrication, and performance. Current understanding of the problem is discussed here
Surface Passivation of GaAs Power FETs
Authors: Tanaka Tsuyoshi , Furukawa Hidetoshi , Miyatsuji Kazuo , Ueda Daisuke 
Published: April 2011

ABSTRACTThe surface passivation of GaAs power FET has been investigated. Intermodulation distortion of GaAs power FET was found to be affected by frequency dispersion which originates from electron trap at the surface in the vicinity of the gate. There are two ways to suppress the frequency dispersion. One is reducing electron trap itself by using surface passivation, the other is making surface insensitive to the surface trapping effect. We found the FET with undoped InGaP layers on the n-GaAs channel is free from surface trapping effects. The undoped InGaP layer acts as an ideal passivation layer for the channel, since it shows only 2% frequency dispersion of drain current at 1MHz compared to DC condition.