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Open AccessArticle

Mechanisms of Ohmic Contact Formation of Ti/Al-Based Metal Stacks on p-Doped 4H-SiC

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Matthias Kocher

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Mathias Rommel

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Paweł Piotr Michałowski

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Tobias Erlbacher

Materials 2022, 15(1), 50; https://doi.org/10.3390/ma15010050 - 22 Dec 2021

Cited by 1 | Viewed by 2748

Abstract

Ohmic contacts on p-doped 4H-SiC are essential for the fabrication of a wide range of power electron devices. Despite the fact that Ti/Al based ohmic contacts are routinely used for ohmic contacts on p-doped 4H-SiC, the underlying contact formation mechanisms are still not [...] Read more.

Ohmic contacts on p-doped 4H-SiC are essential for the fabrication of a wide range of power electron devices. Despite the fact that Ti/Al based ohmic contacts are routinely used for ohmic contacts on p-doped 4H-SiC, the underlying contact formation mechanisms are still not fully understood. TLM structures were fabricated, measured and analyzed to get a better understanding of the formation mechanism. SIMS analyses at the Ti₃SiC₂-SiC interface have shown a significant increase of the surface near Al concentration. By using numerical simulation it is shown that this additional surface near Al concentration is essential for the ohmic contact formation. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessArticle

Induced Superconducting Transition in Ultra-Thin Iron-Selenide Films by a Mg-Coating Process

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Materials 2021, 14(21), 6383; https://doi.org/10.3390/ma14216383 - 25 Oct 2021

Cited by 1 | Viewed by 1288

Abstract

Binary Iron selenide (FeSe) thin films have been widely studied for years to unveil the high temperature superconductivity in iron-based superconductors. However, the origin of superconducting transition in this unconventional system is still under debate and worth deep investigations. In the present work, [...] Read more.

Binary Iron selenide (FeSe) thin films have been widely studied for years to unveil the high temperature superconductivity in iron-based superconductors. However, the origin of superconducting transition in this unconventional system is still under debate and worth deep investigations. In the present work, the transition from insulator to superconductor was achieved in non-superconducting FeSe ultrathin films (~8 nm) grown on calcium fluoride substrates via a simple in-situ Mg-coating by a pulsed laser deposition technique. The Mg-coated FeSe film with an optimized amount of Mg exhibited a superconducting critical temperature as 9.7 K and an upper critical field as 30.9 T. Through systematic characterizations on phase identification, carrier transport behavior and high-resolution microstructural features, the revival of superconductivity in FeSe ultrathin films is mostly attributed to the highly crystallized FeSe and extra electron doping received from external Mg-coating process. Although the top few FeSe layers are incorporated with Mg, most FeSe layers are intact and protected by a stable magnesium oxide layer. This work provides a new strategy to induce superconductivity in FeSe films with non-superconducting behavior, which might contribute to a more comprehensive understanding of iron-based superconductivity and the benefit to downstream applications such as magnetic resonance imaging, high-field magnets and electrical cables. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessArticle

Effect of Nitrogen and Aluminum Doping on 3C-SiC Heteroepitaxial Layers Grown on 4° Off-Axis Si (100)

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Materials 2021, 14(16), 4400; https://doi.org/10.3390/ma14164400 - 06 Aug 2021

Cited by 8 | Viewed by 1702

Abstract

This work provides a comprehensive investigation of nitrogen and aluminum doping and its consequences for the physical properties of 3C-SiC. Free-standing 3C-SiC heteroepitaxial layers, intentionally doped with nitrogen or aluminum, were grown on Si (100) substrate with different 4° off-axis in a horizontal [...] Read more.

This work provides a comprehensive investigation of nitrogen and aluminum doping and its consequences for the physical properties of 3C-SiC. Free-standing 3C-SiC heteroepitaxial layers, intentionally doped with nitrogen or aluminum, were grown on Si (100) substrate with different 4° off-axis in a horizontal hot-wall chemical vapor deposition (CVD) reactor. The Si substrate was melted inside the CVD chamber, followed by the growth process. Micro-Raman, photoluminescence (PL) and stacking fault evaluation through molten KOH etching were performed on different doped samples. Then, the role of the doping and of the cut angle on the quality, density and length distribution of the stacking faults was studied, in order to estimate the influence of N and Al incorporation on the morphological and optical properties of the material. In particular, for both types of doping, it was observed that as the dopant concentration increased, the average length of the stacking faults (SFs) increased and their density decreased. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessArticle

GaAs Nanomembranes in the High Electron Mobility Transistor Technology

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Materials 2021, 14(13), 3461; https://doi.org/10.3390/ma14133461 - 22 Jun 2021

Viewed by 1323

Abstract

A 100 nm MOCVD-grown HEMT AlGaAs/InGaAs/GaAs heterostructure nanomembrane was released from the growth GaAs substrate by ELO using a 300 nm AlAs layer and transferred to sapphire. The heterostructure contained a strained 10 nm 2DEG In_0.23Ga_0.77As channel with a [...] Read more.

A 100 nm MOCVD-grown HEMT AlGaAs/InGaAs/GaAs heterostructure nanomembrane was released from the growth GaAs substrate by ELO using a 300 nm AlAs layer and transferred to sapphire. The heterostructure contained a strained 10 nm 2DEG In_0.23Ga_0.77As channel with a sheet electron concentration of 3.4 × 10¹² cm⁻² and Hall mobility of 4590 cm²V⁻¹s⁻¹, which was grown close to the center of the heterostructure to suppress a significant bowing of the nanomembrane both during and after separation from the growth substrate. The as-grown heterostructure and transferred nanomembranes were characterized by HRXRD, PL, SEM, and transport measurements using HEMTs. The InGaAs and AlAs layers were laterally strained:

~ - 1.5 %

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~ - 0.15 %

. The HRXRD analysis showed the as-grown heterostructure had very good quality and smooth interfaces, and the nanomembrane had its crystalline structure and quality preserved. The PL measurement showed the nanomembrane peak was shifted by 19 meV towards higher energies with respect to that of the as-grown heterostructure. The HEMTs on the nanomembrane exhibited no degradation of the output characteristics, and the input two-terminal measurement confirmed a slightly decreased leakage current. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Review

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Open AccessEditor’s ChoiceReview

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Materials 2022, 15(3), 1164; https://doi.org/10.3390/ma15031164 - 02 Feb 2022

Cited by 13 | Viewed by 4250

Abstract

Currently, a significant portion (~50%) of global warming emissions, such as CO₂, are related to energy production and transportation. As most energy usage will be electrical (as well as transportation), the efficient management of electrical power is thus central to achieve [...] Read more.

Currently, a significant portion (~50%) of global warming emissions, such as CO₂, are related to energy production and transportation. As most energy usage will be electrical (as well as transportation), the efficient management of electrical power is thus central to achieve the XXI century climatic goals. Ultra-wide bandgap (UWBG) semiconductors are at the very frontier of electronics for energy management or energy electronics. A new generation of UWBG semiconductors will open new territories for higher power rated power electronics and solar-blind deeper ultraviolet optoelectronics. Gallium oxide—Ga₂O₃ (4.5–4.9 eV), has recently emerged pushing the limits set by more conventional WBG (~3 eV) materials, such as SiC and GaN, as well as for transparent conducting oxides (TCO), such asIn₂O₃, ZnO and SnO₂, to name a few. Indeed, Ga₂O₃ as the first oxide used as a semiconductor for power electronics, has sparked an interest in oxide semiconductors to be investigated (oxides represent the largest family of UWBG). Among these new power electronic materials, Al_xGa_1-xO₃ may provide high-power heterostructure electronic and photonic devices at bandgaps far beyond all materials available today (~8 eV) or ZnGa₂O₄ (~5 eV), enabling spinel bipolar energy electronics for the first time ever. Here, we review the state-of-the-art and prospects of some ultra-wide bandgap oxide semiconductor arising technologies as promising innovative material solutions towards a sustainable zero emission society. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessEditor’s ChoiceReview

Structural and Insulating Behaviour of High-Permittivity Binary Oxide Thin Films for Silicon Carbide and Gallium Nitride Electronic Devices

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Materials 2022, 15(3), 830; https://doi.org/10.3390/ma15030830 - 22 Jan 2022

Cited by 10 | Viewed by 3300

Abstract

High-κ dielectrics are insulating materials with higher permittivity than silicon dioxide. These materials have already found application in microelectronics, mainly as gate insulators or passivating layers for silicon (Si) technology. However, since the last decade, the post-Si era began with the pervasive introduction [...] Read more.

High-κ dielectrics are insulating materials with higher permittivity than silicon dioxide. These materials have already found application in microelectronics, mainly as gate insulators or passivating layers for silicon (Si) technology. However, since the last decade, the post-Si era began with the pervasive introduction of wide band gap (WBG) semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), which opened new perspectives for high-κ materials in these emerging technologies. In this context, aluminium and hafnium oxides (i.e., Al₂O₃, HfO₂) and some rare earth oxides (e.g., CeO₂, Gd₂O₃, Sc₂O₃) are promising high-κ binary oxides that can find application as gate dielectric layers in the next generation of high-power and high-frequency transistors based on SiC and GaN. This review paper gives a general overview of high-permittivity binary oxides thin films for post-Si electronic devices. In particular, focus is placed on high-κ binary oxides grown by atomic layer deposition on WBG semiconductors (silicon carbide and gallium nitride), as either amorphous or crystalline films. The impacts of deposition modes and pre- or postdeposition treatments are both discussed. Moreover, the dielectric behaviour of these films is also presented, and some examples of high-κ binary oxides applied to SiC and GaN transistors are reported. The potential advantages and the current limitations of these technologies are highlighted. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessReview

Status of Aluminum Oxide Gate Dielectric Technology for Insulated-Gate GaN-Based Devices

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Anthony Calzolaro

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Thomas Mikolajick

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Andre Wachowiak

Materials 2022, 15(3), 791; https://doi.org/10.3390/ma15030791 - 21 Jan 2022

Cited by 5 | Viewed by 3576

Abstract

Insulated-gate GaN-based transistors can fulfill the emerging demands for the future generation of highly efficient electronics for high-frequency, high-power and high-temperature applications. However, in contrast to Si-based devices, the introduction of an insulator on (Al)GaN is complicated by the absence of a high-quality [...] Read more.

Insulated-gate GaN-based transistors can fulfill the emerging demands for the future generation of highly efficient electronics for high-frequency, high-power and high-temperature applications. However, in contrast to Si-based devices, the introduction of an insulator on (Al)GaN is complicated by the absence of a high-quality native oxide for GaN. Trap states located at the insulator/(Al)GaN interface and within the dielectric can strongly affect the device performance. In particular, although AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) provide superior properties in terms of gate leakage currents compared to Schottky-gate HEMTs, the presence of an additional dielectric can induce threshold voltage instabilities. Similarly, the presence of trap states can be detrimental for the operational stability and reliability of other architectures of GaN devices employing a dielectric layer, such as hybrid MIS-FETs, trench MIS-FETs and vertical FinFETs. In this regard, the minimization of trap states is of critical importance to the advent of different insulated-gate GaN-based devices. Among the various dielectrics, aluminum oxide (Al₂O₃) is very attractive as a gate dielectric due to its large bandgap and band offsets to (Al)GaN, relatively high dielectric constant, high breakdown electric field as well as thermal and chemical stability against (Al)GaN. Additionally, although significant amounts of trap states are still present in the bulk Al₂O₃ and at the Al₂O₃/(Al)GaN interface, the current technological progress in the atomic layer deposition (ALD) process has already enabled the deposition of promising high-quality, uniform and conformal Al₂O₃ films to gate structures in GaN transistors. In this context, this paper first reviews the current status of gate dielectric technology using Al₂O₃ for GaN-based devices, focusing on the recent progress in engineering high-quality ALD-Al₂O₃/(Al)GaN interfaces and on the performance of Al₂O₃-gated GaN-based MIS-HEMTs for power switching applications. Afterwards, novel emerging concepts using the Al₂O₃-based gate dielectric technology are introduced. Finally, the recent status of nitride-based materials emerging as other gate dielectrics is briefly reviewed. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessEditor’s ChoiceReview

Recent Advances in Materials and Flexible Sensors for Arrhythmia Detection

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Matthew Guess

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Nathan Zavanelli

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Woon-Hong Yeo

Materials 2022, 15(3), 724; https://doi.org/10.3390/ma15030724 - 18 Jan 2022

Cited by 9 | Viewed by 3251

Abstract

Arrhythmias are one of the leading causes of death in the United States, and their early detection is essential for patient wellness. However, traditional arrhythmia diagnosis by expert evaluation from intermittent clinical examinations is time-consuming and often lacks quantitative data. Modern wearable sensors [...] Read more.

Arrhythmias are one of the leading causes of death in the United States, and their early detection is essential for patient wellness. However, traditional arrhythmia diagnosis by expert evaluation from intermittent clinical examinations is time-consuming and often lacks quantitative data. Modern wearable sensors and machine learning algorithms have attempted to alleviate this problem by providing continuous monitoring and real-time arrhythmia detection. However, current devices are still largely limited by the fundamental mismatch between skin and sensor, giving way to motion artifacts. Additionally, the desirable qualities of flexibility, robustness, breathability, adhesiveness, stretchability, and durability cannot all be met at once. Flexible sensors have improved upon the current clinical arrhythmia detection methods by following the topography of skin and reducing the natural interface mismatch between cardiac monitoring sensors and human skin. Flexible bioelectric, optoelectronic, ultrasonic, and mechanoelectrical sensors have been demonstrated to provide essential information about heart-rate variability, which is crucial in detecting and classifying arrhythmias. In this review, we analyze the current trends in flexible wearable sensors for cardiac monitoring and the efficacy of these devices for arrhythmia detection. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessEditor’s ChoiceReview

Diamond/GaN HEMTs: Where from and Where to?

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Joana C. Mendes

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Michael Liehr

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Changhui Li

Materials 2022, 15(2), 415; https://doi.org/10.3390/ma15020415 - 06 Jan 2022

Cited by 9 | Viewed by 5465

Abstract

Gallium nitride is a wide bandgap semiconductor material with high electric field strength and electron mobility that translate in a tremendous potential for radio-frequency communications and renewable energy generation, amongst other areas. However, due to the particular architecture of GaN high electron mobility [...] Read more.

Gallium nitride is a wide bandgap semiconductor material with high electric field strength and electron mobility that translate in a tremendous potential for radio-frequency communications and renewable energy generation, amongst other areas. However, due to the particular architecture of GaN high electron mobility transistors, the relatively low thermal conductivity of the material induces the appearance of localized hotspots that degrade the devices performance and compromise their long term reliability. On the search of effective thermal management solutions, the integration of GaN and synthetic diamond with high thermal conductivity and electric breakdown strength shows a tremendous potential. A significant effort has been made in the past few years by both academic and industrial players in the search of a technological process that allows the integration of both materials and the fabrication of high performance and high reliability hybrid devices. Different approaches have been proposed, such as the development of diamond/GaN wafers for further device fabrication or the capping of passivated GaN devices with diamond films. This paper describes in detail the potential and technical challenges of each approach and presents and discusses their advantages and disadvantages. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessEditor’s ChoiceReview

Towards Perfect Absorption of Single Layer CVD Graphene in an Optical Resonant Cavity: Challenges and Experimental Achievements

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Materials 2022, 15(1), 352; https://doi.org/10.3390/ma15010352 - 04 Jan 2022

Cited by 2 | Viewed by 1845

Abstract

Graphene is emerging as a promising material for the integration in the most common Si platform, capable to convey some of its unique properties to fabricate novel photonic and optoelectronic devices. For many real functions and devices however, graphene absorption is too low [...] Read more.

Graphene is emerging as a promising material for the integration in the most common Si platform, capable to convey some of its unique properties to fabricate novel photonic and optoelectronic devices. For many real functions and devices however, graphene absorption is too low and must be enhanced. Among strategies, the use of an optical resonant cavity was recently proposed, and graphene absorption enhancement was demonstrated, both, by theoretical and experimental studies. This paper summarizes our recent progress in graphene absorption enhancement by means of Si/SiO₂-based Fabry–Perot filters fabricated by radiofrequency sputtering. Simulations and experimental achievements carried out during more than two years of investigations are reported here, detailing the technical expedients that were necessary to increase the single layer CVD graphene absorption first to 39% and then up to 84%. Graphene absorption increased when an asymmetric Fabry–Perot filter was applied rather than a symmetric one, and a further absorption increase was obtained when graphene was embedded in a reflective rather than a transmissive Fabry–Perot filter. Moreover, the effect of the incident angle of the electromagnetic radiation and of the polarization of the light was investigated in the case of the optimized reflective Fabry–Perot filter. Experimental challenges and precautions to avoid evaporation or sputtering induced damage on the graphene layers are described as well, disclosing some experimental procedures that may help other researchers to embed graphene inside PVD grown materials with minimal alterations. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessReview

Materials and Processes for Schottky Contacts on Silicon Carbide

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Marilena Vivona

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Filippo Giannazzo

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Fabrizio Roccaforte

Materials 2022, 15(1), 298; https://doi.org/10.3390/ma15010298 - 31 Dec 2021

Cited by 7 | Viewed by 3812

Abstract

Silicon carbide (4H-SiC) Schottky diodes have reached a mature level of technology and are today essential elements in many applications of power electronics. In this context, the study of Schottky barriers on 4H-SiC is of primary importance, since a deeper understanding of the [...] Read more.

Silicon carbide (4H-SiC) Schottky diodes have reached a mature level of technology and are today essential elements in many applications of power electronics. In this context, the study of Schottky barriers on 4H-SiC is of primary importance, since a deeper understanding of the metal/4H-SiC interface is the prerequisite to improving the electrical properties of these devices. To this aim, over the last three decades, many efforts have been devoted to developing the technology for 4H-SiC-based Schottky diodes. In this review paper, after a brief introduction to the fundamental properties and electrical characterization of metal/4H-SiC Schottky barriers, an overview of the best-established materials and processing for the fabrication of Schottky contacts to 4H-SiC is given. Afterwards, besides the consolidated approaches, a variety of nonconventional methods proposed in literature to control the Schottky barrier properties for specific applications is presented. Besides the possibility of gaining insight into the physical characteristics of the Schottky contact, this subject is of particular interest for the device makers, in order to develop a new class of Schottky diodes with superior characteristics. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessReview

Intrinsic Point Defects in Silica for Fiber Optics Applications

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Giuseppe Mattia Lo Piccolo

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Marco Cannas

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Simonpietro Agnello

Materials 2021, 14(24), 7682; https://doi.org/10.3390/ma14247682 - 13 Dec 2021

Cited by 7 | Viewed by 2415

Abstract

Due to its unique properties, amorphous silicon dioxide (a-SiO₂) or silica is a key material in many technological fields, such as high-power laser systems, telecommunications, and fiber optics. In recent years, major efforts have been made in the development [...] Read more.

Due to its unique properties, amorphous silicon dioxide (a-SiO₂) or silica is a key material in many technological fields, such as high-power laser systems, telecommunications, and fiber optics. In recent years, major efforts have been made in the development of highly transparent glasses, able to resist ionizing and non-ionizing radiation. However the widespread application of many silica-based technologies, particularly silica optical fibers, is still limited by the radiation-induced formation of point defects, which decrease their durability and transmission efficiency. Although this aspect has been widely investigated, the optical properties of certain defects and the correlation between their formation dynamics and the structure of the pristine glass remains an open issue. For this reason, it is of paramount importance to gain a deeper understanding of the structure–reactivity relationship in a-SiO₂ for the prediction of the optical properties of a glass based on its manufacturing parameters, and the realization of more efficient devices. To this end, we here report on the state of the most important intrinsic point defects in pure silica, with a particular emphasis on their main spectroscopic features, their atomic structure, and the effects of their presence on the transmission properties of optical fibers. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessReview

A Review on Chemical Vapour Deposition of Two-Dimensional MoS₂ Flakes

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Luca Seravalli

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Matteo Bosi

Materials 2021, 14(24), 7590; https://doi.org/10.3390/ma14247590 - 10 Dec 2021

Cited by 18 | Viewed by 4064

Abstract

Two-dimensional (2D) materials such as graphene, transition metal dichalcogenides, and boron nitride have recently emerged as promising candidates for novel applications in sensing and for new electronic and photonic devices. Their exceptional mechanical, electronic, optical, and transport properties show peculiar differences from those [...] Read more.

Two-dimensional (2D) materials such as graphene, transition metal dichalcogenides, and boron nitride have recently emerged as promising candidates for novel applications in sensing and for new electronic and photonic devices. Their exceptional mechanical, electronic, optical, and transport properties show peculiar differences from those of their bulk counterparts and may allow for future radical innovation breakthroughs in different applications. Control and reproducibility of synthesis are two essential, key factors required to drive the development of 2D materials, because their industrial application is directly linked to the development of a high-throughput and reliable technique to obtain 2D layers of different materials on large area substrates. Among various methods, chemical vapour deposition is considered an excellent candidate for this goal thanks to its simplicity, widespread use, and compatibility with other processes used to deposit other semiconductors. In this review, we explore the chemical vapour deposition of MoS₂, considered one of the most promising and successful transition metal dichalcogenides. We summarize the basics of the synthesis procedure, discussing in depth: (i) the different substrates used for its deposition, (ii) precursors (solid, liquid, gaseous) available, and (iii) different types of promoters that favour the growth of two-dimensional layers. We also present a comprehensive analysis of the status of the research on the growth mechanisms of the flakes. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessReview

Diamond for Electronics: Materials, Processing and Devices

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Materials 2021, 14(22), 7081; https://doi.org/10.3390/ma14227081 - 22 Nov 2021

Cited by 18 | Viewed by 3688

Abstract

Progress in power electronic devices is currently accepted through the use of wide bandgap materials (WBG). Among them, diamond is the material with the most promising characteristics in terms of breakdown voltage, on-resistance, thermal conductance, or carrier mobility. However, it is also the [...] Read more.

Progress in power electronic devices is currently accepted through the use of wide bandgap materials (WBG). Among them, diamond is the material with the most promising characteristics in terms of breakdown voltage, on-resistance, thermal conductance, or carrier mobility. However, it is also the one with the greatest difficulties in carrying out the device technology as a result of its very high mechanical hardness and smaller size of substrates. As a result, diamond is still not considered a reference material for power electronic devices despite its superior Baliga’s figure of merit with respect to other WBG materials. This review paper will give a brief overview of some scientific and technological aspects related to the current state of the main diamond technology aspects. It will report the recent key issues related to crystal growth, characterization techniques, and, in particular, the importance of surface states aspects, fabrication processes, and device fabrication. Finally, the advantages and disadvantages of diamond devices with respect to other WBG materials are also discussed. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessReview

Status and Prospects of Cubic Silicon Carbide Power Electronics Device Technology

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Jonathan Edward Evans

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Materials 2021, 14(19), 5831; https://doi.org/10.3390/ma14195831 - 05 Oct 2021

Cited by 16 | Viewed by 4174

Abstract

Wide bandgap (WBG) semiconductors are becoming more widely accepted for use in power electronics due to their superior electrical energy efficiencies and improved power densities. Although WBG cubic silicon carbide (3C-SiC) displays a modest bandgap compared to its commercial counterparts (4H-silicon carbide and [...] Read more.

Wide bandgap (WBG) semiconductors are becoming more widely accepted for use in power electronics due to their superior electrical energy efficiencies and improved power densities. Although WBG cubic silicon carbide (3C-SiC) displays a modest bandgap compared to its commercial counterparts (4H-silicon carbide and gallium nitride), this material has excellent attributes as the WBG semiconductor of choice for low-resistance, reliable diode and MOS devices. At present the material remains firmly in the research domain due to numerous technological impediments that hamper its widespread adoption. The most obvious obstacle is defect-free 3C-SiC; presently, 3C-SiC bulk and heteroepitaxial (on-silicon) display high defect densities such as stacking faults and antiphase boundaries. Moreover, heteroepitaxy 3C-SiC-on-silicon means low temperature processing budgets are imposed upon the system (max. temperature limited to ~1400 °C) limiting selective doping realisation. This paper will give a brief overview of some of the scientific aspects associated with 3C-SiC processing technology in addition to focussing on the latest state of the art results. A particular focus will be placed upon key process steps such as Schottky and ohmic contacts, ion implantation and MOS processing including reliability. Finally, the paper will discuss some device prototypes (diodes and MOSFET) and draw conclusions around the prospects for 3C-SiC devices based upon the processing technology presented. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessReview

New Approaches and Understandings in the Growth of Cubic Silicon Carbide

Materials 2021, 14(18), 5348; https://doi.org/10.3390/ma14185348 - 16 Sep 2021

Cited by 25 | Viewed by 3858

Abstract

In this review paper, several new approaches about the 3C-SiC growth are been presented. In fact, despite the long research activity on 3C-SiC, no devices with good electrical characteristics have been obtained due to the high defect density and high level of stress. [...] Read more.

In this review paper, several new approaches about the 3C-SiC growth are been presented. In fact, despite the long research activity on 3C-SiC, no devices with good electrical characteristics have been obtained due to the high defect density and high level of stress. To overcome these problems, two different approaches have been used in the last years. From one side, several compliance substrates have been used to try to reduce both the defects and stress, while from another side, the first bulk growth has been performed to try to improve the quality of this material with respect to the heteroepitaxial one. From all these studies, a new understanding of the material defects has been obtained, as well as regarding all the interactions between defects and several growth parameters. This new knowledge will be the basis to solve the main issue of the 3C-SiC growth and reach the goal to obtain a material with low defects and low stress that would allow for realizing devices with extremely interesting characteristics. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessReview

Radiation Hardness of Silicon Carbide upon High-Temperature Electron and Proton Irradiation

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Alexander A. Lebedev

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Vitali V. Kozlovski

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Klavdia S. Davydovskaya

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Mikhail E. Levinshtein

Materials 2021, 14(17), 4976; https://doi.org/10.3390/ma14174976 - 31 Aug 2021

Cited by 9 | Viewed by 2081

Abstract

The radiation hardness of silicon carbide with respect to electron and proton irradiation and its dependence on the irradiation temperature are analyzed. It is shown that the main mechanism of SiC compensation is the formation of deep acceptor levels. With increasing the irradiation [...] Read more.

The radiation hardness of silicon carbide with respect to electron and proton irradiation and its dependence on the irradiation temperature are analyzed. It is shown that the main mechanism of SiC compensation is the formation of deep acceptor levels. With increasing the irradiation temperature, the probability of the formation of these centers decreases, and they are partly annealed out. As a result, the carrier removal rate in SiC becomes ~6 orders of magnitude lower in the case of irradiation at 500 °C. Once again, this proves that silicon carbide is promising as a material for high-temperature electronics devices. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessReview

Recent Advances in High-Throughput Nanomaterial Manufacturing for Hybrid Flexible Bioelectronics

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Nathan Zavanelli

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Jihoon Kim

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Woon-Hong Yeo

Materials 2021, 14(11), 2973; https://doi.org/10.3390/ma14112973 - 31 May 2021

Cited by 10 | Viewed by 4193

Abstract

Hybrid flexible bioelectronic systems refer to integrated soft biosensing platforms with tremendous clinical impact. In this new paradigm, electrical systems can stretch and deform with the skin while previously hidden physiological signals can be continuously recorded. However, hybrid flexible bioelectronics will not receive [...] Read more.

Hybrid flexible bioelectronic systems refer to integrated soft biosensing platforms with tremendous clinical impact. In this new paradigm, electrical systems can stretch and deform with the skin while previously hidden physiological signals can be continuously recorded. However, hybrid flexible bioelectronics will not receive wide clinical adoption until these systems can be manufactured at industrial scales cost-effectively. Therefore, new manufacturing approaches must be discovered and studied under the same innovative spirit that led to the adoption of novel materials and soft structures. Recent works have taken mature manufacturing approaches from the graphics industry, such as gravure, flexography, screen, and inkjet printing, and applied them to fully printed bioelectronics. These applications require the cohesive study of many disparate parts. For instance, nanomaterials with optimal properties for each specific application must be dispersed in printable inks with rheology suited to each printing method. This review summarizes recent advances in printing technologies, key nanomaterials, and applications of the manufactured hybrid bioelectronics. We also discuss the existing challenges of the available nanomanufacturing methods and the areas that need immediate technological improvements. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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Open AccessReview

Challenges and Perspectives for Vertical GaN-on-Si Trench MOS Reliability: From Leakage Current Analysis to Gate Stack Optimization

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Materials 2021, 14(9), 2316; https://doi.org/10.3390/ma14092316 - 29 Apr 2021

Cited by 12 | Viewed by 3760

Abstract

The vertical Gallium Nitride-on-Silicon (GaN-on-Si) trench metal-oxide-semiconductor field effect transistor (MOSFET) is a promising architecture for the development of efficient GaN-based power transistors on foreign substrates for power conversion applications. This work presents an overview of recent case studies, to discuss the most [...] Read more.

The vertical Gallium Nitride-on-Silicon (GaN-on-Si) trench metal-oxide-semiconductor field effect transistor (MOSFET) is a promising architecture for the development of efficient GaN-based power transistors on foreign substrates for power conversion applications. This work presents an overview of recent case studies, to discuss the most relevant challenges related to the development of reliable vertical GaN-on-Si trench MOSFETs. The focus lies on strategies to identify and tackle the most relevant reliability issues. First, we describe leakage and doping considerations, which must be considered to design vertical GaN-on-Si stacks with high breakdown voltage. Next, we describe gate design techniques to improve breakdown performance, through variation of dielectric composition coupled with optimization of the trench structure. Finally, we describe how to identify and compare trapping effects with the help of pulsed techniques, combined with light-assisted de-trapping analyses, in order to assess the dynamic performance of the devices. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section)

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