Field Effect Transistors (field + effect_transistor)

Distribution by Scientific Domains

Kinds of Field Effect Transistors

  • heterojunction field effect transistor
  • organic field effect transistor


  • Selected Abstracts


    Processing approaches of AlGaN/GaN Metal Insulator Semiconductor Hetero Field Effect Transistors (MISHFET) on Si (111) substrates

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009
    Martin Eickelkamp
    Abstract We report on the fabrication of AlGaN/GaN MISHFETs using SiO2 and SiN as gate dielectrics. In particular, two different passivation procedures are investigated with respect to the resulting electrical properties. A fluorine based ICP etch step, as used here to remove the gate dielectric prior to passivation layer deposition, is shown to deteriorate the sheet carrier concentration and mobility. Depositing the passivation layer upon the gate dielectric, on the other hand, slightly decreases the sheet resistance as compared to a conventional HFET. Gate diode characteristics reveal significant reduction of gate leakage currents in both, reverse and forward biasing regions, of 1-2 and up to 6 orders of magnitude, respectively. All devices exhibit more pronounced current collapse compared to a conventional passivated HFET. In addition, a clear depencency on the processing scheme is observed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Nitride based nanotransistors as new sources and detectors of THz radiations

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
    A. El Fatimy
    Abstract The plasma waves in gated two-dimensional electron gas have a linear dispersion law, similar to the sound waves. The transistor channel is acting as a resonator cavity for the plasma waves, which can reach frequencies in the Terahertz (THz) range for a sufficiently short gate length Field Effect Transistors (FETs). THz emission and detection by nanometer III-V transistors have been recently reported. In this work we report on THz emission and detection by nanometer GaN/AlGaN HEMTs. In particular, we show that specific GaN properties allow to observe THz emission up to room temperature. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Impact of native oxides beneath the gate contact of AlGaN/GaN HFET devices

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005
    D. 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]


    Novel Butterfly Pyrene-Based Organic Semiconductors for Field Effect Transistors.

    CHEMINFORM, Issue 26 2006
    Daoben Zhu
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


    Fabrication and Properties of Conducting Polypyrrole/SWNT-PABS Composite Films and Nanotubes

    ELECTROANALYSIS, Issue 11 2006

    Abstract We report the electropolymerization and characterization of polypyrrole films doped with poly(m-aminobenzene sulfonic acid (PABS) functionalized single-walled nanotubes (SWNT) (PPy/SWNT-PABS). The negatively charged water-soluble SWNT-PABS served as anionic dopant during the electropolymerization to synthesize PPy/SWNT-PABS composite films. The synthetic, morphological and electrical properties of PPy/SWNT-PABS films and chloride doped polypyrrole (PPy/Cl) films were compared. Characterization was performed by cyclic voltammetry, atomic force microscopy (AFM), scanning electron microscopy (SEM) and Raman spectroscopy. SEM and AFM images revealed that the incorporation of SWNT-PABS significantly altered the morphology of the PPy. Cyclic voltammetry showed improved electrochemical properties of PPy/SWNT-PABS films as compared to PPy/Cl films. Raman Spectroscopy confirmed the presence of SWNT-PABS within composite films. Field effect transistor (FET) and electrical characterization studies show that the incorporation of the SWNT-PABS increased the electronic performance of PPy/SWNT-PABS films when compared to PPy/Cl films. Finally, we fabricated PPy/SWNT-PABS nanotubes which may lead to potential applications to sensors and other electronic devices. [source]


    Defect Tolerance and Nanomechanics in Transistors that Use Semiconductor Nanomaterials and Ultrathin Dielectrics,

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2008
    Jong-Hyun Ahn
    Abstract This paper describes experimental and theoretical studies of the mechanics of free-standing nanoribbons and membranes of single-crystalline silicon transfer printed onto patterned dielectric layers. The results show that analytical descriptions of the mechanics agree well with experimental data, and they explicitly reveal how the geometry of dielectric layers (i.e., the width and depth of the features of relief) and the silicon (i.e., the thickness and widths of the ribbons) affect mechanical bowing (i.e., "sagging") in the suspended regions of the silicon. This system is of practical importance in the use of semiconductor nanomaterials for electronic devices, because incomplete sagging near defects in gate dielectrics provides a level of robustness against electrical shorting in those regions which exceeds that associated with conventional deposition techniques for thin films. Field effect transistors formed using silicon nanoribbons transferred onto a range of ultrathin gate dielectrics, including patterned epoxy, organic self-assembled monolayers, and HfO2, demonstrate these concepts. [source]


    Solution-Deposited Zinc Oxide and Zinc Oxide/Pentacene Bilayer Transistors: High Mobility n-Channel, Ambipolar, and Nonvolatile Devices,

    ADVANCED FUNCTIONAL MATERIALS, Issue 12 2008
    Bhola Nath Pal
    Abstract A solution processed n-channel zinc oxide (ZnO) field effect transistor (FET) was fabricated by simple dip coating and subsequent heat treatment of a zinc acetate film. The field effect mobility of electrons depends on ZnO grain size, controlled by changing the number of coatings and zinc acetate solution concentration. The highest electron mobility achieved by this method is 7.2,cm2 V,1 s,1 with On/Off ratio of 70. This electron mobility is higher than for the most recently reported solution processed ZnO transistor. We also fabricated bilayer transistors where the first layer is ZnO, and the second layer is pentacene, a p-channel organic which is deposited by thermal evaporation. By changing the ZnO grain size (or thickness) this type of bilayer transistor shows p-channel, ambipolar and n-channel behavior. For the ambipolar transistor, well balanced electron and hole mobilities are 7.6,×,10,3 and 6.3,×,10,3,cm2 V,1 s,1 respectively. When the ZnO layer is very thin, the transistor shows p-channel behavior with very high reversible hysteresis. The nonvolatile tuning function of this transistor was investigated. [source]


    Synthesis of silicon-bridged polythiophene derivatives and their applications to EL device materials

    JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2007
    Joji Ohshita
    Abstract Palladium-catalyzed oxidative homo-coupling of 2,6-bis(tributylstannyl)dithienosiloles with CuCl2 afforded poly(dithienosilole-2,6-diyl)s as novel polythiophene derivatives with intra-chain silicon bridges, which exhibited red-shifted UV absorption maxima by about 100 nm from those of the corresponding silole-free polythiophenes. Alternate copolymers also were prepared by palladium-catalyzed cross-coupling reactions of 2,6-dibromodithienosiloles with distannylthiophene or bithophene. These polymer films were applied to single and double-layered organic electroluminescence devices. It was found that some of the resulting polymers exhibited electroluminescence properties and emitted red light in EL devices with the structure of ITO/polymer/Mg-Ag. Introducing an electron-transporting Alq3 layer between the polymer film and the Mg-Ag cathode led to a remarkable improvement in the devices performance. An application of the copolymer to a field effect transistor was also studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4588,4596, 2007 [source]


    Implementation of the GaN lateral polarity junction in a MESFET utilizing polar doping selectivity

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010
    Ramón Collazo
    Abstract The difference in surface energies between the Ga-polar orientation and the N-polar orientation of GaN translates into a completely different behavior for the incorporation of intentional and unintentional impurities. Oxygen is found to be an impurity with higher concentration in the N-polar films than in Ga-polar films and is the cause of n-type conductivity observed in N-polar films. Utilizing this doping selectivity we fabricated a depletion-mode metal-semiconductor field effect transistor (MESFET) with n-type N-polar domains as source and drain and a Ga-polar channel on polarity-patterned wafers. The difference in the electronic properties of the different domains, i.e., as-grown N-polar domains are n-type conductive and Ga-polar domains are insulating, allows for laterally selective doped areas that can be realized for improving contact resistance to the n-type conduction channel. Basically, the N-polar domains acted as the ohmic contacts to the channel localized in a Ga-polar domain. A MESFET with a Schottky gate was fabricated as an example of implementation of this novel structure showing a lowering in the specific contact resistivity. [source]


    Design, process, and performance of all-epitaxial normally-off SiC JFETs

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2009
    Rajesh 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]


    Crystalline ZnO/SrTiO3 transparent field effect transistor

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008
    E. Bellingeri
    Abstract We fabricated field effect transistors which are transparent at visible wavelength, by realizing epitaxial ZnO/SrTiO3 heterostructures. High crystalline quality ZnO layers were grown by pulsed laser deposition on 110 oriented strontium titanate single crystals. By conventional photolithographic techniques we realized micrometric sized devices in both bottom-gate stacked layers geometry and planar side-gate configuration. Our transistors show 80% light transmittance, on/off ratios up to 106 and field effect mobilities up to 30 cm2/Vs at 77 K. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Influence of top layer geometries on the electronic properties of pentacene and diindenoperylene thin films

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2008
    M. Scharnberg
    Abstract Top layers have a pronounced influence on the electronic properties of molecular organic thin films. Here, we report about the changes induced by metallic and polymeric top layers and contacts. As test structures, model systems of diindenoperylene and pentacene crystalline molecular organic thin films are used. A very sensitive radiotracer technique is introduced to study the details of metal penetration during top contact formation. The influence of temperature, evaporation time, adhesion promoter and grain size of the organic film were examined. The electric currents passing through metal top contacts were found to vary by more than a factor of three, depending on the preparation conditions of the metal contact. Furthermore, the series resistance of chemically identical contacts that only differed in the morphology of the interface were found to show pronounced asymmetric conductivity behaviour. We also show that with the help of electret top layers, based on the Teflon-AF fluropolymer, the threshold voltage of an organic field effect transistor can be tuned by several volts. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Strain-engineered novel III,N electronic devices with high quality dielectric/semiconductor interfaces

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003
    M. Asif Khan
    Abstract Since the early demonstration of 2D-electron gas [M. A. Khan et al., Appl. Phys. Lett. 60, 3027 (1992)] and a heterojunction field effect transistor (HFET) [M. Asif Khan et al., Appl. Phys. Lett. 63, 1214 (1993)] in III,N materials, rapid progress has been made to improve the DC and RF performance of GaN,AlGaN based HFETs. Stable and impressive microwave powers as high as 4,8 W/mm have been reported for device operation frequencies from 10 to 35 GHz. The key reason for these high performance numbers is an extremely large sheet carrier densities (>1 × 1013 cm,2) that can be induced at the interfaces in III,N hetereojunction [A. Bykhovsk et al., J. Appl. Phys. 74, 6734 (1993); M. Asif Khan et al., Appl. Phys. Lett. 75, 2806 (1999)]. These are instrumental in screening the channel dislocations thereby retaining large room temperature carrier mobilities (>1500 cm2/Vs) and sheet resistance as low as 300 ,/sq. These numbers and the high breakdown voltages of the large bandgap III,N material system thus enable rf-power approximately 5,10 times of that possible with GaAs and other competitor's technologies. We have recently introduced a unique pulsed atomic layer epitaxy approach to deposit AlN buffer layers and AlN/AlGaN superlattices [J. Zhang et al., Appl. Phys. Lett. 79, 925 (2001); J. P. Zhang et al., Appl. Phys. Lett. 80, 3542 (2002)] to manage strain and decrease the dislocation densities in high Al-content III,N layers. This has enabled us to significantly improve GaN/AlGaN hetereojunctions and the device isolation. The resulting low defect layers are not only key to improving the electronic but also deep ultraviolet light-emitting diode devices. For deep UV LED's they enabled us to obtain peak optical powers as high as 10 mW and 3 mW for wavelengths as short as 320 nm and 278 nm. Building on our past work [M. Asif Khan et al., Appl. Phys. Lett. 77, 1339 (2000); X. Hu et al., Appl. Phys. Lett. 79, 2832 (2001)] we have now deposited high quality SiO2/Si3N4 films over AlGaN with low interface state densities. They have then been used to demonstrate III,N insulating gate transistors (MOSHFET (SiO2) and MISHFET (Si3N4) with gate leakage currents 4,6 order less than those for conventional GaN,AlGaN HFETs. The introduction of the thin insulator layers (less then 100 Å) under the gate increases the threshold voltage by 2,3 V. In addition, it reduces the peak transconductance gm. However the unity cut-off frequency, the gain and the rf-powers remain unaffected as the gm/Cgs (gate-source capacitance) ratio remains unchanged. In addition to managing the defects and gate leakage currents we have also employed InGaN channel double heterojunction structures (AlInGaN,InGaN,GaN) to confine the carriers thereby reducing the spillover into trappings states. These InGaN based MOS-DHFETs exhibited no current-collapse, extremely low gate leakage currents (<10,10 A/mm) and 10,26 GHz rf-powers in excess of 6 W/mm. We have also demonstrated the scalability and stable operation of our new and innovative InGaN based insulating gate heterojunction field effect transistor approach. In this paper we will review the III,N heterojunction field-effect transistors progress and pioneering innovations including the excellent work from several research groups around the world. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Crystallographically oriented high resolution lithography of graphene nanoribbons by STM lithography

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 4 2010
    G. Dobrik
    Abstract Due to its exciting physical properties and sheet-like geometry graphene is in the focus of attention both from the point of view of basic science and of potential applications. In order to fully exploit the advantage of the sheet-like geometry very high resolution, crystallographicaly controlled lithography has to be used. Graphene is a zero gap semiconductor, so that a field effect transistor (FET) will not have an "off" state unless a forbidden gap is created. Such a gap can be produced confining the electronic wave functions by etching narrow graphene nanoribbons (GNRs) typically of a few nanometers in width and with well defined crystallographic orientation. We developed the first lithographic method able to achieve GNRs that have both nanometer widths and well defined crystallographic orientation. The lithographic process is carried out by the local oxidation of the sample surface under the tip of a scanning tunneling microscopy (STM). Crystallographic orientation is defined by acquiring atomic resolution images of the surface to be patterned. The cutting of trenches with controlled depth and of a few nanometer in width, folding and manipulation of single graphene layers is demonstrated. The narrowest GNR cut by our method is of 2.5,nm width, scanning tunneling spectroscopy (STS) showed that it has a gap of 0.5,eV, comparable to that of germanium, which allows room temperature operation of graphene nanodevices. [source]


    Measuring carrier mobility in conventional multilayer organic light emitting devices by delayed exciton generation

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2008
    S. Reineke
    Abstract The authors present an alternative method for the determination of the charge carrier mobility of organic thin films. In contrast to known methods like space charge limited current, field effect transistor and time of flight approaches, we determine the charge carrier mobility of a mixed film, serving as emission layer, within the conventional multilayer device architecture. We make use of a strong delayed generation feature in the electroluminescent decay, following a short voltage pump pulse in a time-resolved set-up. Taking into account the preferentially electron transporting properties of the film, the mobility of a N,N ,-di(naphthalen-2-yl)- N,N ,-diphenyl-benzidine (NPB):tris(1-phenylisoquinoline) iridium [Ir(piq)3] mixed film is found to be on the order of 10,5 cm2 (Vs),1. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    High drive current and high frequency response of GaN nanowire metal-oxide-semiconductor field-effect transistor

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010
    Jeng-Wei Yu
    Abstract We report the techniques of lateral epitaxial growth of horizontally aligned [110] GaN NWs and the photo-enhanced chemical (PEC) oxidation process to enable the registration of crystalline gallium oxide (Ga2O3)/GaN NWs onto their growth sites over the SiO2/p-Si substrates. This method allows the implementation of top-gate Ga2O3/GaN NW-metal oxide semiconductor field effect transistor (MOSFET) using the conventional optical lithography and the metal lift-off procedures. This scheme enables photolithographic fabrication of top-gate Ga2O3/GaN NW-MOSFET of 60 nm dia. and 2 ,m gate length. Device parameters with gm of 40 ,S, saturation current of 90 ,A, and cut-off frequency fT at 22 GHz have been extracted (© 2010 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 deposition

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
    H. 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]


    High-Performance Photoresponsive Organic Nanotransistors with Single-Layer Graphenes as Two-Dimensional Electrodes

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
    Yang Cao
    Abstract Graphene behaves as a robust semimetal with the high electrical conductivity stemming from its high-quality tight two-dimensional crystallographic lattice. It is therefore a promising electrode material. Here, a general methodology for making stable photoresponsive field effect transistors, whose device geometries are comparable to traditional macroscopic semiconducting devices at the nanometer scale, using cut graphene sheets as 2D contacts is detailed. These contacts are produced through oxidative cutting of individual 2D planar graphene by electron beam lithography and oxygen plasma etching. Nanoscale organic transistors based on graphene contacts show high-performance FET behavior with bulk-like carrier mobility, high on/off current ratio, and high reproducibility. Due to the presence of photoactive molecules, the devices display reversible changes in current when they are exposed to visible light. The calculated responsivity of the devices is found to be as high as ,8.3,A,W,1. This study forms the basis for making new types of ultrasensitive molecular devices, thus initiating broad research interest in the field of nanoscale/molecular electronics. [source]


    High Definition Digital Fabrication of Active Organic Devices by Molecular Jet Printing,

    ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007
    J. Chen
    Abstract We introduce a high resolution molecular jet (MoJet) printing technique for vacuum deposition of evaporated thin films and apply it to fabrication of 30,,m pixelated (800,ppi) molecular organic light emitting devices (OLEDs) based on aluminum tris(8-hydroxyquinoline) (Alq3) and fabrication of narrow channel (15,,m) organic field effect transistors (OFETs) with pentacene channel and silver contacts. Patterned printing of both organic and metal films is demonstrated, with the operating properties of MoJet-printed OLEDs and OFETs shown to be comparable to the performance of devices fabricated by conventional evaporative deposition through a metal stencil. We show that the MoJet printing technique is reconfigurable for digital fabrication of arbitrary patterns with multiple material sets and high print accuracy (of better than 5,,m), and scalable to fabrication on large area substrates. Analogous to the concept of "drop-on-demand" in Inkjet printing technology, MoJet printing is a "flux-on-demand" process and we show it capable of fabricating multi-layer stacked film structures, as needed for engineered organic devices. [source]


    Majority Carrier Type Conversion with Floating Gates in Carbon Nanotube Transistors

    ADVANCED MATERIALS, Issue 47 2009
    Woo Jong Yu
    A charge trapping layer can serve not only for designing multilevel nonvolatile memory but also for type conversion from p- to n-type and vice versa of carbon nanotube (CNT) channels. Type conversion from p- to n-type and vice versa for CNT field effect transistors can be realized by changing the polarity of trapped charges (see figure). [source]


    The Role of the Oxygen/Water Redox Couple in Suppressing Electron Conduction in Field-Effect Transistors

    ADVANCED MATERIALS, Issue 30 2009
    Carla M. Aguirre
    The suppression of electron (n-type) conduction observed in back-gated field effect transistors is the result of an electrochemical charge transfer process to the oxygen/water layer adsorbed on hydrophilic substrates. The impact of this phenomenon is demonstrated with nanoscale and thin-film carbon nanotube transistors. [source]


    Advanced silicon microstructures, sensors, and systems

    IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2007
    Oliver Paul Non-Member
    Abstract This paper presents the progress in silicon-based biomedical microstructures, material characterization techniques, and mechanical microsystems by the authors' research team. Microneedle and microelectrode arrays with fluidic through-wafer vias and electrical contacts were developed. The structures are designed for dermatological and biological applications such as allergy testing, surface electromyography, and spatially resolved impedance spectroscopy. The characterization of thin films has relied on the bulge test. By the formulation of more powerful models, the application range of the bulge test was extended to elastically supported thin-film multilayers. This enables the mechanical properties of thin films to be determined reliably. Finally, progress in the operation and application of novel stress sensors based on CMOS diffusions and field effect transistors and exploiting the pseudo-Hall effect is reported. Their integration into powerful single-chip microsystems is described. Applications include stress mapping, force and torque measurements, and tactile surface probing of microcomponents. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]


    Advantageous 3D Ordering of ,-Conjugated Systems: A New Approach Towards Efficient Charge Transport in any Direction,

    ADVANCED MATERIALS, Issue 24 2007
    H. Pang
    A new organic semiconductor based on a benzobisthiazole core has been studied as a hole transport material in field effect transistors; remarkably, the material self-assembles in the solid state to give intermolecular short contacts in all three dimensions. [source]


    A Nitrogen Dioxide Sensor Based on an Organic Transistor Constructed from Amorphous Semiconducting Polymers,

    ADVANCED MATERIALS, Issue 22 2007
    A. Das
    Organic field effect transistors based on amorphous semiconducting polymers are used as highly effective sensors for the detection of low concentrations of NO2. The figure shows the experimental setup used to detect the toxic odor. The threshold voltage rather than the charge carrier mobility is seen to be greatly modified by exposure to NO2. [source]


    Microwave operation of sub-micrometer gate surface channel MESFETs in polycrystalline diamond

    MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2009
    P. Calvani
    Abstract Submicron gate-length metal semiconductor field effect transistors (MESFETs) were fabricated on hydrogen-terminated,large grain polycrystalline diamond. Devices showed high drain-source current (140 ma/mm) and large transconductance values (50 ms/mm), with a cut-off frequency ft = 10 GHz and a maximum oscillation frequency, fmax, up to 35 GHz. These values are obtained through the fabrication of devices with geometry and active region dimensions (200,500 nm gate length) compatible with available microelectronic technologies. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2786,2788, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24738 [source]


    HfO2/AlGaN/GaN structures with HfO2 deposited at ultra low pressure using an e-beam

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5 2007
    V. Tokranov
    Abstract We show that HfO2/AlGaN/GaN structures with HfO2 layer deposited using an e-beam in ultra high vacuum are suitable for field effect transistors. The dielectric constant of the HfO2 was found ,HfO > 23,24, which is close to the highest re- ported values for this material. The leakage current did not exceed 10,4 A/cm2 at the threshold voltage. The comparison of the losses in the samples with and without HfO2 indicates low concentration of the interface traps. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Current collapse and reliability of III-N heterostructure field effect transistors

    PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 3 2007
    A. Koudymov
    Abstract Measurements of GaN HFET lifetime as a function of temperature show that different degradation mechanisms are involved at low temperatures (close to room temperature) and high temperatures (above 150 °C). The degradation at low temperatures is linked to the trap generation and can be explained using the current collapse model. At higher tempe- ratures, other degradation mechanisms become important or even dominant. The current collapse related degradation can be diminished by using improved device design, which will greatly increase the overall lifetime (up to long lifetimes obtained by extrapolating high temperature data to room temperature). (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Extreme temperature 6H-SiC JFET integrated circuit technology

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2009
    Philip G. Neudeck
    Abstract Extreme temperature semiconductor integrated circuits (ICs) are being developed for use in the hot sections of aircraft engines and other harsh-environment applications well above the 300 °C effective limit of silicon-on-insulator IC technology. This paper reviews progress by the NASA Glenn Research Center and Case Western Reserve University (CWRU) in the development of extreme temperature (up to 500 °C) integrated circuit technology based on epitaxial 6H-SiC junction field effect transistors (JFETs). Simple analog amplifier and digital logic gate ICs fabricated and packaged by NASA have now demonstrated thousands of hours of continuous 500 °C operation in oxidizing air atmosphere with minimal changes in relevant electrical parameters. Design, modeling, and characterization of transistors and circuits at temperatures from 24 °C to 500 °C are also described. CWRU designs for improved extreme temperature SiC JFET differential amplifier circuits are demonstrated. Areas for further technology maturation, needed prior to beneficial system insertion, are discussed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Crystalline ZnO/SrTiO3 transparent field effect transistor

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008
    E. Bellingeri
    Abstract We fabricated field effect transistors which are transparent at visible wavelength, by realizing epitaxial ZnO/SrTiO3 heterostructures. High crystalline quality ZnO layers were grown by pulsed laser deposition on 110 oriented strontium titanate single crystals. By conventional photolithographic techniques we realized micrometric sized devices in both bottom-gate stacked layers geometry and planar side-gate configuration. Our transistors show 80% light transmittance, on/off ratios up to 106 and field effect mobilities up to 30 cm2/Vs at 77 K. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Dielectric layers for organic field effect transistors as gate dielectric and surface passivation

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2008
    T. 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]