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Device Characteristics (device + characteristic)
Selected AbstractsDevice characteristics and metal,dielectric high reflectivity coating analysis of ,,,,1.3,µm InGaAsP/InGaAsP MQW PBH lasersPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010J. W. Leem Abstract The cavity length-dependent characteristics of compressively strained InGaAsP/InGaAsP multiple quantum well planar buried heterostructure lasers operating at ,,,,1.3,µm were investigated under continuous-wave mode. The uncoated 600,µm long laser exhibits Pmax,=,33.6,mW and Ith,=,12.9,mA at 25,°C with d,/dT,=,0.35,nm/K and d,/dPe,=,0.044,nm/mW, leading to stable beam characteristics of 19.7° (parallel),×,24.1° (perpendicular). From the inverse slope efficiency versus cavity length plot, the loss parameters of internal differential efficiency (,i) and internal optical loss (,i) were extracted, i.e., ,i,=,78% and ,i,=,10.6,cm,1. The transparent current density of Jtr,=,0.12,kA/cm2 and modal gain of G,=,49.5,cm,1 were also estimated from cavity length-dependent threshold current density measurements. Metal,dielectric Au/Ti/SiO2 layers for high reflectivity (HR) coating were analyzed using theoretical calculations and experimental results. For the HR-coated 600,µm long laser with Au (150,nm)/Ti (5,nm)/SiO2 (250,nm), Pmax increased up to 61,mW at 25,°C with a reduced Ith of 10.6,mA compared to the uncoated laser, providing an HR of about 94%. [source] Hydrogen- and carbon-related defects in heavily carbon-doped GaAs induced degradation under minority-carrier injectionELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 5 2010Hiroshi Fushimi Abstract GaAs/AlGaAs heterojunction bipolar transistors (HBTs) have attracted much attention because of their high-speed performance. However, long-term operation seriously degrades the device characteristics: the current gain decreases and the low-bias-leakage current increases. This degradation has long been an issue in GaAs-based devices operated under minority-carrier injection, such as laser diodes. The cause of degradation is thought to lie in the carbon-doped base, but this is not yet certain. In this paper the degradation of HBTs is described, especially that of GaAs/AlGaAs HBTs with a heavily carbon-doped base layer. Two types of device degradation are found, namely, hydrogen-related degradation and carbon-related degradation. The mechanisms governing the degradation are discussed in the framework of the recombination-enhanced defect reaction (REDR) and charge state effect (CSE). © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(5): 33,41, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10208 [source] Synthesis, Morphology, and Properties of Poly(3-hexylthiophene)- block -Poly(vinylphenyl oxadiazole) Donor,Acceptor Rod,Coil Block Copolymers and Their Memory Device ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Yi-Kai Fang Abstract Novel donor,acceptor rod,coil diblock copolymers of regioregular poly(3-hexylthiophene) (P3HT)- block -poly(2-phenyl-5-(4-vinylphenyl)-1,3,4-oxadiaz-ole) (POXD) are successfully synthesized by the combination of a modified Grignard metathesis reaction (GRIM) and atom transfer radical polymerization (ATRP). The effects of the block ratios of the P3HT donor and POXD pendant acceptor blocks on the morphology, field effect transistor mobility, and memory device characteristics are explored. The TEM, SAXS, WAXS, and AFM results suggest that the coil block fraction significantly affects the chain packing of the P3HT block and depresses its crystallinity. The optical absorption spectra indicate that the intramolecular charge transfer between the main chain P3HT donor and the side chain POXD acceptor is relatively weak and the level of order of P3HT chains is reduced by the incorporation of the POXD acceptor. The field effect transistor (FET) hole mobility of the system exhibits a similar trend on the optical properties, which are also decreased with the reduced ordered P3HT crystallinity. The low-lying highest occupied molecular orbital (HOMO) energy level (,6.08 eV) of POXD is employed as charge trap for the electrical switching memory devices. P3HT- b -POXD exhibits a non-volatile bistable memory or insulator behavior depending on the P3HT/POXD block ratio and the resulting morphology. The ITO/P3HT44 - b - POXD18/Al memory device shows a non-volatile switching characteristic with negative differential resistance (NDR) effect due to the charge trapped POXD block. These experimental results provide the new strategies for the design of donor-acceptor rod-coil block copolymers for controlling morphology and physical properties as well as advanced memory device applications. [source] Fabrication of Sub-10,nm Metallic Lines of Low Line-Width Roughness by Hydrogen Reduction of Patterned Metal,Organic Materials,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Mihaela Nedelcu Abstract The fabrication of very narrow metal lines by the lift-off technique, especially below sub-10,nm, is challenging due to thinner resist requirements in order to achieve the lithographic resolution. At such small length scales, when the grain size becomes comparable with the line-width, the built-in stress in the metal film can cause a break to occur at a grain boundary. Moreover, the line-width roughness (LWR) from the patterned resist can result in deposited metal lines with a very high LWR, leading to an adverse change in device characteristics. Here a new approach that is not based on the lift-off technique but rather on low temperature hydrogen reduction of electron-beam patterned metal naphthenates is demonstrated. This not only enables the fabrication of sub-10,nm metal lines of good integrity, but also of low LWR, below the limit of 3.2,nm discussed in the International Technology Roadmap for Semiconductors. Using this method, sub-10,nm nickel wires are obtained by reducing patterned nickel naphthenate lines in a hydrogen-rich atmosphere at 500,°C for 1,h. The LWR (i.e., 3 ,LWR) of these nickel nanolines was found to be 2.9,nm. The technique is general and is likely to be suitable for fabrication of nanostructures of most commonly used metals (and their alloys), such as iron, cobalt, nickel, copper, tungsten, molybdenum, and so on, from their respective metal,organic compounds. [source] Interface Modifications of InAs Quantum-Dots Solids and their Effects on FET PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Michal Soreni-Harari Abstract InAs nanocrystals field-effect transistors with an ON/OFF ratio of 105 are reported. By tailoring the interface regions in the active layer step-by-step, the evolution of the ON/OFF ratio can be followed from approximately 5 all the way to around 105. The formation of a semiconducting solid from colloidal nanocrystals is achieved through targeted design of the nanocrystal,nanocrystal interaction. The manipulation characteristics of the nanocrystal interfaces include the matrix surrounding the inorganic core, the interparticle distance, and the order of nanocrystals in the 3D array. Through careful analysis of device characteristics following each treatment, the effect of each on the physical properties of the films are able to be verified. The enhanced performance is related to interparticle spacing, reduction in sub-gap states, and better electronic order (lower , parameter). Films with enhanced charge transport qualities retain their quantum-confined characteristics throughout the procedure, thus making them useful for optoelectronic applications. [source] Variable Temperature Mobility Analysis of n-Channel, p-Channel, and Ambipolar Organic Field-Effect TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Joseph A. Letizia Abstract The temperature dependence of field-effect transistor (FET) mobility is analyzed for a series of n-channel, p-channel, and ambipolar organic semiconductor-based FETs selected for varied semiconductor structural and device characteristics. The materials (and dominant carrier type) studied are 5,5,,,-bis(perfluorophenacyl)-2,2,:5,,2,:5,,2,,,-quaterthiophene (1, n-channel), 5,5,,,-bis(perfluorohexyl carbonyl)-2,2,:5,,2,:5,,2,,,-quaterthiophene (2, n-channel), pentacene (3, p-channel); 5,5,,,-bis(hexylcarbonyl)-2,2,:5,,2,:5,,2,,,-quaterthiophene (4, ambipolar), 5,5,,,-bis-(phenacyl)-2,2,: 5,,2,:5,,2,,,-quaterthiophene (5, p-channel), 2,7-bis((5-perfluorophenacyl)thiophen-2-yl)-9,10-phenanthrenequinone (6, n-channel), and poly(N -(2-octyldodecyl)-2,2,-bithiophene-3,3,-dicarboximide) (7, n-channel). Fits of the effective field-effect mobility (µeff) data assuming a discrete trap energy within a multiple trapping and release (MTR) model reveal low activation energies (EAs) for high-mobility semiconductors 1,3 of 21, 22, and 30,meV, respectively. Higher EA values of 40,70,meV are exhibited by 4,7 -derived FETs having lower mobilities (µeff). Analysis of these data reveals little correlation between the conduction state energy level and EA, while there is an inverse relationship between EA and µeff. The first variable-temperature study of an ambipolar organic FET reveals that although n-channel behavior exhibits EA,=,27,meV, the p-channel regime exhibits significantly more trapping with EA,=,250,meV. Interestingly, calculated free carrier mobilities (µ0) are in the range of ,0.2,0.8,cm2,V,1 s,1 in this materials set, largely independent of µeff. This indicates that in the absence of charge traps, the inherent magnitude of carrier mobility is comparable for each of these materials. Finally, the effect of temperature on threshold voltage (VT) reveals two distinct trapping regimes, with the change in trapped charge exhibiting a striking correlation with room temperature µeff. The observation that EA is independent of conduction state energy, and that changes in trapped charge with temperature correlate with room temperature µeff, support the applicability of trap-limited mobility models such as a MTR mechanism to this materials set. [source] Low-Temperature-Grown Transition Metal Oxide Based Storage Materials and Oxide Transistors for High-Density Non-volatile MemoryADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Myoung-Jae Lee Abstract An effective stacked memory concept utilizing all-oxide-based device components for future high-density nonvolatile stacked structure data storage is developed. GaInZnO (GIZO) thin-film transistors, grown at room temperature, are integrated with one-diode (CuO/InZnO),one-resistor (NiO) (1D,1R) structure oxide storage node elements, fabricated at room temperature. The low growth temperatures and fabrication methods introduced in this paper allow the demonstration of a stackable memory array as well as integrated device characteristics. Benefits provided by low-temperature processes are demonstrated by fabrication of working devices over glass substrates. Here, the device characteristics of each individual component as well as the characteristics of a combined select transistor with a 1D,1R cell are reported. X-ray photoelectron spectroscopy analysis of a NiO resistance layer deposited by sputter and atomic layer deposition confirms the importance of metallic Ni content in NiO for bi-stable resistance switching. The GIZO transistor shows a field-effect mobility of 30,cm2,V,1,s,1, a Vth of +1.2,V, and a drain current on/off ratio of up to 108, while the CuO/InZnO heterojunction oxide diode has forward current densities of 2,×,104,A,cm,2. Both of these materials show the performance of state-of-the-art oxide devices. [source] Enhancement of Carrier Mobilities of Organic Semiconductors on Sol,Gel Dielectrics: Investigations of Molecular Organization and Interfacial Chemistry EffectsADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Tommy Cahyadi Abstract The dielectric-semiconductor interfacial interactions critically influence the morphology and molecular ordering of the organic semiconductor molecules, and hence have a profound influence on mobility, threshold voltage, and other vital device characteristics of organic field-effect transistors. In this study, p-channel small molecule/polymer (evaporated pentacene and spin-coated poly(3,3,;-didodecylquarterthiophene) , PQT) and n-channel fullerene derivative ({6}-1-(3-(2-thienylethoxycarbonyl)-propyl)-{5}-1-phenyl-[5,6]-C61 , TEPP-C61) show a significant enhancement in device mobilities ranging from ,6 to ,45 times higher for all classes of semiconductors deposited on sol,gel silica gate-dielectric than on pristine/octyltrichlorosilane (OTS)-treated thermally grown silica. Atomic force microscopy, synchrotron X-ray diffraction, photoluminescence/absorption, and Raman spectroscopy studies provide comprehensive evidences that sol,gel silica dielectrics-induced enhancement in both p- and n-channel organic semiconductors is attributable to better molecular ordering/packing, and hence reduced charge trapping centers due to lesser structural defects at the dielectric-semiconductor interface. [source] Influences of Connecting Unit Architecture on the Performance of Tandem Organic Light-Emitting Devices,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2007Y. Chan Abstract The present work investigates the influence of the n-type layer in the connecting unit on the performance of tandem organic light-emitting devices (OLEDs). The n-type layer is typically an organic electron-transporting layer doped with reactive metals. By systematically varying the metal dopants and the electron-transporting hosts, we have identified the important factors affecting the performance of the tandem OLEDs. Contrary to common belief, device characteristics were found to be insensitive to metal work functions, as supported by the ultraviolet photoemission spectroscopy results that the lowest unoccupied molecular orbitals of all metal-doped n-type layers studied here have similar energy levels. It suggests that the electron injection barriers from the connecting units are not sensitive to the metal dopant used. On the other hand, it was found that performance of the n-type layers depends on their electrical conductivities which can be improved by using an electron-transporting host with higher electron mobility. This effect is further modulated by the optical transparency of constituent organic layers. The efficiency of tandem OLEDs would decrease as the optical transmittance decreases. [source] Reliability of Organic Field-Effect TransistorsADVANCED MATERIALS, Issue 38-39 2009Henning Sirringhaus Abstract In this article, we review current understanding of the reliability of organic field-effect transistors, with a particular focus on degradation of device characteristics under bias stress conditions. We discuss the various factors that have been found to influence the operational stability of different material systems, including dependence on stress voltage and duty cycle, gate dielectric, environmental conditions, light exposure, and contact resistance. A key question concerns the role of extrinsic factors, such as oxidation or presence of moisture, and that of intrinsic factors, such as the inherent structural and electronic disorder that is present in thin organic semiconductor films. We also review current understanding of the microscopic defects that could play a role in charge trapping in organic semiconductors. [source] Non-linear circuit modelling via nodal methodsINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 4 2005Ricardo Riaza Abstract We discuss in this paper several interrelated nodal methods for setting up the equations of non-linear, lumped electrical circuits. A rather exhaustive framework is presented, aimed at surveying different approaches and terminologies in a comprehensive manner. This framework includes charge-oriented, conventional, and hybrid systems. Special attention is paid to so-called augmented node analysis (ANA) models, which somehow articulate the tableau and modified node analysis (MNA) approaches to non-linear circuit modelling. We use a differential,algebraic formalism and, extending previous results proved in the MNA context, we provide index-1 conditions for augmented systems, which are shown to be transferred to tableau models. This approach gives, in particular, precise conditions for the feasibility of certain state-space reductions. We work with very general assumptions on device characteristics; in particular, our approach comprises a wide range of resistive devices, going beyond voltage-controlled ones. Copyright © 2005 John Wiley & Sons, Ltd. [source] Syntheses of New 3,6-Carbazole-Based Donor/Acceptor Conjugated Copolymers for Optoelectronic Device ApplicationsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2010Mei-Hsiu Lai Abstract The syntheses, properties, and optoelectronic device characteristics of four new 3,6-carbazole-based donor/acceptor conjugated copolymers are reported. Such copolymers are used to explore the effects of acceptor strength and backbone coplanarity on the electronic and optoelectronic properties. The optical bandgaps of the studied copolymers are PCzQ (2.29,eV),>,PCzDTQ (1.91,eV),>,PCzTP (1.75,eV),>,PCzDTTP (1.49,eV), which are much smaller than the parent poly(3,6-carbazole). The power conversion efficiency of the photovoltaic cells fabricated from blends of copolymer/PC61BM or PC71BM reached 1.01 and 1.73% by varying the film thickness or blend ratio. The experimental results suggest the potential application of 3,6-carbazole acceptor conjugated copolymers in optoelectronic devices. [source] Selective-area growth and fabrication of recessed-gate GaN MESFET using plasma-assisted molecular beam epitaxyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006Seung Jae Hong Abstract For the first time, selective-area growth (SAG) technique has been developed using plasma-assisted molecular beam epitaxy (PAMBE), enabling fabrication of a recessed-gate structure for the metal-semiconductor field-effect transistor (MESFET) without etching. On patterned SiO2 samples, polycrystalline GaN and single crystal n+ -GaN were observed to grow in the masked and unmasked regions, respectively. The regrown layers were analyzed using AFM. Ohmic contact formed on the n+ -GaN exhibited a vastly improved contact resistivity of 1.8 × 10,8 , cm2, giving rise to excellent device characteristics including a peak drain current of 360 mA/mm and a maximum transconductance of 46 mS/mm. The advantages of SAG were further investigated by comparing the dc characteristics of recessed-gate and unrecessed MESFET. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] 6th International Workshop on Expert Evaluation & Control of Compound Semiconductor Materials & TechnologiesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003Bálint P The EXMATEC workshops are a series of biannial conferences with the aim to bring together research and development specialists involved in compound semiconductor material physics, chemistry, process technology, characterization and device fabrication. EXMATEC 2002 is the continuation of successful meetings, previously held in Lyon, Parma, Freiburg, Cardiff and Heraklion. The central topics were development, improvement and application of new and advanced methods in the fabrication and evaluation of compound semiconductor materials and structures to develop understanding of the interrelationship between structural, electrical and other material properties and device characteristics, such as performance, reliability, reproducibility, lifetime, yield, etc. The conference topics apply to all compound semiconductor materials (III,V, II,VI, IV,IV, II,IV,V2), related structures and processing steps (from substrate and epitaxial growth to complete devices) and cover instrumentation and characterization issues. The full Proceedings of EXMATEC 2002 are published in the second issue of the new journal series physica status solidi , conferences Vol. 0, No. 2 (2003). As one representative example of the topics presented at this conference, the cover picture of the present issue issue of phys. stat. sol. (a) shows the band scheme of a typical GaInAs/AlInAs superlattice quantum cascade laser, taken from the invited paper by Razeghi and Slivken [1]. [source] Current spreading and thermal effects in blue LED dicePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2007K. A. Bulashevich Abstract We have applied simulations to study current the spreading and heat transfer in blue III-nitride light-emitting diodes (LEDs) with the focus on self-heating and its effect on the device characteristics. A conventional planar design of an LED die is considered for the heat sink through a sapphire substrate. The computations predict a great current crowding at the contact electrode edges, resulting in a non-uniform temperature distribution over the die. The thermal effect on the current-voltage characteristic, output optical power, and series resistance of the diode is analyzed and the theoretical predictions are compared with available observations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The iliac bifurcation device for endovascular iliac aneurysm repair: indications, deployment options and results at 1-year follow-up of 25 casesANZ JOURNAL OF SURGERY, Issue 11 2009Ravi L. Huilgol Abstract Background:, The iliac bifurcation device (William A Cook Australia, Brisbane, QLD, Australia) is a new endovascular device for iliac aneurysm repair. We review the indications for use, device characteristics, deployment options and the results of our case series. Methods:, The most common indication for deployment is endovascular aortic aneurysm repair (EVAR) with common iliac aneurysm repair. The standard deployment sequence can be adapted to increase the utility of the device. Data were collected prospectively. Follow-up was performed with plain X-ray, ultrasound and computed tomography (CT) scan. Results:, Between 2004 and 2007, 25 patients had their common iliac artery aneurysm repaired using the iliac bifurcation device. There were 23 male and 2 female patients. Median age was 75 years (range 60,85). The median follow-up was 12 months (range 1,38). Twenty-one procedures were combined with EVAR. The median abdominal aortic aneurysm diameter was 60 mm (range 31,97), and the median common iliac artery aneurysm diameter was 37 mm (range 24,71). Technical success was achieved in 100% of cases. There were no acute branch vessel occlusions. There was one early type I endoleak (4%). There was one death (4%) in the 30-day period post-procedure. There was one late type I endoleak (4%). Conclusions:, The iliac bifurcation device achieves endovascular common iliac artery aneurysm repair with preservation of internal iliac artery flow. There are multiple different applications of the device and complementary deployment techniques. High rates of technical success and low rates of branch vessel occlusion are possible. [source] | ||||||||||||||||