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Drain Current (drain + current)
Kinds of Drain Current Selected AbstractsLow-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] Influence of Electric Field on Microstructures of Pentacene Thin-Films in Field-Effect Transistors,ADVANCED FUNCTIONAL MATERIALS, Issue 2 2008L. Cheng Abstract We report on electric-field-induced irreversible structural modifications in pentacene thin films after long-term operation of organic field-effect transistor (OFET) devices. Micro-Raman spectroscopy allows for the analysis of the microstructural modifications of pentacene in the small active channel of OFET during device operation. The results suggest that the herringbone packing of pentacene molecules in a solid film is affected by an external electric field, particularly the source-to-drain field that parallels the a,b lattice plane. The analysis of vibrational frequency and Davydov splitting in the Raman spectra reveals a singular behavior suggesting a reduced separation distance between pentacene molecules after long-term operations and, thus, large intermolecular interactions. These results provide evidence for improved OFET performance after long-term operation, related to the microstructures of organic semiconductors. It is known that the application of large electric fields alters the semiconductor properties of the material owing to the generation of defects and the trapping of charges. However, we first suggest that large electric fields may alter the molecular geometry and further induce structural phase transitions in the pentacene films. These results provide a basis for understanding the improved electronic properties in test devices after long-term operations, including enhanced field-effect mobility, improved on/off current ratio, sharp sub-threshold swing, and a slower decay rate in the output drain current. In addition, the effects of source-to-drain electric field, gate electric field, current and charge carriers, and thermal annealing on the pentacene films during OFET operations are discussed. [source] Extracting Parameters from the Current,Voltage Characteristics of Organic Field-Effect TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 11 2004G. Horowitz Abstract Organic field-effect transistors were fabricated with vapor-deposited pentacene on aluminum oxide insulating layers. Several methods are used in order to extract the mobility and threshold voltage from the transfer characteristic of the devices. In all cases, the mobility is found to depend on the gate voltage. The first method consists of deriving the drain current as a function of gate voltage (transconductance), leading to the so-called field-effect mobility. In the second method, we assume a power-law dependence of the mobility with gate voltage together with a constant contact resistance. The third method is the so-called transfer line method, in which several devices with various channel length are used. It is shown that the mobility is significantly enhanced by modifying the aluminum oxide layer with carboxylic acid self-assembled monolayers prior to pentacene deposition. The methods used to extract parameters yield threshold voltages with an absolute value of less than 2 V. It is also shown that there is a shift of the threshold voltage after modification of the aluminum oxide layer. These features seem to confirm the validity of the parameter-extraction methods. [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] A physics-based model of DC and microwave characteristics of GaN/AlGaN HEMTsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2007Jonathan C. Sippel Abstract A physics-based model of AlGaN/GaN High Electron Mobility Transistor (HEMT) is developed for the analysis of DC and microwave characteristics. Large- and small-signal parameters are calculated for a given device dimensions and operating conditions. Spontaneous and piezoelectric polarizations at the heterointerface and finite effective width of the 2DEG gas have been incorporated in the analysis. The model predicts a maximum drain current of 523 mA/mm and transconductance of 138 mS/mm for a 1 ,m × 75 ,m device, which are in agreement with the experimental data. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. [source] AlInN HEMT grown on SiC by metalorganic vapor phase epitaxy for millimeter-wave applicationsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2010Shiping Guo Abstract In this work we present the epitaxial and device results of AlInN/GaN HEMTs grown on SiC by metalorganic vapor phase epitaxy. High quality AlInN/GaN HEMT structures with sub-10,nm AlInN barrier were grown with very low Ga background level (<1%). The low Rsh of 215,,/sq was obtained with an excellent standard deviation of 1.1% across 3, wafers. Lehighton RT contactless Hall tests show a high mobility of 1617,cm2/V,s and sheet charge density of 1.76,×,1013/cm2. DC characteristics of an AlInN/GaN HEMT with a gate length of 0.1,µm and 25,nm Al2O3 passivation show maximum drain current (IDS,max) of 2.36,A/mm at VGS,=,2,V. Gate recessed devices with 0.15,µm gate length and 25,nm Al2O3 passivation resulted in maximum transconductance (gm) of 675,mS/mm, the highest value ever reported in AlInN transistors. Excellent frequency response was obtained. The maximum fT is 86,GHz and fmax is 91.7,GHz. [source] Over 55 A, 800 V high power AlGaN/GaN HFETs for power switching applicationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2007Nariaki Ikeda Abstract We developed new ohmic electrodes combined with an Al-silicide and a molybdenum for AlGaN/GaN HFETs to realize a high power switching application. As a result, the maximum drain current of the HFET was over 55 A and the breakdown voltage was about 800 V. The specific on-state resistance of the HFET was smaller than that of a Si Cool MOSFET. Furthermore, we examined the dynamic characteristics. The turn-off and turn-on delay time were 14.8 nsec. and 8.4 nsec. at the condition of 100 V, respectively. These values were considerbly smaller compared with those of Si Cool MOSFETs. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [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] Temperature dependence of normally off mode AlGaN/GaN heterostructure field-effect transistors with p-GaN gatePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2010Takayuki Sugiyama Abstract We demonstrated high-temperature operation of normally off-mode junction-heterostructure-field-effect transistors (JHFETs) with a p-GaN gate that shows a very small shift of the threshold voltage against ambient temperature. Distinct normally off-mode operation with a maximum drain current of 93.2 mA/mm at 300 °C was realized. Therefore, normally off-mode GaN-based JFETs are greatly superior to Si-based devices as high-temperature switching devices. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] AlGaN/GaN HFETs on Fe-doped GaN substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Yoshinori Oshimura Abstract AlGaN/GaN HFETs with different undoped GaN thicknesses were grown on Fe-doped freestanding GaN substrates by conventional MOVPE. To realize a high drain current, thick undoped GaN is found to be necessary. SIMS measurement shows that Fe is redistributed into the epilayer, by which the scattering center is generated at the channel when the thickness of the undoped GaN is insufficient. We also observed a similar Fe profile in the GaN/sapphire template placed on the side of the Fe-doped GaN substrate during growth. Therefore, Fe in the Fe-doped GaN substrate is redistributed not only through a solid but also through vapor. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High power AlGaN/GaN HFETs on 4 inch Si substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009Nariaki Ikeda Abstract In this paper, we successfully demonstrate an AlGaN/GaN HFET with a high breakdown voltage on 4-inch Si substrates. In order to obtain the high breakdown voltage and to improve the crystalline quality of GaN layers, a thick GaN epitaxial layer including a buffer layer was grown. The breakdown voltage and the maximum drain current were achieved to be over 1.3 kV and 120 A, respectively. Furthermore, the suppression of a current collapse phenomenon was examined. The on-resistance was not significantly increased up to a high drain off-bias-stress of 900 V. (© 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] Analysis of minority carrier lifetime for InAlAs/InGaAs high electron mobility transistors by using 1.55-,m femto-second pulse laserPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Hirohisa Taguchi Abstract The minority carrier lifetime (,) of High electron mobility transistors (HEMTs) made using the InAlAs/InGaAs material system lattice-matched to the InP substrate had been obtained from optical response measurements with a 1.55-,m femto-second pulse laser where the laser was illuminated onto the backside of a wafer. The drain current of HEMTs associated with the optical pulse was detected using a digitizing oscilloscope, and , was estimated from the exponential dependence of drain current on time. In our current investigation, we found that , is dominated by the following modes: (1) the amount of time required for holes to transit across the channel toward the source, and (2) the amount of time required for the holes accumulated in the source region to recombine with two-dimensional electron gas (2DEG) through the Auger mechanism. Because the sheet concentration (ps) of holes accumulated in source region is low at a low source-to-drain voltage (VDS), Auger recombination is not predominant, and , was only dominated by the hole transit time. At a high VDS, ps became high enough for Auger recombination to occur and dominate ,. Furthermore, we investigated the optical power dependence of , where the optical power was supplied in a continuous wave (CW) to generate photo-excited holes in a steady state. The value of , decreased monotonically as VDS increased and saturated in as little as 6x10,10 s when the optical power was increased. The theoretical investigation was made to understand this saturation phenomenon. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] High drain current and low on resistance normally-off-mode AlGaN/GaN junction HFETs with a p-type GaN gate contactPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008T. Fujii Abstract The normally-off-mode junction HFETs with a p-type GaN gate contact showing high drain current and an extremely large on/off ratio were successfully fabricated by MOVPE. The drain currents were found to be very sensitive to the surface of the u-AlGaN barrier exposed by RIE etching. A reproducible and stable high drain current was achieved using a very thin SiN passivation layer. The maximum drain current was 1.58×10,1 A/mm at VGS = 4 V, while the drain current at VGS = 0 V was as low as 1.45×10,8 A/mm. Therefore, an on/off ratio of 107 has been achieved. The sub-threshold swing was as small as 90 mV/dec.. The on resistance was 3.4 m,cm2, the threshold voltage was +0.45 V, and the breakdown voltage was over 325 V. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A low-leakage and reduced current collapse AlGaN/GaN heterojunction field effect transistor with AlOx gate insulator formed by metal-organic chemical vapor depositionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008H. Sazawa Abstract We report on metal-insulator-semiconductor (MIS) heterostructure field-effect transistor (HFET) with AlOx gate insulator formed by metal-organic chemical vapor deposition (MOCVD) method designed for achieving low gate leak and less current collapse. The AlOx insulator was formed successively onto the MOCVD-grown AlGaN/GaN using trimethylaluminum (TMA) and n-butyl ether as precursors. Flowing gas during the AlOx/AlGaN interface formation was mainly consisted of ammonia and nitrogen with the aim of preventing N vacancy creation and oxide formation on the AlGaN that could lead to the current collapse. The fabricated devices were evaluated under direct current mode. The gate leak current of the MIS-HFET was three orders of magnitude lower than that of conventional (no insulator) HFET. The change in transition drain current examined as indicator of magnitude of the current collapse was found to be smaller in the MIS-HFET than in the HFET. Advantages of the novel wafer preparation method and the MIS-HFET were demonstrated. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] AlGaN/GaN dual-gate high electron mobility transistors on SiC substrates for high-power mixersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005K. Shiojima Abstract We have demonstrated dual-gate AlGaN/GaN high-electron-mobility transistors on SiC substrates for high-power mixers and examined DC and up-conversion RF measurements with drain-source bias voltages (VDS) to analyze the possible output level. The 0.7 × 300 µm-gate device exhibited the maximum transconductance of 47 mS, maximum RF power of 19.6 dBm and up-conversion gain of 11 dB at 2 GHz when VDS = 15 V. For VDS of over 15 V, the devices occasionally broke down, because, although the device can handle more drain current, but the voltage swing reached the breakdown voltage of about 30 V. These results indicate that a Watt-class output mixer can be easily achieved with this simple dual-gate structure. (© 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] Fabrication of AlGaN/GaN MIS-HFET using an Al2O3 high k dielectricPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Ki-Yeol Park Abstract We report on a metal,insulator,semiconductor AlGaN/GaN heterostructure field-effect transistor (MIS-HFET) using Al2O3 simultaneously for channel passivation layer and as a gate insulator which was deposited by plasma enhanced atomic layer deposition(PE-ALD). Capacitance,voltage measurements show successful surface passivation by the Al2O3 dielectric layer. For a gate length 1.2 ,m with 15 ,m source-to-drain spacing the maximum drain current was 1.22 A/mm, the maximum transconductance was 166 mS/mm and the gate leakage current was 4 nA/mm at Vgs = ,20 V which is at least three orders of magnitude lower than that of conventional AlGaN/GaN HFETs. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Investigation of AlGaN/GaN HEMTs on Si Substrate Using BackgatingPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2003M. Marso Abstract The influence of a substrate voltage on the dc characteristics of an AlGaN/GaN HEMT on silicon (111) substrate is investigated. This effect, known as backgating, is used to study traps that are located between substrate and 2DEG channel. The transient of the drain current after applying a negative substrate voltage is evaluated for measurements with and without illumination. Several trap contributions are resolved by measurements at different photon energies. A photocurrent is observed up to 600 nm wavelength. Up to this wavelength the backgating effect can be compensated and the drain current restored by a short light pulse. The experiments are performed on completed HEMTs, allowing investigation of the influence of device fabrication technology. [source] Dielectric layers for organic field effect transistors as gate dielectric and surface passivationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2008T. Diekmann Abstract Organic field effect transistors with the organic semiconductor pentacene, using silicon substrates, were successfully built on conventional inorganic dielectrics like silicon dioxide or silicon nitride. They can drive drain currents up to 15 mA. Beyond that, polymer films were investigated as gate dielectrics in order to achieve transistors on plastic films. On polyester substrates with an inorganic,organic gate dielectric, devices reach drain currents comparable to transistors on silicon dioxide and charge carrier mobilities of up to 0.35 cm2/V s. Analysis of the pentacene surface by atomic force microscopy showed pentacene crystallites achieving dimensions of more than 1.5 µm. The unprotected organic devices suffer from degradation due to water and oxygen incorporation. Therefore, the application of a hydrophobic polytetrafluoroethylene layer as capping layer is studied. Because of the reduced influence of water, a shift to positive threshold voltages is caused. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||