The Experts below are selected from a list of 9351 Experts worldwide ranked by ideXlab platform

Robert W. Dutton - One of the best experts on this subject based on the ideXlab platform.

  • High-frequency noise in nanoscale metal oxide semiconductor field effect transistors
    Journal of Applied Physics, 2007
    Co-Authors: Reza Navid, Christoph Jungemann, Thomas H. Lee, Robert W. Dutton
    Abstract:

    The noise characteristics of today’s short-channel Devices are shown to have a better resemblance to ballistic Devices than to long-channel metal oxide semiconductor field effect transistors (MOSFETs). Therefore the noise characteristics of these Devices are best modeled using a ballistic-MOSFET-based noise model. Extensive Hydrodynamic Device simulations are presented in support of this hypothesis and a simple compact model is introduced. This model is used for predicting the noise behavior of future nanoscale Devices. Most of the findings of this work can also be applied to carbon nanotubes and nanowires because of their similarities to MOSFETs.

  • Accuracy assessment of compact RF noise models for SiGe HBTs by Hydrodynamic Device simulation
    Noise in Devices and Circuits II, 2004
    Co-Authors: Christoph Jungemann, Bernd Meinerzhagen, Burkhard Neinhues, Robert W. Dutton
    Abstract:

    The accuracy of the SPICE and unified compact noise models is assessed in the RF range by comparison with the Hydrodynamic Device model for a state-of-the-art SiGe HBT with a low base resistance. Despite the low base resistance, as a general result, it turns out that the noise is dominated by the thermal fluctuations of the holes within the base and the exact determination of the base noise resistance is a prerequisite for accurate compact noise modeling. It is shown that the base noise resistance equals the base resistance and can be evaluated with standard parameter extraction schemes. Based on an accurate base resistance the SPICE model yields good results as long as the frequency is considerably below the peak cutoff frequency. The unified model, on the other hand, is found to yield good results even at frequencies comparable to the peak cutoff frequency. But this is achieved at the expense of an additional parameter which is difficult to determine without physics-based numerical noise simulation. Moreover, it is shown that the drift-diffusion model should not be used to assess the accuracy of compact noise models, because it yields erroneous noise results for state-of-the-art SiGe HBTs.

  • Investigation of compact models for RF noise in SiGe HBTs by Hydrodynamic Device simulation
    IEEE Transactions on Electron Devices, 2004
    Co-Authors: Christoph Jungemann, B. Neinhus, Bernd Meinerzhagen, Robert W. Dutton
    Abstract:

    A comprehensive investigation of the SPICE and unified compact noise models is performed by comparison with the more fundamental hierarchical Hydrodynamic Device model. It is shown that the rather simple SPICE and unified compact noise models yield good results for frequencies up to 10 GHz for state-of-the-art SiGe HBTs with a low base resistance. The base noise resistance, a key parameter of the compact noise models turns out to be independent of frequency and bias. It can be well estimated based on the sheet resistance of the intrinsic and extrinsic base or with the modified circle-fit method. The unified model, which in comparison to the SPICE model considers in addition the finite transit time of shot noise, is found to be somewhat more accurate than the SPICE model, especially at higher frequencies and collector currents. But this is achieved at the expense of a transit time parameter which cannot be determined without accurate and detailed noise measurements or physics-based numerical simulations.

  • Investigation of Compact Models for RF Noise in
    2004
    Co-Authors: Christoph Jungemann, B. Neinhus, Bernd Meinerzhagen, Robert W. Dutton
    Abstract:

    A comprehensive investigation of the SPICE and unified compact noise models is performed by comparison with the more fundamental hierarchical Hydrodynamic Device model. It is shown that the rather simple SPICE and unified compact noise models yield good results for frequencies up to 10 GHz for state-of-the-art SiGe HBTs with a low base resistance. The base noise resistance, a key parameter of the compact noise models turns out to be independent of frequency and bias. It can be well estimated based on the sheet resistance of the intrinsic and extrinsic base or with the modified circle-fit method. The unified model, which in comparison to the SPICE model considers in addition the finite transit time of shot noise, is found to be somewhat more accurate than the SPICE model, especially at higher frequencies and collector currents. But this is achieved at the expense of a transit time parameter which cannot be determined without accurate and detailed noise measurements or physics-based numerical simulations.

  • Simulation of the Hydrodynamic Device model on distributed memory parallel computers
    IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, 1996
    Co-Authors: Narayana R Aluru, Kincho H. Law, Robert W. Dutton
    Abstract:

    Stable and robust finite element methods for the convective Hydrodynamic model of semiconductor Devices are developed and implemented on distributed memory parallel computers. Specifically, a stable and accurate space-time and Galerkin/least-squares finite element formulation is developed for the Hydrodynamic transport equations for the conservation laws. In addition, Galerkin finite element methods are employed for the Poisson and lattice thermal diffusion equations. The inclusion of the lattice thermal diffusion equation in the numerical solution of the convective Hydrodynamic model is presented for the first time. Numerical results for a bipolar transistor are included to illustrate the effectiveness of the numerical methods. Numerical simulations of semiconductor Devices using the convective Hydrodynamic model require a significant amount of computations. A single-program-multiple-data (SPMD) programming model is proposed for the implementation of the Hydrodynamic model on distributed memory parallel computers. Employing the SPMD programming model, a serial program developed on a workstation can be converted into a parallel program with minimal changes. The parallel program has been ported to a wide range of distributed memory parallel computers including the iPSC/860 hypercube, the Touchstone Delta machine, and the IBM SP-1. Parallel performance results are reported for a bipolar transistor, silicon MESFET and diodes. The results indicate that the parallel Hydrodynamic Device simulator exhibits excellent speedups and scalability on distributed memory parallel computers with minimum communication overhead.

Joh V. Ringwood - One of the best experts on this subject based on the ideXlab platform.

  • Hierarchical Robust Control of Oscillating Wave Energy Converters With Uncertain Dynamics
    IEEE Transactions on Sustainable Energy, 2014
    Co-Authors: Francesco Fusco, Joh V. Ringwood
    Abstract:

    Energy-maximizing controllers for wave energy Devices are normally based on linear Hydrodynamic Device models. Such models ignore nonlinear effects which typically manifest themselves for large Device motion (typical in this application) and may also include other modeling errors. The effectiveness of a controller is, in general, determined by the match between the model the controller is based on and the actual system dynamics. This match becomes especially critical when the controller is highly tuned to the system. In this paper, we present a methodology for reducing this sensitivity to modeling errors and nonlinear effects by the use of a hierarchical robust controller, which shows small sensitivity to modeling errors, but allows good energy maximization to be recovered through a passivity-based control approach.

  • CCA - Robust Control of Wave Energy Converters
    2014 IEEE Conference on Control Applications (CCA), 2014
    Co-Authors: Francesco Fusco, Joh V. Ringwood
    Abstract:

    Energy-maximising controllers for wave energy Devices are normally based on linear Hydrodynamic Device models. Such models ignore nonlinear effects which typically manifest themselves for large Device motion (typical in this application) and may also include other modelling errors. In this paper, we present a methodology for reducing the sensitivity to modelling errors and nonlinear effects by the use of a hierarchical robust controller, which also allows good energy maximisation to be recovered through a passivity-based control approach. I. INTRODUCTION The use of energy-maximising control has been accepted as crucial to the development of economic wave-energy conversion (WEC) (1), allowing the effective bandwidth of WECs to be increased, generating a near resonance condition at a wide range of wave frequencies. Despite the prevalent use of linear models in WEC evaluation, simulation and control (2), (3), there is an ac- knowledgement that such models are relatively simplistic in their representation of many nonlinear effects, including nonlinear Froude-Krylov forces (4), (5) and viscous drag forces (6), (7). In particular, the concept of linearisation around an equilibrium point (the zero displacement point) where operation is in the region of this equilibrium point is often violated, since the objective is to amplify the WEC motion (via resonance) in order to maximise energy capture. The achievement of resonance also produces large Device velocities (particularly in large seas), resulting in significant viscous drag forces and vortex shedding. The danger is that energy maximising controllers based on linear models may become significantly mismatched with the real WEC dynamics over significant portions of the operational space, if such controllers are sensitive to variations in the model. The result of such a mismatch will be significant reduction in energy capture, with consequences for the economic performance of the WEC Device. However, linear models are attractive due to intuitive connection with physical Device quantities, their compact algebraic representation (permitting model-based control de- sign) and their relatively low computational overhead. An ideal situation, therefore, is that we utilise a linear model for WEC control, but address the issues associated with a lack of fidelity of the model for more significant Device motion. This is addressed as follows:

Bernd Meinerzhagen - One of the best experts on this subject based on the ideXlab platform.

  • Accuracy assessment of compact RF noise models for SiGe HBTs by Hydrodynamic Device simulation
    Noise in Devices and Circuits II, 2004
    Co-Authors: Christoph Jungemann, Bernd Meinerzhagen, Burkhard Neinhues, Robert W. Dutton
    Abstract:

    The accuracy of the SPICE and unified compact noise models is assessed in the RF range by comparison with the Hydrodynamic Device model for a state-of-the-art SiGe HBT with a low base resistance. Despite the low base resistance, as a general result, it turns out that the noise is dominated by the thermal fluctuations of the holes within the base and the exact determination of the base noise resistance is a prerequisite for accurate compact noise modeling. It is shown that the base noise resistance equals the base resistance and can be evaluated with standard parameter extraction schemes. Based on an accurate base resistance the SPICE model yields good results as long as the frequency is considerably below the peak cutoff frequency. The unified model, on the other hand, is found to yield good results even at frequencies comparable to the peak cutoff frequency. But this is achieved at the expense of an additional parameter which is difficult to determine without physics-based numerical noise simulation. Moreover, it is shown that the drift-diffusion model should not be used to assess the accuracy of compact noise models, because it yields erroneous noise results for state-of-the-art SiGe HBTs.

  • Investigation of compact models for RF noise in SiGe HBTs by Hydrodynamic Device simulation
    IEEE Transactions on Electron Devices, 2004
    Co-Authors: Christoph Jungemann, B. Neinhus, Bernd Meinerzhagen, Robert W. Dutton
    Abstract:

    A comprehensive investigation of the SPICE and unified compact noise models is performed by comparison with the more fundamental hierarchical Hydrodynamic Device model. It is shown that the rather simple SPICE and unified compact noise models yield good results for frequencies up to 10 GHz for state-of-the-art SiGe HBTs with a low base resistance. The base noise resistance, a key parameter of the compact noise models turns out to be independent of frequency and bias. It can be well estimated based on the sheet resistance of the intrinsic and extrinsic base or with the modified circle-fit method. The unified model, which in comparison to the SPICE model considers in addition the finite transit time of shot noise, is found to be somewhat more accurate than the SPICE model, especially at higher frequencies and collector currents. But this is achieved at the expense of a transit time parameter which cannot be determined without accurate and detailed noise measurements or physics-based numerical simulations.

  • Impact of the Floating Body Effect on Noise in SOI Devices Investigated by Hydrodynamic Simulation
    Simulation of Semiconductor Processes and Devices 2004, 2004
    Co-Authors: Christoph Jungemann, B. Neinhus, C.d. Nguyen, Bernd Meinerzhagen
    Abstract:

    Without a tie, the body of an SOI Devices floats and majority carrier generation causes a kink in the output characteristics. The underlying feedback mechanism strongly amplifies the noise at low frequencies. This effect is investigated for the first time by 2D bipolar Hydrodynamic Device simulation including a quantum correction and consistent mobility and noise models for the channel. The simulations reproduce the noise behavior observed experimentally and support the conclusions drawn based on analytical modeling. Not only noise due to impact ionization but also due to other generation/recombination processes is found to be amplified by the floating body effect.

  • Investigation of Compact Models for RF Noise in
    2004
    Co-Authors: Christoph Jungemann, B. Neinhus, Bernd Meinerzhagen, Robert W. Dutton
    Abstract:

    A comprehensive investigation of the SPICE and unified compact noise models is performed by comparison with the more fundamental hierarchical Hydrodynamic Device model. It is shown that the rather simple SPICE and unified compact noise models yield good results for frequencies up to 10 GHz for state-of-the-art SiGe HBTs with a low base resistance. The base noise resistance, a key parameter of the compact noise models turns out to be independent of frequency and bias. It can be well estimated based on the sheet resistance of the intrinsic and extrinsic base or with the modified circle-fit method. The unified model, which in comparison to the SPICE model considers in addition the finite transit time of shot noise, is found to be somewhat more accurate than the SPICE model, especially at higher frequencies and collector currents. But this is achieved at the expense of a transit time parameter which cannot be determined without accurate and detailed noise measurements or physics-based numerical simulations.

  • Noise Analysis for a SiGe HBT by Hydrodynamic Device Simulation
    32nd European Solid-State Device Research Conference, 2002
    Co-Authors: Christoph Jungemann, Burkhard Neinhues, Bernd Meinerzhagen
    Abstract:

    A detailed analysis of the terminal current noise for a realistic SiGe HBT by HydrodynamicDevice simulation including noise due to electron scattering, hole scattering, Shockley-Read-Hallrecombination,andimpactionization is presented for the first time. It is shown that close to high injection the collector current noise exceeds the corresponding shot noise due to hole scattering within the base. The cross-correlation spectrum of the base and collector current fluctuations is found to be not negligible as often assumed in compact models.

J F Gibbons - One of the best experts on this subject based on the ideXlab platform.

  • fabrication and analysis of deep submicron strained si n mosfet s
    IEEE Transactions on Electron Devices, 2000
    Co-Authors: J L Hoyt, J F Gibbons
    Abstract:

    Deep submicron strained-Si n-MOSFETs were fabricated on strained Si/relaxed Si/sub 0.8/Ge/sub 0.2/ heterostructures. Epitaxial layer structures were designed to yield well-matched channel doping profiles after processing, allowing comparison of strained and unstrained Si surface channel Devices. In spite of the high substrate doping and high vertical fields, the MOSFET mobility of the strained-Si Devices is enhanced by 75% compared to that of the unstrained-Si control Devices and the state-of-the-art universal MOSFET mobility. Although the strained and unstrained-Si MOSFETs exhibit very similar short-channel effects, the intrinsic transconductance of the strained Si Devices is enhanced by roughly 60% for the entire channel length range investigated (1 to 0.1 /spl mu/m) when self-heating is reduced by an ac measurement technique. Comparison of the measured transconductance to Hydrodynamic Device simulations indicates that in addition to the increased low-field mobility, improved high-field transport in strained Si is necessary to explain the observed performance improvement. Reduced carrier-phonon scattering for electrons with average energies less than a few hundred meV accounts for the enhanced high-field electron transport in strained Si. Since strained Si provides Device performance enhancements through changes in material properties rather than changes in Device geometry and doping, strained Si is a promising candidate for improving the performance of Si CMOS technology without compromising the control of short channel effects.

M.f. Zybura - One of the best experts on this subject based on the ideXlab platform.

  • 125–145 GHz stable depletion layer transferred electron oscillators
    Solid-state Electronics, 1996
    Co-Authors: M.f. Zybura, Stephen H. Jones, J.d. Crowley, J.e. Carlstrom
    Abstract:

    Abstract In this paper, the improved performance of transferred electron Devices utilizing current limiting contacts is clearly illuminated. With the appropriate cathode contact, these Devices operate in a novel stable depletion layer mode characterized by an oscillating stable depletion layer rather than an unstable propagating accumulation layer or dipole. A small-signal model is offered to explain the stable small-signal resistance of the Device over a broad frequency range. Large-signal analysis is completed using a Hydrodynamic Device simulator employing the temperature-dependent drift-diffusion equation and Poisson's equation combined with a novel harmonic-balance circuit analysis technique. Analysis of the electric fields, electron concentration, and Device temperature is included for steady-state large-signal operation. Embedding impedances are extracted for a D-band cavity, and performance comparisons are made with experimental data for second-harmonic operation from 125 to 145 GHz with excellent correlation. High reliability operation and as much as 65 mW of output power at 138 GHz is achievable.

  • 125–145 GHz stable depletion layer transferred electron oscillators
    Solid-State Electronics, 1996
    Co-Authors: M.f. Zybura, Stephen H. Jones, J.d. Crowley, B.w. Lim, J.e. Carlstrom
    Abstract:

    Abstract In this paper, the improved performance of transferred electron Devices utilizing current limiting contacts is clearly illuminated. With the appropriate cathode contact, these Devices operate in a novel stable depletion layer mode characterized by an oscillating stable depletion layer rather than an unstable propagating accumulation layer or dipole. A small-signal model is offered to explain the stable small-signal resistance of the Device over a broad frequency range. Large-signal analysis is completed using a Hydrodynamic Device simulator employing the temperature-dependent drift-diffusion equation and Poisson's equation combined with a novel harmonic-balance circuit analysis technique. Analysis of the electric fields, electron concentration, and Device temperature is included for steady-state large-signal operation. Embedding impedances are extracted for a D-band cavity, and performance comparisons are made with experimental data for second-harmonic operation from 125 to 145 GHz with excellent correlation. High reliability operation and as much as 65 mW of output power at 138 GHz is achievable.

  • Simulation of 100-300 GHz solid-state harmonic sources
    IEEE Transactions on Microwave Theory and Techniques, 1995
    Co-Authors: M.f. Zybura, J.r. Jones, S.h. Jones, G.b. Tait
    Abstract:

    Accurate and efficient simulations of the large-signal time-dependent characteristics of second-harmonic transferred electron oscillators (TEO's) and heterostructure barrier varactor (HBV) frequency triplers have been obtained. This is accomplished by using a novel and efficient harmonic-balance circuit analysis technique which facilitates the integration of physics-based Hydrodynamic Device simulators. The integrated Hydrodynamic Device/harmonic-balance circuit simulators allow TEO and HBV circuits to be co-designed from both a Device and a circuit point of view. Comparisons have been made with published experimental data for both TEO's and HBV's. For TEO's, excellent correlation has been obtained at 140 GHz and 188 GHz in second-harmonic operation. Excellent correlation has also been obtained for HBV frequency triplers operating near 200 GHz. For HBV's, both a lumped quasi-static equivalent circuit model and the Hydrodynamic Device simulator have been linked to the harmonic-balance circuit simulator. This comparison illustrates the importance of representing active Devices with physics-based numerical Device models rather than analytical Device models. >

  • Heterostructure barrier varactor simulation using an integrated Hydrodynamic Device/harmonic-balance circuit analysis technique
    IEEE Microwave and Guided Wave Letters, 1994
    Co-Authors: J.r. Jones, S.h. Jones, G.b. Tait, M.f. Zybura
    Abstract:

    Accurate and efficient simulations of the large-signal time-dependent behaviour of GaAs-AlGaAs Heterostructure Barrier Varactor (REV) frequency tripler circuits have been obtained. This is accomplished by combining a novel harmonic-balance circuit analysis technique with a physics-based Hydrodynamic Device simulator. The integrated HBV Hydrodynamic Device/harmonic-balance circuit simulator allows HBV multiplier circuits to be co-designed from both a Device and a circuit point of view. Comparisons are made with the experimental results of Choudhury et al. (see IEEE Trans. Microwave Theory Tech., vol. 41, no. 4, p. 595-9, 1993) for GaAs-AlGaAs HBV frequency triplers operating near 200 GHz. These comparisons illustrate the importance of representing active Devices with physics-based numerical Device models rather than analytical Device models based on lumped quasi-static equivalent circuits. >

  • 100-300 GHz Gunn oscillator simulation through harmonic balance circuit analysis linked to a Hydrodynamic Device simulator
    IEEE Microwave and Guided Wave Letters, 1994
    Co-Authors: M.f. Zybura, G.b. Tait, S.h. Jones, J.r. Jones
    Abstract:

    Accurate and efficient calculations of the large-signal AC behavior of second-harmonic InP transferred electron oscillators (TEOs) are presented. This is accomplished by combining a novel harmonic balance circuit analysis technique with a Hydrodynamic Device simulator employing the temperature dependent drift and diffusion equations. The electron transport simulations include a detailed heat flow analysis to update the temperature profile in the Device. The nonlinear circuit analysis utilizes a fixed-point iterative method derived from the robust multiple reflection algorithm. To expedite the process and aid in convergence, an acceleration technique is also employed in this algorithm. The associated reduction in computation time allows for the inclusion of a Hydrodynamic treatment of the transferred electron Device (TED) using the modified drift and diffusion equations. Comparisons are made with the published experimental data reported by Rydberg on second-harmonic 188 GHz InP TEOs. >