Harsh Environment Electronics Research Articles

High stability and reliability additively manufactured metal-insulator-metal capacitors for high-temperature applications

Throughout the last few years, there has been a significant increase in demand for high-temperature capacitors due to the rising need for electronics in harsh environments, including aerospace, automotive, and oil and gas industries. With the continued growth of electronics in these environments, there is a need for the development of new materials and manufacturing techniques to drive advances in high temperature capacitor technology. Additive manufacturing is one promising approach for producing electronics that can withstand high temperatures, leading to improved performance and reliability in a wide range of applications. The present work describes the fabrication and testing of MIM (metal-insulator-metal) capacitors at high temperatures using gold as the conductor material. The substrates used in this work is 3D printed Lithoz 350D 99.8% alumina. The work details the fabrication process and evaluates the relative permittivity and the dielectric loss of high-temperature dielectric material at temperatures up to 800°C. The adhesion strength at the interfaces is examined before and after aging for up to 250 hours at temperatures as high as 750°C. The leakage current is measured for 100 hours at varying temperatures and the insulation resistance is calculated. Furthermore, the capacitance is monitored during aging at temperatures up to 700°C and frequencies as high as 1 MHz. Finally, the capacitance is measured at room temperature before and after subjecting the capacitors to 100 cycles of thermal cycling at three different temperature ranges. The adhesion between all interfaces of the MIM capacitors is found to remain high even after aging at 700°C, leakage currents are minimal and stable, and the capacitance remained very stable during and after aging and after thermal cycling.

A stable and efficient quasi-solid-state photo/betavoltaic-powered electrochemical cell based on 3-dimensional CdS/ZnO heterostructure

Electrochemical betavoltaic (EBV) cells are promising power sources for low-power electronics in remote and harsh environments. However, their practical applications are limited by the organic liquid electrolytes with the inferior temperature stability and narrow electrochemical window. In this work, a quasi-solid-state EBV cell was fabricated using a high-conductive gel-based quasi-solid-electrolyte (QSE), a CdS-modificated ZnO nanorod arrays (ZNRAs) structure as the anode material, a radioactive 63Ni sheet as the cathode as well as the irradiation source. Monte Carlo (MC) simulations are utilized to determine the optimized length (2.97 μm) of the ZNRAs filled by electrolyte, Electrochemical photovoltaic (EPV) cells were used to assess and optimize the content of CdS loaded on the ZNRAs. The optimum EBV cell demonstrated an excellent long-term stability and a high energy-conversion efficiency of 10.09 % with a short-circuit current density of 0.755 μA cm−2 and an open-circuit voltage of 0.288 V. The porous CdS@ZNRAs core–shell structure filled by soft ionic liquids (IL)/gel-based QSE enables a large specific area of electrochemical interface network. The synergistic effects of 3-D CdS/ZnO heterostructure with type-II band alignment and IL/gel-based QSE are responsible for the enhanced ECE and improved long-term stability of EBV/EPV cells.

High-temperature polymer dielectric films with excellent energy storage performance utilizing inorganic outerlayers

The optimization of high-temperature polymer capacitors is critical to the development of power electronics in harsh environments. The conduction loss of polymers increases dramatically at high temperatures, leading to a decrease in energy density and charge/discharge efficiency, which is a major impediment for capacitor applications. In this work, polyetherimide (PEI) composite films with trilayer structures are designed, in which the boron nitride nanosheet (BNNS) outer layers are optimized for charge blocking effect at multiple interfaces. The modulation of the inorganic layers not only increases the barrier height for charge injection from the electrodes, but also creates a PEI layer/BNNS layer interface that facilitates the formation of traps, thus effectively suppressing further carrier transport. Experiment and simulation verify that the construction of the trilayer structure promotes electric field redistribution, which significantly enhances high-temperature energy storage performance. At 200 °C, the energy density of the trilayer composite film is 3.81 J cm−3 with a charge/discharge efficiency >90 %, which is 766 % higher than PEI film (0.44 J cm−3 with a charge/discharge efficiency >90 %). Notably, the energy storage performance of trilayer composite film at high temperature is far superior to the reported high-temperature polymer dielectric films. This work demonstrates the promising potential of multilayer structures applied to dielectric polymer composite films at high temperatures.

Electrical Properties of Ga2O3 Schottky Barrier Diodes with and without Mesa Structure

Devices based on wide bandgap (WBG) semiconductors like silicon carbide (SiC), gallium nitride (GaN), and gallium oxide (Ga2O3) are ideal for high-power electronics in harsh environments. Among the WBG semiconductors, ultrawide bandgap (UWBG) β-phase gallium oxide (Ga2O3), EG ≈ 4.8 eV, is emerging as a replacement for the current commercially available wide bandgap (WBG) power electronics due to its generational improvements in performance and manufacturing cost [1]. Ga2O3 has a high theoretical breakdown electrical field of 8 MV/cm which in turn gives its Baliga’s figure of merit for power devices that is larger than other WBG materials. The availability of high-quality Ga2O3 substrates produced from melt-grown bulk single crystals also facilitates the development of vertical power devices.In the current stage, the vertical Schottky barrier diode (SBD) with Ga2O3 can have an improved current spreading effect when compared to power diode devices from Si, SiC, and GaN. Especially, the Ga2O3 is expected to surpass the trade-off relationship between breakdown voltage (BV) and on resistance (Ron,sp) that other materials have [2]. Nevertheless, the Ga2O3 vertical SBD still cannot achieve the theoretical breakdown electric field. One of the key topics for WBG semiconductors application is a structure for improved electrical management such as field rings, junction termination extension, and field plates to reduce the leakage current in the reverse bias state.Here, we investigate the characteristics of Ga2O3 SBDs with and without mesa structure in extreme environments at high and low temperature. Conventional and mesa Ga2O3 SBDs were fabricated on the halide vapor phase epitaxy (HVPE) grown β-Ga2O3 (001). A Sn-doped substrate with 61016 cm-3 was used for the HVPE growth. In the SBD with mesa structure, the circular mesa with a diameter of 162 μm and a depth of 500 nm was formed around anode electrodes. The Ti/Au metal stack on the back side of the substrate acted as a cathode and the anode electrode deposited Ni/Au/Pt layers. After the fabrication process, current-voltage (I-V) measurements were performed on the SBDs between -5 V and 1 V. From the results, the values of Ron,sp at 0.7 V are 46.4 Ω•cm2 and 46.2 Ω•cm2 in conventional and mesa SBDs, respectively. And additionally, the leakage current at -5 V is reduced by approximately 44.3% in the mesa structure. To obtain the Schottky barrier height (SBH) from I-V and capacitance-voltage (C-V) measurements, the C-V was observed in the range of -5 V to 0.5 V at 100 kHz. The SBH values from I-V and C-V measurements, the mesa SBDs have 1% - 5% larger SBH compared to the conventional structure, and it could be related to lower leakage current. Moreover, the depletion depths of conventional and mesa SBDs were 52.2 nm and 57.8 nm, respectively, from C-V measurements. For considering the electrical characteristics in extreme temperatures, the I-V measurements of both SBDs structure will be measured between 75 K to 525 K. From an initial low temperature measurement series, we determine a Richardson constant of 49 A/cm2 comparable to what has been reported by other groups. Furthermore, we will extend the study by performing deep-level transient spectroscopy (DLTS) to understand the defect information in Ga2O3.

Improving Printability of Polytetrafluoroethylene (PTFE) with the Help of Plasma Pre-Treatment.

Polytetrafluoroethylene (PTFE) is a potential candidate for the fabrication of flexible electronics devices and electronics with applications in various extreme environments, mainly due to its outstanding chemical and physical properties. However, to date, the utilization of PTFE in printing trials has been limited due to the material's low surface tension and wettability, which do not ensure good adhesion of the printing ink at the level of the substrate. Within this paper, successful printing of PTFE is realized after pre-treating the surface of the substrate with the help of dielectric barrier discharge non-thermal plasma. The efficiency of the pre-treatment is demonstrated with respect to both silver- and carbon-based inks that are commercially available, and finally, the long-lasting pre-treatment effect is demonstrated for periods of time spanning from minutes to days. The experimental results are practically paving the way toward large-scale utilization of PTFE as substrate in fabricating printed electronics in harsh working environments. After 3 s of plasma treatment of the foil, the WCA decreased from approximately 103° to approximately 70°. The resolution of the printed lines of carbon ink was not time dependent and was unmodified, even if the printing was realized within 1 min from the time of applying the pre-treatment or 10 days later. The evaluation of the surface tension (σ) measured with Arcotest Ink Pink showed an increase in σ up to 40 < σ < 42 mN/m for treated Teflon foil and from σ < 30 mN/m corresponding to the untreated substrate. The difference in resolution was distinguishable when increasing the width of the printed lines from 500 μm to 750 μm, but when increasing the width from 750 μm to 1000 μm, the difference was minimal.

SЕNSORS BASED ON POLYCRYSTALLINE 3C-SiC: IMPACT OF BORON DOPING

As a chemically inert wide bandgap semiconductor material with high hardness and thermal conductivity, stable electrical characteristics, silicon carbide SiC is attractive for harsh environment electronics and sensors applications. The concept of harsh environment includes extremes of temperature, pressure, shock loads, radiation and chemical attacks those arise in aircraft and automotive engines, industrial gas turbines, during oil and gas exploration, etc.&#x0D; Lower growing temperatures of polycrystalline cubic silicon carbide, pc-3C-SiC, compared to monocrystalline allow to significantly reduce its cost and expand the possibilities of application. It follows from previous works that the thermal sensitivity of pc -3C-SiC can be significantly increased by doping with an acceptor impurity of boron during the growth of the material. The purpose of this work is to determine the properties of pc-3C-SiC doped with boron for the creation of photosensors and thermosensors, as well as thermal anemometers for extreme operating conditions.&#x0D; It is shown that pс-3C-SiC doping with a boron impurity in the growth process causes the formation of acceptor-type centers in the band gap and the appearance of features in the photosensitivity spectrum, which may be of practical interest for photovoltaics. For temperatures T &gt; 150K, the conductivity of the doped sample increases almost exponentially with an activation energy of 0.28 eV, which is close to the activation energy of the photoconductivity of the same sample. This indicates that the ionization process of equilibrium and non-equilibrium charge carriers occurs from the same impurity centers. Boron doping causes the appearance of a broad photoconductivity band with a maximum at 1.7 eV in the impurity absorption region of pc-3C-SiC, similar to the situation in single crystal 3C-SiC.&#x0D; It was determined that the temperature coefficient of resistance for boron-doped pc-3C-SiC is 3.0´10-2 K-1 at T=300K and 1.1´10-2 K-1 at T=700K, which is almost an order of magnitude higher than for thermocouples, as well as for metals from which anemometer threads are made. The discussion of the obtained results allows to associate the value of the activation energy E=0.28 eV with the level of shallow boron in pc-3C-SiC and to assume this center is a point defect containing a boron atom that replaces a silicon atom in the 3C-SiC lattice, i.e. BSi.&#x0D; Photosensors that can be used as solar cells in the near-IR range of 0.6 - 1.8 μm, and as photocells in the visible range of 0.4 - 0.6 μm are proposed. The ability of pc-3C-SiC to work in extreme operating conditions, as well as the low cost of device manufacturing technology based on it, compared to other SiC polytypes, allow it to be considered a suitable material for creating temperature sensors, thermo-anemometers and photosensors, as well as detectors for monitoring nuclear facilities.

Polysiloxane-containing non-isocyanate polyurethane: From soybean oil and CO2-based compound to flexible sensors designed for availability in a wide temperature range

Flexible sensors have been widely developed in recent years with the growing popularity of the Internet of Things, resulting in a large amount of electronic waste that poses potential environmental problems. Due to the increasing concern about environment, the use of biomass resources to prepare environmentally friendly and recyclable materials is of significant research interest. Meanwhile, self-healing, sensitive monitoring of signal changes, and the ability to be used in extreme environments are also critical features of flexible sensors. Herein, a bio-based conductive non-isocyanate polyurethane (NIPU) was obtained by the reaction of carbonated soybean oil (CSBO) with polyaminopropylmethylsiloxane (PAPMS). And carbon black (CB) was introduced as a conductive filler. The mechanical properties and electrical conductivity of the NIPU were adjusted by changing the molar ratio of amino to cyclic carbonate and adding CB. The prepared NIPU can show excellent thermal stability, solvent resistance, tensile properties, and self-healing ability (above 90% healing rate). In addition, due to the flexible segment of siloxane in the network, NIPU can exhibit high tensile strain (> 400%) at extremely low temperatures (−40 °C) without being destroyed, and the actions of volunteers can be sensed and converted into sensitive and stable electrical signals over a wide temperature range (−40 to 60 °C). The highly elastic NIPU sensor displays great promise for applications in wearable electronics in harsh environments.

Solution Processed Schottky Diodes Enabled by Silicon Carbide Nanowires for Harsh Environment Applications.

Silicon carbide nanowires (SiC NWs) exhibit promising features to allow solution-processable electronics to be deployed in harsh environments. By utilizing a nanoscale form of SiC, we were able to disperse the material into liquid solvents, while maintaining the resilience of bulk SiC. This letter reports the fabrication of SiC NW Schottky diodes. Each diode consisted of just one nanowire with an approximate diameter of 160 nm. In addition to analyzing the diode performance, the effects of elevated temperatures and proton irradiation on the current-voltage characteristics of SiC NW Schottky diodes were also examined. The device could maintain similar values for ideality factor, barrier height, and effective Richardson constant upon proton irradiation with a fluence of 1016 ion/cm2 at 873 K. As a result, these metrics have clearly demonstrated the high-temperature tolerance and irradiation resistance of SiC NWs, ultimately indicating that they may provide utility in allowing solution-processable electronics in harsh environments.

Development and analysis of a simple structured and economic miniature vapor compression refrigerator for cooling electronics in harsh environment

Compared with the previous cooling technologies for electronics, the miniature refrigeration technology can effectively eliminate hot spots and ensure that the junction temperature is at a lower level to ensure that electronics operate with better performance, especially in harsh environments. However, the high cost and low performance of the refrigeration system hinder its practical application. In this paper, based on a simple porous media evaporator, a simple structured and economic miniature vapor compression refrigeration system is proposed and developed. The overall size of the system is 380 mm × 350 mm × 58 mm and the total weight is only 2.0 kg. It can achieve a heat dissipation of 100 W with a total energy efficiency ratio (EER) of 2.25 and ensure that the chip temperature is approximately the ambient temperature (e.g., 30 ℃). The effects of the compressor speed and heat load on the cooling performance of the system under steady-state conditions are studied. Meanwhile, the transient processes of the system at different heat loads are systematically examined. The results show that the system can maintain a chip temperature lower than/close to the ambient temperature, which is critical for autonomous vehicle electronics in harsh environments.

Design and Test of a Spoke-like Piezoelectric Energy Harvester.

With the development of industry IoT, microprocessors and sensors are widely used for autonomously transferring information to cyber-physics systems. Massive quantities and huge power consumption of the devices result in a severe increment of the chemical batteries, which is highly associated with problems, including environmental pollution, waste of human/financial resources, difficulty in replacement, etc. Driven by this issue, mechanical energy harvesting technology has been widely studied in the last few years as a great potential solution for battery substitution. Therefore, the piezoelectric generator is characterized as an efficient transformer from ambient vibration into electricity. In this paper, a spoke-like piezoelectric energy harvester is designed and fabricated with detailed introductions on the structure, materials, and fabrication. Focusing on improving the output efficiency and broadening the pulse width, on the one hand, the energy harvesting circuit is optimized by adding voltage monitoring and regulator modules. On the other hand, magnetic mass is adopted to employ the magnetic field of repulsive and upper repulsion–lower attraction mode. The spoke-like piezoelectric energy harvester suggests broadening the frequency domain and increasing the output performance, which is prepared for wireless sensors and portable electronics in remote areas and harsh environments.

Tendon-inspired anti-freezing tough gels

SummaryHydrogels have gained tremendous attention due to their versatility in soft electronics, actuators, biomedical sensors, etc. Due to the high water content, hydrogels are usually soft, weak, and freeze below 0°C, which brings severe limitations to applications such as soft robotics and flexible electronics in harsh environments. Most existing anti-freezing gels suffer from poor mechanical properties and urgently need further improvements. Here, we took inspirations from tendon and coniferous trees and provided an effective method to strengthen polyvinyl alcohol (PVA) hydrogel while making it freeze resistant. The salting-out effect was utilized to create a hierarchically structured polymer network, which induced superior mechanical properties (Young's modulus: 10.1 MPa, tensile strength: 13.5 MPa, and toughness: 127.9 MJ/m3). Meanwhile, the cononsolvency effect was employed to preserve the structure and suppress the freezing point to −60°C. Moreover, we have demonstrated the broad applicability of our material by fabricating PVA hydrogel-based hydraulic actuators and ionic conductors.

High-resolution planar electron beam induced current in bulk diodes using high-energy electrons

Understanding the impact of high-energy electron radiation on device characteristics remains critical for the expanding use of semiconductor electronics in space-borne applications and other radiation harsh environments. Here, we report on in situ measurements of high-energy electron radiation effects on the hole diffusion length in low threading dislocation density homoepitaxial bulk n-GaN Schottky diodes using electron beam induced current (EBIC) in high-voltage scanning electron microscopy mode. Despite the large interaction volume in this system, quantitative EBIC imaging is possible due to the sustained collimation of the incident electron beam. This approach enables direct measurement of electron radiation effects without having to thin the specimen. Using a combination of experimental EBIC measurements and Monte Carlo simulations of electron trajectories, we determine a hole diffusion length of 264 ± 11 nm for n-GaN. Irradiation with 200 kV electron beam with an accumulated dose of 24 × 1016 electrons cm−2 led to an approximate 35% decrease in the minority carrier diffusion length.

A review of geometric and structural design for reliable flexible electronics

Recently, flexible electronics have attracted significant attention as they can be integrated on diverse platforms from curved to flexible surfaces. As flexible electronics are used on a curved surface of wearable or manufacturing devices for health and system monitoring, the working environment of such applications forces electronics to be exposed to diverse stimuli such as deformation, temperature, humidity, and gas, resulting in performance changes. Therefore, rather than research on improving the specific performance of electronics, research on maintaining a stable performance in various environmental stimuli has been receiving tremendous interest. Reflecting the latest research trends, this paper introduces efforts in structural designs heading for both improving and maintaining the performance of flexible electronics in diverse environmental stimuli. Firstly, we will sequentially explain the geometric and structural designs introduced for achieving (a) reliable electronics insensitive to undesired mechanical stimuli, (b) reliable electronics in harsh environments, and (c) flexible electrodes. Also, (d) diverse applications of reliable and flexible electronics are introduced. Finally, a perspective on reliable and flexible electronic devices has been presented for suggesting next-generation research.

Evaluation of Different Processor Architecture Organizations for On-Site Electronics in Harsh Environments

Microcontrollers to be used in harsh environmental conditions, e.g., at high temperatures or radiation exposition, need to be fabricated in robust technology nodes in order to operate reliably. However, these nodes are considerably larger than cutting-edge semiconductor technologies and provide less speed, drastically reducing system performance. In order to achieve low silicon area costs, low power consumption and reasonable performance, the processor architecture organization itself is a major influential design point. Parameters like data path width, instruction execution paradigm, code density, memory requirements, advanced control flow mechanisms etc., may have large effects on the design constraints. Application characteristics, like exploitable data parallelism and required arithmetic operations, have to be considered in order to use the implemented processor resources efficiently. In this paper, a design space exploration of five different architectures with MIPS- or ARM-compatible instruction set architectures, as well as transport-triggered instruction execution is presented. Using a 0.18 upmu m SOI CMOS technology for high temperature and an exemplary case study from the fields of communication, i.e., powerline communication encoder, the influence of architectural parameters on performance and hardware efficiency is compared. For this application, a transport-triggered architecture configuration has an 8.5times higher performance and 2.4times higher computational energy efficiency at a 1.6times larger total silicon area than an off-the-shelf ARM Cortex-M0 embedded processor, showing the considerable range of design trade-offs for different architectures.

High Strain Rate Mechanical Properties of SAC-Q With Sustained Elevated Temperature Storage at 100 °C

Abstract Leadfree electronics in harsh environments often may be exposed to elevated temperature for the duration of storage, transport, and usage in addition to high strain rate triggering loads during drop-impact, vibration, and shock. These electronic components may get exposed to high strain rates of 1 to 100 s−1 and operating temperatures up to 200 °C in critical surroundings. Doped SAC solder alloys such as SAC-Q are being considered for use in fine-pitch electronic components. SAC-Q consists of Sn-Ag-Cu alloy in addition to Bi (SAC+Bi). Prior data presented to date for lead-free solders, such as SAC-Q alloy, at high aging temperature and high strain rate are for 50 °C sustained exposure. In this paper, the effect of sustained exposure to temperature of 100 °C on high strain rate properties of SAC-Q is studied. Thermally aged SAC-Q samples at 100 °C have been tested at a range of strain rates including 10, 35, 50, and 75 s−1 and operating temperatures ranging from 25 °C up to 200 °C. Stress–strain curves are established for the given range of strain rates and operating temperatures. Also, the computed experimental results and data have been fitted to the Anand viscoplasticity model for SAC-Q for comparison.

Interconnections for Additively Manufactured Hybridized Printed Electronics in Harsh Environments

The ability to fabricate functional 3D conductive elements via additive manufacturing has opened up a unique sector of ‘hybridized printed electronics’. In doing so, many of the rigid standards (i.e., planar circuit boards, potting, etc.,) of traditional electronics are abandoned. However, one critical challenge lies in producing robust and reliable interconnections between conductive inks and traditional hardware, especially when subjected to harsh environments. This research examines select material pairings for the most resilient interconnection. The method of test is wire bond pull testing that would represent a continuous strain on a connection and high acceleration testing of up to 50,000 g that would represent a sudden shock that electronics may experience in a drop or crash. Although these two environments may be similar to an overall energy exerted on the connection, the rate of force exerted may lead to different solutions. The results of this research provide insight into material selection for printed electronic interconnections and a framework for interconnection resiliency assessment, which is a critical aspect in realizing the production of next generation electronics technologies for the most demanding environments.

Giant permittivity materials with low dielectric loss over a broad temperature range enabled by weakening intermolecular hydrogen bonds

High-temperature polymer dielectrics are of great interest for next generation capacitors demanded in harsh-environment electronics and electrical-power applications. Although some high-Tg engineering polymers have been considered as possible high-temperature dielectric materials, the low permittivity has significantly limited their development. Hence it is still a great challenge in dielectric polymers to achieve a high permittivity while maintain low dielectric loss over a broad temperature range. Here we report a highly scalable and low cost strategy to develop such high-performance polymer dielectrics. Two high-Tg glassy state dipolar polymers, i.e., poly(ether imide) and poly(ether-methyl-ether-urea) are blended by properly engineered to increase dipole mobility in polymer chains caused by combined effects of disruption of hydrogen bonds and improved free volume for dipoles in the glassy state blend. Consequently, such polymer blend displays thermally stable dielectric properties with an intrinsic giant permittivity of 5.8 and low dielectric loss (<1%) over a broad temperature.

A Scalable, High-Throughput, and Environmentally Benign Approach to Polymer Dielectrics Exhibiting Significantly Improved Capacitive Performance at High Temperatures.

High-temperature capability is critical for polymer dielectrics in the next-generation capacitors demanded in harsh-environment electronics and electrical-power applications. It is well recognized that the energy-storage capabilities of dielectrics are degraded drastically with increasing temperature due to the exponential increase of conduction loss. Here, a general and scalable method to enable significant improvement of the high-temperature capacitive performance of the current polymer dielectrics is reported. The high-temperature capacitive properties in terms of discharged energy density and the charge-discharge efficiency of the polymer films coated with SiO2 via plasma-enhanced chemical vapor deposition significantly outperform the neat polymers and rival or surpass the state-of-the-art high-temperature polymer nanocomposites that are prepared by tedious and low-throughput methods. Moreover, the surface modification of the dielectric films is carried out in conjunction with fast-throughput roll-to-roll processing under ambient conditions. The entire fabrication process neither involves any toxic chemicals nor generates any hazardous by-products. The integration of excellent performance, versatility, high productivity, low cost, and environmental friendliness in the present method offers an unprecedented opportunity for the development of scalable high-temperature polymer dielectrics.

Low-Parasitic-Capacitance Self-Aligned 4H-SiC nMOSFETs for Harsh Environment Electronics

Low-parasitic-capacitance 4H-SiC nMOSFETs using a novel self-aligned process were suggested and demonstrated. In these nMOSFETs, device characteristics including parasitic capacitances (gate-source, gate-drain, drain-source capacitance) were investigated and low parasitic capacitance was achieved by the self-aligned structure.

(Keynote) Gallium Oxide Electronics: Beyond SiC and GaN

Ultrawide bandgap (UWBG) semiconductors, which are defined in terms of a bandgap energy larger than those of SiC and GaN, are getting attention as emerging materials. Gallium oxide (Ga2O3) is one of the typical UWBG materials and has attractive material properties represented by an extremely large bandgap of about 4.5 eV [1]. Furthermore, availability of high-quality, large-area native wafers manufactured from bulk single crystals synthesized by melt growth methods is another important material feature of Ga2O3 [2]. In this talk, I will introduce our state-of-the-art Ga2O3 metal-oxide-semiconductor field-effect transistor (MOSFET) and Schottky barrier diode (SBD) technologies developed for applications to power and harsh environment electronics. The first single-crystal Ga2O3 transistors by means of metal-semiconductor FETs were demonstrated in 2011 [3]. As a result of continuous efforts, we developed lateral depletion-mode (D-mode) Ga2O3 MOSFETs with a gate-connected field plate (FP) [4]. The devices showed a large off-state breakdown voltage of 755 V, a large drain current on/off ratio of over nine orders of magnitude, stable device operation at temperatures up to 300°C, and negligible DC–RF dispersion. A high gamma-ray tolerance was also demonstrated for the bulk Ga2O3 channel by virtue of weak radiation effects on their output current and threshold voltage. Lateral enhancement-mode Ga2O3 MOSFETs enabling normally-off operation were fabricated by Si-ion implantation doping in an undoped Ga2O3 layer to form source/drain contacts and access regions [5]. The undoped Ga2O3 channel layer that was fully depleted at thermal equilibrium gave rise to positive threshold voltage. A decent on-state drain current of 1.4 mA/mm and a sufficiently large drain current on/off ratio of six orders of magnitude were also achieved. Recently, our FET development took a step forward to vertical D-mode Ga2O3 MOSFETs. In the device structure, the source was electrically isolated from the drain by a current blocking layer formed by Mg-ion implantation except at an aperture opening for drain current conduction. Despite a large source–drain leakage current due to an imperfect function of the current blocking layer, the drain current modulation by applied gate bias was successfully demonstrated. We have also been developing vertical Ga2O3 SBDs. Ga2O3 FP-SBDs were fabricated on n --Ga2O3 drift layers grown by halide vapor phase epitaxy on n +-Ga2O3 (001) substrates [6]. The illustrative device with a net donor concentration of 1.8×1016 cm-3 exhibited a specific on-resistance of 5.1 mΩ·cm2 and an ideality factor of 1.05 at room temperature. Successful FP engineering resulted in a high breakdown voltage of 1076 V. Note that at the breakdown condition, the peak electric field in the Ga2O3 drift layer was estimated to be over 5 MV/cm, which was much larger than theoretical limits for SiC and GaN. Steady and rapid progress has been made on developing building blocks such as bulk wafers, epitaxial films, and device process techniques for realization of Ga2O3 electronics. We fabricated and characterized relatively simple Ga2O3 MOSFET and SBD structures. Both types of developed devices revealed excellent characteristics and thus demonstrated great potential of Ga2O3. Research and development in the next decade is certainly crucial for the road to industrialization of Ga2O3 electronic devices. This work was partially supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), “Next-generation power electronics” (funding agency: NEDO). [1] T. Onuma, S. Saito, K. Sasaki, T. Masui, T. Yamaguchi, T. Honda, and M. Higashiwaki, Jpn. J. Appl. Phys. 54, 112601 (2015). [2] A. Kuramata, K. Koshi, S. Watanabe, Y. Yamaoka, T. Masui, and S. Yamakoshi, Jpn. J. Appl. Phys. 55, 1202A2 (2016). [3] M. Higashiwaki, K. Sasaki, A. Kuramata, T. Masui, and S. Yamakoshi, Appl. Phys. Lett. 100, 013504 (2012). [4] M. H. Wong, K. Sasaki, A. Kuramata, S. Yamakoshi, and M. Higashiwaki, IEEE Electron Device Lett. 37, 212 (2016). [5] M. H. Wong, Y. Nakata, A. Kuramata, S. Yamakoshi, and M. Higashiwaki, Appl. Phys. Express 10, 041101 (2017). [6] K. Konishi, K. Goto, H. Murakami, Y. Kumagai, A. Kuramata, S. Yamakoshi, and M. Higashiwaki, Appl. Phys. Lett. 110, 103506 (2017).