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18 pages, 3698 KiB

Open AccessEditor’s ChoiceArticle

Electronic Properties of Group-III Nitride Semiconductors and Device Structures Probed by THz Optical Hall Effect

by Nerijus Armakavicius, Philipp Kühne, Alexis Papamichail, Hengfang Zhang, Sean Knight, Axel Persson, Vallery Stanishev, Jr-Tai Chen, Plamen Paskov, Mathias Schubert and Vanya Darakchieva

Materials 2024, 17(13), 3343; https://doi.org/10.3390/ma17133343 - 5 Jul 2024

Cited by 1 | Viewed by 1177

Abstract

Group-III nitrides have transformed solid-state lighting and are strategically positioned to revolutionize high-power and high-frequency electronics. To drive this development forward, a deep understanding of fundamental material properties, such as charge carrier behavior, is essential and can also unveil new and unforeseen applications. [...] Read more.

Group-III nitrides have transformed solid-state lighting and are strategically positioned to revolutionize high-power and high-frequency electronics. To drive this development forward, a deep understanding of fundamental material properties, such as charge carrier behavior, is essential and can also unveil new and unforeseen applications. This underscores the necessity for novel characterization tools to study group-III nitride materials and devices. The optical Hall effect (OHE) emerges as a contactless method for exploring the transport and electronic properties of semiconductor materials, simultaneously offering insights into their dielectric function. This non-destructive technique employs spectroscopic ellipsometry at long wavelengths in the presence of a magnetic field and provides quantitative information on the charge carrier density, sign, mobility, and effective mass of individual layers in multilayer structures and bulk materials. In this paper, we explore the use of terahertz (THz) OHE to study the charge carrier properties in group-III nitride heterostructures and bulk material. Examples include graded AlGaN channel high-electron-mobility transistor (HEMT) structures for high-linearity devices, highlighting the different grading profiles and their impact on the two-dimensional electron gas (2DEG) properties. Next, we demonstrate the sensitivity of the THz OHE to distinguish the 2DEG anisotropic mobility parameters in N-polar GaN/AlGaN HEMTs and show that this anisotropy is induced by the step-like surface morphology. Finally, we present the temperature-dependent results on the charge carrier properties of 2DEG and bulk electrons in GaN with a focus on the effective mass parameter and review the effective mass parameters reported in the literature. These studies showcase the capabilities of the THz OHE for advancing the understanding and development of group-III materials and devices. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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16 pages, 6087 KiB

Open AccessArticle

Conductometric H₂S Sensors Based on TiO₂ Nanoparticles

by Yassine Alaya, Malek Madani, Noureddine Bouguila, Lassaad El Mir, Enza Fazio, Carmelo Corsaro and Giovanni Neri

Materials 2024, 17(13), 3283; https://doi.org/10.3390/ma17133283 - 3 Jul 2024

Viewed by 770

Abstract

High-performance hydrogen sulfide (H₂S) sensors are mandatory for many industrial applications. However, the development of H₂S sensors still remains a challenge for researchers. In this work, we report the study of a TiO₂-based conductometric sensor for H [...] Read more.

High-performance hydrogen sulfide (H₂S) sensors are mandatory for many industrial applications. However, the development of H₂S sensors still remains a challenge for researchers. In this work, we report the study of a TiO₂-based conductometric sensor for H₂S monitoring at low concentrations. TiO₂ samples were first synthesized using the sol-gel route, annealed at different temperatures (400 and 600 °C), and thoroughly characterized to evaluate their morphological and microstructural properties. Scanning electronic microscopy, Raman scattering, X-ray diffraction, and FTIR spectroscopy have demonstrated the formation of clusters of pure anatase in the TiO₂ phase. Increasing the calcination temperature to 600 °C enhanced TiO₂ crystallinity and particle size (from 11 nm to 51 nm), accompanied by the transition to the rutile phase and a slight decrease in band gap (3.31 eV for 400 °C to 3.26 eV for 600 °C). Sensing tests demonstrate that TiO₂ annealed at 400 °C displays good performances (sensor response Ra/Rg of ~3.3 at 2.5 ppm and fast response/recovery of 8 and 23 s, respectively) for the detection of H₂S at low concentrations in air. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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7 pages, 1884 KiB

Open AccessEditor’s ChoiceCommunication

Three-Dimensional Epitaxy of Low-Defect 3C-SiC on a Geometrically Modified Silicon Substrate

by Gerard Colston, Kelly Turner, Arne Renz, Kushani Perera, Peter M. Gammon, Marina Antoniou and Vishal A. Shah

Materials 2024, 17(7), 1587; https://doi.org/10.3390/ma17071587 - 30 Mar 2024

Viewed by 973

Abstract

We demonstrate the growth of 3C-SiC with reduced planar defects on a micro-scale compliant substrate. Heteroepitaxial growth of 3C-SiC on trenches with a width and separation of 2 µm, etched into a Si(001) substrate, is found to suppress defect propagation through the epilayer. [...] Read more.

We demonstrate the growth of 3C-SiC with reduced planar defects on a micro-scale compliant substrate. Heteroepitaxial growth of 3C-SiC on trenches with a width and separation of 2 µm, etched into a Si(001) substrate, is found to suppress defect propagation through the epilayer. Stacking faults and other planar defects are channeled away from the center of the patterned structures, which are rounded through the use of H₂ annealing at 1100 °C. Void formation between the columns of 3C-SiC growth acts as a termination point for defects, and coalescence of these columns into a continuous epilayer is promoted through the addition of HCl in the growth phase. The process of fabricating these compliant substrates utilizes standard processing techniques found within the semiconductor industry and is independent of the substrate orientation and offcut. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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10 pages, 5275 KiB

Open AccessArticle

Fast Joule Heating for the Scalable and Green Production of Graphene with a High Surface Area

by Zakhar Ivanovich Evseev, Aisen Ruslanovich Prokopiev, Petr Stanislavovich Dmitriev, Nikolay Nikolaevich Loskin and Dmitrii Nikolaevich Popov

Materials 2024, 17(3), 576; https://doi.org/10.3390/ma17030576 - 25 Jan 2024

Viewed by 1825

Abstract

The rapid development of electric vehicles, unmanned aerial vehicles, and wearable electronic devices has led to great interest in research related to the synthesis of graphene with a high specific surface area for energy applications. However, the problem of graphene synthesis scalability, as [...] Read more.

The rapid development of electric vehicles, unmanned aerial vehicles, and wearable electronic devices has led to great interest in research related to the synthesis of graphene with a high specific surface area for energy applications. However, the problem of graphene synthesis scalability, as well as the lengthy duration and high energy intensity of the activation processes of carbon materials, are significant disadvantages. In this study, a novel reactor was developed for the green, simple, and scalable electrochemical synthesis of graphene oxide with a low oxygen content of 14.1%. The resulting material was activated using the fast joule heating method. The processing of mildly oxidized graphene with a high-energy short electrical pulse (32 ms) made it possible to obtain a graphene-based porous carbon material with a specific surface area of up to 1984.5 m²/g. The increase in the specific surface area was attributed to the rupture of the original graphene flakes into smaller particles due to the explosive release of gaseous products. In addition, joule heating was able to instantly reduce the oxidized graphene and decrease its electrical resistance from >10 MΩ/sq to 20 Ω/sq due to sp² carbon structure regeneration, as confirmed by Raman spectroscopy. The low energy intensity, simplicity, and use of environment-friendly chemicals rendered the proposed method scalable. The resulting graphene material with a high surface area and conductivity can be used in various energy applications, such as Li-ion batteries and supercapacitors. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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12 pages, 7496 KiB

Open AccessArticle

Single-Ion Counting with an Ultra-Thin-Membrane Silicon Carbide Sensor

by Enrico Sangregorio, Lucia Calcagno, Elisabetta Medina, Andreo Crnjac, Milko Jakšic, Anna Vignati, Francesco Romano, Giuliana Milluzzo, Marzio De Napoli and Massimo Camarda

Materials 2023, 16(24), 7692; https://doi.org/10.3390/ma16247692 - 18 Dec 2023

Viewed by 1215

Abstract

In recent times, ion implantation has received increasing interest for novel applications related to deterministic material doping on the nanoscale, primarily for the fabrication of solid-state quantum devices. For such applications, precise information concerning the number of implanted ions and their final position [...] Read more.

In recent times, ion implantation has received increasing interest for novel applications related to deterministic material doping on the nanoscale, primarily for the fabrication of solid-state quantum devices. For such applications, precise information concerning the number of implanted ions and their final position within the implanted sample is crucial. In this work, we present an innovative method for the detection of single ions of MeV energy by using a sub-micrometer ultra-thin silicon carbide sensor operated as an in-beam counter of transmitted ions. The SiC sensor signals, when compared to a Passivated Implanted Planar Silicon detector signal, exhibited a 96.5% ion-detection confidence, demonstrating that the membrane sensors can be utilized for high-fidelity ion counting. Furthermore, we assessed the angular straggling of transmitted ions due to the interaction with the SiC sensor, employing the scanning knife-edge method of a focused ion microbeam. The lateral dimension of the ion beam with and without the membrane sensor was compared to the SRIM calculations. The results were used to discuss the potential of such experimental geometry in deterministic ion-implantation schemes as well as other applications. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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15 pages, 5830 KiB

Open AccessArticle

Large-Area Mapping of Voids and Dislocations in Basal-Faceted Sapphire Ribbons by Synchrotron Radiation Imaging

by Tatiana S. Argunova, Victor G. Kohn, Jae-Hong Lim, Vladimir M. Krymov and Mikhail Yu. Gutkin

Materials 2023, 16(19), 6589; https://doi.org/10.3390/ma16196589 - 7 Oct 2023

Cited by 1 | Viewed by 1001

Abstract

The understanding of structural defects in basal-faceted sapphire ribbons was improved through X-ray imaging at a synchrotron source. The combination of phase contrast and X-ray diffraction makes it possible to visualize and characterize both gas voids and dislocations in the bulk of the [...] Read more.

The understanding of structural defects in basal-faceted sapphire ribbons was improved through X-ray imaging at a synchrotron source. The combination of phase contrast and X-ray diffraction makes it possible to visualize and characterize both gas voids and dislocations in the bulk of the ribbons grown by the Stepanov–LaBelle technology. Dislocations were directly related to gas voids. X-ray diffraction topography was employed to investigate the distribution, configurations, and character of the dislocations. The formation of voids of irregular shapes was detected by large-area mapping with spatial resolution in the μm range. Computer simulations of the experimental phase contrast images of microvoids were performed. The sizes of the spherical microvoids were determined. The results are discussed with reference to the available data on the emission of dislocations from the voids. The evolution of the shape, size, and arrangement of the voids during growth provides clues on the formation of block structure in basal-faceted sapphire ribbons. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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29 pages, 5763 KiB

Open AccessArticle

Control of Coherent Light through Microperiodic Director Modulation in Nematic Films under Low-Voltage DC Electric Field

by Georgi B. Hadjichristov

Materials 2023, 16(17), 6014; https://doi.org/10.3390/ma16176014 - 1 Sep 2023

Cited by 1 | Viewed by 1053

Abstract

This work addresses the achievement of efficient control of laser light transmission through stationary microperiodic parallel stripe textures formed in films of nematic liquid crystals (NLCs) in planar-oriented cells upon a direct-current (DC) electric field. By varying the field intensity and, thereby, the [...] Read more.

This work addresses the achievement of efficient control of laser light transmission through stationary microperiodic parallel stripe textures formed in films of nematic liquid crystals (NLCs) in planar-oriented cells upon a direct-current (DC) electric field. By varying the field intensity and, thereby, the field-induced periodic modulation of the nematic director and hence the complex transmittance function corresponding to the longitudinal domain texture induced in NLC films with initial planar alignment, the intensity of a linearly polarized laser beam passed through the films can be well controlled. In 25 µm-thick films of room-temperature NLCs pentylcyanobiphenyl (5CB), this results in a low-voltage (~4 V) sharp and deep V-shaped behavior of their electro-optically controlled transmittance. Such a reversible electro-optical effect is interesting for active control of laser beam intensity and other applications. The relevant physical mechanism is analyzed and explained. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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27 pages, 19024 KiB

Open AccessEditor’s ChoiceArticle

Temperature Field, Flow Field, and Temporal Fluctuations Thereof in Ammonothermal Growth of Bulk GaN—Transition from Dissolution Stage to Growth Stage Conditions

by Saskia Schimmel, Daisuke Tomida, Tohru Ishiguro, Yoshio Honda, Shigefusa F. Chichibu and Hiroshi Amano

Materials 2023, 16(5), 2016; https://doi.org/10.3390/ma16052016 - 28 Feb 2023

Cited by 4 | Viewed by 2399

Abstract

With the ammonothermal method, one of the most promising technologies for scalable, cost-effective production of bulk single crystals of the wide bandgap semiconductor GaN is investigated. Specifically, etch-back and growth conditions, as well as the transition from the former to the latter, are [...] Read more.

With the ammonothermal method, one of the most promising technologies for scalable, cost-effective production of bulk single crystals of the wide bandgap semiconductor GaN is investigated. Specifically, etch-back and growth conditions, as well as the transition from the former to the latter, are studied using a 2D axis symmetrical numerical model. In addition, experimental crystal growth results are analyzed in terms of etch-back and crystal growth rates as a function of vertical seed position. The numerical results of internal process conditions are discussed. Variations along the vertical axis of the autoclave are analyzed using both numerical and experimental data. During the transition from quasi-stable conditions of the dissolution stage (etch-back process) to quasi-stable conditions of the growth stage, significant temperature differences of 20 K to 70 K (depending on vertical position) occur temporarily between the crystals and the surrounding fluid. These lead to maximum rates of seed temperature change of 2.5 K/min to 1.2 K/min depending on vertical position. Based on temperature differences between seeds, fluid, and autoclave wall upon the end of the set temperature inversion process, deposition of GaN is expected to be favored on the bottom seed. The temporarily observed differences between the mean temperature of each crystal and its fluid surrounding diminish about 2 h after reaching constant set temperatures imposed at the outer autoclave wall, whereas approximately quasi-stable conditions are reached about 3 h after reaching constant set temperatures. Short-term fluctuations in temperature are mostly due to fluctuations in velocity magnitude, usually with only minor variations in the flow direction. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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8 pages, 1819 KiB

Open AccessArticle

Features of the Carrier Concentration Determination during Irradiation of Wide-Gap Semiconductors: The Case Study of Silicon Carbide

by Alexander A. Lebedev, Vitali V. Kozlovski, Klavdia S. Davydovskaya, Roman A. Kuzmin, Mikhail E. Levinshtein and Anatolii M. Strel’chuk

Materials 2022, 15(23), 8637; https://doi.org/10.3390/ma15238637 - 3 Dec 2022

Cited by 5 | Viewed by 1585

Abstract

In this paper, the features of radiation compensation of wide-gap semiconductors are discussed, considering the case study of silicon carbide. Two classical methods of concentration determination are compared and analyzed: capacitance-voltage (C–V) and current-voltage (I–V) characteristics. The [...] Read more.

In this paper, the features of radiation compensation of wide-gap semiconductors are discussed, considering the case study of silicon carbide. Two classical methods of concentration determination are compared and analyzed: capacitance-voltage (C–V) and current-voltage (I–V) characteristics. The dependence of the base resistance in high-voltage 4H-SiC Schottky diodes on the dose of irradiation by electrons and protons is experimentally traced in the range of eight orders of magnitude. It is demonstrated that the dependence of the carrier concentration on the irradiation dose can be determined unambiguously and reliably in a very wide range of compensation levels, based on the results of measuring the I–V characteristics. It is shown that the determination of the carrier removal rate using the I–V characteristics is more correct than using the C–V characteristics, especially in the case of high radiation doses. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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10 pages, 2578 KiB

Open AccessEditor’s ChoiceArticle

Charge Trap States of SiC Power TrenchMOS Transistor under Repetitive Unclamped Inductive Switching Stress

by Juraj Marek, Jozef Kozarik, Michal Minarik, Aleš Chvála, Matej Matus, Martin Donoval, Lubica Stuchlikova and Martin Weis

Materials 2022, 15(22), 8230; https://doi.org/10.3390/ma15228230 - 19 Nov 2022

Cited by 2 | Viewed by 1871

Abstract

Silicon carbide (SiC) has been envisioned as an almost ideal material for power electronic devices; however, device reliability is still a great challenge. Here we investigate the reliability of commercial 1.2-kV 4H-SiC MOSFETs under repetitive unclamped inductive switching (UIS). The stress invoked degradation [...] Read more.

Silicon carbide (SiC) has been envisioned as an almost ideal material for power electronic devices; however, device reliability is still a great challenge. Here we investigate the reliability of commercial 1.2-kV 4H-SiC MOSFETs under repetitive unclamped inductive switching (UIS). The stress invoked degradation of the device characteristics, including the output and transfer characteristics, drain leakage current, and capacitance characteristics. Besides the shift of steady-state electrical characteristics, a significant change in switching times points out the charge trapping phenomenon. Transient capacitance spectroscopy was applied to investigate charge traps in the virgin device as well as after UIS stress. The intrinsic traps due to metal impurities or

Z_{1, 2}

transitions were recognized in the virgin device. The UIS stress caused suppression of the second stage of the

Z_{1, 2}

transition, and only the first stage,

Z_{1}^{0}

, was observed. Hence, the UIS stress is causing the reduction of multiple charging of carbon vacancies in SiC-based devices. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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13 pages, 2883 KiB

Open AccessEditor’s ChoiceArticle

A Low Temperature Growth of Cu₂O Thin Films as Hole Transporting Material for Perovskite Solar Cells

by Anna L. Pellegrino, Francesca Lo Presti, Emanuele Smecca, Salvatore Valastro, Giuseppe Greco, Salvatore Di Franco, Fabrizio Roccaforte, Alessandra Alberti and Graziella Malandrino

Materials 2022, 15(21), 7790; https://doi.org/10.3390/ma15217790 - 4 Nov 2022

Cited by 6 | Viewed by 2568

Abstract

Copper oxide thin films have been successfully synthesized through a metal–organic chemical vapor deposition (MOCVD) approach starting from the copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate), Cu(tmhd)₂, complex. Operative conditions of fabrication strongly affect both the composition and morphologies of the copper oxide thin films. The [...] Read more.

Copper oxide thin films have been successfully synthesized through a metal–organic chemical vapor deposition (MOCVD) approach starting from the copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate), Cu(tmhd)₂, complex. Operative conditions of fabrication strongly affect both the composition and morphologies of the copper oxide thin films. The deposition temperature has been accurately monitored in order to stabilize and to produce, selectively and reproducibly, the two phases of cuprite Cu₂O and/or tenorite CuO. The present approach has the advantages of being industrially appealing, reliable, and fast for the production of thin films over large areas with fine control of both composition and surface uniformity. Moreover, the methylammonium lead iodide (MAPI) active layer has been successfully deposited on the ITO/Cu₂O substrate by the Low Vacuum Proximity Space Effusion (LV-PSE) technique. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM) analyses have been used to characterize the deposited films. The optical band gap (E_g), ranging from 1.99 to 2.41 eV, has been determined through UV-vis analysis, while the electrical measurements allowed to establish the p-type conductivity behavior of the deposited Cu₂O thin films with resistivities from 31 to 83 Ω cm and carrier concentration in the order of 1.5–2.8 × 10¹⁶ cm⁻³. These results pave the way for potential applications of the present system as a hole transporting layer combined with a perovskite active layer in emergent solar cell technologies. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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13 pages, 2023 KiB

Open AccessArticle

Application of Grazing-Incidence X-ray Methods to Study Terrace-Stepped SiC Surface for Graphene Growth

by Boris S. Roschin, Tatiana S. Argunova, Sergey P. Lebedev, Victor E. Asadchikov, Alexander A. Lebedev, Yuri O. Volkov and Alexander D. Nuzhdin

Materials 2022, 15(21), 7669; https://doi.org/10.3390/ma15217669 - 31 Oct 2022

Viewed by 1749

Abstract

The synthesis of graphene by the graphitization of SiC surface has been driven by a need to develop a way to produce graphene in large quantities. With the increased use of thermal treatments of commercial SiC substrates, a comprehension of the surface restructuring [...] Read more.

The synthesis of graphene by the graphitization of SiC surface has been driven by a need to develop a way to produce graphene in large quantities. With the increased use of thermal treatments of commercial SiC substrates, a comprehension of the surface restructuring due to the formation of a terrace-stepped nanorelief is becoming a pressing challenge. The aim of this paper is to evaluate the utility of X-ray reflectometry and grazing-incidence off-specular scattering for a non-destructive estimate of depth-graded and lateral inhomogeneities on SiC wafers annealed in a vacuum at a temperature of 1400–1500 °C. It is shown that the grazing-incidence X-ray method is a powerful tool for the assessment of statistical parameters, such as effective roughness height, average terrace period and dispersion. Moreover, these methods are advantageous to local probe techniques because a broad range of spatial frequencies allows for faster inspection of the whole surface area. We have found that power spectral density functions and in-depth density profiles manifest themselves differently between the probing directions along and across a terrace edge. Finally, the X-ray scattering data demonstrate quantitative agreement with the results of atomic force microscopy. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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7 pages, 1236 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of Effective Mass in InGaAsN/GaAs Quantum Wells Using Transient Spectroscopy

by Lubica Stuchlikova, Beata Sciana, Arpad Kosa, Matej Matus, Peter Benko, Juraj Marek, Martin Donoval, Wojciech Dawidowski, Damian Radziewicz and Martin Weis

Materials 2022, 15(21), 7621; https://doi.org/10.3390/ma15217621 - 30 Oct 2022

Viewed by 1760

Abstract

Transient spectroscopies are sensitive to charge carriers released from trapping centres in semiconducting devices. Even though these spectroscopies are mostly applied to reveal defects causing states that are localised in the energy gap, these methods also sense-charge from quantum wells in heterostructures. However, [...] Read more.

Transient spectroscopies are sensitive to charge carriers released from trapping centres in semiconducting devices. Even though these spectroscopies are mostly applied to reveal defects causing states that are localised in the energy gap, these methods also sense-charge from quantum wells in heterostructures. However, proper evaluation of material response to external stimuli requires knowledge of material properties such as electron effective mass in complex structures. Here we propose a method for precise evaluation of effective mass in quantum well heterostructures. The infinite well model is successfully applied to the InGaAsN/GaAs quantum well structure and used to evaluate electron effective mass in the conduction and valence bands. The effective mass m/m₀ of charges from the conduction band was 0.093 ± 0.006, while the charges from the valence band exhibited an effective mass of 0.122 ± 0.018. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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Review

Jump to: Research

91 pages, 19320 KiB

Open AccessEditor’s ChoiceReview

Ammonothermal Crystal Growth of Functional Nitrides for Semiconductor Devices: Status and Potential

by Thomas Wostatek, V. Y. M. Rajesh Chirala, Nathan Stoddard, Ege N. Civas, Siddha Pimputkar and Saskia Schimmel

Materials 2024, 17(13), 3104; https://doi.org/10.3390/ma17133104 - 25 Jun 2024

Viewed by 1632

Abstract

The state-of-the-art ammonothermal method for the growth of nitrides is reviewed here, with an emphasis on binary and ternary nitrides beyond GaN. A wide range of relevant aspects are covered, from fundamental autoclave technology, to reactivity and solubility of elements, to synthesized crystalline [...] Read more.

The state-of-the-art ammonothermal method for the growth of nitrides is reviewed here, with an emphasis on binary and ternary nitrides beyond GaN. A wide range of relevant aspects are covered, from fundamental autoclave technology, to reactivity and solubility of elements, to synthesized crystalline nitride materials and their properties. Initially, the potential of emerging and novel nitrides is discussed, motivating their synthesis in single crystal form. This is followed by a summary of our current understanding of the reactivity/solubility of species and the state-of-the-art single crystal synthesis for GaN, AlN, AlGaN, BN, InN, and, more generally, ternary and higher order nitrides. Investigation of the synthesized materials is presented, with a focus on point defects (impurities, native defects including hydrogenated vacancies) based on GaN and potential pathways for their mitigation or circumvention for achieving a wide range of controllable functional and structural material properties. Lastly, recent developments in autoclave technology are reviewed, based on GaN, with a focus on advances in development of in situ technologies, including in situ temperature measurements, optical absorption via UV/Vis spectroscopy, imaging of the solution and crystals via optical (visible, X-ray), along with use of X-ray computed tomography and diffraction. While time intensive to develop, these technologies are now capable of offering unprecedented insight into the autoclave and, hence, facilitating the rapid exploration of novel nitride synthesis using the ammonothermal method. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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27 pages, 3452 KiB

Open AccessReview

Amorphous SiC Thin Films Deposited by Plasma-Enhanced Chemical Vapor Deposition for Passivation in Biomedical Devices

by Scott Greenhorn, Edwige Bano, Valérie Stambouli and Konstantinos Zekentes

Materials 2024, 17(5), 1135; https://doi.org/10.3390/ma17051135 - 29 Feb 2024

Cited by 2 | Viewed by 1699

Abstract

Amorphous silicon carbide (a-SiC) is a wide-bandgap semiconductor with high robustness and biocompatibility, making it a promising material for applications in biomedical device passivation. a-SiC thin film deposition has been a subject of research for several decades with a variety of approaches investigated [...] Read more.

Amorphous silicon carbide (a-SiC) is a wide-bandgap semiconductor with high robustness and biocompatibility, making it a promising material for applications in biomedical device passivation. a-SiC thin film deposition has been a subject of research for several decades with a variety of approaches investigated to achieve optimal properties for multiple applications, with an emphasis on properties relevant to biomedical devices in the past decade. This review summarizes the results of many optimization studies, identifying strategies that have been used to achieve desirable film properties and discussing the proposed physical interpretations. In addition, divergent results from studies are contrasted, with attempts to reconcile the results, while areas of uncertainty are highlighted. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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22 pages, 4778 KiB

Open AccessReview

Silicon and Silicon Carbide Recrystallization by Laser Annealing: A Review

by Daniele Arduino, Stefano Stassi, Chiara Spano, Luciano Scaltrito, Sergio Ferrero and Valentina Bertana

Materials 2023, 16(24), 7674; https://doi.org/10.3390/ma16247674 - 16 Dec 2023

Cited by 4 | Viewed by 3472

Abstract

Modifying material properties within a specific spatial region is a pivotal stage in the fabrication of microelectronic devices. Laser annealing emerges as a compelling technology, offering precise control over the crystalline structure of semiconductor materials and facilitating the activation of doping ions in [...] Read more.

Modifying material properties within a specific spatial region is a pivotal stage in the fabrication of microelectronic devices. Laser annealing emerges as a compelling technology, offering precise control over the crystalline structure of semiconductor materials and facilitating the activation of doping ions in localized regions. This obviates the necessity for annealing the entire wafer or device. The objective of this review is to comprehensively investigate laser annealing processes specifically targeting the crystallization of amorphous silicon (Si) and silicon carbide (SiC) samples. Silicon finds extensive use in diverse applications, including microelectronics and solar cells, while SiC serves as a crucial material for developing components designed to operate in challenging environments or high-power integrated devices. The review commences with an exploration of the underlying theory and fundamentals of laser annealing techniques. It then delves into an analysis of the most pertinent studies focused on the crystallization of these two semiconductor materials. Full article

(This article belongs to the Special Issue Feature Papers in Electronic Materials Section (Volume 2)—15th Anniversary of Materials)

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