Modelling of field-effect transistors based on 2D materials targeting high-frequency applications

New technologies are necessary for the unprecedented expansion of connectivity and communications in the modern technological society. The specific needs of wireless communication systems in 5G and beyond, as well as devices for the future deployment of Internet of Things has caused that the International Technology Roadmap for Semiconductors, which is the strategic planning document of the semiconductor industry, considered since 2011, graphene and related materials (GRMs) as promising candidates for the future of electronics. Graphene, a one-atom-thick of carbon, is a promising material for high-frequency applications due to its intrinsic superior carrier mobility and very high saturation velocity. These exceptional carrier transport properties suggest that GRM-based field-effect transistors could potentially outperform other technologies. This thesis presents a body of work on the modelling, performance prediction and simulation of GRM-based field-effect transistors and circuits. The main goal of this work is to provide models and tools to ease the following issues: (i) gaining technological control of single layer and bilayer graphene devices and, more generally, devices based on 2D materials, (ii) assessment of radio-frequency (RF) performance and microwave stability, (iii) benchmarking against other existing technologies, (iv) providing guidance for device and circuit design, (v) simulation of circuits formed by GRM-based transistors.Comment: Thesis, 164 pages, http://hdl.handle.net/10803/40531

Compact Modeling Technology for the Simulation of Integrated Circuits Based on Graphene Field-Effect Transistors

The progress made toward the definition of a modular compact modeling technology for graphene field-effect transistors (GFETs) that enables the electrical analysis of arbitrary GFET-based integrated circuits is reported. A set of primary models embracing the main physical principles defines the ideal GFET response under DC, transient (time domain), AC (frequency domain), and noise (frequency domain) analysis. Another set of secondary models accounts for the GFET non-idealities, such as extrinsic-, short-channel-, trapping/detrapping-, self-heating-, and non-quasi static-effects, which can have a significant impact under static and/or dynamic operation. At both device and circuit levels, significant consistency is demonstrated between the simulation output and experimental data for relevant operating conditions. Additionally, a perspective of the challenges during the scale up of the GFET modeling technology toward higher technology readiness levels while drawing a collaborative scenario among fabrication technology groups, modeling groups, and circuit designers, is provided.European Commission 881603Spanish Government European Commission RTI2018-097876-B-C21 European CommissionDepartament de Recerca i Universitat 001-P-00170

Large-Signal Model of Graphene Field-Effect Transistors -- Part I: Compact Modeling of GFET Intrinsic Capacitances

We present a circuit-compatible compact model of the intrinsic capacitances of graphene field-effect transistors (GFETs). Together with a compact drain current model, a large-signal model of GFETs is developed combining both models as a tool for simulating the electrical behavior of graphene-based integrated circuits, dealing with the DC, transient behavior, and frequency response of the circuit. The drain current model is based in a drift-diffusion mechanism for the carrier transport coupled with an appropriate field-effect approach. The intrinsic capacitance model consists of a 16-capacitance matrix including self-capacitances and transcapacitances of a four-terminal GFET. To guarantee charge conservation, a Ward-Dutton linear charge partition scheme has been used. The large-signal model has been implemented in Verilog-A, being compatible with conventional circuit simulators and serving as a starting point toward the complete GFET device model that could incorporate additional non-idealities.Comment: 6 pages, 6 figures. Action H2020: Research & Innovation Actions (RIA), Title: Graphene-based disruptive technologies. GrapheneCore1, Grant no. 696656 European Union (EU) Horizon 2020. IEEE Transactions on Electron Devices (2016). arXiv admin note: text overlap with arXiv:1512.0715

Small-signal model for 2D-material based field-effect transistors targeting radio-frequency applications: the importance of considering non-reciprocal capacitances

A small-signal equivalent circuit of 2D-material based field-effect transistors is presented. Charge conservation and non-reciprocal capacitances have been assumed so the model can be used to make reliable predictions at both device and circuit levels. In this context, explicit and exact analytical expressions of the main radio-frequency figures of merit of these devices are given. Moreover, a direct parameter extraction methodology is provided based on S-parameter measurements. In addition to the intrinsic capacitances, transconductance and output conductance, our approach allows extracting the series combination of drain/source metal contact and access resistances. Accounting for these extrinsic resistances is of upmost importance when dealing with low dimensional field-effect transistors.Comment: 8 pages, 10 figures, 4 table

Large-Signal Model of Graphene Field-Effect Transistors -- Part II: Circuit Performance Benchmarking

This paper presents a circuit performance benchmarking using the large-signal model of graphene field effect transistor reported in Part I of this two-part paper. To test the model, it has been implemented in a circuit simulator. Specifically we have simulated a high-frequency performance amplifier, together with other circuits that take advantage of the ambipolarity of graphene, such as a frequency doubler, a radio-frequency subharmonic mixer and a multiplier phase detector. A variety of simulations comprising DC, transient dynamics, Bode diagram, S-parameters, and power spectrum have been compared with experimental data to assess the validity of the model.Comment: 6 pages, 11 figures. Action H2020: Research & Innovation Actions (RIA), Title: Graphene-based disruptive technologies. GrapheneCore1, Grant no. 696656 / European Union (EU) / Horizon 2020. IEEE Transactions on Electron Devices (2016

Two-dimensional tellurium-based diodes for RF applications

The research of two-dimensional (2D) Tellurium (Te) or tellurene is thriving to address current challenges in emerging thin-film electronic and optoelectronic devices. However, the study of 2D-Te-based devices for high-frequency applications is still lacking in the literature. This work presents a comprehensive study of two types of radio frequency (RF) diodes based on 2D-Te flakes and exploits their distinct properties in two RF applications. First, a metal-insulator-semiconductor (MIS) structure is employed as a nonlinear device in a passive RF mixer, where the achieved conversion loss at 2.5 GHz and 5 GHz is as low as 24 dB and 29 dB, respectively. Then, a metal-semiconductor (MS) diode is tested as a zero-bias millimeter-wave power detector and reaches an outstanding linear-in-dB dynamic range over 40 dB, while having voltage responsivities as high as 257 V ⋅ W−1 at 1 GHz (up to 1 V detected output voltage) and 47 V ⋅ W−1 at 2.5 GHz (up to 0.26 V detected output voltage). These results show superior performance compared to other 2D material-based devices in a much more mature technological phase. Thus, the authors believe that this work demonstrates the potential of 2D-Te as a promising material for devices in emerging high-frequency electronics.MCIN/AEI/10.13039/501100011033European Union NextGenerationEU/PRTRGerman Research Foundation (DFG) under the projects GLECS2 (No. 653408)MOSTFLEX (653414),The Natural Sciences and Engineering Research Council (NSERC) (RGPIN-2017-05810 and ALLRP 577611-22)The European Commission under the Horizon 2020 projects Graphene Flagship (No. 785219 and 881603)PAIDI 2020 and European Social Fund Operational Programme 2014-2020 no. 20804Ministerio de UniversidadesGrant no. CAS21/ 00483Canada Foundation for Innovation (CFI)British Columbia Knowledge Development Fund (BCKDF)Western Economic Diversification Canada (WD)Simon Fraser Universit

Large-signal model of the Metal-Insulator-Graphene diode targeting RF applications

We present a circuit-design compatible large-signal compact model of metal-insulator-graphene (MIG) diodes for describing its dynamic response for the first time. The model essentially consists of a voltage-dependent diode intrinsic capacitance coupled with a static voltage-dependent current source, the latter accounts for the vertical electron transport from/towards graphene, which has been modeled by means of the Dirac-thermionic electron transport theory through the insulator barrier. Importantly, the image force effect has been found to play a key role in determining the barrier height, so it has been incorporated into the model accordingly. The resulting model has been implemented in Verilog A to be used in existing circuit simulators and benchmarked against an experimental 6-nm TiO2 barrier MIG diode working as a power detector.Comment: 4 pages, 5 figures, 1 tabl

Promoção da inteligência emocional em contextos da Educação Pré-escolar e Ensino do 1.º Ciclo do Ensino Básico

Relatório das Práticas de Ensino do Mestrado em Educação Pré-escolar e Ensino do 1.º Ciclo do Ensino Básico: Promoção da Inteligência Emocional em contextos de Educação Pré-escolar e Ensino do 1.º Ciclo do Ensino Básico. No âmbito do Mestrado em Educação Pré-escolar e Ensino do 1.º Ciclo do Ensino Básico surge o presente relatório atendendo ao processo investigativo, desenvolvido durante as Práticas Profissionais II e III. Nas escolas observam-se, com frequência, situações que demonstram dificuldades de autorregulação das emoções. Múltiplos são os estudos que existem sobre as variáveis em causa. Procurou-se compreender e promover práticas educativas, entre as quais, a meditação e o mindfulness, com o objetivo de desenvolver a capacidade de Inteligência Emocional nos dois contextos educativos, orientadas por visões pedagógicas que privilegiam a regulação emocional. Em cooperação com as titulares de grupo/turma, procurou-se construir ambientes e momentos com vista à construção do currículo mais contextualizado às necessidades emocionais das crianças. Teve-se como base a revisão da literatura referente à concepção do conceito de Inteligência Emocional na tentativa de experimentar as suas potencialidades, assim como os documentos orientadores curriculares. Foi aplicada a metodologia de investigação-ação por possibilitar reajustes necessários ao longo das intervenções, ser dinâmica e potenciar a constante reflexão sobre a ação e para a ação. Os instrumentos de recolha de dados foram a observação participante e as notas de campo que permitiram selecionar evidências e a reflexão escrita. O desenvolvimento de práticas educativas que estimulam a inteligência emocional revelou-se uma metodologia bastante enriquecedora nos dois contextos, surgindo atividades em que o envolvimento não só das crianças como também da comunidade escolar e das famílias foram visíveis