Showing papers on "Field effect published in 2009"
TL;DR: In this article, a photodetector is provided to generate an electric field across the conductive layers in response to an input optical gate signal, which is modulated by interaction with a plasmon wave generated at the semiconductor/conductive layer interface.
Abstract: The invention is a system and method for performing all-optical modulation. A semiconductor layer having a defined thickness has an insulator adjacent one surface of the semiconductor. Conductive layers are provided adjacent the semiconductor layer and the insulator. A photodetector is provided to generate an electric field across the conductive layers in response to an input optical gate signal. An input optical signal is modulated by interaction with a plasmon wave generated at the semiconductor/conductive layer interface. By defining the thickness of the semiconductor layer, a desired wavelength of light supports the plasmon waves. Operation of the all-optical modulator requires the provision of an input optical signal of a desired wavelength and the provision of a gate optical signal. An output optical signal is recovered and can be used to store, display or transmit information, for example over a fiber optic communication system, such as a telecommunication system.
493 citations
TL;DR: In this paper, the effects of the indium content on characteristics of nanocrystalline InGaZnO (IGZO) films grown by a solgel method and their thin film transistors (TFTs) have been investigated.
Abstract: The effects of the indium content on characteristics of nanocrystalline InGaZnO (IGZO) films grown by a sol-gel method and their thin film transistors (TFTs) have been investigated Excess indium incorporation into IGZO enhances the field effect mobilities of the TFTs due to the increase in conducting path ways and decreases the grain size and the surface roughness of the films because more InO2− ions induce cubic stacking faults with IGZO These structural variations result in a decrease in density of interfacial trap sites at the semiconductor-gate insulator interface, leading to an improvement of the subthreshold gate swing of the TFTs
202 citations
TL;DR: In this article, a low-driven-voltage and high mobility ZnO thin-film transistor with sputtering Ta2O5 film as the dielectric is presented.
Abstract: The authors report on the fabrication of low-driven-voltage and high mobility ZnO thin-film transistor with sputtering Ta2O5 film as the dielectric. The device shows a field effect mobility of 60.4 cm2/V s, a threshold voltage of 1.1 V, an on/off ratio of 1.22×107, and a subthreshold swing of 0.23 V/decade. The high mobility partially resulted from the fringing-electric-field effect due to the undefined active layer. Therefore, considering our device geometry, the actual mobility is about 40.5 cm2/V s. We contribute the high performance to the proper dielectric thickness, smooth insulator surface, and relatively low trap state densities in the insulator/channel interface.
151 citations
TL;DR: In this paper, uniform regio-regular poly(3-hexylthiophene) nanofibers and their blend poly(e-caprolactone) with PCL were compared.
Abstract: Uniform regio-regular poly(3-hexylthiophene) nanofibers and their blend nanofibers with poly(e-caprolactone) have been obtained by electrospinning and their electrical properties in single nanofiber field effect transistors have been compared. The key to the success was restricting the precipitation of P3HT at the nozzle tip, therefore preventing the nozzle from being clogged. The field effect mobility of pure P3HT fibers was 0.017 cm2V−1 s−1 which is acceptable for device fabrication. Blend fibers with PCL also showed field effect behaviour with slightly degraded electrical properties by an order or two.
123 citations
Patent•
19 Oct 2009
TL;DR: In this article, an oxide semiconductor whose composition is represented by InMO3(ZnO)m, where m is one or a plurality of elements selected from Ga, Fe, Ni, Mn, Co, and Al, and m is preferably a non-integer number of greater than 0 and less than 1.
Abstract: An object is to control composition and a defect of an oxide semiconductor, another object is to increase a field effect mobility of a thin film transistor and to obtain a sufficient on-off ratio with a reduced off current. A solution is to employ an oxide semiconductor whose composition is represented by InMO3(ZnO)m, where M is one or a plurality of elements selected from Ga, Fe, Ni, Mn, Co, and Al, and m is preferably a non-integer number of greater than 0 and less than 1. The concentration of Zn is lower than the concentrations of In and M. The oxide semiconductor has an amorphous structure. Oxide and nitride layers can be provided to prevent pollution and degradation of the oxide semiconductor.
104 citations
TL;DR: In this paper, the effects of an O2 plasma-treated SiNX-based insulator on the interfacial property and the device performances of amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) were investigated.
Abstract: The effects of an O2 plasma-treated SiNX-based insulator on the interfacial property and the device performances of amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) were investigated. We tried to improve the interfacial characteristics by reducing the trap density between the SiNX gate insulator and a-IGZO channel by the O2 plasma treatment. The plasma treated-device performances were remarkably improved. The drastic improvements obtained for the O2 plasma-treated a-IGZO TFTs included excellent bias stability as well as a high field effect mobility (μFE) of 19.4 cm2/V s, an on/off current (ION/IOFF) of 108, and a subthreshold value (S) of 0.5 V/decade.
94 citations
TL;DR: In this article, a solution-based approach to the synthesis of semiconducting chalcogenide films for use in thin-film transistor (TFT) devices was proposed.
Abstract: Low-cost and high-performance materials fabricated at low temperatures via solution processes are of great interest in the field of printable and flexible electronics. We have investigated a new solution-based approach to the synthesis of semiconducting chalcogenide films for use in thin-film transistor (TFT) devices in an attempt to develop a simple and robust solution process for the synthesis of inorganic semiconductors. Our material design strategy is to use a sol−gel reaction for the deposition of a spin-coated CdS film that can then be converted to a xerogel material. By carrying out the spin-coating of a L2Cd(S(CO)CH3)2 (L = 3,5-lutidine) precursor, which condenses at low temperatures to form a CdS network, and then hard-baking at 300 °C under atmospheric pressure, microscopically flat films were successfully obtained. To determine the field effect mobilities of the spin-coated CdS films, we constructed TFTs with an inverted structure consisting of Mo gate electrodes and ZrO2 gate dielectrics. Thes...
94 citations
TL;DR: In this article, the authors employ high-performance, elastomeric, photolithographically patterned single-crystal field effect transistors as tools for the characterization of short-channel effects and bias-dependent parasitic contact resistance and field effect mobility.
Abstract: The organic field-effect transistor (OFET) has proven itself invaluable as both the fundamental element in organic circuits and the primary tool for the characterization of novel organic electronic materials. Crucial to the success of the OFET in each of these venues is a working understanding of the device physics that manifest themselves in the form of electrical characteristics. As commercial applications shift to smaller device dimensions and structure/property relationships become more refined, the understanding of these phenomena become increasingly critical. Here, we employ high-performance, elastomeric, photolithographically patterned single-crystal field-effect transistors as tools for the characterization of short-channel effects and bias-dependent parasitic contact resistance and field-effect mobility. Redundant characterization of devices at multiple channel lengths under a single crystal allow the morphology-free analysis of these effects, which is carried out in the context of a device model previously reported. The data show remarkable consistency with our model, yielding fresh insight into each of these phenomena, as well as confirming the utility of our FET design.
74 citations
TL;DR: In this article, it was shown that the field-effect mobilities extracted from undefined nanoparticulate zinc oxide (ZnO) TFTs at the channel ratio of 2.5 are overestimated by 418%, and the choice of large channel ratios gives the real value of field effect mobilities.
Abstract: Field-effect mobilities are the most important figures of merit to evaluate the feasibility of semiconductors for thin-film transistors (TFTs). They are, however, sometimes extracted from TFTs with the active semiconductor area undefined and in small channel ratios without the effect of the fringing electric field at the ends of source/drain electrodes taken into account. In this letter, it is demonstrated that the field-effect mobilities extracted from undefined nanoparticulate zinc oxide (ZnO) TFTs at the channel ratio of 2.5 are overestimated by 418%, and the choice of large channel ratios gives the real value of field-effect mobilities.
70 citations
TL;DR: In this article, three crystalline polymorphs are found from the thin films of DHDAP according to their (001) spacing (layer periodicity) and the field effect mobility is extremely sensitive to the polymorphs with the 12.9 A phase yielding a mobility of 0.45 cm2 V−1 s−1, which is over 5000 times higher than those of the other two phases.
Abstract: 6,13-Dihydro-6,13-diazapentacene (DHDAP) has two nitrogen atoms replacing two carbon atoms of pentacene, the leading organic semiconductor for organic thin film transistors (OTFTs). This report details a comprehensive investigation of DHDAP highlighting the relationship between charge transport, polymorphs, and electronic structures. Three crystalline polymorphs are found from the thin films of DHDAP according to their (001) spacing (layer periodicity). Our surprising finding is that the field effect mobility of DHDAP is extremely sensitive to the polymorphs with the “12.9 A phase” yielding a mobility of 0.45 cm2 V−1 s−1, which is over 5000 times higher than those of the other two phases. This unusually large effect of the crystalline polymorph on charge transport can be understood in terms of molecular packing using the models developed by de Wijs and Bredas. The comparable field effect mobilities and highly relevant structures of DHDAP and pentacene imply that the common structural features shared by th...
66 citations
TL;DR: In this article, the effect of threshold voltage shift in the field effect mobility of thin film transistors is investigated. But the authors consider the case where the transistors exhibit large instability during the measurement, typically exhibiting hysteresis in the static characteristics.
Abstract: The field effect (FE) mobility of thin film transistors is normally extracted using static measurement methods, which inherently rely on the assumption that the device remains stable during the measurement duration. However, these devices, particularly those based on emerging materials, can show large instability during the measurement, typically exhibiting hysteresis in the static characteristics. This letter looks at the effect of threshold voltage shift in FE mobility extracted using the conventional method, and introduces an alternative and more accurate technique of measuring device characteristics. The technique decouples the effect of transient phenomena, thus permitting extraction of the true device FE mobility, which turns out to be either over or underestimated depending on the magnitude and direction of threshold voltage shift.
TL;DR: In this article, the authors demonstrate the first metal-semiconductor field effect transistor with a self-assembled planar GaAs nanowire channel with a subthreshold slope of ~150 mV/dec, maximum gm of 23 mS/mm, and excellent on-current saturation.
Abstract: We demonstrate the first metal-semiconductor field-effect transistor with a self-assembled planar lang110rang GaAs nanowire channel. Well-defined dc output and transfer characteristics have been observed with a subthreshold slope of ~150 mV/dec, maximum gm of 23 mS/mm, and excellent on-current saturation. Bulklike mobility of ~4100 cm2/Vmiddots with corresponding electron concentration of 2.3middot1017 cm-3 is derived by fitting the experimental data using a self-consistent long channel field effect device model.
TL;DR: In this article, a novel rf sputtering technology in which a high density plasma is created in a remote chamber has been used to reactively deposit zinc oxide and indium zinc oxide (IZO) thin films at room temperature from metallic sputtering targets at deposition rates ∼50 nm min −1, which is approximately an order of magnitude greater than that of rf magnetron sputtering.
Abstract: A novel rf sputtering technology in which a high density plasma is created in a remote chamber has been used to reactively deposit zinc oxide (ZnO) and indium zinc oxide (IZO) thin films at room temperature from metallic sputtering targets at deposition rates ∼50 nm min −1 , which is approximately an order of magnitude greater than that of rf magnetron sputtering. Thin film transistors have been fabricated using IZO with a maximum processing temperature of 120 ◦ C, which is defined by the curing of the photoresist used in patterning. Devices have a saturated field effect mobility of 10 cm 2 V −1 s −1 and a switching ratio in excess of 10 6 . Gate bias stress experiments performed at elevated temperatures show a consistent apparent increase in the field effect mobility with time, which is attributed to a charge trapping phenomenon.
TL;DR: High-performance field-effect transistors fabricated by etching the channel regions of surface-doped Si nanowires function similarly to traditional metal-oxide semiconductor field- effect transistors; in accumulation, the device current is controlled by channel conductance modulation, while n(+)-n junctions determine subthreshold characteristics as the channel is depleted.
Abstract: High-performance field-effect transistors were fabricated by etching the channel regions of surface-doped Si nanowires. On/off ratios of 106 and field effect mobilities up to 525 cm2/(V·s) represen...
TL;DR: In this article, a self-consistent numerical model for silicon-based field effect nanowire biosensors is developed to study the impact of various surfacerelated physical and chemical processes, including transport of semiconductor carriers and electrolyte mobile ions, protonation and deprotonation of surface charge groups, and charges, and orientations and surface binding dynamics of immobilized biomolecules.
Abstract: A self-consistent numerical model for silicon-based field effect nanowire biosensors is developed to study the impact of various surface-related physical and chemical processes, including transport of semiconductor carriers and electrolyte mobile ions, protonation and deprotonation of surface charge groups, and charges, and orientations and surface binding dynamics of immobilized biomolecules. It is shown that the sensing signal levels are affected by the gate biasing points, nonlinear screening from both electrolytes and surface charge groups, as well as the biomolecule charges and orientations. The critical role of the nanowire surface heterogeneity in determining the sensing input dynamic range is indicated based on correlations with experimental data.
Patent•
06 May 2009
TL;DR: In this article, the authors describe a device where current flow in the device is confined between the rectifying junctions (e.g., p-n junctions or metal-semiconductor junctions).
Abstract: Semiconductor devices are described wherein current flow in the device is confined between the rectifying junctions (e.g., p-n junctions or metal-semiconductor junctions). The device provides non-punch-through behavior and enhanced current conduction capability. The devices can be power semiconductor devices as such as Junction Field-Effect Transistors (VJFETs), Static Induction Transistors (SITs), Junction Field Effect Thyristors, or JFET current limiters. The devices can be made in wide bandgap semiconductors such as silicon carbide (SiC). According to some embodiments, the device can be a normally-off SiC vertical junction field effect transistor. Methods of making the devices and circuits comprising the devices are also described.
TL;DR: In this paper, the authors demonstrate solution processable large area field effect transistors (FETs) from aligned arrays of carbon nanotubes (CNTs) using ac dielectrophoresis technique.
Abstract: We demonstrate solution processable large area field effect transistors (FETs) from aligned arrays of carbon nanotubes (CNTs). Commercially available, surfactant free CNTs suspended in aqueous solution were aligned between source and drain electrodes using ac dielectrophoresis technique. After removing the metallic nanotubes using electrical breakdown, the devices displayed p-type behavior with on-off ratios up to ∼2×104. The measured field effect mobilities are as high as 123 cm2/V s, which is three orders of magnitude higher than typical solution processed organic FET devices.
TL;DR: In this paper, a field plate structure for a diamond Schottky barrier diode was fabricated and the electric breakdown properties were tested for electric field concentration and passivation, and the field plate with a field oxide of Al 2 O 3 showed about three times higher reverse blocking voltage than an unterminated one.
TL;DR: In this article, single-crystal transistors of highly electron-affine organic compounds were constructed on solid dielectrics to study intrinsic constraints for the n-channel field effect in ambient atmosphere.
Abstract: Single-crystal transistors of highly electron-affine organic compounds were constructed on solid dielectrics to study intrinsic constraints for the n-channel field effect in ambient atmosphere. Tetracyanoquinodimethane field-effect devices reproducibly operate with a high mobility of 0.2–0.5 cm2/V s in the air. The threshold gate voltage is negligible unlike most other air-stable n-type organic transistors reported, including polycrystal film devices of the same compound. Together with the other example of less electron-affine semiconductor crystal showing air-stable field effect but with notable threshold voltage, the result suggests that crucial in air-stable n-channel field effect is sufficient electron-affinity of the organic semiconductors.
Patent•
17 Dec 2009TL;DR: In this paper, tunnel field effect devices and methods of fabricating tunnel field effects are described, where the authors describe a tunnel-field effect device with a first drain region of a first conductivity type disposed in a first region of the substrate, a first source region disposed in the substrate and a first gate stack overlying the first channel region.
Abstract: Tunnel field effect devices and methods of fabricating tunnel field effect devices are described. In one embodiment, the semiconductor device includes a first drain region of a first conductivity type disposed in a first region of a substrate, a first source region of a second conductivity type disposed in the substrate, the second conductivity type being opposite the first conductivity type, a first channel region electrically coupled between the first source region and the first drain region, the first source region underlying a least a portion of the first channel region, and a first gate stack overlying the first channel region.
TL;DR: In this paper, a new gate dielectric material is used to fabricate hydrogenated amorphous-silicon (a-Si:H) thin-film transistors with high field-effect mobilities.
Abstract: A new gate dielectric material is used to fabricate hydrogenated amorphous-silicon (a-Si:H) thin-film transistors (TFTs) with high field-effect mobilities The dielectric is a homogeneous SiO2-silicone hybrid, which is deposited by plasma-enhanced chemical vapor deposition system at nominal room temperature This new dielectric results in a-Si:H TFTs with measured field-effect mobilities of ∼2 cm2/V s for electrons and ∼01 cm2/V s for holes
TL;DR: The results introduce a new dimension to present sensing systems by enabling dual purpose silicon transistor-heaters that serve both as field effect sensors as well as temperature controllers that could perform localized bio-chemical reactions in Lab on Chip applications.
Abstract: We demonstrate electrically addressable localized heating in fluid at the dielectric surface of silicon-on-insulator field-effect transistors via radio-frequency Joule heating of mobile ions in the Debye layer. Measurement of fluid temperatures in close vicinity to surfaces poses a challenge due to the localized nature of the temperature profile. To address this, we developed a localized thermometry technique based on the fluorescence decay rate of covalently attached fluorophores to extract the temperature within 2 nm of any oxide surface. We demonstrate precise spatial control of voltage dependent temperature profiles on the transistor surfaces. Our results introduce a new dimension to present sensing systems by enabling dual purpose silicon transistor-heaters that serve both as field effect sensors as well as temperature controllers that could perform localized bio-chemical reactions in Lab on Chip applications.
TL;DR: In this article, the authors show that the vertical electric field should be at least 10 times higher than the lateral electric filed in order to suppress the short channel effects of transistors, and that the field effect mobility of long channel devices is about an order of magnitude larger than small channel devices (L from 0.3 to 2.5 μm).
Abstract: Organic thin film transistors with P3HT (poly-3-hexylthiophene) as active semiconducting layer, channel lengths from 0.3 to 20 μm, and gate oxide thicknesses from 15 to 170 nm have been successfully fabricated on Si substrates. The measurement results show that the channel length over oxide thickness ratio should be large enough (i.e., the vertical electric field should be at least 10 times higher than the lateral electric filed) in order to suppress the short channel effects of transistors. The field effect mobility of long channel devices (L ≥ 5 μm) is about an order of magnitude larger than small channel devices (L from 0.3 to 2.5 μm), which could be attributed to the more severe contact resistance effects between organic materials and metal contacts for devices with smaller dimensions.
TL;DR: It is demonstrated that the concentration of molecules is a consequence of ionic charge accumulation at the tip screening the electric field, thereby slowing down the electrophoretic motion of the molecules, which is further slowed down or stopped by the oppositely directed electro-osmosis.
Abstract: Concentration of molecules within the tips of nanopipettes when applying a DC voltage is herein investigated using finite-element simulations. The ion concentrations and fluxes due to diffusion, electro-migration, and electro-osmotic flow, and the electric potential are determined by the simultaneous solution of the Nernst−Planck, Poisson, and Navier−Stokes equations within the water solution containing sodium and chloride ions and negatively charged molecules. The electric potential within the pipette glass wall is at the same time determined by the Poisson equation together with appropriate boundary conditions and accounts for a field effect through the wall. Fixed negative surface charge on both the internal and external glass surfaces of the nanopipette is included together with the field effect through the glass wall to account for the electric double layer and the electro-osmosis. The inclusion of the field effect through the pipette wall is new compared to previous modeling of similar structures an...
TL;DR: In this paper, the carrier injection mechanism of top-contact pentacene field effect transistors (FETs) was investigated in terms of Schottky injection, and the authors showed that injected holes contributed to carrier injection, while the external electric field was cancelled by the space charge field formed by holes accumulated in the FET channel.
Abstract: By probing optical second harmonic generation (SHG) signals enhanced around the injection electrode, the carrier injection mechanism of top-contact pentacene field-effect transistors (FETs) was investigated in terms of Schottky injection. At the Au source electrode, the SHG signal disappeared immediately after applying the driving voltage: the applied external electric field was cancelled by the space charge field formed by holes accumulated in the FET channel. At the Ag source electrode, the SH intensity decayed slowly. Its dependence on the device operation voltage suggested that the electric field was not relaxed by injected holes. The Schottky effect regulated carrier injection. The space charge field effect attributable to accumulated holes contributed to the carrier injection.
Patent•
22 Dec 2009
TL;DR: In this paper, an oxide cluster having higher electrical conductance than the oxide semiconductor layer is formed between the oxide layer and a gate insulating layer, whereby field effect mobility of the thin film transistor can be increased and increase of off current can be suppressed.
Abstract: In a thin film transistor including an oxide semiconductor, an oxide cluster having higher electrical conductance than the oxide semiconductor layer is formed between the oxide semiconductor layer and a gate insulating layer, whereby field effect mobility of the thin film transistor can be increased and increase of off current can be suppressed.
TL;DR: In this paper, a field effect hydrogen-sensing device with a simple structure based on GaN was fabricated by means of a simple process analogous to the fabrication process of a Schottky diode.
Abstract: A field effect hydrogen-sensing device with a simple structure based on GaN was fabricated by means of a simple process analogous to the fabrication process of a Schottky diode. Current–voltage characteristics between the source and the drain electrodes were studied, and response to hydrogen was measured under floating gate condition. The device has a wide detection region from a few ppm to 1% hydrogen. When oxygen and hydrogen are present at higher hydrogen concentrations, a large change in voltage occurs with an increase in oxygen concentration. The effect of gate length was investigated. When a longer gate electrode was employed, a larger change in voltage between the source and drain electrodes VDS was obtained. The sensing mechanism is discussed by reference to the channel resistance change model, and the model explains the experimental results fully. The influence of gate bias was also studied, and the results show that when the gate was connected to the source and biased, a larger change in voltage VDS was obtained.
TL;DR: Tetrachlorotetracene is an organic semiconductor and has possible applications in flexible organic devices as mentioned in this paper, and it has been synthesized in multigram quantities in three steps from commercially available substances, with an overall yield of 52%.
Abstract: Tetrachlorotetracene is an organic semiconductor and has possible applications in flexible organic devices. We have synthesized tetrachlorotetracene in multigram quantities in three steps from commercially available substances, with an overall yield of 52%. X-ray crystallographic analysis of tetrachlorotetracene and its precursor dihydroxytetracenedione showed similar packing structures, with better pitch stacking and roll stacking angles observed for tetrachlorotetracene. Single crystals of tetrachlorotetracene are semiconducting with field effect hole mobility values up to 0.2 cm2/V s. The hole mobility has been measured in the temperature range of 230−290 K, and Arrhenius behavior was observed, with an activation energy of nearly 200 meV. Such a large activation energy suggests significant carrier trapping. Air stability studies showed slow degradation of the crystal surface by atomic force microscopy, along with degradation of the semiconducting properties. We hypothesize that the instability of tetra...