Molecular beam epitaxy (MBE)-grown L/sub g/=1.7- mu m pseudomorphic Al/sub 0.38/Ga/sub 0.62/As/n/sup +/-In/sub 0.15/Ga/sub 0.85/As metal-insulator-doped channel FETs (MIDFETs) are presented that display extremely broad plateaus in both f/sub T/ and f/sub max/ versus V/sub GS/, with f/sub T/ sustaining 90% of its peak over a gate swing of 2.6 V. Drain current is highly linear with V/sub GS/ over this swing, reaching 514 mA/mm. No frequency dispersion in g/sub m/ up to 3 GHz was found, indicating the absence of electrically active traps in the undoped AlGaAs pseudoinsulator layer. These properties combine to make the pseudomorphic MIDFET highly suited to linear, large-signal, broadband applications. >

A pseudomorphic AlGaAs/n/sup +/-InGaAs metal-insulator-doped channel FET for broad-band, large-signal applications

Fermi-level pinning phenomena due to DX centers in AlGaAs/GaAs HEMTs (high electron mobility transistors) are analyzed using two-dimensional numerical simulation based on a drift-diffusion model A DX center model is introduced assuming Fermi-Dirac statistics for ionized donor density with the aluminum mole fraction dependence of the deep-donor energy level The calculated results reveal that the decrease in transconductance of AlGaAs/GaAs HEMTs in a high-gate-bias region is caused by the existence of DX centers This is because the Fermi level is pinned at deep-donor levels in the n-AlGaAs layer Furthermore, the superiority of AlGaAs/InGaAs pseudomorphic HEMTs is discussed in terms of the Fermi-level pinning >

/pdf/two-dimensional-numerical-simulation-of-fermi-level-pinning-5fsacilqaw.pdf

Two-dimensional numerical simulation of Fermi-level pinning phenomena due to DX centers in AlGaAs/GaAs HEMTs

High-frequency measurements at cryogenic temperatures to 125 K of 0.3- mu m gate length GaAs-Al/sub 0.3/Ga/sub 0.7/As metal-insulator-semiconductor field-effect transistors (MISFETs) with a doped channel are discussed. Experimental results demonstrate significant improvement in performance including an increase in the maximum frequency of oscillation from 70 to 81 GHz and an increase in the unity current gain cutoff frequency from 46 to 57 GHz. Independently determined decreases in electron mobility and increases in electron velocity under similar conditions lead to the conclusion that carrier velocity and not mobility controls transport in these devices. These results show the high-speed potential of doped channel MISFETs at both room temperature and cryogenic temperatures. >

Characteristics of GaAs/AlGaAs-doped channel MISFET's at cryogenic temperatures

Mimo pid controllers synthesis using orthogonal functions

A two-dimensional finite-difference analysis is used to simulate the current flow and charge distribution in undoped AlGaAs/GaAs MODFET structures called heterostructure insulated-gate field-effect transistors (HIGFETs). How an electron channel can be induced at the AlGaAs/GaAs interface when there is no doped supply layer is studied. The origins of the charge in this channel are studied by comparing its behavior in equilibrium with that when a current flows. By considering the different geometries of a Schottky gate and implanted source and drain contacts, the interrelationship between gate control and electron injection from the doped contact regions is shown and a graphic view of the origins of the interfacial charge in a HIGFET is given. >

The importance of contact injection in undoped AlGaAs/GaAs heterostructures

A study of DX centres in AlGaAs layers is presented, both experimental and theoretical. It is shown that owing to DX centres, at room temperature, the microwave transconductance of HEMTs can be considerably higher than that obtained from the DC regime, and approaches the values which could be expected if DX centres did not exist. As a result, for room temperature applications, special structures designed to eliminate DX centres are not really necessary.

Investigation of influence of DX centres on HEMT operation at room temperature

A very simple analytical relation, without any fitting parameters, between the gate current in a HIGFET or SISFET and the 2D electron concentration giving rise to the drain current is proposed. The theoretical background which allows us to obtain this relation is first presented. Then good agreement is shown with experimental results obtained with an AlGaAs/GaAs HIGFET. Lastly, characteristics of structures which should yield high values of 2D electron concentration without too high a value of gate current are discussed.

Gate current and 2D electron concentration in HIGFET and SISFET

A method of Field Effect Transistor modeling is described which is simple enough to be implemented on a microcomputer and sufficiently realistic to account for all physical phenomena occurring in the device. Our aim is to achieve a simulator which allows device optimization and real-time control of technological processes with fabrication, as well. We describe the methodology used in order to obtain all the electrical characteristics of the transistor as functions of the electrical and geometrical features of the designed structure. Examples of applications are demonstrated for the GaAs MESFET, the TEGFET and the AlGaAs/GaAs MISFET (or HIGFET) On se propose de decrire une methode de modelisation du transistor a effet de champ suffisamment simple pour etre utilisable sur microordinateur et neanmoins suffisamment realiste pour tenir compte de l'ensemble des phenomenes physiques se produisant dans le composant. Il s'agit en effet de mettre au point un procede permettant l'optimisation et le controle en temps reel des procedes technologiques de realisation du composant. Apres avoir decrit la methodologie suivie pour obtenir l'ensemble des caracteristiques electriques du transistor en fonction des caracteristiques electriques et geometriques de la structure utilisee, on decrit ensuite quelques exemples d'applications du modele au MESFET AsGa, au TEGFET, et enfin au MISFET (ou HIGFET) AlGaAs/GaAs

/pdf/methode-generale-de-modelisation-du-transistor-a-effet-de-cpu2pzgj97.pdf

Méthode générale de modélisation du transistor à effet de champ à hétérojonction

A novel method for modelling field effect transistors is described. It is applied to the study of a number of devices like FETs, MODFETs, SISFETs, DMTs and multiple HEMTs. This method includes the most important physical effects occuring in these devices, but it is very simple and easy to implement on a microcomputer. It is used for the control of technological device processes realized in the laboratory as well as for designing more efficient structures.

http://ieeexplore.ieee.org/iel2/706/573/00015346.pdf

Centre Hyperfrequences et Semiconducteurs Universite des Sciences et Techniques de Lille Flandres Artois

A novel method for modelling field effect transistors (FETs) is described It is applied to the study of a number of devices, including FETs, MODFETs, SISFETs, DMTs and multiple HEMTs (high-electron-mobility transistors) This method includes the most important physical effects in these devices, but is very simple and easy to implement on a microcomputer It is used for the control of technological device processes realized in the laboratory as well as for the design of more efficient structures >

A novel method for the modelling and the design of MESFETs and of any kind of heterojunction FET

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