bluuebunny/crossref_metadata_2025_split huggingface dataset:
Approaches to High Temperature Contacts to Silicon Carbide
Authors: Delucca J. M. , Mohney S. E. 
Published: April 2011

AbstractMetallurgical reactions between contacts and SiC can alter the electrical characteristics of the contacts, either beneficially or detrimentally. Simultaneously, consumption of the underlying SiC epilayer takes place. During prolonged operation at elevated temperature, contacts that are not in thermodynamic equilibrium with SiC may continue to react with it. For this reason, interest in thermally stable carbide and silicide contacts to SiC has been growing. To select appropriate carbides or silicides for further study, however, knowledge of the transition metal-silicon-carbon (TM-Si-C) phase equilibria is required. A significant body of literature on the TM-Si-C systems exists and should therefore be examined in the context of electronic applications. In this paper, phase equilibria for representative TM-Si-C systems are presented, trends in these systems with respect to temperature and position of the metal in the periodic table are discussed, and attractive carbide and silicide contacts and processing schemes for thermally stable contacts are highlighted.
Characterization of Zirconium - Diamond Interfaces
Authors: Baumann P. K. , Bozeman S. P. , Ward B. L. , Nemanich R. J. 
Published: April 2011

AbstractThin Zr films were deposited on natural single crystal diamond (100) substrates by ebeam evaporation in ultra-high vacuum (UHV). Before metal deposition the surfaces were cleaned by UHV anneals at either 500°C or 1150°C. Following either one of these treatments a positive electron affinity was determined by means of UV photoemission spectroscopy (UPS). Depositing 2Å of Zr induced a NEA on both surfaces. Field emission current - voltage measurements resulted in a threshold field (for a current of 0.1 µA) of 79 V/µm for positive electron affinity diamond surfaces and values as low as 20 V/µm for Zr on diamond.
Photocurrent Sensitivities, Surface Color, and Auger Spectroscopy of Silicon Carbide (siC) by Photoelectro-Chemical (Pec) Etching
Authors: Collins D. M. , Harris G. L. , Chen Naiqun 
Published: April 2011

AbstractThis novel technique involves the ultraviolet (UV) lamp-assisted photoelectrochemical etching of n-type 3C- and 6H-SiC for device processing. In order for this method to be effective, the UV light must be able to enhance the production of holes in the SiC during the etching process thus providing larger currents with light from the photocurrents generated than those currents with no light. Otherwise dark methods would be used as in the case of p-type 3C-SiC.Experiments have shown that the I/V characteristics of the SiC-electrolyte interface reveal a minimum etch voltage of 3 V and 4 V for n- and p-type 3C-SiC, respectively. Hence, it is possible for etch-stops to occur. From Auger spectroscopy, an oxide formation is present on n-type 3C-SiC where after etching a yellowish layer corresponds to a low silicon to carbon (Si/C) ratio with large photocurrents and a white layer corresponds to a high Si/C ratio with small photocurrents. P-type 3C-SiC shows a grayish or silver layer with a high Si/C ratio and a green layer with a low Si/C ratio. Additionally, n-type 6H-SiC shows a brown or blue layer with a minimum etch voltage of 3 V.The colors of the etched regions of SiC represent layers that have some degree of porousity formed by the electrochemical process. As a result, the photo-excitation allows control of the porousity and changes the electrical properties of SiC. The nature of these porous layers with its increased resistivity can lead to the formation of devices.
Ion Beam Synthesis By Tungsten Implantation Into 6h-Silicon Carbide At Elevated Temperatures
Authors: Weishart Hannes , Matz W. , Skorupa W. 
Published: April 2011

AbstractWe studied high dose implantation of tungsten into 6H-silicon carbide in order to synthesize an electrically conductive layer. Implantation was performed at 200 keV with a dose of 1×1017 W+cm−2 at temperatures of 90°C and 500°C. The samples were subsequently annealed either at 950°C or 1100°C. The influence of implantation and annealing temperatures on the reaction of W with SiC was investigated. Rutherford backscattering spectrometry (RBS), x-ray diffiraction (XRD) and Auger electron spectroscopy (AES) contributed to study the structure and composition of the implanted layer as well as the chemical state of the elements. The implantation temperature influences the depth distribution of C, Si and W as well as the damage production in SiC. The W depth profile exhibits a bimodal distribution for high temperature implantation and a customary gaussian distribution for room temperature implantation. Formation of tungsten carbide and silicide was observed in each sample already in the as-implanted state. Implantation at 90°C and annealing at 950°C lead to crystallization of W2C; tungsten silicide, however, remains amorphous. After implantation at 500°C and subsequent annealing at 11007deg;C crystalline W5Si3 forms, while tungsten carbide is amorphous.
Gallium Nitride Thick Films Grown by Hydride Vapor Phase Epitaxy
Authors: Molnar R. J. , Maki P. , Aggarwal R. , Liau Z. L. , Brown E. R. , Melngailis I. , Götz W. , Romano L. T. , Johnson N. M. 
Published: April 2011

AbstractGallium nitride (GaN) thick films (to 150 μm) have been deposited by hydride vapor phase epitaxy (HVPE). These films are unintentionally doped n-type (n = 1–2 × 1017 cm−3 at 300 K) and exhibit structural and electronic properties which are comparable with the best reported for GaN films grown by organometallic vapor phase epitaxy. Additionally, these properties are found to be uniform over 2-in diameter films grown on sapphire substrates. The use of either a GaCl or ZnO surface pretreatment has been found to substantially enhance the nucleation density, resulting in improved surface morphology and film properties, even though it appears that the ZnO film is thermochemically desorbed early on in the growth. Dislocation densities as low as ˜5×107 cm−2 have been attained for films 40 μtm thick. Homoepitaxial overgrowths both by electron-cyclotron-resonance plasma enhanced molecular beam epitaxy and OMVPE proceed in a straightforward manner, essentially replicating the defect structure of the HVPE GaN film.
High Resolution X-Ray Diffraction Analysis Of Gallium Nitride Grown On Sapphire By Halide Vapor Phase Epitaxy
Authors: Matyi R. J. , Zhi D. , Perkins N. R. , Horton M. N. , Kuech T. F. 
Published: April 2011

AbstractWe report a structural analysis of GaN layers with thicknesses ranging from 10 μm to 250 μm which have been grown on sapphire substrates by halide vapor phase epitaxy (HVPE). The effect of growth rate during HVPE growth has also been examined. The growth was performed using GaCl and ammonia as reactants; growth rates in excess of 90 μm/hr have been achieved. The structural characteristics of these layers have been performed wit'i high resolution x-ray diffractometry. Longitudinal scans parallel to the GaN [0002] direction, transverse scans perpendicular to the [0002], and reciprocal space maps of the total diffracted intensity have been obtained from a variety of GaN layers. The transverse scans typically show broad rocking curves with peak breadths of several hundreds of arcseconds. In contrast, the longitudinal scans (or “θ/2θ scans”) which are sensitive only to strains in the GaN layers (and not their mosaic distributions) showed peak widths that were at least an order of magnitude smaller and in some cases were as narrow as 16 arcseconds. These results suggest that the defect structure of the GaN layers grown by HVPE is dominated by a dislocation-induced mosaic distribution, with the effects of strain in these materials being negligible in comparison.
Growth and Characterization of AllnGaN/InGaN Heterostructures
Authors: Roberts J. C. , Mcintosh F. G. , Aumer M. , Joshkin V. , Boutros K. S. , Piner E. L. , He Y. W. , El-Masry N. A. , Bedair S. M. 
Published: April 2011

AbstractThe emission wavelength of the InxGa1−xN ternary system can span from the near ultraviolet through red regions of the visible spectrum. High quality double heterostructures with these InxGa1−xN active layers are essential in the development of efficient optoelectronic devices such as high performance light emitting diodes and laser diodes. We will report on the MOCVD growth and characterization of thick and thin InGaN films. Thick InxGa1−xN films with values of x up to 0.40 have been deposited and their photoluminescence (PL) spectra measured. AlGaN/InGaN/AlGaN double heterostructures (DHs) have been grown that exhibit PL emission in the violet, blue, green and yellow spectral regions, depending on the growth conditions of the thin InGaN active layer. Preliminary results of an AllnGaN/InGaN/AllnGaN DH, with the potential of realizing a near-lattice matched structure, will also be presented.
Particle-Assisted Oriented Deposition of Diamond Thin Films
Authors: Lee Dong-Gu , Singh Rajiv K. 
Published: April 2011

AbstractWe have developed a method for <111> oriented diamond film synthesis using micron-sized diamond particles. Different size of diamond powders were electrophoretically seeded on silicon substrates using diamond suspensions in organic solvents (acetone, methanol, and ethanol). Diamond suspension in acetone was found to be the best for obtaining uniform diamond seeding by electrophoresis. The thickness of diamond seeded films was changed by varying the applied voltage to observe the effect on the orientation of diamond particles. Then diamond films were deposited by the hot filament chemical vapor deposition (HFCVD) process. A preferred orientation with <111> direction normal to the substrate was obtained for monolayer coatings. The surface morphology, crystal orientation, and quality of diamond films were investigated using scanning electron microscopy, x-ray diffractometry, and Raman spectroscopy.
The Influence of Hydrogen Plasma Passivation on Electrical and Optical Properties of Aigan Samples Grown on Sapphire
Authors: Polyakov A. Y. , Shin M. , Pearton S. J. , Skowronski M. , Greve D. W. , Freitas J. A. 
Published: April 2011

AbstractHydrogen plasma passivation effects are studied for undoped AlGaN layers grown by MOCVD. Hydrogen treatment at 200°C for lh led to a substantial decrease in carrier concentration accompanied by an increase in electron mobility. The magnitude of the near-band edge absorption tails also dramatically decreased after hydrogen passivation. The effect is explained by pairing of negatively charged hydrogen acceptors with positively charged native donors commonly believed to be related to nitrogen vacancies. The bond strength in such hydrogen complexes increases as the composition of AlGaN moves towards AIN, as revealed by results of post hydrogenation annealing.
Theoretical Study of Hydrogen in Cubic Gan
Authors: Estreicher Stefan K. , Maric Djordje M. 
Published: April 2011

AbstractPreliminary results of theoretical studies of hydrogen and hydrogen-related defects in cubic GaN are reported. Our calculations contrast with those of other authors in that the host crystal is represented by molecular clusters rather than periodic supercells, and that they are obtained using an all-electron methodology rather than the single effectiveparticle approach of density-functional theory. Our results confirm some predictions of other authors but conflict with others.
Diffusion of Hydrogen in 6H Silicon Carbide
Authors: Linnarsson M. K. , Doyle J. P. , Svensson B. G. 
Published: April 2011

Abstract6H polytype silicon carbide (SiC) samples of n-type have been implanted with 50 keV H+ ions and subsequently annealed at temperatures between 200 °C and 1150 °C. Using depth profiling by secondary ion mass spectrometry motion of hydrogen is observed in the implanted region for temperatures above 700 °C. A diffusion coefficient of ∼10−14 cm2/s is extracted at 800°C with an approximate activation energy of ∼3.5 eV. Hydrogen displays strong interaction with the implantation-induced defects and stable hydrogen-defect complexes are formed. These complexes anneal out at temperatures in excess of 900°C and are tentatively identified as Carbon-Hydrogen centers at a Si vacancy.
Fabrication of Highly Oriented, Smooth Diamond Films on Silicon for Electronic Devices
Authors: Wolter S. D. , Borst T. H. , Gluche P. , Ebert W. , Vescan A. , Kohn E. 
Published: April 2011

AbstractA new bias-enhanced nucleation method based on an AC-bias step to form highly oriented diamond (HOD) nuclei on silicon substrates is presented. The uniformity of the nucleated film and the bias time strongly depended on the substrate temperature and the substrate holder. In our case the shortest bias time and highest nucleation densities were achieved at ∼ 850°C while using a graphite susceptor. Following this nucleation enhancement step the diamond films were grown out using conditions employing an α-parameter slightly greater than 2. This ultimately leads to extremely smooth and well-faceted (100) textured HOD films which could be used as substrates for the fabrication of electronic devices.Schottky diodes with high rectification ratios and high breakdown voltages have been fabricated for the first time via selective growth of the active boron doped diamond layers on these HOD films. Results of the growth procedure and diode performance will be given.
Photoluminescence Properties of CVD Diamond Excited by Ultra-Violet Synchrotron Radiation
Authors: Won Jaihyung , Hatta Akimitsu , Ito Toshimichi , Sasaki Takatomo , Hiraki Akio 
Published: April 2011

AbstractPhotoluminescence (PL) properties of microwave-assisted chemical-vapor- deposition (CVD) diamond have been studied using ultraviolet synchrotron radiation. The defect-related 5RL PL feature, which was not detected in cathodoluminescence (CL), was observed for both undoped and boron-doped (200ppm) CVD diamond. The defect formation in the thin near- surface layer is discussed in relation to dependence of PL spectra on incident photon energy. In the case of boron-doped diamond, the boron-related peak was detected at 2.3eV while the band-A feature was not observed at 2.9eV. PL excitation (PLE) spectra associated with these emissions are also discussed in relation to absorption coefficients at energies above the band gap.
Surface Chemical Effects on the Optical Properties of Thin Nanocrystalline Diamond Films
Authors: Khomich A. V. , Polyakov V. I. , Perov P. I. , Varnin V. P. , Teremetskaya I. G. , Balakirev V. G. , Obraztsova E. D. 
Published: April 2011

AbstractThe effect of annealing in air on internal structure and optical properties of hot filament CVD nanocrystalline diamond films was investigated. Oxidation of the films lead to selective removal of intercrystallite layers with formation of highly porous structure with characteristic dimensions of several nanometers. Dramatic changes in optical transmission and Raman spectra were also observed. The origin of the two Raman spectrum maxima at 1140 and 500 cm−1 is discussed. Hydrogen absorption and desorption processes in porous diamond were studied.
Thermomodulated Reflectivity Spectra of Gan/Sapphire Epilayer
Authors: Li Y. , Lu Y. , Shen H. , Wraback M. , Schurman M. , Koszi L. , Stall R. A. 
Published: April 2011

AbstractThermomodulation spectra from the metalorganic chemical vapor deposition (MOCVD) grown GaN have been measured in the temperature range 20 K - 310 K. A theoretical model is established to explain the modulation spectrum by considering the modulation of epilayer thickness and dielectric constant. By performing the lineshape analysis, the bandgap energy and broadening parameter were determined in the temperature range. The nonlinear temperature coefficient (Varshni coefficient) of energy gap is measured to be 5.9×10−4 eV/K. The temperature dependence of broadening parameter is also measured for the first time.
Optical Characterization of GaN Films Grown on (0001) Sapphire Substrate
Authors: Yang K. , Zhang R. , Zheng Y. D. , Qin L. H. , Shen B. , Shi H. T. , Huang Z. C. , Chen J. C. 
Published: April 2011

AbstractThe optical properties of single crystal hexagonal GaN films grown on (0001) sapphire substrate by metalorganic chemical vapor deposition were investigated. The energy gap of hexagonal GaN was determined as 3.39 and 3.400 eV by optical transmission and photoreflectance, respectively. The refractive index of GaN as a function of photon energy was drawn from the transmission spectrum. Furthermore, Raman scattering spectra were employed to study the phonon modes of the GaN film. The properties of LO phononplasmon coupled modes were further studied, and the carrier concentration and damping constant were determined by line-shape fitting of the coupled modes.
Field Emission and Band Bending Considerations From High-Quality NEA Diamond
Authors: Bandis C. , Pate B. B. , Phillips W. , Plano M. A. , Moyer M. D. , Moreno M. A. 
Published: April 2011

AbstractThe near band gap photoelectric emission and field emission properties of diamond are investigated. Our results find three characteristic photoelectric yield spectra which have been observed from both polycrystalline CVD diamond films and single crystal diamond. The categories correspond to differences in bulk doping/surface preparation and illustrate the importance of band bending at the surface. Field emission experiments also find that the same three categories have distinct field emission properties. Our field emission observations are discussed in terms of electron transport properties from the bulk to the surface.
Characterization of 4H-SiC MOS Capacitors by a Fast-Ramp Response Technique
Authors: Sudarshan T. S. , Madangarli V. P. , Gradinaru G. , Tin C. C. , Hu R. , Isaacs-Smith T. 
Published: April 2011

AbstractThe current vs voltage characteristics of 4H-SiC MOS capacitors under deep depletion are obtained by a fast ramp response technique so as to obtain the maximum field that can be applied to the MOS structure without the failure of either the semiconductor or the oxide layer. The experiments on n-type 4H SiC wafers having a 5 μm thick epilayer of 1015 – 1016 cm−3 doping concentration and an oxide layer 1200Å – 1500Å thick, indicate the significant influence of the oxide quality and defects in the semiconductor on the nature of the current response during accumulation and deep depletion measurements. The effect of the conductivity of the oxide layer is reflected clearly in the current response, even though classical C-V measurements do not indicate any abnormality. Apart from obtaining the maximum breakdown fields of the semiconductor and the oxide, the fast-ramp response technique provides useful information about the generation processes associated with defects in the MOS structure.
Polysilicon Thin Film Transistors with Cobalt amd Nickel Silicide Source and Drain Contacts
Authors: Sarcona G. T. , Hatalis M. K. 
Published: April 2011

AbstractPolysilicon n-type thin film transistors have been fabricated with self-aligned cobalt and nickel silicide contacts to the source and drain regions. The sheet resistance of the source and drain without silicide is above 200 Ω/‪. The cobalt and nickel silicide films have sheet resistance below 30 Ω/‪. The contact resistance of the silicided devices is also much lower. The reduced extrinsic resistance is shown to improve the current in the “on” state, without increasing the leakage current. This study includes examination of cobalt and nickel silicidation on thin polysilicon films at temperatures compatible with polysilicon TFT-LCD processes.
Performance of Poly-Si Tfts with Double Gate Oxide Layers
Authors: Min Byung-Hyuk , Park Cheol-Min , Jun Jae-Hong , Bae Byung-Sung , Han Min-Koo 
Published: April 2011

AbstractWe have fabricated a poly-Si TFT with double gate insulator composed of ECR oxide and APCVD oxide to improved the performance of poly-Si TFTs. The poly-Si TFT with double gate oxide exhibits the remarkable enhancement of the electrical parameters compared with the conventional poly-Si TFTs which has APCVD gate oxide, such as improvement of the subthreshold swing and the low threshold voltage. The proposed poly-Si TFT has a higher oxide breakdown electrical field and the device characteristics are not degraded significantly after an electrical stress. It is found that the ECR oxide plays a key role to improve the device performances and prevent the poly-Si TFTs from degradation due to the electrical stress.
Novel N2O Plasma Passivation on Polycrystalline Silicon Thin-Film Transistors
Authors: Wang Fang-Shing , Huang Chun-Yao , Cheng Huang-Chung 
Published: April 2011

AbstractA novel defect passivation process of polycrystalline silicon thin-film transistors (poly-Si TFT's) utilizing nitrous oxide (N2O) plasma was investigated. In terms of the gas flow rate, chamber pressure, and plasma exposure time, the optimum plasma condition has been found to significantly improve the electrical characteristics of poly-Si TFTs. The performance is even better than those passivated with conventional hydrogen plasma. It is believed that the nitrogen radicals from the N2O gas as well as the hydrogen ones from the residual H2O both can diffuse into the gate-oxide/poly-Si interface and the channel poly-Si layer to passivate the defect-states. Furthermore, the gate-oxide leakage current significantly decreases and the oxide breakdown voltage slightly increases after applying N2O-plasma treatment. This novel process is promising for the applications of TFT/liquid crystal displays and TET/static random access memories.
Solution Grown Polysilicon for Flat Panel Displays
Authors: Wallace R. L. , Anderson W. A. 
Published: April 2011

AbstractThin-film poly-Si on low-cost substrates is useful for thin-film transistors in flat panel displays or for photovoltaics. The films reported herein were formed at 600°C by d.c. magnetron sputtering from a Si-target onto a SiO2/Mo substrate, pre-coated with Sn or In/Ti to give a liquid phase growth. Poly-Si films have given a preferred (111) orientation, grain size up to 20μm, a carrier mobility exceeding 100cm2/Vs and carrier lifetime of 8μs when using the Sn pre-layer. The Sn pre-layer typically gave smaller grain size than did the In/Ti solvent but the latter gave lower carrier lifetime from Ti incorporation in the film. The film from the Sn pre-layer gave carrier mobility of 140cm2/V-s after hydrogenation by microwave electron cyclotron resonance. Properties of the Si thin-film can be controlled by type of pre-layer, doping of the target, substrate temperature and deposition environment.
Amorphous Silicon Tfts and Flat Panel Displays
Authors: Tsukada T. 
Published: April 2011

AbstractThe current status and next-generation technologies for liquid-crystal displays based on amorphous silicon TFTs are described. Panel size, resolution, design rule, and viewing angle are discussed from the standpoint of panel performance, productivity, and product application. The material properties for future TFT/LCDs are specified based on the discussions of design rule.