FinFET is a multiple-gate silicon transistor structure that nowadays is attracting an extensive attention to progress further into the nanometer era by going beyond the downscaling limit of the conventional planar CMOS technology. Although the interest for this architecture has been mainly devoted to digital applications, the analysis at high frequency is crucial for targeting a successful mixed integration of analog and digital circuits. In view of that, the purpose of this review paper is to provide a clear and exhaustive understanding of the state of art, challenges, and future trends of the FinFET technology from a microwave modeling perspective. Inspired by the traditional modeling techniques for conventional MOSFETs, different strategies have been proposed over the last years to model the FinFET behavior at high frequencies. With the aim to support the development of this technology, a comparative study of the achieved results is carried out to gain both a useful feedback to investigate the microwave FinFET performance as well as a valuable modeling know-how. To accomplish a comprehensive review, all aspects of microwave modeling going from linear (also noise) to non-linear high-frequency models are addressed.

A comprehensive review on microwave FinFET modeling for progressing beyond the state of art

This paper, for the first time, analyzes in detail the kink phenomenon in S22 as observed in GaN HEMT technology. To gain a comprehensive understanding, the kink effect (KE) is studied with respect to temperature and bias conditions. The achieved results clearly show that the dependence of the KE on the operating condition should be mainly ascribed to the transconductance, which plays a determinant role in the appearance of this effect. Furthermore, the analysis is extended to investigate the peak in the magnitude of h21 showing its disappearance at low drain-source voltage, due to the increase of the intrinsic output conductance. The importance of this investigation originates from the fact that an accurate and complete characterization of these anomalous phenomena enables microwave engineers to properly take them into account during the modeling and design phases.enables microwave engineers to properly take them into account during the modeling and design phases.

An Extensive Experimental Analysis of the Kink Effects in ${ S}_{22}$ and ${ h}_{21}$ for a GaN HEMT

The validity of the proposed small-signal model (SSM) and the developed extraction method in for large GaN devices is investigated Extraction of parasitic elements is performed for different size devices to show the scaling of these elements with the gate width The model shows a very good result for describing the parasitic distributed effect, which is considerable for large devices

An accurate small-signal model for AlGaN-GaNHEMT suitable for scalable large-signal model construction

The purpose of this invited paper is to give readers a comprehensive and critical overview on how to extract equivalent-circuit models for GaN HEMTs, which are the preferred devices for high-power high-frequency applications. This overview is meant to provide a practical modeling know-how for this advanced type of transistor, in order to support its development for improving device technology and circuit design. With the aim to broaden knowledge to empower models, experimental results are presented as illustrative examples of the most crucial challenges faced by the microwave engineers in modeling high-power GaN HEMTs. All the relevant aspects are covered, going from linear (also noise) to nonlinear models. The analysis is mainly focused on the modeling of distinctive peculiarities of GaN HEMTs. Particular attention is paid to study the importance of accurately modeling the kink effect in the output reflection coefficient, because of the relatively high transconductance, the peak in the magnitude of the short circuit current-gain, because of the relatively large intrinsic capacitances, and the low-frequency dispersion, because of trapping and thermal effects. Furthermore, to emphasize the key role of accurate device models for a successful circuit design, a practical example of power amplifier is discussed. Copyright © 2015 John Wiley & Sons, Ltd.

Empowering GaN HEMT models: The gateway for power amplifier design

Summary

This paper proposes an efficient parameter extraction algorithm for GaN high electron mobility transistors small-signal equivalent circuit model. The algorithm combines parameter scanning and iteration methods to solve the problem of error accumulation in conventional methods and is implemented in matlab programming. By using the iteration method, the algorithm each time uses more accurate element values thus makes the results converge to the optimal value faster. A 20-element small-signal equivalent circuit model of GaN high electron mobility transistors is used to validate the proposed algorithm, and the results show that the calculated S-parameters agree well with the measured S-parameters within the frequency range of 0.1 to 40 GHz. Copyright © 2015 John Wiley & Sons, Ltd.

An efficient parameter extraction method for GaN HEMT small‐signal equivalent circuit model

A novel theory based on dual-feedback circuit methodology is proposed to explain the kink phenomenon of transistor scattering parameter S/sub 22/. Our results show that the output impedance of all transistors intrinsically shows a series RC circuit at low frequencies and a parallel RC circuit at high frequencies. It is this inherent ambivalent characteristic of the output impedance that causes the appearance of kink phenomenon of S/sub 22/ in a Smith chart. It was found that an increase of transistor transconductance enhances the kink effect while an increase of drain-to-source (or collector-to-emitter) capacitance obscures it. This explains why it is much easier to see the kink phenomenon in bipolar transistors, especially heterojunction bipolar transistors, rather than in field-effect transistors (FETs). It also explains why the kink phenomenon is seen in larger size FETs and not in smaller size FETs. Our model not only can predict the behavior of S/sub 22/, but also calculate all S-parameters accurately. Experimental data of submicrometer gate Si MOSFETs and GaAs FETs are used to verify our theory. A simple method for extracting transistor equivalent-circuit parameters from measured S-parameters is also proposed based on our theory. Compared with traditional Z- or Y-parameter methods, our theory shows another advantage of giving deep insight into the physical meaning of S-parameters.

C. Meng

Papers

The origin of the kink phenomenon of transistor scattering parameter S/sub 22/