D. K. Ferry

Degeneracy in the ensemble Monte Carlo method for high-field transport in semiconductors

An algorithm to include the Pauli exclusion principle in the Ensemble Monte Carlo method is presented. The results indicate that significant changes in the transport properties of GaAs have to be expected when degenerate conditions are reached. Important repercussions should be found in the modeling of microwave devices, where one often deals with highly doped regions.

Dielectric screening enhanced performance in graphene FET.

We have studied the transport properties of graphene transistors in different solvents with dielectric constant varying over 2 orders of magnitude. Upon increasing the dielectric constant, the carrier mobility increases up to 3 orders of magnitude and reaches approximately 7 x 10(4) cm(2)/v.s at the dielectric constant of approximately 47. This mobility value changes little in higher dielectric constant solvents, which indicates that we are approaching the intrinsic limit of room temperature mobility in graphene supported on SiO(2) substrates. The results are discussed in terms of long-range Coulomb scattering originated from the charged impurities underneath graphene.

Physics of nonlinear transport in semiconductors

The Lectures.- 1. Phenomenological Physics of Hot Carriers in Semiconductors.- The Carrier Temperature Model.- Drift, Diffusion, and Generation-Recombination of Hot Electrons.- The Influence of Classical Magnetic Fields on Hot Electrons.- Hot Electrons in Semiconductor Devices and Layered Structures.- Appendices,.- 2. Electronic Structure of Semiconductors.- The Single Particle Description: Bonds and Bands.- Many-Body Effects on the Electronic Structure of Semiconductors.- 3 The Electron-Phonon Interaction in Semiconductors.- The Adiabatic Approximation.- The Deformation Potential Interaction.- Non-polar Optical Phonon Scattering.- Polar-Optical Interaction.- Piezoelectric Interaction.- A Microscopic Approach.- Applications.- The Electron-Phonon Interaction in Nonperfect Semiconductors.- 4. Semi-Classical Boltzmann Transport Theory in Semiconductors.- Displaced Maxwellian.- Numerical Techniques.- 5. Quantum Transport Theory.- Concepts.- Structure of High Field Quantum Kinetic Theory.- Many-Body Formulation and the Screening Problem.- 6. Carrier-Carrier Interactions and Screening.- The Intercarrier Interaction.- The Critical Concentrations.- Distribution Functions.- 7. Multiphonon Scattering.- Electron-multiphonon Processes.- Electron-Two phonon Processes.- Results.- Summary.- 8. Experimental Studies of Nonlinear Transport in Semiconductors.- Transport Parameters.- Electron Temperature.- Hot Electron Distribution Functions.- Conclusions.- 8a. Time-of-Flight Techniques..- Description of ToF Techniques.- Types of Information Available from ToF Techniques.- Alternative Techniques.- Summary of ToF Most Significant Applications.- 9. Hot-Electron Transport in Quantizing Magnetic Fields.- The Shubnikov-de Haas Effect.- The Magnetophonon Effect.- Magneto-Impurity Resonance.- 10. Hot Electron Distribution Function in Quantizing Magnetic Fields.- Quantitative Estimates of Electron Temperature.- Study of the Electron Distribution Function in Crossed Fields.- Conclusions.- 11. Hot Electron Effects in Semiconductor Devices.- Transient Hot Electron Effects in Semiconductor Devices.- Conclusions.- 12. Optical Excitation of Hot Carriers.- Optical Excitation of Electron-Hole Pairs.- Carrier Heating by Optical Injection.- Band Filling by Optical Excitation.- Oscillatory Photoconductivity and Photoluminescence.- Conclusions.- 13. Theoretical Concepts of Photoexcited Hot Carriers.- The Barker-Hearn Model.- Solution of the Integral Equation.- Photoexcited Holes in Cu-Doped Germanium.- Effects of Optical Phonons, 360 Further Physical Effects.- 14. The Physics of Nonlinear Absorption and Ultrafast Carrier Relaxation in Semiconductors.- Review of the Germanium Band Structure.- Physical Processes.- Initial Models.- Conclusion.- 15. Nonequilibrium Phonon Processes.- Phonon Instabilities.- Phonon Lifetimes.- Steady-State Effects of Nonthermal Phonons.- Some Further Aspects of PH-Disturbances in Solids.- 16. Noise and Diffusion of Hot Carriers.- Fluctuations and Noise: General Considerations.- Noise Temperatures of Hot Carriers.- Diffusion of Hot Carriers.- Experimental Techniques.- Theoretical Determinations.- Noise Sources.- Noise of Hot Carriers in Devices.- Some Quantum Effects.- Conclusion.- The Seminars.- 1. High-Field Transport of Holes in Elemental Semiconductors.- Theoretical Model.- Results and Discussion.- Conclusions.- 2. Nonlinear Transport in Quasi-One-Dimensional Conductors.- Nonlinear Transport in Organic Charge Transfer Salts: TTF-TCNQ and Related Compounds.- Non-Ohmic Effects in KCP.- Non-Ohmic Conductivity of Quasi-ID Trichalcogenides: NbSe3.- Nonlinear Transport in Highly Conducting Polymers.- Summary.- 3. Optical Absorption of Solids Under Laser Irradiation.- Band Structure Effects.- Optical Properties.- Conclusions.- 4. High Intensity Picosecond Photoexcitation of Semiconductors.- Dynamic Saturation of the Optical Absorption.- High Photogenerated-Carrier Densities.- Hot Phonons,.- The Relaxation-Diffusion-Recombination Model.- Summary.- 5. Hot Electron Contributions in Two and Three Terminal Semiconductor Devices.- Two-Terminal Devices.- Three-Terminal Devices.- 6. Modeling of Carrier Transport in the Finite Collision Duration Regime: Effects in Submicron Semiconductor Devices.- The Intracollisional Field Effect.- The Retarded Equations.- Discussion.- 7. On the Physics of Sub-Micron Semiconductor Devices..- Physical Scales and Phenomena.- On Medium Small Devices.- Very Small Scale Devices.- Synergetic Effects and New Device Concepts.- Formal Theory of Coupled Device Arrays.- List of Participants.

Quantum effects in MOSFETs: use of an effective potential in 3D Monte Carlo simulation of ultra-short channel devices

We incorporate an effective potential in a three-dimensional MOSFET simulation, in which the transport is handled by an ensemble Monte Carlo approach. We find that the threshold voltage is shifted and the carrier density is moved away from the interface, both effects given by quantization provided within the channel. However, the mean velocity of the carriers is not affected significantly by the introduction of this effective potential, and is only reduced by about 10%.

A Wigner function-based quantum ensemble Monte Carlo study of a resonant tunneling diode

We present results of resonant tunneling diode operation achieved from a particle-based quantum ensemble Monte Carlo (EMC) simulation that is based on the Wigner distribution function (WDF). Methods of including the Wigner potential into the EMC, to incorporate natural quantum phenomena, via a particle property we call the affinity are discussed. Dissipation is included via normal Monte Carlo procedures and the solution is coupled to a Poisson solver to achieve fully selfconsistent results.

Electron transport properties of a strained Si layer on a relaxed Si1−xGex substrate by Monte Carlo simulation

The in‐plane transport properties of a strained (100) Si layer on a relaxed Si1−xGex substrate are studied with an ensemble Monte Carlo technique. Similar velocity (‐field) characteristics are found for strained Si with any valley splitting energy ΔE≥0.1 eV. These phonon‐limited electron mobilities reach 4000 cm2/V s at 300 K, and 23 000 cm2/V s at 77 K. There is only a slight increase in the saturation velocity at both temperatures. However, a significant overshoot peak transient velocity is found to depend upon ΔE, and for ΔE=0.4 eV, reaches 4.1×107 cm/s at 300 K, and 5.2×107 cm/s at 77 K.

Scaled silicon MOSFETs: degradation of the total gate capacitance

We use a fully quantum-mechanical model to study the influence of image and exchange-correlation effects on the inversion layer and total gate capacitance in scaled Si MOSFETs. We show that, when the device is in weak and moderate inversion, the inclusion of image and many-body exchange-correlation effects increases both the inversion layer and total gate capacitances and shifts the N/sub s/=N/sub s/(VG) characteristics of the device toward lower gate voltages.

MODFET Ensemble Monte Carlo model including the quasi-two-dimensional electron gas

We present an ensemble Monte Carlo model for the modulation-doped field-effect transistor in which quantization in the conduction channel is included using a two-subband triangular-well approximation. The subband population is investigated under different bias conditions in order to evaluate the influence of quantum effects on the electron conduction. It is found that, according to the model, the subband population may be severely reduced at high drain voltages, and that the appearance of stray conduction paths across the AlGaAs region may be a source of performance degradation.

Nanowires in Nanoelectronics

Connecting circuit layers with nanowires and nanotransistors may bring about a paradigm shift in microchip design.

Time-resolved Raman studies of the decay of the longitudinal optical phonons in wurtzite GaN

Decay of the longitudinal-optical (LO) phonons in wurtzite GaN has been studied by subpicosecond time-resolved Raman spectroscopy. Our experimental results show that among the various possible decay channels, the LO phonons in wurtzite GaN decay primarily into a large wave-vector TO and a large wave-vector LA or TA phonon. These experimental results are consistent with the recent theoretical calculations of the phonon dispersion curves for wurtzite GaN.Decay of the longitudinal-optical (LO) phonons in wurtzite GaN has been studied by subpicosecond time-resolved Raman spectroscopy. Our experimental results show that among the various possible decay channels, the LO phonons in wurtzite GaN decay primarily into a large wave-vector TO and a large wave-vector LA or TA phonon. These experimental results are consistent with the recent theoretical calculations of the phonon dispersion curves for wurtzite GaN.