bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of Amorphous Silicon Thin Film Transistors for Analog Circuit Applications
Authors: Hornsey R. I. , Mahnke T. , Madeira P. , Aflatooni K. , Nathan A. 
Published: April 2011

ABSTRACTAnalog circuits using amorphous silicon thin film transistors offer significant advantages for in situ signal processing in large-area optical and x-ray imagers. However such circuits are susceptible to gate-bias-induced shifts in the threshold voltages of the constituent transistors. In this work, the change of threshold voltage for devices undergoing cycles of stress, relaxation and reverse bias is measured in order to determine the feasibility of resetting the threshold voltage electrically. It is concluded that, although the reverse bias does assist the recovery of the threshold voltage, the process is still not sufficiently rapid. An analog amplifier circuit is then described which uses negative feedback to achieve a gain that is stable to within 6% over a period of 8 hours.
On the Compensation Mechanism of Amorphous Silicon Films: Study of Stability
Authors: Caputo D. , De Cesare G. , Palma F. , Tucci M. , Minarini C. , Terzini E. 
Published: April 2011

ABSTRACTWe investigated a-Si:H compensated materials deposited over a wide range of gas dopant concentrations, from 0.125 ppm up to 103 ppm.We achieved compensation for different ratio in the gas phase of diborane and phosphine, depending on their concentration. As a relevant result, we found that at constant boron concentration compensation occurs by using two different values of phosphine flow. This behavior can be described by a change of formation mechanism involving active dopants, defects and boron-phosphorus complex, that occurs in a different way depending on the dopant concentrations.The two compensation regimes are evidenced also by a different behavior under light soaking. Furthermore we found that photocurrent evolution under illumination is determined by two concurrent mechanisms: activation of dopant species and increase of defect density.
Amorphous/Crystalline Silicon Two Terminal Visibleænfrared Tunable Photodetector: Modeling and Realization
Authors: De Cesare G. , Irrera F. , Tucci M. 
Published: April 2011

ABSTRACTDifference in the absorption coefficient profile of the amorphous and crystalline silicon is the key idea for the realization of a new visible/infrared tunable photodetector (VIP). The device consists on a n-doped a-Si:H/intrinsic a-Si:H/p-doped a-SiC:H multilayer grown by PECVD on a p-type crystalline silicon wafer doped by a phosphourus diffusion. A grid-shaped aluminum front contact with transparent conductive oxide coating is used as window for the incident light. Tunable sensitivity in the visible and near infrared spectral range can be achieved under different values of the external voltage, with excellent spectral separation between the two quantum efficiencies peaks at 480 nm and 800 nm.A simple analytical model taking into account the absorption profile, diffusion and drift lengths, and layer thicknesses reproduces fairly well the experimental results.
Growth and Characterization of In-Based Nitride Compounds and their Double Heterostructures
Authors: Joshkin V. A. , Roberts J. C , Piner E. L. , Behbehani M. K. , McIntosh F. G. , Wang L. , Lin S. , Shmagin I. , Krishnankutty S. , Kolbas R. M. , El-Masry N. A. , Bedair S. M. 
Published: April 2011

ABSTRACTWe report on the growth and characterization of InGaN bulk films and AlGaN/InGaN/AlGaN double heterostructures (DHs). Good quality bulk InGaN films have been grown by metalorganic chemical vapor deposition (MOCVD) with up to 40% InN as characterized by x-ray diffraction. The effect of hydrogen in the growth ambient on the lnN% incorporation in the InGaN films is presented. Photoluminescence (PL) spectra of AlGaN/InGaN/AlGaN DHs exhibit emission wavelengths from the violet through yellow depending on the growth conditions of the active InGaN layer. The PL spectra are fairly broad both at room temperature and 20 K, and could be a result of native defects or impurity related transitions. We also observed a linear dependence between the PL intensity and excitation power density in the 0.001 W/cm2 to 10 MW/cm2 range. Time resolved PL of one of these DHs suggest a recombination lifetime on the order of 520 ps.
Growth of Bulk, Polycrystalline Gallium and Indium Nitride at Sub-Atmospheric Pressures
Authors: Angus John C. , Argoitia Alberto , Hayman Cliff C. , Wang Long , Dyck Jeffrey S. , Kash Kathleen 
Published: April 2011

ABSTRACTBulk, polycrystalline gallium nitride and indium nitride were crystallized at sub-atmospheric pressures by saturating the pure metals with nitrogen from a microwave electron cyclotron resonance source. Saturation of Ga/In melts with nitrogen led only to the crystallization of gallium nitride. The polycrystalline samples were wurtzitic. The gallium nitride was well faceted, with narrow Raman lineshapes, and showed near-band-edge and yellow band photo-luminescence at both 4K and 300K. The indium nitride was formed in smaller amounts, was less well faceted, and showed no photoluminescence.
Dependence of the Residual Strain in GaN on the AlN Buffer Layer Annealing Parameters
Authors: Le Vaillant Y.-M. , Ciur S. , Andenet A. , Briot O. , Gil B. , Aulombard R. L. , Bisaro R. , Olivier J. , Durand O. , Duboz J.-Y. 
Published: April 2011

ABSTRACTThe problem of residual strain in GaN epilayers is currently the attention of many studies, since it affects the optical and electrical properties of the epilayers. In order to discuss the origin of this residual strain, we have grown a series of GaN epilayers onto AlN buffer layers, sapphire (0001) being used as substrate. The buffer layer is usually deposited in an amorphous state and is recrystallized by a thermal annealing. Here we have made a systematic study of the buffer recrystallization by changing the annealing temperature and the annealing time. The surface morphology is probed using Atomic Force Microscopy (AFM). The lattice parameter c is carried out from accurate x-ray diffraction measurements. The GaN layers were studied by low temperature photoluminescence and reflectivity. The amount of residual strain is calibrated from the position of the A exciton and the optical quality of the layers is assessed from the photoluminescence linewidths. The longer the annealing time the better the strain relaxation in AlN buffer layers and the higher the lattice mismatch with GaN overlayers.
Plasma Cleaning and Nitridation of Sapphire Substrates for AlxGa1-xN Epitaxy as Studied by ARXPS and XPD
Authors: Seelmann-Eggebert M. , Zimmermann H. , Obloh H. , Niebuhr R. , Wachtendorf B. 
Published: April 2011

ABSTRACTThe influence of plasma and thermal treatments on the structure and composition of sapphire (00–1) surfaces have been studied by hemispherically recorded x-ray photoelectron spectroscopy in view of substrate preparation for the epitaxy of GaN. Producing well-ordered surfaces, O2 plasma based treatments are found to efficiently remove surface contamination. AlN films with good short-range order are obtained by a simple high temperature nitridation step in the MOCVD reactor.
Mosaic Structure and Cathodoluminescence of GaN Epilayer Grown by LP-MOVPE
Authors: Duan Shukun , Teng Xuegong , Li Yenran , Wang Yutian , Han Peide , Lu Dacheng 
Published: April 2011

ABSTRACTWe have studied the growth of GaN on (0001) sapphire and (111) spinel substrates by LP-MOVPE and compared the mosaic structure and cathodoluminescence for the heteroepitaxial films of GaN grown on these substrates.
X-Ray Photoelectron Diffraction Measurements of Hexagonal GaN(0004) Thin Films
Authors: Denecke R. , Morais J. , Wetzel C. , Liesegang J. , Haller E. E. , Fadley C. S. 
Published: April 2011

ABSTRACTWe report on the first scanned-angle x-ray photoelectron diffraction measurements on GaN(0001) in the wurtzite structure, as grown on sapphire substrates using MOCVD. These as-grown samples reveal forward scattering peaks in agreement with a theoretical calculation using a single scattering cluster calculation. The surface contamination by O and C does not exhibit any clear structure. From the combination of experiment and theoretical calculation and from a simple intensity ratio argument the surface termination for these samples could be determined to be N. The data also indicate that C is on average closer to the GaN surface than O.
Complete Characterization of AlxGa1-xN/InxGa1-xN/GaN Devices by Sims
Authors: Huang C. , Mitha S. , Erickson J. W. , Clark-Phelps R. , Sheng Jack , Gao Y. 
Published: April 2011

ABSTRACTSIMS analysis was applied to the characterization of GaN, AlGaN/GaN and InGaN/GaN grown by MOCVD. Such characterization enables the control of purity and doping, and the determination of growth rate and alloy composition. The analysis can be performed on finished optoelectronic and electronic devices and this makes SIMS technique a powerful tool for failure analysis, reverse engineering, and concurrent engineering.
Photoelectrochemical etching of GaN
Authors: Youtsey C. , Bulman G. , Adesida I. 
Published: April 2011

ABSTRACTA photoelectrochemical etching process for n-type GaN using KOH solution and broad-area Hg arc lamp illumination is described. Etch rates as high as 320 nm/min are obtained. The etch rate is investigated as a function of light intensity for stirred and unstirred solutions. Preliminary results on etching of Al0.1Ga0.9N layers are reported.
Patterning of GaN in High-Density Cl2- and BCl3-Based Plasmas
Authors: Shul R. J. , Briggs R. D. , Han J. , Pearton S. J. , Lee J. W. , Vartuli C. B. , Killeen K. P. , Ludowise M. J. 
Published: April 2011

ABSTRACTFabrication of group-Ill nitride electronic and photonic devices relies heavily on the ability to pattern features with anisotropie profiles, smooth surface morphologies, etch rates often exceeding 0.5 μm/min, and a low degree of plasma-induced damage. Patterning these materials has been especially difficult due to their high bond energies and their relatively inert chemical nature as compared to other compound semiconductors. However, high-density plasma etching has been an effective patterning technique due to ion fluxes which are 2 to 4 orders of magnitude higher than conventional RIE systems. GaN etch rates as high as -1.3 μm/min have been reported in ECR generated ICI plasmas at -150 V dc-bias. In this study, we report high-density GaN etch results for ECR- and ICP-generated plasmas as a function of Cl2- and BCl3-based plasma chemistries.
Dry Etching of GaN Using Reactive Ion Beam Etching and Chemically Assisted Reactive Ion Beam Etching
Authors: Lee Jae-Won , Park Hyong-Soo , Park Yong-Jo , Yoo Myong-Cheol , Kim Tae-Il , Kim Hyeon-Soo , Yeom Geun-Yong 
Published: April 2011

ABSTRACTDry etching characteristics of GaN using reactive ion beam etching (RIBE) were studied. Etching profile, etching rate and etching selectivity to a photoresist (PR) mask were investigated as a function of various etching parameters. Characteristics of chemically assisted reactive ion beam etching (CARIBE) and RIBE were compared at varied mixtures of CH4 and Cl2. A highly anisotropie etching profile with a smooth surface was obtained for tilted RIBE with Ch at room temperature. Etching selectivity to a PR was dramatically improved in RIBE and CARIBE when a volume fraction of CH4 to the mixture of CH4 and Ch was larger than 0.83.
Plasma Damage Effects in InAlN Field Effect Transistors
Authors: Ren F. , Lothian J. R. , Chen Y. K. , Mackenzie J. D. , Donovan S. M. , Abernathy C. R. , Varturi C. B. , Lee J. W. , Pearton S. J. , Wilson R. G. 
Published: April 2011

ABSTRACTDuring gate mesa plasma etching of InN/InAlN field effect transistors the apparent conductivity in the channel can be either increased through three different mechanisms. If hydrogen is part of the plasma chemistry, hydrogen passivation of the shallow donors in the InAlN can occur, we find diffusion depths for 2H of ≥ 0.5 micron in 30 mins at 200°C. The hydrogen remains in the material until temperatures ≥ 700°C Energetic ion bombardment in SF6/O2 or BCl/Ar plasmas also compensates the doping in the InAlN by creation of deep acceptor states. Finally the conductivity of the immediate InAlN surface can be increased by preferential loss of N during BCl3 plasma etching, leading to poor rectifying contact characteristics when the gate metal is deposited on this etched surface. Careful control of plasma chemistry, ion energy and stoichiometry of the etched surface are necessary for acceptable pinch-off characteristics.
New Precursor Routes to Nanocrystalline Cubic/Hexagonal Gallium Nitride, GaN
Authors: Wells R. L. , Janik J. F. , Gladfelter W. L. , Coffer J. L. , Johnsons M. A. , Steffey B. D. 
Published: April 2011

ABSTRACTTwo precursor routes culminating in bulk nanocrystalline gallium nitride materials are reported, with emphasis on the materials' XRD/crystalline features and photoluminescence (PL). First, the new polymeric gallium imide, {Ga(NH)3/2}n, can be converted to nanocrystalline, cubic/hexagonal GaN ranging in color from yellow to light gray. Second, a new route to gallazane, [H2GaNH2]x, from the combination of LiGaH4 and NH4X (X = Cl, Br) in Et2O is shown to result in a material that slowly converts to a polymeric solid via H2 and NH3 elimination-condensation pathways. Both the gallazane and the polymeric solid are pyrolyzed to dark gray nanocrystalline, phase-inhomogeneous GaN as above. Specific variations in the pyrolysis conditions enable some control over the particle nanosize and a degree of crystalline phase-inhomogeneity of the materials. These nanophase GaN materials have also been characterized by room temperature photoluminescence (PL) measurements. In general, the observed emission spectra are strongly dependent on pyrolysis temperature and typically exhibit weak defect yellow-green emission. While the as-prepared GaN does not exhibit band-edge PL, a brief hydrofluoric acid etch yields nanophase GaN exhibiting an intense blue-emitting PL spectrum with an emission maximum near 420 nm.
Phase Formation and Morphology in Nickel and Nickel/Gold Contacts to Gallium Nitride
Authors: Venugopalan H. S. , Mohney S. E. , Luther B. P. , DeLucca J. M. , Wolter S. D. , Redwing J. M. , Bulman G. E. 
Published: April 2011

ABSTRACTMetallurgical reactions between Ni and GaN have been explored at temperatures between 400 and 900 °C in N2, Ar, and forming gas. A trend of increasing Ga content in the reacted films was observed with increasing temperature. The reactions are consistent with the thermodynamics of the Ni-Ga-N system. Changes in the film morphology on annealing were also examined. Metal island formation and a corresponding deep, non-uniform metal penetration into GaN were observed at high temperatures. The relevance of the observed nature of phase formation and morphology in these thin films to electrical properties of Ni/GaN and Au/Ni/GaN contacts is also considered.
Comparison of Electron and Hole Initiated Impact Ionization in Zincblende and Wurtzite Phase Gallium Nitride
Authors: Bellotti E. , Oguzman I. H. , Kölnik J. , Brennan K. F. , Wang R. , Ruderi P. P. 
Published: April 2011

ABSTRACTIn this paper, we present the first calculations of the electron and hole impact ionizatioi coefficients for both wurtzite and zincblende phase GaN as a function of the applied electrii field. The calculations are made using an ensemble Monte Carlo simulator including the ful details of the conduction and valence bands derived from an empirical pseudopotentia calculation. The interband impact ionization transition rates for both carrier species an determined by direct numerical integration including a wavevector dependent dielectric function It is found that the electron and hole ionization coefficients are comparable in zincblende Ga> at an applied field of ∼ 3 MV/cm, yet vary to a slight degree at both higher and lower applied field strengths. In the wurtzite phase, the electron and hole coefficients are comparable at hig] fields but diverge at lower applied fields. The most striking result is that the ionization rates an predicted to be substantially different for both carrier species between the two phases. It i predicted that the ionization rates for both carrier species in the zincblende phase are significanti; higher than in the wurtzite phase over the full range of applied fields examined.
Aluminum Nitride Thin Films Grown by Plasma-Assisted Pulsed Laser Deposition on Si Substrates
Authors: Okamoto M. , Ogawa T. , Mori Y. , Sasaki T. 
Published: April 2011

ABSTRACTThe smooth and highly oriented AlN films were obtained using pulsed laser deposition from sintered AlN target in a nitrogen ambient. The XRD investigation revealed that highly oriented AlN thin films along the c-axis (AlN (0002)) normal to the substrate were obtained both on Si(111) and on Si(100) substrates. The (0002) x-ray peak width became narrower with increasing substrate temperature. The CL investigation showed that AlN films at high laser energy density (Ed) indicated CL peak at shorter wavelength (306nm) than that at low Ed (394nm). N/Al atomic ratio in AlN films grown at high Ed also increased as comparison with the films grown at low Ed.
High Performance High Dielectric Constant Films Deposited by Dual Spectral Source Rapid Isothermal Assisted Metalorganic Chemical Vapor Deposition (MOCVD)
Authors: Chen Y. , Singh R. , DeBoer S. , Thakur R.P.S. 
Published: April 2011

ABSTRACTDual spectral source assisted MOCVD is an ideal technique for the deposition of high dielectric constant materials as well as other electronic and optical materials. Tungsten halogen lamps and a deuterium lamp are used as the sources of optical and thermal energy. Ta2O5films were deposited at 200°C for 30 minutes and annealed at 600°C for 30 minutes have shown leakage current densities as low as 10−10A/ cm2for gate voltage under 5V. To the best of our knowledge, these are the best results reported to date by other researchers. The high energy photons used in thein-situcleaning and deposition process play an important role in obtaining high quality films of Ta2O5.
Rapid Verticai Processor for Fast-Ramp Small-Batch Diffusion and Oxidation Applications
Authors: Porter Cole , Laser Allan , Ratliff Christopher 
Published: April 2011

ABSTRACTFast-ramp small-batch vertical furnace technology improves batch furnace processing capabilities. Reducing cycle time and improving diffusion control while still maintaining a low cost of ownership and film thickness uniformity are the key benefits of this new technology. A new high power density furnace has been designed to accommodate accelerated wafer temperature ramp up and cool down rates. Unique quartz fixturing is also used to minimize thermal stress across the wafers. This paper will describe both thermal uniformity and film uniformity results for a 65Å Gate Oxide Process for the Rapid Vertical Processor (RVP). In addition, thermal stress data and throughput results will be presented.
In-Situ Oxygen Monitoring of Rapid Thermal Process Chamber: Diagnosis of Gas Flow Dynamics and Wafer Processing
Authors: Kondoh E. , Maex K. 
Published: April 2011

ABSTRACTTwo types of real-time oxygen monitoring are investigated for RTP applications, i.e. addressing the basis for a state-of-the-art clean ambient technology and understanding its impact on real processes. Diagnosing of gas flow dynamics in the chamber is carried out by tracer experiments. Deviation from plug flow, which decreases purge efficiency, is found to be a function of gas flow rate. The monitoring of a typical two-step RTP process for silicidation of Ti or Co show that both adsorption and desorption take place. Oxygen is desorbed first at lower temperatures (during temperature ramp) then starts to be adsorbed at higher temperatures. In the case of Ti, a few monolayers of oxygen is adsorbed during the first RTP but less oxygen is adsorbed during the second RTP. The amount of oxygen adsorbed during Co RTP is found to be not as high as during Ti RTP.
Kinetics of Pt Silicide Formation Studied by Spectral Ellipsometry
Authors: Schwarz R. , Dittrich A. , Zhou S. M. , Hundhausen M. , Ley L. , Chen L. Y. , Woerle D. , Manke C. , Schulz M. 
Published: April 2011

ABSTRACTSuicide formation during thermal annealing of thin Pt layers deposited by evaporation onto crystalline silicon substrates was studied by in-situ spectral ellipsometry. As was shown in an earlier study, Pt suicide is formed in a two-step process with intermediate stages of Pt2Si and PtSi at temperatures of about 190 and 240 °C, respectively. We observed a shift of about 15 °C of the di- and monosilicide formation, when the anneal rate was lowered from 3 to 1 K/min. The analysis of the reaction kinetics using the normalized ellipsometric angle δ yields a good fit to the data for different anneal rates with an activation energy of (1.6 ± 0.2) eV. The underlying model of suicide formation through a multilayer system was checked with depth profiles and compositional information obtained from Rutherford Backscattering.
Laser-Assisted TiSi2 Formation for ULSI Applications
Authors: Shamma Nader , Talwar Somit , Verma Gaurav , Kramer Karl-Josef , Farrar Nigel , Chi Chiu , Greene Wayne , Weiner Kurt 
Published: April 2011

ABSTRACTIn this paper, we describe the results of recent work in which TiSi2 formation on deep-submicron polysilicon gates is achieved using pulsed excimer laser irradiation. Formation of low resistivity titanium suicide on sub-0.1 μm polysilicon lines is confirmed by sheet resistance measurements. High-resolution TEM examination shows exceptionally smooth interface between suicide and heavily-doped silicon substrate. Gate to source/drain bridging is not observed. Analytical techniques including Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD) have been used to characterize the irradiated films. This laser-assisted suicide formation process is a promising technology for extreme submicron MOSFET applications.
Rapid Thermal Process Requirements for The Annealing of Ultra-Shallow Junctions
Authors: Downey Daniel F. , Daryanani Sonu L. , Meloni Marylou , Brown Kristen M. , Felch Susan B. , Lee Brian S. , Marcus Steven D. , Gelpey Jeff 
Published: April 2011

ABSTRACT2. 0 keV 11B+, 2.2 keV 49BF2+ ion implanted and 1.0 kV Plasma Doped (PLAD) wafers of a dose of 1E15/cm2 were annealed at various times and temperatures in a variety of ambiente: 600 to 50,000 ppm O2 in N2; 5% NH3 in N2; N2O; N2 or Ar, in order to investigate the effects of the annealing ambient on the formation of ultra-shallow junctions. RGA data was collected during some (if the anneals to assist in identifying the complex surface chemistry responsible for boron out-diffusion. Subsequent to the anneals, ellipsometric, XPS, four-point probe sheet resistance and SJJVIS measurements were performed to further elucidate the effects of the different ambients on the r etained boron dose, the sheet resistance value, the RTP grown oxide layer and the junction depth. In the cases where oxygen was present, e.g. N2O and O2 in N2, an oxidation enhanced diffusion of the boron was observed. This was most dramatic for the N2O anneals, which at 1050°C 10s diffused the boron an additional 283 to 427 Å, depending on the particular doping condition and species. For the case of BF2 implants and PLAD, anneals in 5% NH3 in N2 reduced the junction depth by a nitridation reduced diffusion mechanism. RGA data indicated that the out-diffusion mechanisms for B and BF2 implanted wafers are different, with the BF2 exhibiting dopant loss mechanisms during the 950°C anneals, producing F containing compounds. B implants did not show doping loss mechanisms, ais observed by the RGA, until the 1050°C anneals and these signals did not contain F containing compounds. Equivalent effective energy boron implants of 8.9 keV BF2 vs. 2.0 keV B, however, indicated that the overall effect of the F in the BF2 implants is very beneficial in the creation of ultra-shallow junctions (compared to B implants): reducing the junction depth by 428 Å, and increasing the electrical activation (determined by SRP) by 11.7%, even though the retained dose (resulting from an increased out-diffusion of B), was decreased by 5.4%.