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4H‐SiC is a key enabler for realizing integrated electronics operating in harsh environments, which exhibit very high temperatures. Through advances in 4H‐SiC process technology, different sensor and circuit types have been demonstrated to operate stable at temperatures as high as 800 °C, paving the way toward harsh‐environment immune smart sensors. In this work, for the first time the operation of ion‐implanted 4H‐SiC Hall sensors realized in a wafer scale Bipolar‐CMOS‐DMOS technology is demonstrated at a wide operation temperature range spanning room temperature up to 500 °C in addition to short‐term operation up to 600 °C. The temperature‐dependent sensor characteristics of 15–22 samples are evaluated in terms of sensitivity and noise. The small inter‐device variations reflect the stability of the used process for very high temperature Hall sensors. The noise‐limited detectivity is further evaluated, revealing a best value of 950 nT/Hz$\sqrt{\mathrm{Hz}}$ and a mean detectivity of 1 µT/Hz$\sqrt{\mathrm{Hz}}$ at 500 °C. This is the best value reported up to date for very high temperature Hall sensors, besides being the first demonstration of ion‐implanted wide‐bandgap Hall sensors. Overall, the results reflect the potential of the demonstrated Hall sensors for the next generation of integrated magnetic field sensors in harsh environments. [ABSTRACT FROM AUTHOR]

With the increasing development of semiconductors materials and technology, higher demands are emphasized on the packaging methods and materials for the high-temperature electronics. In this investigation, a novel packaging method by eutectic SnIn solder foils using transient liquid phase (TLP) bonding without pressure was introduced, and the microstructures as well as performance evolution of joint bonded at different bonding parameters were analyzed. During the bonding process, the solder alloy as well as weak Cu2In were gradually consumed, and full Cu6(In, Sn)5 bondline could be obtained without any obvious defects at only 200 °C. Higher temperature and longer time could give a further enhancement on the microstructure and the mechanical performance, where dense robust Cu3(In, Sn) bondline formed. Owing to the microstructure optimization, the average shear strength of bonded joint increased by 301.87%. With the great performance and eco-efficiency, this novel TLP-bonding method using SnIn solder foil is capable to meet the increasing requirement of high-temperature packaging. [ABSTRACT FROM AUTHOR]

Power Schottky barrier diodes (SBDs) face an inherent trade-off between forward conduction loss and reverse blocking capability. This limitation becomes more severe for ultra-wide bandgap (UWBG) SBDs due to the large junction field. A high Schottky barrier is usually required to suppress the reverse leakage current at the price of an increased forward voltage drop (VF). This work demonstrates a Ga2O3 junction barrier Schottky (JBS) diode that employs the embedded p-type NiO grids to move the peak electric field away from the Schottky junction, thereby allowing for the use of an ultra-low barrier TiN Schottky contact. This JBS diode concurrently realizes a low VF of 0.91 V (at forward current of 100 A/cm2) and a high breakdown voltage over 1 kV, with the VF being the lowest in all the reported vertical UWBG power diodes. Based on the device characteristics measured up to 200 °C, we further analyze the power loss of this JBS diode across a wide range of operational duty cycles and temperatures, which is found to outperform the TiN/Ga2O3 SBDs or NiO/Ga2O3 PN diodes. These findings underscore the potential of low-barrier UWBG JBS diodes for high-frequency, high-temperature power electronics applications. [ABSTRACT FROM AUTHOR]

The sintering process of Cu nanoparticles is challenging due to the oxidation of Cu and the formation of voids in the die-attach layer. In this work, a simple and cost-effective bimodal-sized Cu composite paste was prepared for a high-strength Cu-Cu joint. The joint microstructure and sintering properties were systematically investigated by adjusting the mass ratio of the particle dimensions from 80 nm to 300 nm and varying the sintering parameters. Die attachment by pressure (20 MPa)-assisted sintering in air at 250°C was rapidly achieved using bimodal-sized Cu particles. The joint sintered for 1 min exhibited shear strength of 85.63 MPa, while 5-min sintering was able to obtain a dense bondline structure, and the shear strength reached 102.46 MPa. The sintered layers in nitrogen had the highest thermal conductivity of 284 W/m K and low resistivity of 4.42 µΩ cm. These results confirm that bimodal-sized Cu composite paste can be considered as an inexpensive potential die-attach material for high-temperature electronics packaging. [ABSTRACT FROM AUTHOR]

Rapid design and development of the emergent ultrawide-bandgap semiconductors Ga2O3 and Al2O3 require a compact model of their electronic structures, accurate over the broad energy range accessed in future high-field, high-frequency, and high-temperature electronics and visible and ultraviolet photonics. A minimal tight-binding model is developed to reproduce the first-principles electronic structures of the β- and α-phases of Ga2O3 and Al2O3 throughout their reciprocal spaces. Application of this model to α-Ga2O3=α-Al2O3 superlattices reveals that intersubband transitions can be engineered to the 1:55 μm telecommunications wavelength, opening new directions in oxide photonics. Furthermore, by accurately reproducing the bandgap, orbital character, effective mass, and high-energy features of the conduction band, this compact model will assist in the investigation and design of the electrical and optical properties of bulk materials, devices, and quantum confined heterostructures. [ABSTRACT FROM AUTHOR]

Rapid design and development of the emergent ultrawide-bandgap semiconductors Ga2O3 and Al2O3 require a compact model of their electronic structures, accurate over the broad energy range accessed in future high-field, high-frequency, and high-temperature electronics and visible and ultraviolet photonics. A minimal tight-binding model is developed to reproduce the first-principles electronic structures of the β- and α-phases of Ga2O3 and Al2O3 throughout their reciprocal spaces. Application of this model to α-Ga2O3=α-Al2O3 superlattices reveals that intersubband transitions can be engineered to the 1:55 μm telecommunications wavelength, opening new directions in oxide photonics. Furthermore, by accurately reproducing the bandgap, orbital character, effective mass, and high-energy features of the conduction band, this compact model will assist in the investigation and design of the electrical and optical properties of bulk materials, devices, and quantum confined heterostructures. [ABSTRACT FROM AUTHOR]

Integrated circuits based on wide bandgap semiconductors are considered an attractive option for meeting the demand for high-temperature electronics. Here, we report an analog-to-digital converter fabricated in a silicon carbide complementary metal–oxide–semiconductor technology now available through Europractice. The MOSFET component in this technology was measured up to 500 °C, and the key parameters, such as threshold voltage, field-effect mobility, and channel-length modulation parameters, were extracted. A 4-bit flash data converter, consisting of 266 transistors, is implemented with this technology and demonstrates correct operation up to 400 °C. Finally, the gate oxide quality is investigated by time-dependent dielectric breakdown measurements at 500 °C. A field-acceleration factor of 4.4 dec/(MV/cm) is obtained by applying the E model. [ABSTRACT FROM AUTHOR]

The ceramic oxide Na2Ba2Pr2W2Ti4Nb4O30 (NBPWTN) is prepared by a mechanical mixed oxide route. The compound formation and the phase are concluded from the x‐ray diffraction pattern taken at room temperature (XRD). The uniform distribution of grains of various sizes with negligible voids is studied from scanning electron micrograph of the sample pellet. The presence of dielectric dispersion and ferroelectric phase in the material is observed from the temperature‐dependent dielectric parameters at selected frequencies. The existence of ferroelectricity in the material is further confirmed by the room temperature hysteresis loop. Impedance spectroscopic studies informed about the correlation between the microstructure and electrical behavior. The frequency variation of AC conductivity refers to Jonscher's law. The temperature variation of frequency exponent term n indicates OLPT (overlapping large polaron‐tunneling) model of the conduction mechanism in the sample. NBPWTN is a strong candidate for applications involving thermistor‐related devices because of the temperature dependency of resistance. The value of temperature sensitivity coefficient β in our investigation is achieved between 2000 and 11 000 K, confirming that the material has a high‐temperature stability property and is ideal for high‐temperature electronics applications. The high room temperature dielectric constant value of the ceramic (around 500) is useful for dielectric capacitor applications. [ABSTRACT FROM AUTHOR]

Among all the functions that electronics currently perform, clock synthesis has a backbone role. Charge pump phase-locked loops (CP-PLL) are widely used to accomplish clock synthesis thanks to their versatility. One of the most critical parts of CP-PLLs is the charge pump, which greatly influences the system's performance. Even though several high-performance charge pumps have been proposed in the past, with the quick spread of electronics in all the engineering fields, the design of such electronic devices has encountered several additional challenges dictated by external environmental conditions. Examples of these engineering sectors are space, aerospace, industrial, and automotive applications, where the charge pump has to face high environmental temperatures and radiation effects. As a consequence, its design and experimental characterization have to be performed to ensure reliability when operating in harsh conditions. However, to the best of the authors' knowledge, no works in the literature have ever presented a complete charge pump design and characterization in such harsh environments. Therefore, to fill this gap, this paper presents a charge pump for PLL applications specifically designed to reach operating temperatures up to 200 °C and total ionizing dose levels up to 100 Mrad. All design choices have been experimentally verified and are discussed throughout the paper in detail. With the proposed design, we obtained an output current variation of less than 8% at 200 °C and less than 2.5% at 100 Mrad. As opposed to the CPs that can be found in the literature, these results were measured on silicon. The performed measurements confirm that the current variation at 200 °C is better than that of the state-of-the-art CPs operating at lower temperatures, which, moreover, were only simulated. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the challenges at the device and circuit level that must be addressed to design reliable silicon CMOS integrated circuits operating in high-temperature environments. We present experimental results on representative devices fabricated with a 180 nm CMOS SOI platform, which have been characterized up to 300°C, discuss issues arising at high temperature, and propose possible solutions. A BJT-based temperature sensor core is also described and evaluated across the same extended temperature range. We also propose and discuss design criteria optimized for a wide range of operating temperature. A sufficient on/off current ratio can be achieved by taking advantage of the isolation provided by low-leakage CMOS SOI process, while operation at low current density must be ensured to mitigate electromigration effects. Within these conditions, low-power precise sensing circuits can be effectively implemented with operating temperature up to 300°C, that are extremely relevant for industrial, mobility, and space applications.

In this letter, molybdenum nitride (MoN) gate AlGaN/GaN HEMT has been investigated with MoN developed in various physical vapour deposition (PVD) conditions. The Schottky gate is studied through forward and reverse characteristics with different processed MoN, which is compared with the standard Ni gate. Similar DC and radio frequency (RF) performances are obtained with MoN and Ni gate, while MoN demonstrated higher reliability than Ni gate through RF aging test. [ABSTRACT FROM AUTHOR]

One of the most interesting wide-bandgap semiconductor is 4H-SiC that has an indirect wide-bandgap of 3.3 eV. This material holds great potential to develop power devices that find applications in the field of high-voltage and high-temperature electronics and harsh environments. In this study, we employed complementary noninvasive characterization techniques, including micro-Raman, optical absorption, steady-state, and time-resolved photoluminescence spectroscopy, to investigate the characteristics of a 12 μm thick epitaxial layer of 4H-SiC grown on 4H-SiC. Furthermore, we explored the impact of ionizing radiation on this material, utilizing β-rays and two x-ray sources. The doses are in the range of 1–100 kGy for electrons with energy of 2.5 MeV, 16 kGy for the first x-ray source (an x-ray tube with a W target operating at an anode bias voltage of 28 kV), and 100 kGy for the second x-ray source (an x-ray tube with a W target operating at an anode bias voltage of 100 kV). When exposed to the electron beam, the excitonic band at 3.2 eV exhibits a reduction in its lifetime as the deposited dose increases. In particular, in samples characterized by a greater amount of native defects, both extended and point defects, this effect becomes evident at lower deposited doses. Conversely, in the samples subjected to x-ray irradiation, these effects are not observed. These findings indicate that electron beam irradiation triggers the formation of defects associated with atomic displacement. Ultimately, we have examined the impact of thermal treatments in air, ranging from 100 to 900 °C, to investigate the recovery characteristics of 4H-SiC. [ABSTRACT FROM AUTHOR]

As the modern electronic technology extends into operating in harsh working conditions, it calls for a system that is capable of uncompromising performance in extreme environments, thus providing a strong motivation to look for advanced materials and electronics with the capability of high‐throughput and rapid prototyping. Coupled with additive manufacturing, molecular decomposition metals bypass the challenging oddities of traditional material‐limited and thermally initiated metalworking, enabling high throughput and rapid prototyping of stoichiometry and composition‐controlled metals. Here, a new paradigm for the design and additive manufacturing of copper metallic alloy materials onto ceramics is described by printing molecular decomposable metal materials, capable of withstanding thermo‐mechanical loading, operating in extreme environments in static and dynamic conditions. The resulting printed hybrid electronics are electrically stable for 25 h of aging at 1000 °C. This curious fact paves a way for printed antenna and sensor electronics that reliably operate up to 1000 °C. These results can be further extended to establish other printable molecular decomposable materials as a platform for rapid prototyping of high temperature electronics that are suitable for harsh environments. [ABSTRACT FROM AUTHOR]

To date, it has remained challenging to achieve N-polar AlN, which is of great importance for high power, high frequency, and high temperature electronics, acoustic resonators and filters, ultraviolet (UV) optoelectronics, and integrated photonics. Here, we performed a detailed study of the molecular beam epitaxy and characterization of N-polar AlN on C-face 4H-SiC substrates. The N-polar AlN films grown under optimized conditions exhibit an atomically smooth surface and strong excitonic emission in the deep UV with luminescence efficiency exceeding 50% at room temperature. Detailed scanning transmission electron microscopy (STEM) studies suggest that most dislocations are terminated/annihilated within ∼200 nm AlN grown directly on the SiC substrate due to the relatively small (1%) lattice mismatch between AlN and SiC. The strain distribution of AlN is further analyzed by STEM and micro-Raman spectroscopy, and its impact on the temperature-dependent deep UV emission is elucidated. [ABSTRACT FROM AUTHOR]

High-temperature capable materials, metals, and ceramics are attracting significant interest for applications in extreme environmental conditions. Herein, a hybrid metal-reinforced ceramic matrix material consisting of preceramic-derived high-temperature SiOC and copper nanoplates is reported, enabling the manufacturing of high-temperature sensing electronics. The preceramic polymer precursors including polydimethylsiloxane and polydimethylsilane, together with copper nanoplates, are thermally converted into durable copperreinforced SiOC ceramics. The presence of copper in SiOC ceramics enhances its electrical conductivity, while SiOC suppresses oxygen uptake and acts as a shield for oxidation to achieve high-temperature thermal resistance and negative temperature coefficient at high temperatures. A comprehensive electric and sensing performance, combined with cost-effectiveness and scalability, can facilitate the utilization of hybrid Cu and SiOC composites in high-temperature electronics. [ABSTRACT FROM AUTHOR]

Refractory metals offer exceptional benefits for high temperature electronics including high‐temperature resistance, corrosion resistance and excellent mechanical strength, while their high melting temperature and poor processibility poses challenges to manufacturing. Here this work reports a direct ink writing and tar‐mediated laser sintering (DIW‐TMLS) technique to fabricate three‐dimensional (3D) refractory metal devices for high temperature applications. Metallic inks with high viscosity and enhanced light absorbance are designed by utilizing coal tar as binder. The printed patterns are sintered into oxidation‐free porous metallic structures using a low‐power (<10 W) laser in ambient environment, and 3D freestanding architectures can be rapidly fabricated by one step. Several applications are presented, including a fractal pattern‐based strain gauge, an electrically small antenna (ESA) patterned on a hemisphere, and a wireless temperature sensor that can work up to 350 °C and withstand burning flames. The DIW‐TMLS technique paves a viable route for rapid patterning of various metal materials with wide applicability, high flexibility, and 3D conformability, expanding the possibilities of harsh environment sensors. [ABSTRACT FROM AUTHOR]

Currently, research on capacitor materials for high-temperature and power electronics focuses on achieving new record-breaking limits for dielectric properties or energy storage densities, with little regard for the stability of key parameters during operation or component reliability. While environmental conditions usually do not exceed 300 °C, the voltage ratings of capacitors are still unclear. Within this work, multilayer ceramic capacitors based on lead-free sodium bismuth titanate with AgPd inner electrodes have exhibited exceptional stability of properties and capacitance at high temperatures and voltages during operation. Despite the lack of precise requirements and limits specified by manufacturers and industry, these prototype MLCCs can help to open up the field of high-temperature and power electronics. Their extensive stability of dielectric properties allows for a rather universal application. [ABSTRACT FROM AUTHOR]

Crystalline wurtzite zinc oxide (w-ZnO) can be used as a wide bandgap semiconductor for light emitting devices and transparent or high temperature electronics. The use of amorphous zinc oxide (a-ZnO) can be an advantage in these applications. In this paper, we report on x-ray amorphous a-ZnOx thin films (∼500 nm) deposited at cryogenic temperatures by reactive magnetron sputtering. The substrates were cooled by a nitrogen flow through the copper substrate holder during the deposition. The films were characterized by x-ray diffraction, Raman, infrared, UV–Vis-near-infrared spectroscopies, and ellipsometry. The a-ZnOx films on glass and Ti substrates were obtained at the substrate holder temperature of approximately −100 °C. New vibration bands at 201, 372, and 473 cm−1 as well as O–H stretch and bend absorption bands in the a-ZnOx films were detected by Fourier transform infrared spectroscopy. Raman spectra showed characteristic ZnO2 peaks at 386 and 858 cm−1 attributed to the peroxide ion O22− stretching and libration modes, respectively. In addition, the films contain neutral and ionized O2 and O2− species. The a-ZnOx films are highly transparent in the visible light range (≈87%) and exhibit a refractive index of 1.68 at 2.25 eV (550 nm). An optical bandgap is 4.65 eV with an additional band edge absorption feature at 3.50 eV. It has been shown that the deposition on actively cooled substrates can be a suitable technique to obtain low temperature phases that cannot be deposited at room temperature. [ABSTRACT FROM AUTHOR]

This Letter reports on the mechanisms of reverse leakage current transport in InAlN/GaN heterostructure Schottky diodes with intentionally oxidized iridium oxide (IrOx) contacts across a wide temperature range. Current–voltage characteristics were experimentally measured from 25 to 500 °C (≈ 300 to 773 K). Three distinct regions in the reverse bias regime of operation and their corresponding dominant current transport mechanisms are identified. A trap-assisted tunneling mechanism is observed at low reverse bias, and trap energy levels are between 1.12 and 1.99 eV. At medium reverse bias, Poole–Frenkel emission is decomposed into low-field, mid-field, and high-field regions and the related trap activation energies vary from 0.38 to 2.04 eV. At high reverse bias, the Fowler–Nordheim model is applied and the effective barrier height to tunneling is 0.78 eV. The model of the reverse leakage current constructed using the parameters associated with these transport mechanisms closely aligns with the experimental data and supports the advancement of high-temperature electronics based on IrOx -gated InAlN/GaN heterostructure technology. [ABSTRACT FROM AUTHOR]

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The raised demand for portable electronics in high‐temperature environments (>150 °C) stimulates the search for solutions to release the temperature constraints of power supply. All‐solid‐state microsupercapacitors (MSCs) are envisioned as promising on‐chip power supply components, but at present, nearly none of them can work at temperature over 200 °C, mainly restricted by the electrolytes which possess either low thermal stability or incompatible fabrication process with on‐chip integration. In this work, we have developed a novel process to fabricate highly thermally stable ionic liquid/ceramic composite electrolytes for on‐chip integrated MSCs. Remarkably, the electrolytes enable MSCs with graphene‐based electrodes to operate at temperatures as high as 250 °C with a high areal capacitance (~72 mF cm−2 at 5 mV s−1) and good cycling stability (70 % capacitance retention after 1000 cycles at 1.4 mA cm−2). [ABSTRACT FROM AUTHOR]

With the development of electronic technology towards high power, miniaturization, and system integration, power electronic packaging is facing increasing challenges, especially for die attachment. This research aims to explore silver-coated copper (Cu@Ag) paste with sufficient mechanical properties and high-temperature reliability, as an alternative solution for silver sintering with lower cost. Firstly, micro-Cu@Ag sintering pastes were investigated under four kinds of polyol-based solvent systems and two types of particle morphologies, which included sphere-type (SCu@Ag) and flake-type (FCu@Ag). Sintering performance and microstructural evolution were compared and analyzed. Notably, sintered joints employing the terpineol–polyethylene glycol solvent system and flake-type morphology displayed a denser microstructure in comparison to SCu@Ag joints. Its bonding strength reached 36.15 MPa, which was approximately 20% higher than SCu@Ag joints. Subsequently, the influence of key sintering process parameters on Cu@Ag joints was analyzed, including sintering temperature, pressure and time. Additionally, high-temperature aging and thermal cycling tests were conducted on the optimized Cu@Ag joints to assess their reliability. Finally, the micromechanical properties of Cu@Ag joints before and after high-temperature aging were further evaluated by nanoindentation including creep properties. The elastoplastic constitutive models of Cu@Ag sintered materials with different particle morphologies were constructed, providing valuable insights for reliability evaluation. The results indicated that FCu@Ag joints exhibited satisfactory creep resistance and high-temperature reliability. In conclusion, the FCu@Ag micro-paste based on the terpineol–polyethylene glycol solvent system proposed in this study demonstrated sufficient bonding strength, high reliability, and adequate mechanical properties as an attractive solution for high-temperature power electronics packaging. [ABSTRACT FROM AUTHOR]

High temperature operation of enhancement-mode (E-mode) and depletion-mode (D-mode) AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) was demonstrated. By using the circular device structure, off-state current was effectively suppressed, and record high Ion/Ioff ratio around 108 was obtained at 400 °C. Atomic layer etching was used for formation of the gate recess structure in the E-mode device, and good interface was made which enabled stable normally-off operation up to 400 °C. D-mode device experienced positive threshold voltage shift during the high temperature operation and after cooling down to room temperature, due to strain relaxation. On the other hand, due to the very thin AlGaN layer retained under the gate of the E-mode device, the threshold voltage of the E-mode device is nearly unchanged when the sample is heated up and cooled down. A direct coupled field-effect transistor logic (DCFL) inverter was fabricated based on the E-mode and D-mode devices and showed stable operation up to 400 °C.

Beta-phase gallium oxide (β-Ga2O3) has attracted attention in recent years as a potentially low cost, large area substrate and active layer material for high power, high temperature power electronics and sensing devices. However, growth of β-Ga2O3 crystals is complicated by easily activated (100) and (001) cleavage planes, the presence of low angle grain boundaries (LAGBs) and twins, and the potential formation of polycrystalline grains. In this study, β-Ga2O3 crystals were grown by the edge-defined film-fed growth technique with an (010) principal face. Two crystals with apparently randomly formed high angle grain boundaries (HAGBs) were selected and analyzed by electron backscatter diffraction, electron channeling contrast imaging, and cathodoluminescence to investigate the nature of the LAGBs and the source of the HAGB formation. It was discovered that planar LAGBs lying parallel to the (010) plane exist in the region immediately preceding the start of an HAGB. Increased misorientation across the LAGB was observed, approaching the initiation of a new grain. We present multimodal microscopy characterization, correlating misorientation and variation in optoelectronic properties with LAGBs and the associated dislocations. [ABSTRACT FROM AUTHOR]

At present, interest in silicon carbide is growing, as it has promising properties in some applications: high-temperature electronics, high-frequency power electronics and others. In this regard, it is necessary to produce high quality silicon carbide substrates from which device structures will be created. The proper quality is achieved through the operations, one of which is polishing. Currently, chemical-mechanical polishing method is widely used for this operation, which has some disadvantages: long processing time, high cost and low technical flexibility. A more promising technology for polishing SiC substrates may be electron-beam treatment, which leads to thermal modification of the silicon carbide surface and, as a sequence, to a reduction in roughness. In this paper, a heating model is discussed in relation to a possible polishing mechanism of silicon carbide during its electron-beam treatment, related to the sublimation of silicon formed by the thermal dissociation of SiC. The heating process of a model (rough) silicon carbide surface was modeled in COMSOL Multiphysics® as a solution to the heat conduction problem. The model SiC surface is an array of straight pyramids. The simulation showed that as a result of electron beam heating, the tops of the pyramids are heated more strongly than their bases, which will lead to selective sublimation of silicon and reduction of roughness. [ABSTRACT FROM AUTHOR]

Packaging is a pivotal step in electronic device manufacturing, determining the translational performance of bare chips. In summary, although emerging technologies might be quite different when electronic devices turn "soft", the essence of electronic packaging technology will always focus on the interconnection, integration, and protection of associated microsystems. More broadly, for the development of mainstream "Hard" packaging technology, that is, "More Moore" or "More-than-Moore", gives us opportunities to explore the unknown with non-generic packaging designs for integrated circuit (IC), micro-electro-mechanical system (MEMS), optoelectronics, lasing photonics, and power electronics, among others. Currently, the total number of micro-bumps in a single advanced integrated circuit (IC) chip has already surpassed 100,000, and the pitch size between adjacent microbumps can be lower than 20 m. Therefore, the continuing pursuit of bonding technology [[5]] is driven by the down-scaling trend of microbumps with an ultra-fine pitch for a more compact and reliable design of 3D packaging architectures. [Extracted from the article]

Advanced materials, electrically conductive and oxidation resistant, are frontrunners for technological advancements in cutting‐edge high‐temperature electronics. Rational design and manufacturing of hierarchical material structures is indispensable to achieve such disparate functionalities. Here, high‐temperature copper–graphene conductors, through additive manufacturing, which prohibits oxygen adsorbates and serves as the barrier for oxygen migration to enable electric stability and reliability at high temperatures, are reported. The combination of graphene and alumina surface passivation enables the electric stability of copper–graphene under thermal impact above 1000 °C. The findings shown here, the synergistic combination of high conductivity and oxidation resistance, enunciate the passivation capabilities for additively manufactured flexible electronics operating under harsh conditions. [ABSTRACT FROM AUTHOR]

Barometers floating on high‐altitude balloons in the relatively clement cloud layer on Venus could detect and characterize acoustic waves generated by seismic activity, avoiding the need for high‐temperature electronics required for surface seismology. Garcia et al. (2022, https://doi.org/10.1029/2022GL098844) recently demonstrated the detection of low‐frequency sound (infrasound) caused by earthquakes of magnitudes 7.3 and 7.5 from stratospheric balloons nearly 3,000 km away from the epicenter. They provided a preliminary demonstration of earthquake magnitude and location inversion, and the determination of S‐ and Rayleigh wave velocities using only their acoustic signature. Large earthquakes produce low‐frequency seismic waves that penetrate the interiors of planets; their detection at continental‐scale distances from a high‐vantage point demonstrates the feasibility of balloon‐based investigations of Venus' interior. We contextualize these results within the effort to perform seismology on Venus from balloons, discuss its limitations, and share perspectives on open research questions in this area. Plain Language Summary: Scientists have peered inside Earth, the Moon, and Mars by recording how seismic waves pass through them. Venus' interior is a mystery, though, because the heat and pressure at its surface have thus far prevented direct measurement of seismic activity. Balloons with pressure recorders higher up in the Venusian atmosphere, where it is much cooler, can listen for the sounds the seismic waves make as a proxy for directly measuring ground motion. Before sending the balloons to Venus, it is important to make sure that this idea would actually work. The fact that (Garcia et al., 2022, https://doi.org/10.1029/2022GL098844) were able to record sound from large earthquakes thousands of kilometers away on Earth means that one should be able to do the same thing on Venus as well. While there are still details to work out, listening for quakes on Venus from balloons just got a major boost here on Earth. Key Points: A network of stratospheric balloons captured infrasound from several large earthquakesThis is the first detection of seismic activity from airborne sensors at continental distancesA similar network on Venus could capture and geolocate seismic activity [ABSTRACT FROM AUTHOR]

We have fabricated vertical p-type gallium nitride (GaN) Schottky barrier diodes (SBDs) using various Schottky metals such as Pt, Pd, Ni, Mo, Ti, and Al. Current–voltage characteristics revealed that Schottky barrier heights determined using a thermionic emission (TE) model (ϕBTE) were ranged between 1.90 eV for Pt and 2.56 eV for Mo depending on the work function (ϕm) of the Schottky metals. Despite their low ϕm, Ti and Al gave unusually small ϕBTE probably due to the interfacial reaction between metal and p-type GaN. We also found that Mo/p-GaN SBDs exhibited a clear rectifying property even at 800 K, and the thermionic emission diffusion (TED) model explained well their high-temperature I–V characteristics. Furthermore, the temperature variation of Schottky barrier heights determined using a TED model (ϕBTED) almost agrees with half of the temperature variation of the bandgap energy. These findings will be helpful for the application of p-type GaN Schottky interfaces to high-power and high-temperature electronics. [ABSTRACT FROM AUTHOR]

Power electronics converters operating at elevated temperature usually have degraded performance, such as reduced efficiency, lower noise immunity, and decreased system reliability, compared to those operating at room temperature. Nevertheless, harsh-environment applications, such as deep earth drilling, automotive, avionics, and space exploration, have been utilizing converters in high-temperature environments and are continuously pushing the temperature limits higher and higher with the advances in device technologies and converter design methodologies. This article starts with a literature study to identify the temperature dependence and the temperature limits of individual components. Then, published works about high-temperature converters are examined. Their selection of components is compared. Experimental results are analyzed to reflect on the efficacy of different component selections. Finally, since the latest published high-temperature converter was developed more than five years ago, a 1-kV input, 520-V output, 1-kW, $150$ °C-ambient-temperature-rated dc–dc converter is designed with state-of-the-art devices. Based on the literature review, and the test of the $150$ °C prototype, the main challenges of designing high-temperature power electronics converters are identified and concluded to be time-consuming, difficult, and expensive characterization of components, lack of accurate and computationally efficient models of converters, and optimizing component selection within short development time. [ABSTRACT FROM AUTHOR]

High‐temperature power electronics is an advancing area of research, especially given the widespread availability of wide bandgap semiconductors. Herein, a suitability analysis of (1−x)BiScO3−xPbTiO3 (BSPT) as a material for high‐temperature piezoelectric transformers (PTs) is presented and compared to state‐of‐the‐art Pb(Zr1−xTix)O3 (PZT). Initially, both materials are compared using a variety of metrics to prove the suitability of BSPT as a material for constructing PTs specifically for high‐temperature applications. PTs based on the two materials are designed and fabricated, and then subsequently characterized using impedance measurements. Finally, half‐bridge resonant inverters are constructed using both PTs and the performance of each inverter measured over a range of ambient temperatures. The result of these experiments confirms the suitability of BSPT for PT applications and shows the excellent performance of BSPT PTs at temperatures in excess of that possible with PZT‐based PTs. [ABSTRACT FROM AUTHOR]

In order to reduce the thermal discomfort and fire accidents caused by overheating of electronics and high temperature of buildings, high-performance thermal insulation and fire-resistant materials are urgently desirable. Cellulose nanofiber cryogel derived from regenerative resources holds wide promise in the field of thermal insulation, but its inherent flammability, poor mechanical strength and water resistance make it face great challenges in practical application. Herein, a lightweight, porous, anisotropic cellulose nanofiber/hydroxylated boron nitride nanosheet/methyltrimethoxysilane composite cryogel (Si-CNF/BNNS) was prepared by unidirectional freeze-casting technique. Attributed to the hydrogen bond and silylation cross-linking of CNFs with BNNS and MTMS, as well as the aligned structure of cryogel, Si-CNF/BNNS cryogel was robust axially and compressible radially. The thermal conductivity of cryogel was 0.0621 W m−1 K−1 in the axial direction and 0.0339 W m−1 K−1 in the radial direction, demonstrating an anisotropic thermal insulation performance. In addition, the silylation modification and the addition of BNNS endowed cryogel with excellent flame retardant and hydrophobic properties, as evidenced by extremely low peak heat release rate of 14.05 kW m−2 and water contact angle of 136.6°. Surprisingly, the high reflectivity of CNFs and BNNS with white appearance in the solar spectral range enabled the composite cryogel to have superior radiative cooling performance. This high-performance anisotropic Si-CNF/BNNS cryogel shows great potential for improving thermal comfort and environmental safety in the field of electronic packaging and energy efficient buildings. Moreover, this preparation procedure mainly includes liquid nitrogen orientation and freeze-drying, and can be further expanded for large-scale production of cellulose-based cryogels. [ABSTRACT FROM AUTHOR]

High-quality film capacitors are widely used in many fields such as new energy vehicles, electronic communications, etc., due to their advantages in wide frequency response and low dielectric loss. The dielectric film is a crucial part of the film capacitor, and its properties have an important impact on the performance and use conditions of the film capacitor. In this work, a novel high-temperature-resistant dielectric film was prepared. Firstly, the Bi2S3/rGO-CN fillers were prepared by hydrothermal method combined with cyanation treatment, and then added to the poly(arylene ether nitrile) (PEN) matrix to prepare the dielectric film materials (PEN/Bi2S3/rGO-CN). After high temperature treatment, the fillers Bi2S3/rGO-CN reacted with the PEN matrix, and the composites materials transformed into a thermosetting hybrid film (PEN-Bi2S3/rGO) with gel content of 97.88%. The prepared hybrid dielectric films did not decompose significantly before 400 °C, and showed a glass transition temperature (Tg) of up to 252.4 °C, which could increase the effective use temperature of the materials. Compared with the composite films without heat treatment, they exhibit better mechanical properties, with further improvement in tensile strength and elastic modulus, and a decrease in elongation at break. The dielectric constant of the hybrid films can be up to 6.8 while the dielectric loss is only about 0.02 at 1 kHz. Moreover, the hybrid films showed excellent dielectric stability during temperature changes, and remain relatively stable before 250 °C, which is suitable as a high-temperature-resistant high-dielectric material and is more advantageous for practical applications. [ABSTRACT FROM AUTHOR]

Dielectric materials with excellent thermal stability, mechanical properties, and thermal conductivity are highly desirable for advanced electronics and electrical equipment. However, it remains a significant challenge to develop a single material with these properties. Here we describe a new strategy to prepare dielectric paper by combining one-dimensional aramid nanofiber (ANF) with two-dimensional fluorinated graphene (F-graphene) through a vacuum-assisted filtration method. The obtained ANF/F-graphene paper exhibits a low dielectric constant of 1.92 at 103 Hz and its electrical breakdown strength is 17.6% higher than that of the neat ANF paper, owing to the presence of F-graphene, which significantly suppresses the accumulation of space charge in the prepared paper. Moreover, high mechanical strength (>200 MPa), thermal conductivity (6.29 Wm−1K−1), and thermal decomposition temperature (>500°C) are simultaneously achieved for the ANF/F-graphene paper. These findings highlight the fabrication of multifunctional dielectric materials and broaden their practical applications in the field of high-temperature electronics and devices. [ABSTRACT FROM AUTHOR]

In order to explore the effect of nano-SiO2 on asphalt properties, modified asphalt mixtures with different nano-SiO2 doping contents were prepared. The properties of nano-SiO2 modified asphalt mixtures were characterized by rutting test, water immersion Marshall test, freeze-thaw splitting test and low temperature cracking resistance test. The results show that the modified asphalt with 5wt% doping content of nano-SiO2 has the lowest penetration and higher softening point and viscosity. Compared with the base asphalt, the rutting depth of 5% (mass fraction) nano-SiO2 modified asphalt mixture was reduced by 45.90% and 52.27% at 45 and 60 min, respectively, the dynamic stability was improved by 60.57%, and the residue was stable after immersion in water for 48 h. The tensile strength is up to 90.69%, the freeze-thaw splitting strength ratio is up to 91.24%, the flexural tensile strength is increased by 17.70%, the maximum flexural tensile strain is increased by 11.36%, and the bending stiffness modulus is increased by 8.86%. On the whole, the high temperature performance, water stability and low temperature crack resistance of 5wt% nano-SiO2 modified asphalt mixture have been significantly improved, and it has good road performance and application prospects. [ABSTRACT FROM AUTHOR]

The refractive index and its variation with temperature, i.e. the thermo-optic coefficient, are basic optical parameters for all those semiconductors that are used in the fabrication of linear and non-linear opto-electronic devices and systems. Recently, 4H single-crystal silicon carbide (4H-SiC) and gallium nitride (GaN) have emerged as excellent building materials for high power and high-temperature electronics, and wide parallel applications in photonics can be consequently forecasted in the near future, in particular in the infrared telecommunication band of λ = 1500–1600 nm. In this paper, the thermo-optic coefficient (dn/dT) is experimentally measured in 4H-SiC and GaN substrates, from room temperature to 480 K, at the wavelength of 1550 nm. Specifically, the substrates, forming natural Fabry–Perot etalons, are exploited within a simple hybrid fiber free-space optical interferometric system to take accurate measurements of the transmitted optical power in the said temperature range. It is found that, for both semiconductors, dn/dT is itself remarkably temperature-dependent, in particular quadratically for GaN and almost linearly for 4H-SiC. [ABSTRACT FROM AUTHOR]

As one of the conductive ink materials with high electric conductivity, elemental copper (Cu) based nanocrystals promise for printable electronics. Here, single crystalline Cu nanoplates were synthesized using a facile hydrothermal method. Size engineering of Cu nanoplates can be rationalized by using the LaMer model and the versatile Cu conductive ink materials are suitable for different printing technologies. The printed Cu traces show high electric conductivity of 6 MS mâˆ'1, exhibiting electro-magnetic interference shielding efficiency value of 75 dB at an average thicknesses of 11 ÎĽ m. Together with flexible alumina ceramic aerogel substrates, it kept 87% conductivity at the environmental temperature of 400 °C, demonstrating the potential of Cu conductive ink for high-temperature printable electronics applications. [ABSTRACT FROM AUTHOR]

High-Bi alloys are being explored to understand their potential as replacement for high-Pb alloys in high-temperature die-attach applications. Thermal conductivity of these alloys is an important consideration for die-attach applications, where heat dissipation is necessary for reliable operation of the devices. Pure Bi has a thermal conductivity of about 8 W/ $\text{m}\cdot \text{K}$ , which is the lowest among metals. The addition of the alloying elements to Bi had been explored to tailor its thermal, mechanical, and other physical properties. In this study, the role of Cu and Sb on the effective thermal conductivity of the resultant alloys was investigated. The thermal conductivities of these alloys in the bulk form and the three-layer die-attach form were measured using a flash diffusivity technique. Test specimens were developed to replicate a die-attach assembly between the Ni-metallized Si die and Cu substrate using the Bi– $x$ Sb–10Cu alloy (where $x =10$ –20 wt%). The three-layered structure was modeled with the unknown diffusivity of an intermediate layer of the Bi alloy. The alloy microstructure comprises a composite of Bi–Sb solid solution filled with Cu2Sb intermetallic particles. The presence of these intermetallic phases is responsible for an effective increase in thermal conductivity of this alloy. With the optimized microstructure developed, the resultant thermal conductivity was obtained at $\sim 24$ W/ $\text{m}\cdot \text{K}$ , which is a threefold increase compared to pure Bi. [ABSTRACT FROM AUTHOR]

SiC is an important wide‐bandgap semiconductor for high‐power electronics and high‐temperature applications. Its Z1/2 center, recognized as a carrier lifetime killer, has been extensively studied as it is a key issue impeding many applications of SiC. It is well established that the Z1/2 center originates from carbon vacancies (VC), but direct access to the microscopic mechanism underlying its nonradiative recombination process is lacking. Herein, to consolidate such identification, the multiphonon‐assisted nonradiative recombination rates of previously proposed different candidates of the Z1/2 center are evaluated by performing first‐principles calculations. The calculated electron transition cross sections of the VC (σn=2.5×10−15cm2 at the k‐site and σn=3.4×10−15cm2 at the h‐site) are in accordance with the experimental values [from σn=3.0×10−15cm2 to σn=1.0×10−14cm2] for the Z1/2 center. However, all of the other candidates are orders of magnitudes smaller in transition cross sections. This provides further evidence that the carbon vacancy (VC) is the Z1/2 center from the electron transition cross sections. However, it is also found that the hole transition cross sections of the VC are very small. Various hypotheses are provided to consolidate this fact with the conclusion that Z1/2 is the carrier lifetime killer. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (hBN), a two dimensional (2D) material is used to protect the 2D materials from environment through encapsulation due to its oxidation resistant ability. High temperature electronics based on graphene and hBN hetrostructures have the potential to operate in extreme environments. Thus, it is critical to investigate the oxidation behavior of bulk hBN single crystals at high temperatures in different environments. This study reports on the thermal oxidation of single hBN crystals in dry air, from 800 to 1100°C, for 20 to 60 min, and is compared to the oxidation in ambient air. Oxidation in both dry and ambient air produced etch pits and particles. Pit formation was localized and non-uniform across the hBN crystal surfaces. Increasing the temperature and duration in dry air did not significantly change the surface pit sizes, that was in contrast to the thermal oxidation in ambient air (which contains a small water concentration). Elemental analysis by SEM/EDX revealed the major elements of the particles were boron and oxygen. [ABSTRACT FROM AUTHOR]

BaBi2Sb2Ti4O15, a four-fold layered structured ceramic compound is synthesized by the mixed oxide process at sintering temperature 875 °C. The structural and electrical properties of the material measured in a broad temperature (25–500 °C) and frequency (103–106 Hz) range are presented here. From the preliminary X-ray structural analysis, it is confirmed that this compound has an orthorhombic structure. The temperature and frequency-dependent dielectric constant of the material is observed. Modified Curie Weiss's law explains the extent of diffusivity observed in a phase transition. The presence of grain and grain boundary effects is confirmed from the Nyquist plots. Non-Debye-like relaxation is noticed from complex impedance and modulus analyses. Reduction in grain resistance is noticed with the enhancement of temperature indicating the existence of negative temperature coefficient of resistance (NTCR) properties in the compound. It is concluded from the above results that this compound may have wide applications in electronics as well as high-temperature devices. [ABSTRACT FROM AUTHOR]

Hotspot cooling by heat spreader is essential to avoid reliability issues of the power electronic devices. Herein, the evaluation of the heat spreading capability of mono‐ and multi‐layer graphene using a Pt/Cu/Ti micro‐coil heater‐thermometer is reported. Monolayer graphene is grown and transferred onto the test structure which consists of micro‐coil, pads, and heat sinks. The temperature coefficient of resistance of the bare coil is around 0.0087 °C−1. During Joule heating, the bare structure dissipates heat from the coil mainly via stage. Deposited graphene helps carry heat from the coil to the peripheral heat sinks. In transient‐state Joule heating, graphene reduced all stage, coil, and hotspot temperatures. However, stage temperature cannot be reduced during steady‐state Joule heating. The thickening of the graphene layer did improve the heat dissipation from the coil. The optimum number of layers is suggested to be 3‐layers graphene with a hotspot reduction from 5.86 °C W−1 down to 4.97 °C W−1. More than 3‐layers result in a slight increase in hotspot temperature due to heat accumulation within the films. Findings in this work give insight into thermal management strategies in high‐temperature power electronics. [ABSTRACT FROM AUTHOR]

Polymer-based dielectric films with desirable heat dissipation property hold great promise as thermal management materials in advanced electronics and high power devices. Herein, we report a new strategy for preparing thermally conductive films by synergistically combining one-dimensional (1D) aramid nanofiber (ANF) with 2D edge-hydroxylated boron nitride nanosheet (OH-BNNS) via a vacuum-assisted self-assembly technique. The obtained ANF/OH-BNNS film exhibits an ultrahigh in-plane thermal conductivity of 32.3 W m−1K−1 at 40 wt% BNNS-OH loading, which is 3530% greater than that of the pure ANF film. The excellent thermal conductivity results from the special 'brick-and-mortar' layered structure of ANF/OH-BNNS, in which the increased contacting and overlapping of OH-BNNS promotes the formation of the thermal conduction pathways. In addition, the rigid ANFs act as bridges linking OH-BNNS by favorable hydrogen bonding interactions, which efficiently enhance phonon propagation and stress transfer in the film. Moreover, the ANF/OH-BNNS film simultaneously shows low dielectric loss (~0.03), high tensile strength (~88 MPa), and a high decomposition temperature (>510 °C). We believe that these findings are of great importance for the fabrication and practical application of thermal management materials in high-temperature electronics and devices. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to quickly manufacture full Cu3Sn-microporous copper composite joints for high-temperature power electronics applications and study the microstructure evolution and the shear strength of Cu3Sn at different bonding times. Design/methodology/approach: In this paper, a novel structure of Cu/composite solder sheet/Cu was designed. The composite solder sheet was made of microporous copper filled with Sn. The composite joint was bonded by thermo-compression bonding under pressure of 0.6 MPa at 300°C. The microstructure evolution and the growth behavior of Cu3Sn at different bonding times were observed by electron microscope and metallographic microscope. The shear strength of the joint was measured by shear machine. Findings: At initial bonding stage the copper atoms in the substrate and the copper atoms in the microporous copper dissolved into the liquid Sn. Then the scallop-liked Cu6Sn5 phases formed at the interface of liquid Sn/microporous copper and liquid Sn/Cu substrates. During the liquid Sn changing to Cu6Sn5 phases, Cu3Sn phases formed and grew at the interface of Cu6Sn5/Cu substrates and Cu6Sn5/microporous copper. After that the Cu3Sn phases continued to grow and the Cu3Sn-microporous copper composite joint with a thickness of 100 µm was successfully obtained. The growth rule of Cu3Sn was parabolic growth. The shear strength of the composite joints was about 155 MPa. Originality/value: This paper presents a novel full Cu3Sn-microporous copper composite joint with high shear strength for high-temperature applications based on transient liquid phase bonding. The microstructure evolution and the growth behavior of Cu3Sn in the composite joints were studied. The shear strength and the fracture mechanism of the composite joints were studied. [ABSTRACT FROM AUTHOR]

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Polycrystalline samples of composition CuIn1–xHgxTe2 (x=0–0.21) were synthesized from elements of 5N purity using a solid state reaction. The phase purity of the products was verified by X-ray diffraction. Samples for transport property measurements were prepared using hot-pressing. The samples were characterized by measurement of the electrical conductivity, Hall coefficient, Seebeck coefficient, and thermal conductivity over a temperature range of 300–675 K. All samples show p-type conductivity. We discuss the influence of Hg substitution on the free carrier concentration and thermoelectric performance. The investigation of the thermoelectric properties shows up to a 40% improvement of ZT in the temperature range of 300–600 K. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of composition CuIn1–xHgxTe2 (x=0–0.21) were synthesized from elements of 5N purity using a solid state reaction. The phase purity of the products was verified by X-ray diffraction. Samples for transport property measurements were prepared using hot-pressing. The samples were characterized by measurement of the electrical conductivity, Hall coefficient, Seebeck coefficient, and thermal conductivity over a temperature range of 300–675 K. All samples show p-type conductivity. We discuss the influence of Hg substitution on the free carrier concentration and thermoelectric performance. The investigation of the thermoelectric properties shows up to a 40% improvement of ZT in the temperature range of 300–600 K. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) is the material of choice for high-temperature, high-voltage, and other harsh environment applications in high-energy physics, outer space, etc., because of its high critical electric field and radiation tolerance. In this work, single- and double-gate junctionless transistors (SGJLT, DGJLT) are studied extensively using TCAD device simulations, taking SiC as a substrate material. Junctionless transistors (JLTs) offer better high-temperature performances compared to a conventional metal-oxide-semiconductor field-effect transistor (MOSFET). To investigate the temperature dependence of the drain current (ID), the intrinsic gain is studied for the devices under high-temperature conditions. Unlike a conventional MOSFET, at the zero temperature coefficient (ZTC) point, output current slightly increases with temperature for a JLT, which is beneficial in electronics applications at high temperatures. After the ZTC point, the output current decreases with an increase in temperature, similar to a conventional MOSFET. Taking the advantages of high-performance JLT, SiC device's compatibility with high temperatures and high voltages, a boost converter has been designed. It was shown that efficiencies as high as 80% can be achieved even at temperatures of 380K. [ABSTRACT FROM AUTHOR]

In this research, a waterproof and stretchable sensing electronics with high temperature and pressure sensitivity is designed. For pressure sensitivity, the sensor can detect linearly between 20 and 2000 g, the dynamic response frequency is within 10 Hz, the repeatability is more than 1 million times, and the error range is less than ± 5%. For temperature sensitivity, the positive temperature coefficient silicon-based thermistor used in sensor has a quick thermal response time of 0.6 s, the resistance changes linearly with temperature, the temperature error is less than ± 1%, and its small size is easy to integrate. The performance of this sensor has reached or even exceeded the performance of existing sensing devices. In the design, the cost of the sensor is fully considered, and the self-waterproof requirement can be achieved by using the selected material. The unit price of the pressure sensor unit used is $2, the unit price of the silicon-based thermistor is $0.4, and the unit price per gram of PDMS is $0.17. The total price of the finished flexible wearable sensor made by this design is $38.6. The design of the "W"-shaped wire is proposed. It can maintain sensor's tensile performance and make the temperature sensor and the strain sensor fit well, which can accurately measure the temperature and the strain. Experiments prove that the thin-film flexible sensor uses a reasonable and ingenious design to show good performance. This design hopefully can be further developed and applied in smart wear and can be extended to other application devices. [ABSTRACT FROM AUTHOR]