bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Properties of a P-Implanted GaN Light-Emitting Diode
Authors: Kikawa J. , Yoshida S. , Itoh Y. 
Published: April 2011

ABSTRACTElectroluminescence measurements of P-implanted GaN light-emitting diodes were performed. The measured peak densities of P in the GaN were 5×10 cm−3 and 4×10 cm−3 based on secondary ion mass spectroscopy. The EL spectra had a broad blue-band emission at the peak energy from around 2.8 eV to 3.3 eV and yellow-band emission at an energy centered at 2.2 eV. The blue-band emission could decompose into two components at energy positions of 2.9 eV and 3.2 eV. The former component is considered to be emission due to the recombination of the bounding exciton by P atoms, known as an isoelectronic trap in GaN.
Surface acoustic wave resonator from thick MOVPE-grown layers of GaN(0001) on sapphire
Authors: Pettersen Sverre V. , Tybell Thomas , Rønnekleiv Arne , Rooth Stig , Schwegler Veit , Grepstad Jostein K. 
Published: April 2011

ABSTRACTWe report on fabrication and measurement of a surface acoustic wave resonator prepared on ∼10m thick GaN(0001) films. The films were grown by metal-organic vapor phase epitaxy on a c-plane sapphire substrate. The surface morphology of the films were examined with scanning electron and atomic force microscopy. A metallic bilayer of Al/Ti was subsequently evaporated on the nitride film surface. Definition of the resonator interdigital transducers, designed for a wavelength of λ=7.76m, was accomplished with standard UV lithography and lift-off. S-parameter measurements showed a resonator center frequencyf0=495MHz at room temperature, corresponding to a surface acoustic wave velocity of 3844m/s. The insertion loss at center frequency was measured at 8.2dB, and the loaded Q-factor was estimated at 2200. Finally, measurements of the resonator center frequency for temperatures in the range 25–155°C showed a temperature coefficient of -18ppm/°C. The intrinsic GaN SAW velocity and electromechanical coupling coefficient were estimated at νSAW=383 1m/s andK2=1.8±0.4·10−3.
High Power 325 Light Emitting Diode Arrays by Flip-Chip Packaging
Authors: Chitnis Ashay , Shatalov Maxim , Adivarahan Vinod , Zhang Jian Ping , Wu Shuai , Sun Jie , Asif Khan M. 
Published: April 2011

ABSTRACTWe report flip-chip 325 nm emission light emitting diodes over sapphire with dc powers as high as 0.84 mW at 180mA and pulse powers as high as 6.68 mW at 1A. These values to date are the highest reported powers for such short wavelength emitters. Our data shows the device output power under dc operation to be limited by the package heat dissipation. A study is presented to determine the role of thermal management in controlling the power output for the reported 325 nm ultraviolet light emitting diodes.
Epitaxial Growth for Solar-Blind AlGaN Photodetector Imaging Arrays by Metalorganic Chemical Vapor Deposition
Authors: Chowdhury Uttiya , Collins Charles J. , Wong Michael M. , Zhu Ting Gang , Denyszyn Jonathan C. , Choi Jin Ho , Yang Bo , Campbell Joe C. , Dupuis Russell D. 
Published: April 2011

ABSTRACTSolar-blind imaging arrays based on AlGaN p-i-n structures are of high interest for defense applications. We have studied the material issues involved in development of such imaging arrays and have developed discrete photodetector devices with a high external quantum efficiency (EQE) and imaging arrays of high operability.For the discrete devices, a record EQE of 58.1% peaking at 274 nm under zero volt bias was obtained without using an anti-reflecting (AR) coating. The EQE was seen to have a slight voltage dependence: going up to 64.5% at –5V reverse bias. The responsivity had a drop-off by one order of magnitude for a wavelength change of 4 nm on both the shorter and longer wavelength side. The material quality and uniformity was found to be very good leading to the development of 256 × 256 arrays. A high yield along with uniform, high EQE was obtained for the detector devices in the array leading to a high operability of 99.8%.
Self-Heating Effects in Multi-Finger AlGaN/GaN HFETs
Authors: Kuball M. , Rajasingam S. , Sarua A. , Uren M. J. , Martin T. , Balmer R. S. , Hilton K. P. 
Published: April 2011

ABSTRACTWe report on the in-situ measurement of temperature, i.e., self-heating effects, in multi-finger AlGaN/GaN HFETs grown on SiC substrates. Optical micro-spectroscopy was used to measure temperature with 1m spatial resolution. Thermal resistance (temperature rise per W/mm) was measured as a function of device pitch and gate finger width. There is significant thermal cross talk in multi-finger AlGaN/GaN HFETs and this needs to be seriously considered for device performance and ultimately device reliability. A comparison with theoretical modeling is presented. Uncertainties in modeling parameters currently make modeling less reliable than experimental temperature assessment of devices.
Nickel, Platinum and Zirconium Germanosilicide Contacts to Heavily Phosphorous Doped Silicon-Germanium Alloys for Advanced CMOS Source/Drain Junctions
Authors: Mo Hongxiang , Liu Jing , Öztürk Mehmet C. 
Published: April 2011

ABSTRACTAs the MOSFET dimensions continue to shrink, source/drain contact resistance is emerging as the dominant component of the MOSFET parasitic series resistance. To meet the series resistance requirements of future MOSFETs, contact resistivity values near 10-8 ohm-cm2 are required. Selective Si1-xGex source/drain technology has been proposed as an alternative to ionimplantation to form the ultra-shallow junctions of future CMOS technology nodes. One of the key advantages of this technology is the smaller band gap of Si1-xGex, which provides a smaller contact barrier height, an essential requirement for reducing the contact resistivity. We have previously reported low-resistivity of Ni germanosilicide NiSi1-xGex and Pt germanosilicide PtSi1-xGex contacts to boron doped Si1-xGex alloys. In this work, Zr germanosilicide, Zr(Si1-xGex)2 was considered as an alternative material with a higher thermal stability than Ni and Pt germanosilicides. The contact resistivity values for different contact materials were measured using four-terminal Kelvin structures. The results from this work show that both Zr and Pt germanosilicides yield high contact resistivity values around 10-7 ohm-cm2. On the other hand Ni germanosilicide contacts can reach 10-8 ohm-cm2 with further improvements using a thin layer of Pt under Ni.
Ni Silicide Formation on Polycrystalline SiGe and SiGeC Layers
Authors: Haralson Erik , Jarmar Tobias , Seger Johan , Radamson Henry H. , Zhang Shi-Li , Östling Mikael 
Published: April 2011

ABSTRACTThe reactions of Ni with polycrystalline Si, Si0.82Ge0.18 and Si0.818Ge0.18C0.002 films in two different configurations during rapid thermal processing were studied. For the usually studied planar configuration with 20 nm thick Ni on 130–290 nm thick Si1-x-yGexCy, NiSi1-xGex(C) forms at 450°C on either Si0.82Ge0.18 or Si0.818Ge0.18C0.002, comparable to NiSi formed on Si. However, the agglomeration of NiSi1-xGex(C) on Si0.818Ge0.18C0.002 occurs at 625°C, about 50°C higher than that of NiSi1-xGex on Si0.82Ge0.18. For thin-film lateral diffusion couples, a 200-nm thick Ni film was in contact with 80–130 nm thick Si1-x-yGexCy through 1–10 μm sized contact openings in a 170 nm thick SiO2 isolation. While the Ni3Si phase was formed for both the Si0.82Ge0.18 and Si0.818Ge0.18C0.002 samples, the presence of 0.2 at.% C caused a slightly slower lateral growth.
Physical and Electrical Properties of Al2O3, HfO2, and their Alloy Films Prepared by Atomic Layer Deposition for 65nm CMOS Gate Dielectric
Authors: Kawahara Takaaki , Torii Kazuyoshi , Fukuda Seiichi , Maeda Takeshi , Horiuchi Atsushi , Ito Hiroyuki , Muto Akiyoshi , Kato Yoshitake , Kitajima Hiroshi 
Published: April 2011

ABSTRACTWe have investigated physical and electrical properties of Al2O3, HfO2, and their alloy films deposited on 300mm Si wafers by Atomic Layer Deposition (ALD). It is found that Al2O3 films are not crystallized even after the heat treatment of 1050°C, while HfO2 films are already crystallized even after a-Si deposition (530°C). The crystallization temperature can be higher by adding Al2O3 to HfO2. It is confirmed by in-plane XRD and plane views of TEM that HfAlOx films with lower Hf content (Hf/(Hf+Al) <30%) are amorphous without phase separation after annealing at 1050°C and 5sec. The dependences of equivalent oxide thicknesses (EOT) on the physical thicknesses of Al2O3, HfAlOx (Hf/(Hf+Al)∼22%), and HfO2 films in poly-silicon gate capacitors indicate that those dielectric constants k are ∼9, 14, and 23, respectively. The gate dielectric with EOT of 1.5nm and the leakage current density Jg of 3mA/cm2 can be fabricated with 2nm-thick HfAlOx (22%) film.
Copper Diffusion Characteristics in Single Crystal and Polycrystalline TaN
Authors: Wang H. , Tiwari Ashutosh , Zhang X. , Kvit A. , Narayan J. 
Published: April 2011

ABSTRACTTaN has become a very promising diffusion barrier material for Cu interconnections, due to the high thermal stability requirement and thickness limitation for next generation ULSI devices. TaN has a variety of phases and Cu diffusion characteristics vary with different phases and microstructures. We have investigated the diffusivity of copper in single-crystal (NaCl-structured) and polycrystalline TaN thin films grown by pulsed laser deposition. The polycrystalline TaN films were grown directly on Si(100), while the single crystal films were grown with TiN buffer layers. Both of poly and single-crystal films with Cu overlayers were annealed at 500 °C, 600 °C, 650 °C, and 700 °C in vacuum to study the copper diffusion characteristics. The diffusion of copper into TaN was studied using STEM-Z contrast, where the contrast is proportional to Z (atomic number), and TEM. The diffusion distances are found to be about 5nm at 650°C for 30 min annealing. The diffusivity of Cu into single crystal TaN follows the relation D = (160±9.5)exp[-(3.27 ±0.1)eV/kBT]cm2s-1 in the temperature range of 600°C to 700°C. We observe that Cu diffusion in polycrystalline TaN thin films is nonuniform with enhanced diffusivities along the grain boundary.
Low Thermal Budget NiSi Films on SiGe Alloys
Authors: Ray S. K. , Adam T. N. , Kar G. S. , Swann C. P. , Kolodzey J. 
Published: April 2011

ABSTRACTNickel silicides were formed on Si (100) substrates and CVD grown Si0.9Ge0.1/Si layers by low thermal budget annealing of evaporated Ni films to evaluate their utility for ultra shallow junctions. The phase formation and microstructure of silicides formed using conventional furnace and rapid thermal annealing were studied by x-ray diffraction, Rutherford backscattering (RBS), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy. RBS simulations and XPS study revealed the formation of a ternary nickel germanosilicide phase for the SiGe alloy. The incorporation of Ge resulted in a higher temperature window for the stability of low-resistive monosilicide phase. Electrical properties of the grown silicides were characterized by four-probe resistivity and contact resistance measurements.
Atomic Structure, Band Offsets and Hydrogen in High K oxide:Silicon interfaces
Authors: Robertson J , Peacock P W 
Published: April 2011

ABSTRACTThe bonding, electronic structure and valence band offsets are calculated for various atomic models of interfaces between Si and high dielectric constant insulators ZrO2 and SrTiO3. A non-polar face of the oxide does not necessarily give a semiconducting interface, because of the need to fill Si dangling bond states on the Si side. This can be achieved by stoichiometry changes. Band offsets of semiconducting interfaces are generally the same as those found from bulk charge neutrality levels, indicating no dipole layers. Dipole layers are present at some configurations, where the offset is then changed by up to 1 eV. The states of hydrogen in the oxides are also considered.
The Influence of Defects on Compatibility and Yield of the HfO2-PolySilicon Gate Stack for CMOS Integration
Authors: Kaushik V. S. , DeGendt S. , Carter R. , Claes M. , Rohr E. , Pantisano L. , Kluth J. , Kerber A. , Cosnier V. , Cartier E. , Tsai W. , Young E. , Green M. , Chen J. , Jang S-A. , Lin S. , Delabie A. , Elshocht S.V. , Manabe Y. , Richard O. , Zhao C. , Bender H. , Caymax M. , Heyns M. 
Published: April 2011

ABSTRACTHafnium-based dielectrics are under wide consideration for high-K gate dielectric applications. Since the gate electrode typically used in CMOS integration consists of polysilicon with n- or p-type dopants, compatibility of the HfO2layer with the polySi deposition and dopant activation steps is critical. Capacitors were fabricated with HfO2films deposited by ALD and MOCVD, and using polysilicon gate electrodes deposited by CVD processes. These devices showed leakage failures with yields that were observed to depend on the area, dielectric thickness and annealing conditions during the process. Investigation of the root cause of these leakage failures suggested that the leakage failures may be caused by a defect-related mechanism. The implication of this is that the leakage occurs at localized ‘defect’ sites rather than broadly through the HfO2layer. Emission microscopy analysis and physical characterization of the HfO2film were used to corroborate the proposed model. Defect density was observed to be strongly dependent on the processing of the dielectric film. In order to make Hf-based dielectric stacks compatible with polysilicon for conventional CMOS transistor integration with acceptable yield, further postdeposition treatment may be necessary to eliminate or cure the defects.
Conduction Mechanisms in SrTiO3 Thin Films on Silicon
Authors: Mereu Bogdan , Sarau George , Alexe Marin 
Published: April 2011

ABSTRACTNew materials with high dielectric constant are currently being explored to replace silicon dioxide as gate dielectric for device scaling below 0.1 μm. With respect to conventional SiO2, these high permittivity dielectrics provide the required equivalent oxide thickness (EOT) without of further reduction of the insulator physical thickness, which is a key issue to limit gate leakage current and to maintain comparable MOSFET operation and reliability. The present paper presents preliminary results on conduction mechanisms in thin epitaxial SrTiO3 films grown by MBE on Si (100). I-V measurements were performed on Al/STO/Si structures at temperatures ranging from 40 K to 290 K. At temperatures lower than 100 K the conduction mechanism of electrons from gate electrode across the oxide barrier neither Schottky emission nor tunneling. For temperatures higher than 100 K Schottky emission occurs and barrier heights were extracted, showing an approximate linearly increase with temperature. In case of Si/STO interface, a Fowler-Nordheim tunneling mechanism was detected at 40 K and at intermediate fields. The extracted barrier heights are: 0.07 eV at Si/STO interface and from 0.26 eV (130 K) to 0.53 eV (290 K) at Al/STO interface.
Enhancement of Remanent Polarization of BIT-based Thin Films by Ti-site Substitution using Ions with Higher Charge Valences
Authors: Uchida Hiroshi , Okada Isao , Matsuda Hirofumi , Iijima Takashi , Watanabe Takayuki , Funakubo Hiroshi 
Published: April 2011

ABSTRACTBismuth titanate (Bi4Ti3O12; BIT) -based ferroelectric thin films fabricated from a view point of “the site-engineering technique” have been expected to improve the fatal disadvantage of a ferroelectric BIT film, i.e., its low spontaneous polarization; here, Bi- and Ti-site ions in the BIT crystal are cosubstituted by lanthanoid ions and cations with a higher charge valence, respectively, In the present study, we have mainly focused on Ti-site substitution of bismuth titanate (Bi4Ti3O12; BIT)-based thin films using some ions with higher charge valences (V5+, Nb5+, Ta 5+ and W6+; in this study) to enhance the ferroelectric properties of those materials. The BIT-based films with various chemical compositions were fabricated on a (111)Pt/Ti/SiO2/(100)Si substrate by a chemical solution deposition method.Ti-site substitution of BIT films by the higher-valent ions, Bi3.99(Ti2.97V0.03)O12, Bi3.99(Ti2.97Nb0.03)O12, Bi3.99(Ti2.97Ta0.03)O12 and Bi3.98(Ti2.97W0.03)O12, reduced the leakage current density of BIT films from ∼ 10-6 down to ∼ 10-7 A/cm2 at an applied field of 50 kV/cm, while the substitution by the same-valent cation, e.g., Bi4.00(Ti2.97Zr0.03)O12, did not affect the behavior of leakage current. Whereas polarization (P) - electrical field (E) hysteresis loops of non-substituted and Zr-substituted BIT films were distorted due to the leakage current, non-distorted P-E loops were obtained at V5+-, Nb5+-, Ta5+- and W6+-substituted BIT films.Also, Ti-site substitution was effective for improving the ferroelectric properties in lanthanoid-substituted BIT films. In the case of La3+-substituted BIT film (BLT), remanent polarization (Pr) of V5+- and W6+-substituted BLT films, (Bi3.24La0.75)(Ti2.97V0.03)O12 and (Bi3.23La0.75)(Ti2.97W0.03)O12 (13 and 12 μC/cm2, respectively), were larger than those of Zr4+- and non-substituted BLT films, (Bi3.25La0.75)(Ti2.97Zr0.03)O12 and (Bi3.25La0.75)(Ti3.00)O12 (8 and 9 μC/cm2, respectively), while those films had similar coercive field (Ec) of approximately 120 kV/cm. Also in the case of Nd3+-substituted BIT film (BNT), Pr and Ec values of V5+-substituted BNT film, (Bi3.24Nd0.75)(Ti2.98V0.02)O12, were 37 μC/cm2 and 119 kV/cm, respectively, which were comparable with those of conventional Pb-based ferroelectrics such as lead zirconate titanate, Pb(Zr,Ti)O3. We concluded that enhancement of the Pr value was achieved by the charge compensation of oxygen vacancies in BIT-based ferroelectrics using higher-valent cations than Ti4+ ion whereas no obvious differences were found in the crystal orientation and or microstructure of these films.
Preparation of Bi2SiO5-SrBi2Ta2O9 Ferroelectric Thin Films by RF Magnetron Sputtering
Authors: Kikuchi Shin , Ishiwara Hiroshi 
Published: April 2011

ABSTRACTSi-added SrBi2Ta2O9 (SBT) ferroelectric films were prepared by RF magnetron sputtering on a Pt/Ti/SiO2/Si (100) structure. The films were deposited at temperatures below 100°C for preventing Bi evaporation and crystallized at 800°C in air. A typical composition was Sr0.79Bi2.37Ta2.00Si0.2Ox. The remnant polarization value(2Pr) of the Si-added SBT film was 16C/cm2 and leakage current density was 5×10-8A/cm2. The current density was significantly decreased by adding Si atoms.
Microstructure and dielectric properties of epitaxial BaTiO3 films and BaTiO3/SrTiO3 multilayers
Authors: Visinoiu A. , Scholz R. , Alexe M. , Hesse D. 
Published: April 2011

ABSTRACTEpitaxial BaTiO3 films and BaTiO3/SrTiO3 multilayers were grown by pulsed laser deposition (PLD) on (001)-oriented Nb-doped SrTiO3 (SrTiO3:Nb) substrates. Measurements of the dielectric properties were performed comparing BaTiO3 films and BaTiO3/SrTiO3 multilayers of different number of individual layers, but equal overall thickness. The dielectric loss saturates for a thickness above 300 nm, and linearly decreases with decreasing film thickness below a thickness of 75 nm, and it is independent on the number of multilayers, pointing to some interface effect. The thickness dependence of the dielectric constant of BaTiO3 films and BaTiO3/SrTiO3 multilayers exhibits a change in the linear slope at a thickness of 75 nm. This behavior is explained by the change observed in the morphology at a thickness of 75 nm. In order to explain the thickness dependence of the dielectric constant, two approaches are considered in this paper, viz. a “series capacitor” model and a “dead layer” model.
Barium Strontium Titanate Thin Film Capacitors for Low Inductance Decoupling Applications
Authors: Baniecki J. D. , Shioga T. , Kurihara K. 
Published: April 2011

ABSTRACTSputter deposited barium strontium titanate (BST) based thin film capacitors have been developed for use in GHz LSI decoupling applications. The fabricated 1.60×1.85 mm2 BST chip decoupling capacitors with Pt electrodes and 150 μm bump pitch, have a capacitance density of 1.2 μF/cm2, low equivalent series inductance of 15 pH, and a low equivalent series resistance of 0.02 Ω. The impedance of the chip capacitors at 1 GHz is over 1000 times lower than conventional multilayered ceramic capacitors. Fundamental electrical and reliability properties of Pt/BST/Pt thin film capacitor structures were also investigated. Capacitors with 200 nm thick BST thin films deposited at 500 °C by RF magnetron sputtering achieved a C/A of 1.8 μF/cm2, leakage current density < 10-9 A/cm2 at 2 volts, and a breakdown field > 2.5 MV/cm at 20 °C. A fit of the failure data to a Weibull distribution indicated at least two different physical mechanisms causing capacitor failure. The primary failure mechanism for 1.5 volt operation was due to resistance degradation without catastrophic capacitor failure. At higher applied voltages, catastrophic capacitor failure occurred with the breakdown event characterized by a thermal runway process. The physical mechanisms contributing to capacitor failure are interpreted to be due to ionic migration and charge injection, and the contribution of these mechanisms to the degradation process could be partially resolved by bi-polar voltage pulse stressing. The projected mean time to failure for 1.5 volt operation is extrapolated to be in excess of 104 years at 75 °C and 126 years at 125 °C. The results indicate that sputter deposited BST thin film capacitors are promising for future GHz LSI decoupling applications.
Nucleation and growth of thin (Ba,Sr)TiO3 films in a MOCVD reactor
Authors: Regnery S. , Ding Y. , Ehrhart P. , Fitsilis F. , Jia C. L. , Szot K. , Waser R. , Schienle F. , Schumacher M. , McEntee T. 
Published: April 2011

ABSTRACT(BaxSr1-x)TiO3 thin films were deposited on Pt electrodes in a planetary multi-wafer MOCVD reactor combined with a liquid delivery system. The nucleation behavior and the size of the stable nuclei were investigated by different SPM techniques and by XPS. Characteristic differences were observed between deposition temperatures of 565°C and 655°C, i.e. a homogeneous nucleation of small BST grains on the larger Pt grains (100 − 200 nm in-plane size) at low temperatures and a dominating nucleation at the grain boundaries at high temperatures. Further film growth was investigated for nominal film thickness between 5 and 100 nm and details of the grain structure are revealed by HRTEM, e.g., randomly oriented grains (typical in-plane size 10–20nm) with a high density of twins at 565°C and (100)-oriented defect free grains of slightly increased size at 655°C. As the electrical properties like permittivity and also leakage current depend on film thickness the final discussions of the electrical properties are based on thickness series and evaluated within the phenomenological dead layer model.
Thermodynamic Analysis of the Hysteresis Offsets from Polarization Graded Ferroelectric Materials
Authors: Ban Z.-G. , Alpay S. P. , Mantese J. V. 
Published: April 2011

ABSTRACTPolarization graded ferroelectrics exhibit unconventional electrical properties that are not usually observed from homogenous ferroelectrics. Systematic spatial variations in the polarization in a ferroelectric material can be achieved by composition, temperature, and stress gradients; resulting in the displacement of the polarization vs. electric field hysteresis curve along the polarization axis. In this paper, this unusual phenomenon of hysteresis offset has been examined in BaTiO3 and BaxSr1-xTiO3 material systems using a Landau-Ginzburg phenomenological model for the first time. It is shown that the spatial non-uniformities can give rise to non-uniformities in polarization with corresponding spatial variations. This non-uniform polarization results in asymmetrical hysteresis with “up” or “down” charge offsets which are strongly dependent upon the magnitude and direction of the temperature, composition and stress gradients for three graded ferroelectrics.