Oana Moldovan

Explicit Analytical Charge and Capacitance Models of Undoped Double-Gate MOSFETs

An analytical, explicit, and continuous-charge model for undoped symmetrical double-gate (DG) MOSFETs is presented. This charge model allows obtaining analytical expressions of all total capacitances. The model is based on a unified-charge-control model derived from Poissons equation and is valid from below to well above threshold, showing a smooth transition between the different regimes. The drain current, charge, and capacitances are written as continuous explicit functions of the applied bias. We obtained very good agreement between the calculated capacitance characteristics and 2-D numerical device simulations, for different silicon film thicknesses.

Explicit Drain-Current Model of Graphene Field-Effect Transistors Targeting Analog and Radio-Frequency Applications

We present a compact physics-based model of the current-voltage characteristics of graphene field-effect transistors, of especial interest for analog and RF applications where band-gap engineering of graphene could be not needed. The physical framework is a field-effect model and drift-diffusion carrier transport. Explicit closed-form expressions have been derived for the drain current continuously covering all operation regions. The model has been benchmarked with measured prototype devices, demonstrating accuracy and predictive behavior. Finally, we show an example of projection of the intrinsic gain as a figure of merit commonly used in RF/analog applications.

Analytical Charge and Capacitance Models of Undoped Cylindrical Surrounding-Gate MOSFETs

We present an analytical and continuous charge model for cylindrical undoped surrounding-gate MOSFETs, from which analytical expressions of all total capacitances are obtained. The model is based on a unified charge control model derived from Poisson equation. The drain current, charge, and capacitances are written as continuous explicit functions of the applied voltages. The calculated capacitance characteristics show excellent agreement with three-dimensional numerical device simulations

A Quasi-Two-Dimensional Compact Drain–Current Model for Undoped Symmetric Double-Gate MOSFETs Including Short-Channel Effects

A drain-current model for undoped symmetric double-gate MOSFETs is proposed. Channel-length modulation and drain-induced barrier lowering are modeled by using an approximate solution of the 2D Poisson equation. The new model is valid and continuous in linear and saturation regimes, as well as in weak and strong inversions. Excellent agreement was found with Silvaco-ATLAS simulations.

Graphene electronic sensors – review of recent developments and future challenges

Electronic sensors based on graphene have a high potential in many applications, due to the unique properties of the graphene material. This study is a review where the authors discuss the properties of graphene which are useful to sensing applications and they report and describe different types of graphene electronic sensors: biological, mechanical, gas and chemical sensors. They also discuss the ways to functionalise graphene and the used device structures. They compare the performance of the main types of biological, mechanical and chemical sensors. Finally, they explain the future challenges of graphene-based sensors, in order to make graphene sensing systems and smart sensors, which would be their main breakthrough application.

A Compact Explicit Model for Long-Channel Gate-All-Around Junctionless MOSFETs. Part I: DC Characteristics

In this paper, we solved Poisson equation in cylindrical coordinates using approximations to obtain a compact model for the drain current of long-channel junctionless gate-all-around MOSFETs. The resulting model is analytical, explicit, and valid for depletion and accumulation, and consists of simple physically based equations, for better understanding of this device, and also easier implementation and better computation speed as a compact model. The agreement with TCAD simulations is very good.

A Compact Explicit Model for Long-Channel Gate-All-Around Junctionless MOSFETs. Part II: Total Charges and Intrinsic Capacitance Characteristics

Analytical and explicit expressions are derived for intrinsic capacitances of the junctionless gate-all-around transistor, from the charge-control model, valid in the two regions of operation, depletion mode and accumulation mode. The advantage of this model is that it reduces to simple expressions for each region, giving a higher computation speed. We obtain very good agreement between the calculated capacitance characteristics and 3-D numerical device simulations.

Finite Element Simulations of Parasitic Capacitances Related to Multiple-Gate Field-Effect Transistors Architectures

In this paper, the impact of important geometrical parameters such as source and drain thickness, fin spacing, spacer width, etc. on the parasitic fringing capacitance component of multiple-gate field-effect transistors (MuGFET) is deeply analyzed using finite element simulations. Several architectures such as single gate, FinFETs (double gate), triple-gate represented by Pi-gate MOSFETs are simulated and compared in terms of channel and fringing capacitances for the same occupied die area. Simulations highlight the great impact of diminishing the spacing between fins for MuGFETs and the trade-off between the reduction of parasitic source and drain resistances and the increase of fringing capacitances when selective epitaxial growth (SEG) technology is introduced. The impact of these technological solutions on the transistor cut-off frequencies is also discussed.

Theory of graphene-field effect transistors

We present a compact physics-based model of the current-voltage characteristics of graphene field-effect transistors, of especial interest for analog and radio-frequency applications where bandgap engineering of graphene could be not needed. The physical framework is a field-effect model and drift-diffusion carrier transport. Explicit closed-form expressions have been derived for the drain current covering continuosly all operation regions. The model has been benchmarked with measured prototype devices, demonstrating accuracy and predictive behavior.

Errata for “Explicit Analytical Charge and Capacitance Models of Undoped Double-Gate MOSFETs” [Jul 07 1718-1724]

In the above titled paper (ibid., vol. 54, no. 7, pp. 1718-1724, Jul 07), an error was found in Equation (9). The correct equation is presented here.