A detailed full-wave time-domain simulation model for the analysis of electromagnetic effects on the behavior of the submicrometer-gate field-effect transistor (FET's) is presented. The full wave simulation model couples a three-dimensional (3-D) time-domain solution of Maxwell's equations to the active device model. The active device model is based on the moments of the Boltzmann's transport equation obtained by integration over the momentum space. The coupling between the two models is established by using fields obtained from the solution of Maxwell's equations in the active device model to calculate the current densities inside the device. These current densities are used to update the electric and magnetic fields. Numerical results are generated using the coupled model to investigate the effects of electron-wave interaction on the behavior of microwave FET's. The results show that the voltage gain increases along the device width. While the amplitude of the input-voltage wave decays along the device width, due to the electromagnetic energy loss to the conducting electrons, the amplitude of the output-voltage wave increases as more and more energy is transferred from the electrons to the propagating wave along the device width. The simulation confirms that there is an optimum device width for highest voltage gain for a given device structure. Fourier analysis is performed on the device output characteristics to obtain the gain-frequency and phase-frequency dependencies. The analysis shows a nonlinear energy build-up and wave dispersion at higher frequencies.

Electromagnetic wave effects on microwave transistors using a full-wave time-domain model

Models of semiconductor devices that combine complex transport models with full-wave solutions of Maxwell's equations are reviewed. Both hydrodynamic and ensemble Monte Carlo transport models are studied. The coupling of such transport models with electrodynamics is discussed and sample results are presented. The physical consistency of the models is considered and some open computational challenges are reviewed.

A review of global modeling of charge transport in semiconductors and full-wave electromagnetics

Using a two-dimensional hydrodynamic energy model incorporating nonstationary electron dynamics and nonisothermal electron transport (which characterizes submicron-gate MODFETs), the main physical phenomena that govern the device performance at 300 K are highlighted. This covers velocity overshoot effects, stationary-domain formation, and real space transfer. The model is then used systematically to predict the precise values of the small-signal parameters for different bias conditions. The potential performance improvement achieved by reducing the gate length below 0.2 mu m is investigated. It is shown that improvement in transconductance is achieved through gate-length reduction if a severe restriction on the aspect ratio is respected. >

MODFET 2-D hydrodynamic energy modeling: optimization of subquarter-micron-gate structures

Integrated micro electro mechanical systems (iMEMS) include sensors, actuators and circuits made by silicon IC technology combined with micromachining, deposition or electroplating. We present two essential iMEMS development tools: (i) the data base ICMAT of material parameters obtained from measuring process-dependent IC thin film electrical, magnetic, thermal and mechanical properties by using dedicated materials characterisation microstructures and (ii) the toolbox SOLIDIS, providing coupled numerical modelling of the electrical, magnetic, thermal and mechanical phenomena and their boundary and interface conditions occurring in iMEMS devices in a uniform and consistent environment.

Simulation of Semiconductor Devices and Processes

Based on the use of micro electro-mechanical system (MEMS) switches this paper presents a composite right/left-handed (CRLH) transmission line (TL) with a reconflgurable behaviour. The design strategy here adopted consists on the use of metal-insulator- metal (MIM) capacitors and short-circuited stubs resulting in a very compact and monolithic CRLH unit cell well suited for phase shifter applications.

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Design of a 3-State Reconfigurable CRLH Transmission Line Based on MEMS Switches

The surface potential effect in GaAs MESFETs causes a depleted zone to form not only between the source and gate, but also between the gate and drain. The consequences of this phenomenon on the device behavior, the DC and AC characteristics, and the expected performance are studied. For this purpose, a two-dimensional resolution of the basic semiconductor equations is used. This model takes into account relaxation effects by including an energy relaxation equation. The dependence of MESFET characteristics such as transconductance, output conductance, and capacitance on the dimensions of the zone where surface potential effects occur is given. Some interesting conclusions concerning the optimization of recessed-gate structures are drawn. >

Two-dimensional simulation of submicrometer GaAs MESFETs: surface effects and optimization of recessed gate structures

This paper presents a method to construct composite right/left-handed transmission line using coupled lines. A general procedure to design a composite right/left-handed unit cell is presented. The procedure was used on a specific coupled line configuration, which is the coupled microstrip lines with slotted ground. It is shown that by proper design of the slotted ground, the coupling between the two microstrip lines can be increased dramatically keeping practical dimensions for the coupled line width and spacing. Moreover, with accurate slotted ground design, equal even and odd electrical lengths can be achieved. The performance of this composite right/left-handed line, which is characterized by backward waves with phase advance, is demonstrated by both simulated and measured results and they show good agreement. The realized composite right/left-handed transmission line has a broad bandwidth and small size.

/pdf/realization-of-composite-right-left-handed-transmission-line-3iaxpk0140.pdf

Realization of composite right/left-handed transmission line using coupled lines

A novel 2-D numerical model incorporating nonstationary electron dynamics is used to investigate the complex transport phenomena governing the operation of sub-micron gate GaAs MESFET's. A detailed theoretical analysis of different phenomena observed in subhalf micron devices is given. These include velocity overshoot, stationary and travelling domain formation, soft pinch off, excess drain current etc. The small signal parameters g m , g d and C gs and their dependence on bias condition are evaluated. The effects of physical quantities such as mobility and interface barrier on carrier injection and transport and consequently on device performance are presented.

Performance analysis of sub-micron gate GaAs MESFETs

This paper presents a realization of composite right/left handed transmission lines using coupled microstrip lines. This structure exploits the advantages of the microstrip lines, while increases the coupling by a ∞oating conductor at the ground plane. The performance of this composite right/left-handed line is demonstrated by both simulated and measured results, and they show good agreement. The designed line has broad bandwidth with low losses and small size. A novel dominant mode leaky wave antenna design, using the previous structure, is presented with backward to forward scanning capability.

https://www.jpier.org/pierl/pierl11/05.09080901.pdf

Osman Lotfy Elsayed

Papers

MODFET 2-D hydrodynamic energy modeling: optimization of subquarter-micron-gate structures

Two-dimensional simulation of submicrometer GaAs MESFETs: surface effects and optimization of recessed gate structures

Realization of composite right/left-handed transmission line using coupled lines

Performance analysis of sub-micron gate GaAs MESFETs

Leaky Wave Antenna Realization by Composite Right/Left-Handed Transmission Line