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Leakage Current (leakage + current)
Kinds of Leakage Current Terms modified by Leakage Current Selected AbstractsTemperature Dependences of Leakage Currents of ZnO Varistors Doped with Rare-Earth OxidesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2010Jun Hu Rare-earth oxides are doped into ZnO varistors as grain growth inhibitors for increasing the varistors' voltage gradients. However, their leakage currents become large and their nonlinear coefficients decrease at the same time. The reasonable explanation for such a phenomenon has not yet been available. In this paper, the temperature dependences of varistor samples' leakage currents are investigated, which reveal that the increased leakage currents of ZnO varistors with Y2O3 doping are mainly due to the bypass paths through the intergranular materials at grain corners. [source] Leakage current through high permittivity thin filmsANNALEN DER PHYSIK, Issue 1-2 2004H. Schroeder Abstract For the leakage current through high-permittivity, low-electronic mobility, perovskite-type thin films a bulk-limited conduction mechanism is suggested, in contrast to the often assumed interface injection limitation. This model can successfully describe measured leakage data of field, temperature, thickness and electrode dependence in SrTiO3 and Ba0.7Sr0.3TiO3 thin films. [source] MOCVD of Hafnium Silicate Films Obtained from a Single-Source Precusor on Silicon and Germanium for Gate-Dielectric Applications,CHEMICAL VAPOR DEPOSITION, Issue 2-3 2007M. Lemberger Abstract In this work, hafnium silicate layers on Si and Ge wafers for gate dielectric application in metal,oxide,semiconductor devices are investigated. Films are deposited by metal,organic (MO)CVD using the single-source precursor Hf(acac)2(OSitBuMe2)2. This precursor exhibits good properties in terms of hydrolysis stability, volatility, and deposition. However, precursor decomposition is affected by surface conditions. Films deposited on Si wafers reveal high C contamination (up to 20,at,%) and low Si content (up to 20,at,%). In contrast, for film deposition on Ge wafers, no C contamination can be detected and Si incorporation is delayed until after about 15,nm HfO2 dielectric growth. Post-deposition rapid thermal annealing in an O2 atmosphere causes crystallization of deposited films, Si and Ge redistribution in the dielectric, respectively, and interfacial layer growth. However, oxygen annealing was also found to reduce effective oxide thickness (EOT) significantly compared to as-deposited films, which is attributed to crystallization effects. However, scaling of EOT is limited by that interfacial layer growth. Leakage currents are mainly caused by trap-related conduction mechanisms. Energy levels of involved traps decrease with increasing crystallization and/or Hf content, and values of 0.5,eV and 1,eV related to Hf and Si bonds, respectively, are obtained. [source] An experimental study on the transformer coil leakage currentEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2006Mohamed A. A. Wahab This paper is concerned with the transformer coil dc leakage current under different conditions. These conditions include in-air, and in-oil leakage, currents with or without artificial coil deposits. In-oil leakage, currents are investigated when the coil is immersed in new or used transformer oil at different temperatures. The results showed that the leakage current increases with the increase in the applied voltage and oil temperatures. The rate of increase in leakage current with temperature depends on the transformer oil and coil conditions. The in-oil leakage currents are higher than those obtained in air. The leakage currents measured in used oil are higher than those resulted in new oil. Copper deposits cause higher values of leakage current than iron deposits for the same medium, applied voltage and temperature. Deposits increase the leakage current for different coil surrounding media. A linear model for the leakage current as a function of the applied voltage under different conditions has been found and its validity has been justified by statistical consideration. The parameters of this model account for various experimental conditions. Copyright © 2006 John Wiley & Sons, Ltd. [source] Capacitors with an Equivalent Oxide Thickness of <0.5 nm for Nanoscale Electronic Semiconductor MemoryADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Seong Keun Kim Abstract The recent progress in the metal-insulator-metal (MIM) capacitor technology is reviewed in terms of the materials and processes mostly for dynamic random access memory (DRAM) applications. As TiN/ZrO2 -Al2O3 -ZrO2/TiN (ZAZ) type DRAM capacitors approach their technical limits, there has been renewed interest in the perovskite SrTiO3, which has a dielectric constant of >100, even at a thickness ,10 nm. However, there are many technical challenges to overcome before this type of MIM capacitor can be used in mass-production compatible processes despite the large advancements in atomic layer deposition (ALD) technology over the past decade. In the mean time, rutile structure TiO2 and Al-doped TiO2 films might find space to fill the gap between ZAZ and SrTiO3 MIM capacitors due to their exceptionally high dielectric constant among binary oxides. Achieving a uniform and dense rutile structure is the key technology for the TiO2 -based dielectrics, which depends on having a dense, uniform and smooth RuO2 layer as bottom electrode. Although the Ru (and RuO2) layers grown by ALD using metal-organic precursors are promising, recent technological breakthroughs using the RuO4 precursor made a thin, uniform, and denser Ru and RuO2 layer on a TiN electrode. A minimum equivalent oxide thickness as small as 0.45 nm with a low enough leakage current was confirmed, even in laboratory scale experiments. The bulk dielectric constant of ALD SrTiO3 films, grown at 370 °C, was ,150 even with thicknesses ,15 nm. The recent development of novel group II precursors made it possible to increase the growth rate largely while leaving the electrical properties of the ALD SrTiO3 film intact. This is an important advancement toward the commercial applications of these MIM capacitors to DRAM as well as to other fields, where an extremely high capacitor density and three-dimensional structures are necessary. [source] Domain Engineering for Enhanced Ferroelectric Properties of Epitaxial (001) BiFeO Thin FilmsADVANCED MATERIALS, Issue 7 2009Ho Won Jang Two-variant stripe domains in BiFeO3 films on miscut (001) SrTiO3 substrates exhibit square-like, complete ferroelectric switching with low leakage current. Both the preferential distortion of BiFeO3 unit cells and the persistent step-flow growth induced by the substrate anisotropy are the origins of the formation of the two-variant stripe domains in (001) BiFeO3 films. [source] Investigation of multi-layered-gate electrode workfunction engineered recessed channel (MLGEWE-RC) sub-50,nm MOSFET: A novel designINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 3 2009Rishu Chaujar Abstract In this paper, a two-dimensional (2D) analytical sub-threshold model for a novel sub-50,nm multi-layered-gate electrode workfunction engineered recessed channel (MLGEWE-RC) MOSFET is presented and investigated using ATLAS device simulator to counteract the large gate leakage current and increased standby power consumption that arise due to continued scaling of SiO2 -based gate dielectrics. The model includes the evaluation of surface potential, electric field along the channel, threshold voltage, drain-induced barrier lowering, sub-threshold drain current and sub-threshold swing. Results reveal that MLGEWE-RC MOSFET design exhibits significant enhancement in terms of improved hot carrier effect immunity, carrier transport efficiency and reduced short channel effects proving its efficacy for high-speed integration circuits and analog design. Copyright © 2008 John Wiley & Sons, Ltd. [source] The Influence of ZnF2 Doping on the Electrical Properties and Microstructure in Bi2O3,ZnO-Based VaristorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Lihong Cheng ZnO varistors with different amounts of ZnF2 from 0.00 to 0.80 mol% were prepared using a solid-state reaction technique, to explore the potential application of ZnO. The F-doping effects on the microstructure and electrical properties of ZnO-based varistors were investigated. The average grain size of ZnO increased from 4.93 to 6.48 ,m as the ZnF2 content increased. Experimental results showed that as the ZnF2 content increased, the breakdown voltage decreased from 617 to 367 V/mm, and the nonlinear coefficient did not change much. However, a slight increase was observed in the leakage current. Besides, when the ZnF2 content increased, the donor concentration increased from 0.669 × 1018 to 8.720 × 1018 cm,3. The study indicated that ZnF2 played a similar role as sintering aids to promote grain growth and the substitutional F atoms in the bulk served as a donor to increase the donor concentration. [source] Effect of Donor, Acceptor, and Donor,Acceptor Codoping on the Electrical Properties of Ba0.6Sr0.4TiO3 Thin Films for Tunable Device ApplicationsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2009Yuanyuan Zhang We have investigated the effects of donor, acceptor, and donor,acceptor codoping on both the dielectric properties and the leakage current behavior of Ba0.6Sr0.4TiO3 thin films prepared by the metalorganic solution deposition technique. La and Co were selected as donor and acceptor dopants, respectively. The electrical properties depend strongly on the type of dopants. Compared with others, codoped BST films have a much lower loss tangent, higher figure of merit, and lower leakage current. The electronic conduction mechanisms of the three types of dopants are reported. [source] Effect of La Doping on the Phase Conversion, Microstructure Change, and Electrical Properties of Bi2Fe4O9 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2009Ju Hong Miao Undoped and La-doped Bi2Fe4O9 ceramics were synthesized using a soft chemical method. It is observed that in calcining La-doped Bi2Fe4O9, Bi(La)FeO3 phase rather than Bi2,xLaxFe4O9 gradually increases with increasing La doping content. The phase conversion from mullite-type structure of Bi2Fe4O9 to rhombohedrally distorted perovskite one of Bi(La)FeO3 with increasing La doping content indicates that La doping can stabilize the structure of BiFeO3. This is further evidenced that Bi2Fe4O9 can be directly converted to Bi(La)FeO3 by heating the mixtures of nominal composition of Bi2Fe4O9/xLa2O3. Furthermore, the microstructure changes and the room temperature hysteresis loops and leakage current for Bi2,xLaxFe4O9 with x=0 and 0.02 were characterized. [source] Magnetic and Electrical Properties of (Mn, La)-Codoped SrTiO3 Thin FilmsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2008Song-Yin Zhang Mn-doped SrTiO3 -based thin films have been prepared by a simple sol,gel spin-coating method on silicon substrate. X-ray diffraction and high-resolution transmission electron microscopy reveal that these thin films are composed of amorphous and crystalline SrTiO3 phases. Optical and electrical measurements indicate that La codoping can make the band gap of SrTiO3 narrow and cause the leakage current to increase. Ferromagnetic behavior can be observed in these Mn- and/or La-codoped SrTiO3 -based thin films at room temperature, which should be ascribed to the magnetic coupling between the induced free electrons and Mn 3d spins. [source] Preparation and Electrical Properties of an Anodized Al2O3,BaTiO3 Composite FilmJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Xianfeng Du A highly stable, water-based barium titanate BaTiO3, BT, sol was synthesized using a sol,gel route through a chelate lactate technique. Dried BT precursor powders were measured by thermal gravimetry,differential thermal analysis and X-ray diffraction. It was found that BT powders first converted into barium carbonate BaCO3, Ti complex, and intermediate phase Ba2Ti2O5CO3, and then transformed into perovskite phase BaTiO3. The crystallization temperature was about 550°C. The low-voltage etched aluminum foils were covered with BT sol by dip coating, and then annealed at 600°C for 30 min in air. After that, the samples were anodized in a 15 wt% aqueous solution of ammonium adipate. The voltage,time variations during anodizing were monitored, and the electrical properties of the anodic oxide film were examined. It was shown that the specific capacitance, the product of specific capacitance and withstanding voltage, and leakage current of samples with a BT coating were about 48.93%, 38.50%, and 167% larger than that without a BT coating, respectively. [source] Electrical Properties of Superlattice-Structured Bi4Ti3O12,PbBi4Ti4O15 Single CrystalsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2007M. Ikezaki Single crystals of superlattice-structured ferroelectrics composed of Bi4Ti3O12 and PbBi4Ti4O15 were grown and the properties of polarization hysteresis and leakage current along the a -axis were investigated. Oxidation treatment led to a marked increase in leakage current at room temperature, showing that electron hole acts as a detrimental carrier for electrical conduction. A well-developed polarization hysteresis with a remanent polarization of 41 ,C/cm2 was observed, which is suggested to originate from the peculiar ferroelectric displacement of Bi in the Bi2O2 layers. [source] Structural and Electric Properties of Sol,Gel-Derived Ba0.9Sr0.1TiO3 MultilayersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007X. K. Hong Crack-free Ba0.9Sr0.1TiO3 (BST) and Mn-doped Ba0.9Sr0.1TiO3 (BSTM) multilayers with thickness over 2 ,m have been prepared by chemical solution deposition based on one single precursor. Both multilayers exhibit good performance as Bragg reflectors. Mn doping tends to suppress the leakage current in BST multilayers effectively by smoothing the layers and the reduction of the charge carries. The Mn-doped BST multilayer displays an excellent ferroelectric property, with an average remnant polarization (Pr+,Pr,)/2 of 12.69 ,C/cm2 and an average coercive field (E+,E,)/2 of about 72.95 kV/cm under an applied field of 440 kV/cm. [source] Design, process, and performance of all-epitaxial normally-off SiC JFETsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2009Rajesh K. Malhan Abstract This paper reviews the normally-off (N - off) and normally-on (N - on) SiC junction field effect transistor (JFET) concepts and presents an innovative all-epitaxial double-gate trench JFET (DGTJFET) structure. The DGTJFET design combines the advantages of lateral and buried gate JFET concepts. The lateral JFET advantage is the epitaxial definition of the channel width and the buried gate JFET advantage is the small cell size. In the DGTJFET process the epitaxial embedded growth in trenches facilitates the small cell pitch and the vertical direction of the channel. A detailed numerical simulation analysis compares the potential of the DGTJFET design with reported lateral channel and buried gate JFET structures. Migration enhanced embedded epitaxy (ME3) and planarization processes were developed to realize narrow cell pitch DGTJFETs for high-density power integration. The highly doped vertical channel of the DGTJFET defined by the ME3 growth process makes it possible to accurately control the sub-micron channel dimensions in order to realize a low specific on-state resistance (RON) and a high saturation current capability. The anisotropic nature of SiC is taken into account for the channel design considerations. The successful application of the new process technologies for the development of the all-epitaxial DGTJFETs is discussed. Fabricated 5.5 ,m cell pitch 4H-SiC DGTJFETs demonstrate the saturation current density capability of more than 1000 A/cm2. N - off and N - on DGTJFETs with 2.25 mm squared chip size and 9.5 ,m cell pitch output 15 A and 20 A at gate voltage of 2.5 V and drain voltage of 5.0 V. The specific RON of the N - off and N - on DGTJFETs is at room temperature 8.1 m , cm2 and 6.3 m, cm2, respectively, indicating that N - off devices can be realized at the expense of a slight increase in specific RON of approximately 25%. DGTJFETs with a 13 ,m drift layer doped to 5.0 × 1015 cm,3 are demonstrated with a breakdown voltage in the range of 1200 V to 1550 V at the wafer level with a leakage current below 10 ,A. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of K doping and annealing on the grain size and giant dielectric constant of KxTi0.02Ni0.98,xO ceramicsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2007Pradip Kumar Jana Abstract Monovalent ion (MOI) doping effect on the grain size and giant dielectric constant (, , , 104) of lead free environment friendly NiO-based KxTi0.02Ni0.98,xO (KTNO, x = 0.04, 0.25, and 0.30) type ceramics have been investigated. Increasing K concentration (MOI) enhances the grain size along with the increase of , , values. The dielectric constant of KTNO also increases with increase of the sintering time and temperature (within the range of our measurement) due to enhancement of crystalline size. The giant , , value and the leakage current in KTNO show weak field dependent behavior. Estimated temperature coefficient of permittivity (TCP) of KTNO is very low (less than 6%). All these properties meet the requirements of the ceramics used in X7R EIA specification. High , , in KTNO is attributed to the boundary layer mechanism. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fabrication of high performance 3C-SiC vertical MOSFETs by reducing planar defectsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2008Hiroyuki Nagasawa Abstract The planar defect density of 3C-SiC can be reduced by growing it on undulant-Si substrates. However, specific stacking faults (SFs) remain, that expose the Si-face on the (001) surface. These residual SFs increase the leakage current in devices made with 3C-SiC. They can be eliminated using an advanced SF-reduction method called switch-back epitaxy (SBE) that combines polarity conversion with homoepitaxial growth. Vertical metal,oxide,semiconductor field-effect-transistors (MOSFETs) are fabricated on 3C-SiC with SBE, varying in size from a single cell with an area of (30 × 30) ,m2 to 12,000 hexagonal cells on a (3 × 3) mm2 chip. The MOSFET characteristics suggest that currents greater than 100 A are realistic for blocking voltages of 600,1,200 V by increasing the number of cells with reduced cell-pitch. The combination of blocking voltage capability with a demonstrable high current capacity shows that 3C-SiC is well-suited for use in vertical MOSFETs for high- and medium-power electronic applications. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Interface properties and junction behavior of Pd contact on ZnO thin film grown by vacuum deposition techniquePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010Ghusoon M. Ali Abstract In this paper we explain the results of our experimental investigation on interface properties and junction behavior of Pd contact on ZnO thin film based Schottky diode. We used a conventional vacuum evaporation deposition unit for sequential deposition of ZnO film and metallic layer. For the first time a high quality Pd/ZnO Schottky diode is fabricated successfully in our laboratory by vacuum evaporation method. The I-V and C-V characteristics of the devices were studied by using microprobe arrangement. The parameter such as ideality factor, leakage current, resistance-area-product, carrier concentration and barrier height were extracted from the measured data. The surface morphological and the structural properties of thin film were studied by atomic force microscope. The optical band gap of thin film was determined using UV-visible spectrophotometer. The device fabricated by a simple technique exhibited excellent stability for use as an electronic or optoelectronic component. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optimization of the ohmic contact processing in InAlN//GaN high electron mobility transistors for lower temperature of annealingPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2010Karol Abstract In this article, we optimized the ohmic contact processing in InAlN/GaN high electron mobility transistors for the lower temperature of annealing by recessing of metalliza-tion to approach the 2DEG at the InAlN/GaN interface. The ohmic contacts which were recessed down to 5 nm depth and annealed at 700 °C 2 min. exhibited the contact resistance of 0,39 ,mm while the channel sheet resistance was 210 ,/square. These values are comparative to values of contacts processed at more conventional an-nealing conditions (800 °C, 2 min). Moreover we applied the recessed ohmic contact technology to fabricate Schottky barrier (SB) HEMTs and MOSHEMTs with Al2O3 dielectric film. For MOSHEMTs, we measured the maximal reduction of the gate leakage current by about 6 orders of magnitude if compared with SB HEMTs. The maximal drain current of MOSHEMTs was about 750 mA/mm at VGS = 0 V and the maximal extrinsic transconductance (gme) reached 101 mS/mm. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Tunneling current in gate dielectric stack in sub-45 nanometer CMOS devicesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2009Hitender Kumar Tyagi Abstract Direct tunneling current through dual layer SiO2/high-K dielectric structures are investigated for substrate injection. Correlation of dielectric constants and band offsets with respect to silicon has been taken into consideration in order to identify possible materials to construct these devices. The direct tunneling current in oxide/high-K dielectric structures with equivalent oxide thickness (EOT) of 2.0 nm can be significantly lower than that through single layer oxides of the same thickness. Various structures and materials of high-K stacks of interest have been examined and compared to access the reduction of gate current in these structures. It is estimated that HfO2/SiO2 dual stack structure can reduce gate leakage current by four orders of magnitude as compared with pure SiO2 layer of same EOT. The importance of interfacial layer in dual stack structure is high-lighted for the reduction of gate leakage current. The present approach is capable of modeling high-K stack structures consisting of multiple layers of different dielectrics (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Off-state breakdown in InAlN/AlN/GaN high electron mobility transistorsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009J. Kuzmik Abstract Unpassivated InAlN/AlN/GaN high electron mobility transistors off-state breakdown is analyzed for different gate-to-drain distances. The breakdown voltage linearly increases with the gate to drain distance reaching 350 V for a 10 ,m contact separation; the sub-threshold leakage current is < 10,5 A/mm. Similar breakdown voltages and leakage current are obtained on GaN buffer for two Ohmic contacts if their distance is the same. It is suggested that the breakdown is governed by injection/avalanche processes in the GaN buffer layer and is basically not affected by InAlN barrier. Our conclusions are further supported by measuring all currents in the three-terminal configuration of the transistors before and during the breakdown and by using a drain current injection technique. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of barrier thickness on AlInN/AlN/GaN heterostructures and device propertiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009H. Behmenburg Abstract We report on structural and device properties of AlInN/AlN/GaN transistor heterostructures grown by metal organic vapour phase epitaxy (MOVPE) on 2, sapphire substrates with AlInN barriers of thicknesses between 4 nm and 10 nm. The In content and thickness of the thin AlInN barrier is shown to be well determinable by high-resolution X-ray diffraction (HRXRD). Room temperature Hall measurements yielded similar mobility between 1400 cm2V,1s,1 and 1520 cm2V,1s,1 on all samples and increasing sheet carrier concentration ns with rising barrier thickness resulting in a minimum sheet resistance value of 200 Ohm/,. The effect of surface passivation with Si3N4 on the electrical properties is investigated and found to strongly increase sheet carrier concentration ns of the two-dimensional electron gas (2DEG) to values above 2×1013cm,2. Characterization of transistors with gate length Lg of 1.5 ,m produced from the grown samples reveals high transconductance (gm) and a maximum drain current (ID) of 300 mS/mm and ,1 A/mm, respectively. For the sample with 4.6 nm barrier thickness, a reduced gate leakage current (IGL) and a absolute value of the threshold voltage (Vth) of -1.2 V is detected. Radio frequency (RF) measurements of passivated samples lead to maximum current gain cut-off frequencies ft of 11 GHz and maximum oscillating frequencies fmax of 25 GHz. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electro-optic property of ZnO:Mn epitaxial filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008T. Oshio Abstract Mn doping effect on the dielectric and electro-optic (E-O) property of ZnO epitaxial films was studied. The leakage current of the ZnO film is drastically decreased by doping Mn with the concentration of 3-5 at%. Although, ZnO: 4 at% Mn with the lowest leakage current has the largest frequency dispersion of birefringence shift (, n) at 1 kHz, and its E-O coefficient (rc) was larger than that of ZnO single crystal. It is presumably caused by another polarization effect but spontaneous polarization, such as space charge. To investigate the origin of the dispersion of , n, discharging property was evaluated. When the signal at 1 kHz was applied, ZnO: 3 and 5 at% Mn showed the discharging with relaxation time of 5 msec. Furthermore, the discharging property with same relaxation time was observed at 20 kHz at where the dispersion of , n was not observed. However, ZnO: 4 at% Mn does not show such a discharging behavior. Therefore, it is considered that the space charge is not the origin of the dispersion of , n. On the other hand, the dispersion of , n was minimum and no dielectric dispersion was observed at 20 kHz for all samples. The rc of ZnO: 3, 4 and 5 at% Mn measured at 20 kHz, which should be the rc originated from the spontaneous dipolar polarization, were derived to be 0.81, 0.81 and 0.62 pm/V, respectively. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The role of setback layers on the breakdown characteristics of AlGaAs/GaAs/GaN HBTsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Chuanxin Lian Abstract Breakdown voltages (VCBO) of AlGaAs/GaAs/GaAs and AlGaAs/GaAs/GaAs-setback/GaN HBTs have been compared both theoretically and experimentally with respect to setback layer thicknesses and the doping type. VCBO was calculated using a non-local energy model. The hard breakdown voltage was measured on as-grown GaAs homojunctions and AlGaAs/GaAs/GaN HBTs formed by direct wafer fusion. The calculation showed an increase of VCBO from , 20 V to , 325 V by replacing the GaAs collector with GaN, and VCBO ,90 V was indeed measured. The smaller than predicted VCBO is attributed to the large leakage current currently present in the fused junctions. Insertion of a lightly doped GaAs setback layer has resulted in improved current gain of the fused HBTs, but it also degrades the breakdown characteristics. 20-30 nm setback layers were found to maintain VCBO significantly higher than that of GaAs homojunctions and likely reasonable current gains. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ionic and electronic defects in a-BaTiO3 thin films studied by transient and steady state conductivity measurementsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007F. El Kamel Abstract Conduction mechanisms in BaTiO3 films deposited at low temperatures on Cu-electrodes have been investigated in transient and steady regimes as a function of temperatures and electric field. This work aims to identify possible defects which govern the leakage current. Electrical measurements reveal that Space Charge Limited Current (SCLC) constitutes the main leakage mechanism in both the transient and the steady regimes. Based on the theory of SCLC, two types of defects can be detected. At higher temperatures, oxygen vacancies constitute the main defects which migrate across the film to generate an ionic leakage current. Diffusion of these defects is thermally activated with an activation energy around 1 eV. Moreover, at lower temperatures the J - E measurements reveals the presence of a discrete set of shallow traps at 0.45 eV below the conduction band with an effective density of 4 × 1022 m,3. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The effect of Ge doping for lattice-mismatched InGaP/InP (100) with epitaxial lateral overgrowthPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2006Kenichi Higuchi Abstract We have proposed the use of 1.3 ,m InGaAs/InGaP laser on an InP (100) substrate to reduce the leakage current. Because of the lattice-mismatch between InP and InGaP, epitaxial lateral overgrowth (ELO) technique is used. Ge doping is an effective way of increasing the amount of lateral growth in InP/InP lattice-matched ELO. In the InGaP/InP lattice-mismatched ELO, the crystal defects of the Ge-doped InGaP layer decrease compared to undoped sample. The Ge doping is effective for growing InGaP/InP with high crystalline quality by ELO. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Stimulated emission and leakage current in InxGa1,xN lasersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2005Elis Mon Abstract In this paper we calculate the temperature dependence of the transparency concentration n0 for InxGa1,xN/GaN single quantum well laser diodes. To establish the lasing mechanism existing in these lasers, this concentration is compared with that given by the Mott criterion limiting the existence of an excitonic gas or electron-hole plasma. For a typical structure with an In0.13Ga0.87N active layer n0 results higher than the critical excitonic concentration. This result indicates that the conventional electron-hole plasma instead of excitonic recombination is the dominant mechanism responsible for lasing in nitride lasers. The contribution of the diffusion leakage current density to the total threshold current density was also calculated, considering both electron and hole components. We obtain that the electron leakage current density is more than a half of the total threshold current density, confirming it is the main loss mechanism present in these lasers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Phonon-electric effect in nano-scale transistorsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2005D. W. Horsell Abstract A novel dc current is shown to exist in a nano-scale transistor structure. This current is accounted for by a non-equilibrium distribution of electrons generated by hot electrons from the gate. It is shown that by this mechanism the gate leakage current can be substantially magnified. It is this, along with the asymmetry inherent to the mesoscopic system, that can maintain a dc current flow across the channel. We realize this current experimentally and show that it may dominate other currents present in the system. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterization of MOCVD grown GaN on porous SiC templatesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005F. Yun Abstract We have grown GaN layers by MOCVD on a set of nanoporous SiC templates with different porosity and morphology, produced by etching the anodized porous SiC starting material in a H2 environment at temperatures ,1500 °C, in an effort to attain improved films. The hydrogen etching serves to remove surface damage caused during mechanical polishing prior to anodization, remove the skin layer associated with anodization, tune the pore size, and consolidate pore geometry. Growth conditions favoring lateral overgrowth of GaN were employed on this set of samples to obtian GaN to a thickness of 2 µm. Atomically smooth surfaces were obtained for the epitaxial GaN layers. The GaN quality is highly dependent on the specifics of the porous templates used. An intensity increase of up to a factor of 30 was observed in the GaN excitonic peak compared to GaN grown on standard SiC substrate. The I-V data indicated significant reduction in the leakage current (in reverse bias) compared to GaN grown on standard SiC. The dependence of optical properties, crystalline quality, and surface morphology on the particulars of porous SiC templates is discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Impact of native oxides beneath the gate contact of AlGaN/GaN HFET devicesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005D. Mistele Abstract We report on the decisive role of oxides at the surface of AlGaN/GaN Heterostructure Field Effect Transistors (HFETs). The effect of oxides at the surface is twofold, on one hand the 2DEG in the channel is directly influenced by surface charges and surface potential correlated to surface oxides (D. Mistele et al., phys. stat. sol. (a) 194 (2), 452 (2002). [1]), on the other hand, a surface oxide below a subsequently deposited gate contact increases the barrier height and therefore reduces leakage currents by several orders of magnitude. This study includes various surface treatments on AlGaN/GaN heterostructures such as etching by HCl, oxidation by O2 -plasma, and subsequent passivation by Si3N4. Next, we report on the correlation between gate leakage current and the drain current and dedicate this behavior to the Schottky barrier and to surface related charging effects. A model with the surface related charging effects on the 2DEG and the barrier height is discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||