The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
David J Gundlach - One of the best experts on this subject based on the ideXlab platform.
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mobility overestimation due to gated contacts in organic field effect Transistors
Nature Communications, 2016Co-Authors: James I Basham, Emily G Bittle, T N Jackson, Oana D Jurchescu, David J GundlachAbstract:Parameters used to describe the electrical properties of organic field-effect Transistors, such as mobility and threshold voltage, are commonly extracted from measured current–voltage characteristics and interpreted by using the classical metal oxide–semiconductor field-effect Transistor Model. However, in recent reports of devices with ultra-high mobility (>40 cm2 V−1 s−1), the device characteristics deviate from this idealized Model and show an abrupt turn-on in the drain current when measured as a function of gate voltage. In order to investigate this phenomenon, here we report on single crystal rubrene Transistors intentionally fabricated to exhibit an abrupt turn-on. We disentangle the channel properties from the contact resistance by using impedance spectroscopy and show that the current in such devices is governed by a gate bias dependence of the contact resistance. As a result, extracted mobility values from d.c. current–voltage characterization are overestimated by one order of magnitude or more. Charge mobility, extracted from current–voltage curves, is an important parameter for evaluating the performance of organic field-effect Transistors. Bittle et al. show that charge mobility can be overestimated by one order of magnitude due to the gate bias dependence of the charge injection process.
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mobility overestimation due to gated contacts in organic field effect Transistors
Nature Communications, 2016Co-Authors: James I Basham, Emily G Bittle, T N Jackson, Oana D Jurchescu, David J GundlachAbstract:Parameters used to describe the electrical properties of organic field-effect Transistors, such as mobility and threshold voltage, are commonly extracted from measured current-voltage characteristics and interpreted by using the classical metal oxide-semiconductor field-effect Transistor Model. However, in recent reports of devices with ultra-high mobility (>40 cm(2) V(-1) s(-1)), the device characteristics deviate from this idealized Model and show an abrupt turn-on in the drain current when measured as a function of gate voltage. In order to investigate this phenomenon, here we report on single crystal rubrene Transistors intentionally fabricated to exhibit an abrupt turn-on. We disentangle the channel properties from the contact resistance by using impedance spectroscopy and show that the current in such devices is governed by a gate bias dependence of the contact resistance. As a result, extracted mobility values from d.c. current-voltage characterization are overestimated by one order of magnitude or more.
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arbitrary density of states in an organic thin film field effect Transistor Model and application to pentacene devices
IEEE Transactions on Electron Devices, 2007Co-Authors: D Oberhoff, K P Pernstich, David J Gundlach, Bertram BatloggAbstract:We present a modular numerical Model for organic thin-film field-effect Transistors (OTFTs) that allows for an arbitrary density of states to be independently defined for the semiconductor bulk and the semiconductor surface next to the gate insulator. We can derive the surface charge density dependence on the interface field as well as the space-charge-limited current characteristics. Together with a Model of the contacts, we arrive at a physical Model that is applied to a series of OTFTs in staggered inverted (top contact) geometry with various gate insulator treatments
Christian Enz - One of the best experts on this subject based on the ideXlab platform.
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cryogenic mos Transistor Model
IEEE Transactions on Electron Devices, 2018Co-Authors: Arnout Beckers, Farzan Jazaeri, Christian EnzAbstract:This paper presents a physics-based analytical Model for the MOS Transistor operating continuously from room temperature down to liquid-helium temperature (4.2 K) from depletion to strong inversion and in the linear and saturation regimes. The Model is developed relying on the 1-D Poisson equation and the drift-diffusion transport mechanism. The validity of the Maxwell–Boltzmann approximation is demonstrated in the limit to 0 K as a result of dopant freezeout in cryogenic equilibrium. Explicit MOS Transistor expressions are then derived, including incomplete dopant ionization, bandgap widening, mobility reduction, and interface charge traps. The temperature dependence of the interface trapping process explains the discrepancy between the measured value of the subthreshold swing and the thermal limit at deep-cryogenic temperatures. The accuracy of the developed Model is validated by experimental results on long devices of a commercial 28-nm bulk CMOS process. The proposed Model provides the core expressions for the development of physically accurate compact Models dedicated to low-temperature CMOS circuit simulation.
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an mos Transistor Model for rf ic design valid in all regions of operation
IEEE Transactions on Microwave Theory and Techniques, 2002Co-Authors: Christian EnzAbstract:This paper presents an overview of MOS Transistor Modeling for RF integrated circuit design. It starts with the description of a physical equivalent circuit that can easily be implemented as a SPICE subcircuit. The MOS Transistor is divided into an intrinsic part, representing mainly the active part of the device, and an extrinsic part responsible for most of the parasitic elements. A complete charge-based Model of the intrinsic part is presented. The main advantage of this new charge-based Model is to provide a simple and coherent description of the DC, AC, nonquasi-static (NQS), and noise behavior of the intrinsic MOS that is valid in all regions of operation. It is based on the forward and reverse charges q/sub f/ and q/sub r/ defined as the mobile charge densities, evaluated at the source and at the drain. This intrinsic Model also includes a new simplified NQS Model that uses a bias and frequency normalization allowing one to describe the high-order frequency behavior with only two simple functions. The extrinsic Model includes all the terminal access series resistances, and particularly the gate resistance, the overlap, and junction capacitances as well as a substrate network. The latter is required to account for the signal coupling occurring at RF from the drain to the source and the bulk, through the junction capacitances. The noise Model is then presented, including the effect of the substrate resistances on the RF noise parameters. All the aspects of the Model are validated for a 0.25-/spl mu/m CMOS process.
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the ekv 3 0 compact mos Transistor Model accounting for deep submicron aspects
Workshop on Compact Modeling at the International Conference on Modeling and Simulation of Microsystems, 2002Co-Authors: Matthias Bucher, Christian Enz, Christophe Lallement, F Krummenacher, J M Sallese, A S PorretAbstract:Keywords: EKV ; Device Modeling ; MOST Modeling ; RF ; NQS Note: (invited) Reference EPFL-CONF-149508 Record created on 2010-06-24, modified on 2017-06-01
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an analytical mos Transistor Model valid in all regions of operation and dedicated to low voltage and low current applications
Analog Integrated Circuits and Signal Processing, 1995Co-Authors: Christian Enz, F Krummenacher, Eric A VittozAbstract:Afully analytical MOS Transistor Model dedicated to the design and analysis of low-voltage, low-current analog circuits is presented. All the large-and small-signal variables, namely the currents, the transconductances, the intrinsic capacitances, the non-quasi-static transadmittances and the thermal noise are continuous in all regions of operation, including weak inversion, moderate inversion, strong inversion, conduction and saturation. The same approach is used to derive all the equations of the Model: the weak and strong inversion asymptotes are first derived, then the variables of interest are normalized and linked using an appropriate interpolation function. The Model exploits the inherent symmetry of the device by referring all the voltages to the local substrate. It is shown that the inversion chargeQ inv is controlled by the voltage differenceV P — Vch whereV ch is the channel voltage, defined as the difference between the quasi-Fermi potentials of the carriers. The pinch-off voltageV P is defined as the particular value of Vch, such that the inversion charge is zero for a given gate voltage. It depends only on the gate voltage and can be interpreted as the equivalent effect of the gate voltage referred to the channel. The various modes of operation of the Transistor are then presented in terms of voltagesV P —V S andV P —V D Using the charge sheet Model with the assumption of constant doping in the channel, the drain currentIDis derived and expressed as the difference between a forward componentI F and a reverse componentI R. Each of these is proportional to a function ofV P —V S respectivelyV P —V D through a specific currentI S This function is exponential in weak inversion and quadratic in strong inversion. The current in the moderate inversion region is then Modelled by using an appropriate interpolation function resulting in a continuous expression valid from weak to strong inversion. A quasi-static small-signal Model including the transconductances and the intrinsic capacitances is obtained from an accurate evaluation of the total charges stored on the gate and in the channel. The transconductances and the intrinsic capacitances are Modelled in moderate inversion using the same interpolation function and without any additional parameters. This small-signal Model is then extended to higher frequencies by replacing the transconductances by first order transadmittances obtained from a non-quasi-static calculation. All these transadmittances have the same characteristic time constant which depends on the bias condition in a continuous manner. To complete the Model, a general expression for the thermal noise valid in all regions of operation is derived. This Model has been successfully implemented in several computer simulation programs and has only 9 physical parameters, 3 fine tuning fitting coefficients and 2 additional temperature parameters.
Mohammad Taghi Ahmadi - One of the best experts on this subject based on the ideXlab platform.
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development of solution gated graphene Transistor Model for biosensors
Nanoscale Research Letters, 2014Co-Authors: Hediyeh Karimi, Rubiyah Yusof, Rasoul Rahmani, Hoda Hosseinpour, Mohammad Taghi AhmadiAbstract:The distinctive properties of graphene, characterized by its high carrier mobility and biocompatibility, have stimulated extreme scientific interest as a promising nanomaterial for future nanoelectronic applications. In particular, graphene-based Transistors have been developed rapidly and are considered as an option for DNA sensing applications. Recent findings in the field of DNA biosensors have led to a renewed interest in the identification of genetic risk factors associated with complex human diseases for diagnosis of cancers or hereditary diseases. In this paper, an analytical Model of graphene-based solution gated field effect Transistors (SGFET) is proposed to constitute an important step towards development of DNA biosensors with high sensitivity and selectivity. Inspired by this fact, a novel strategy for a DNA sensor Model with capability of single-nucleotide polymorphism detection is proposed and extensively explained. First of all, graphene-based DNA sensor Model is optimized using particle swarm optimization algorithm. Based on the sensing mechanism of DNA sensors, detective parameters (Ids and Vgmin) are suggested to facilitate the decision making process. Finally, the behaviour of graphene-based SGFET is predicted in the presence of single-nucleotide polymorphism with an accuracy of more than 98% which guarantees the reliability of the optimized Model for any application of the graphene-based DNA sensor. It is expected to achieve the rapid, quick and economical detection of DNA hybridization which could speed up the realization of the next generation of the homecare sensor system.
M C J M Vissenberg - One of the best experts on this subject based on the ideXlab platform.
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theory of the field effect mobility in amorphous organic Transistors
Physical Review B, 1998Co-Authors: M C J M Vissenberg, M MattersAbstract:The field-effect mobility in an organic thin-film Transistor is studied theoretically. From a percolation Model of hopping between localized states and a Transistor Model an analytic expression for the field-effect mobility is obtained. The theory is applied to describe the experiments by Brown et al. [Synth. Met. 88, 37 (1997)] on solution-processed amorphous organic Transistors, made from a polymer (polythienylene vinylene) and from a small molecule (pentacene). Good agreement is obtained, with respect to both the gate voltage and the temperature dependence of the mobility.
M Matters - One of the best experts on this subject based on the ideXlab platform.
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theory of the field effect mobility in amorphous organic Transistors
Physical Review B, 1998Co-Authors: M C J M Vissenberg, M MattersAbstract:The field-effect mobility in an organic thin-film Transistor is studied theoretically. From a percolation Model of hopping between localized states and a Transistor Model an analytic expression for the field-effect mobility is obtained. The theory is applied to describe the experiments by Brown et al. [Synth. Met. 88, 37 (1997)] on solution-processed amorphous organic Transistors, made from a polymer (polythienylene vinylene) and from a small molecule (pentacene). Good agreement is obtained, with respect to both the gate voltage and the temperature dependence of the mobility.