Wide Bandgap Semiconductor Devices Research Articles

High Power Density Buck Boost DC/DC Converter Using SIC MOSFET

Abstract High power density is an advance in power electronics. Third generation wide-bandgap semiconductor devices (WBG SICs) offer significantly improved performance compared to standard silicon devices. SIC MOSFET is commonly used in power electronic equipment such as converters due to its low resistance, excellent thermal stability, and rapid switching speed. Increasing the switching frequency effectively reduces the circuit size. This article uses SIC MOSFET and STM32 single-chip MCU to design a high power density and higher frequency buck boost converter and establish a simulation model in LTspice. The driving circuit designed for SIC MOSFET is intended to maximize the converter’s reliability. Synchronous rectification applies to enhance the converter efficiency. Compared to other types of converters, the size of the converter is reduced, achieving the goals of lightweight and high power density of DC/DC converters.

Effect of Surface Microstructure on Joints Using Nanoporous Cu Sheet for Power Devices

Wide-bandgap (WBG) semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) are being developed as promising replacements for Si-based semiconductors. The operating temperature of SiC semiconductor is expected to be much higher. The replacement of soldering with new bonding process has been needed for WBG semiconductor devices. We have proposed a solid-state bonding process using nanoporous metal sheet, as a die-attach bonding method for WBG semiconductor devices. In this study, the bonding process using nanoporous Cu sheet as an insert metal was investigated to achieve a Cu disk/Cu disk bonding without solvent and flux. The shear strength of the joint using nanoporous Cu sheet at 350 and 300°C in formic acid atmosphere exceeded the shear strength of conventional Pb–5Sn solder joints which was approximately 18 MPa.

Guest Editorial: Special Issue on Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications

Guest Editorial: Special Issue on Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications

An MSM photodetector based on an InGaO/TiO2 heterojunction for high-performance UV detection

As typical metal–oxide wide bandgap semiconductor devices, ultraviolet (UV) photodetectors (PDs) based on TiO2 have encountered challenges related to high dark current and low photo-to-dark suppression ratio. In this study, indium (In) was doped into Ga2O3 to create the compound InGaO (IGO). Subsequently, IGO was combined with TiO2 to fabricate IGO/TiO2 heterojunction (ITH) MSM UVPDs. The built-in electric field constructed at the contact interface is capable of depleting the majority carriers in dark and limiting the dark current. The Au interdigital electrodes and the IGO film of the top layer will form an Ohmic contact without the carrier transport barrier to construct a photoconductive device with high photo currents. The results show that the ITH UVPDs exhibit a notable photo current of 1.21 mA and a low dark current of 0.29 nA, leading to an ultrahigh photo-to-dark current ratio of 6 orders of magnitude (4.17 × 106). Additionally, the UVPDs demonstrate a significant responsivity (R) of 1.16 × 104 A/W and a remarkable detectivity (D*) of 7.34 × 1015 Jones under 290 nm UV illumination at 5 V bias. This study provides a potential method for fabricating high-performance UVPDs.

Performance analysis of GaN based dual active bridge converter for electric vehicle charging application

<p><span>The research work proposes a Gallium Nitride (GaN) based dual active bridge (DAB) converter for electric vehicle (EV) charging applications. The wide bandgap semiconductor device, GaN is implemented in the DAB topology of an Isolated Bidirectional DC-DC converter (IBDC). GaN-based DC-DC converters lead to higher efficiency, smaller size, faster charging, and reduced heat generation improving the overall performance of the EV charging system. The performance characteristics of GaN based DAB converter is analyzed both in simulation and hardware for EV charging application. The same analysis is extended to a Si based DAB converter and comparative results are presented. A 14.25 kW GaN based DAB and <br /> 10.5 kW Si based DAB is designed and evaluated using LTspice XVII software and a scaled-down prototype of 0.612 kW GaN based DAB and 0.25 kW Si based DAB is presented for experimental validation. Result analysis under similar operating conditions indicated an improvement of 36% more output power transfer on the GaN based DAB over the traditional Si based DAB. The developed prototype showcased improved levels of power, voltage, and current under same operating conditions. The power transmission in the developed DAB based IBDC topology is controlled using the single-phase-shift (SPS) control strategy.</span></p>

(Invited) Wide Bandgap Semiconductor Based Devices for Digital and Industrial Applications

Wide bandgap (WBG) semiconductor devices based on SiC, GaN and Ga2O3 provide advantages for many strategic initiatives in various industrial sectors, such as data centers, electric vehicles, renewable energy systems like solar and wind power inverters. Innovations in WBG technologies would enable new paths on energy efficiency for pushing towards sustainable perspectives. For instance, higher efficiency and lower power dissipation are always desirable for digital economy/society and power electronic applications owing to the energy saving at the end with the goal to reduce CO2 emissions.Here we will emphasize our ongoing WBG semiconductor related research/development and innovation activities, especially on GaN technology owing its rapid/huge demanding in the market nowadays. Thus, the GaN material growth, device processing/packaging and characterization/verification will be elaborated in detail in this talk.In recent years an epitaxy technique to grow large diameter GaN-on-Si wafers by coalesced nanowire has been established at RISE ProNano Lab. The GaN nanowires are epitaxially grown and then merged into a planar epitaxial film with reduced dislocation density as compared to commercially available substrates. It allows for fabrication of thick GaN layers that required for high-voltage vertical devices on Si. A 4.1-µm-thick GaN device layer on a GaN-on-Si template has been grown successfully. It has a threading dislocation density on the order 108 cm-2 and a root mean square roughness of < 0.4 nm. This result has laid the foundation for scaling to the thicker (10-12 µm) crack-free GaN drift layer on lager wafer diameters up to 200 mm.RISE has long term experience working on GaN based High Electron Mobility Transistors (HEMTs). Since 2019 we have worked on high performance and cost-competitive power HEMTs on buffer-free GaN-on-SiC wafers in frame of EU UltimateGaN project. It has focused not only on verification of the high device performance but also on its yield for revealing its competitiveness in the cost-sensitive power electronics market. The fabricated HEMTs demonstrated the expected threshold voltage, good linearity with gate length and width, Ion/Ioff ratio of 1010 as well as high output current up to 16 A with multiple fingers. In such wafer level device fabrication, different types of multi-finger HEMTs could be included with designed electrodes for flip-chip soldering them into package modules. The power module was designed and produced in house by ceramic additive manufacturing (AM), also known as three-dimensional (3D) printing. The package design has aimed to address the stringent thermal and electrical requirements of these types of HEMTs for power electronic applications. Importantly the ceramic AM package design also enables the incorporation of intricate 3D features into the package structure for achieving increased electrical isolation distance between the source and drain contact pads of the HEMT in the package.In addition, SiC and Ga2O3 based sensors/devices will be briefed in this talk, which will provide a glance for design and fabrication of the hybrid WBG components for various greener applications.

Status and prospects of wide bandgap semiconductor devices

Wide bandgap semiconductor materials, such as silicon carbide (SiC) and gallium nitride (GaN), have attracted significant attention due to their exceptional electronic and thermal properties, making them ideal for high-power and high-frequency applications. This study provides a comprehensive review of SiC and GaN materials and recent developments in power electronics, radio frequency (RF) devices. The study focuses on the unique properties of these materials, which enable them to outperform traditional silicon-based devices in terms of efficiency, power density, and overall performance. The objectives include examining material properties, assessing SiC and GaN-based device performance, comparing electron mobility, on-resistance, and temperature dependence, and identifying areas for future research. The content covers a range of devices, including SiC MOSFETs, IGBTs, GaN HEMTs, and their applications, with a focus on recent advances in material quality and device reliability. The research contribution of the paper lies in its comprehensive analysis, which serves as a valuable reference for researchers, manufacturers, and policymakers working to accelerate the development of advanced materials and technologies. The successful implementation of SiC and GaN-based devices will lead to more energy-efficient systems, enhanced performance across various sectors, and a reduction in global energy consumption and environmental impact, revolutionizing the electronics industry.

(Invited) Wide Bandgap Semiconductor Based Devices for Digital and Industrial Applications

Wide bandgap (WBG) semiconductor devices based on SiC, GaN and Ga2O3 provide advantages for many strategic initiatives in various industrial sectors, such as data centers, electric vehicles, renewable energy systems like solar and wind power inverters. Here we provide an overview of our ongoing WBG semiconductor related research/development and innovation activities, especially on GaN based devices owing to their rapid/huge demanding in the emerging green technology market nowadays. In particular, the innovative GaN material epi growth, the device processing/packaging and related characterization/verification are elaborated.

(Invited, Digital Presentation) Low-Temperature Direct Bonding of Wide-Bandgap Semiconductor Substrates

Low-temperature direct bonding technique of semiconductor substrates has been developed to integrate dissimilar materials (e.g. Si, Ge, III-V) regardless of lattice and thermal expansion mismatches. Among the direct bonding techniques, a hydrophilic bonding method, which initiates a dehydration reaction between OH-terminated substrates, is commonly used because wafer-scale bonding can be fabricated under atmospheric conditions. Recently, our research group achieved direct bonding of wide-gap materials, including SiC, GaN, β-Ga2O3, and diamond substrates, by using this bonding method.The hydrophilic bonding of Si wafers has been practically applied for the fabrication of silicon-on-insulator substrates. In the bonding process, the Si substrates are typically irradiated with reactive ion etching using oxygen plasma, which efficiently generates OH groups on the surface. By contacting the substrates under atmospheric conditions, the activated surfaces can adhere to each other by hydrogen bonds across the OH groups. The annealing at ~200 °C causes the dehydration reaction and forms atomic bonds between the substrates, as shown in the following equation.Si-OH + HO-Si → Si-O-Si +H2OThe bonding process generates a sub-10-nm-thick SiOx layer at the bonding interface, which limits thermal and electrical conductance between the bonding substrates.Our research group demonstrated that the diamond substrates can be bonded with other semiconductor substrates (e.g. Si, InP, β-Ga2O3) by the hydrophilic bonding method. The pre-bonding treatment using oxygen plasma is not suitable for the diamond surface because it is easily etched by the strong oxidizing treatment. Meanwhile, the mild oxidizing treatment using H2SO4/H2O2 (i.e. piranha solution) and NH3/H2O2 (i.e. SC1) mixtures enables OH termination of the diamond substrate without a significant increase in the surface roughness. Figure A shows the photograph of the diamond substrate bonded on the Si substrate. At the Si/diamond and InP/diamond bonding interfaces, ~3-nm-thick SiOx and InPOx layers were observed by an electron microscope, respectively, as displayed in Figure B. These oxide layers were formed by the oxidizing treatment at the pre-bonding step.However, when β-Ga2O3 and diamond substrates were bonded, such an oxide intermediate layer was not observed at the bonding interface. This is because diamond never develops the oxide layer and β-Ga2O3 is an oxide material. As shown in Figure C, we achieved the direct bonding of monocrystalline β-Ga2O3 and diamond substrates with an amorphous intermediate layer thinner than 1 nm. As the intermediate layer was atomically thin, efficient electrical and thermal conductance across β-Ga2O3/diamond substrates was possible, as plotted in Figure D.Qiushi Kang et al. demonstrated that the hydrophilic bonding of the SiC substrate is possible by using oxygen plasma. This treatment develops the ~4-nm-thick SiOx layer on the SiC substrate, which possibly became a thermal and electrical barrier at the bonding interface. However, our research group revealed that the SiC substrate dipped into HF acid can form direct bonding with an atomically thin intermediate layer. It is known that the SiC surface is OH terminated after the removal of the native oxide layer by HF acid, unlike the Si substrate. We revealed that the HF-dipped SiC substrate can form direct bonding with the O2-plasma-activated β-Ga2O3 substrate through an intermediate layer as thin as 1 nm. as displayed in Figure E.About the GaN substrate, we have demonstrated that hydrophilic bonding with the Si substrate is possible using oxygen and nitrogen plasma activations. In addition, the GaN substrate dipped into H2SO4/H2O2 and NH3/H2O2 mixtures can also form direct bonding. The thickness of the GaOx layer at the GaN/Si bonding interface was approximately 1 nm.We believe the low-temperature direct bonding technique will contribute to future wide-bandgap semiconductor devices because it is possible to achieve efficient electrical and thermal conduction across dissimilar materials. Figure 1

Fundamental insight into the formation of the zinc oxide crystal structure

Zinc oxide shows unique properties which are evident in a wide range of applications: as a transparent conducting oxide, wide-bandgap semiconductor, and piezoelectric device. The starting point for understanding the origin of these properties are the subtle details of the crystal structure of ZnO, and thus elucidating its formation process is essential. The in-situ characterization of films deposited at various temperatures provides an important contribution in this regard, especially since this study reports on ZnO film deposition below room temperature down to -240 °C. Systematic investigations on nanocrystalline ZnO films as function of the deposition temperature reveal structural disorders caused by the irregular occupation of oxygen tetrahedra forming dioxygen species in zinc oxide. Three distinct material ranges are identified in the range of deposition temperatures between -240 and 300 °C. The most surprising observations are the segregation of zinc next to ZnO particles for films deposited at room temperature and the disappearance of the Raman bands of the ZnO lattice for those deposited above 100 °C. On both ends of the investigated deposition temperature scale transparent colorless films are obtained, which form a random frozen solid at low temperatures as well as a highly disordered film at high temperatures. The deposits at -80 °C are yellow in color, indicating the presence of superoxide ions. This wide variety in the properties of ZnO is enabled by the high flexibility of the wurtzite structure, which tolerates huge distance variations. This observation and the results presented open up important insights into the behavior of zinc oxide.

Size-Dependent Phase Transition in Ultrathin Ga2O3 Nanowires.

Gallium oxide (Ga2O3) has attracted extensive attention as a potential candidate for low-dimensional metal-oxide-semiconductor field-effect transistors (MOSFETs) due to its wide bandgap, controllable doping, and low cost. The structural stability of nanoscale Ga2O3 is the key parameter for designing and constructing a MOSFET, which however remains unexplored. Using in situ transmission electron microscopy, we reveal the size-dependent phase transition of sub-2 nm Ga2O3 nanowires. Based on theoretical calculations, the transformation pathways from the initial monoclinic β-phase to an intermediate cubic γ-phase and then back to the β-phase have been mapped and identified as a sequence of Ga cation migrations. Our results provide fundamental insights into the Ga2O3 phase stability within the nanoscale, which is crucial for advancing the miniaturization, light weight, and integration of wide-bandgap semiconductor devices.

Call for Papers for a Special Issue of IEEE Transactions on Electron Devices on "Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications"

Call for Papers for a Special Issue of IEEE Transactions on Electron Devices on "Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications"

Call for Papers for a Special Issue of IEEE Transactions on Electron Devices on "Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications"

Call for Papers for a Special Issue of IEEE Transactions on Electron Devices on "Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications"

Parasitic Capacitive Couplings in Medium Voltage Power Electronic Systems: An Overview

Recent development within the field of medium voltage wide-bandgap semiconductor devices are drawing the attention from both researchers and industries, due to the demanding requirements for more efficient high-power energy conversion. The rapid development has entailed an increased awareness of the negative impact of increased rate of change in voltage, d vd t, and its derived issues caused by the inevitable parasitic capacitive couplings. This paper is dedicated to present an overview of the parasitic capacitive couplings in high-power medium voltage power electronic converter systems, using an example reference system enabled by medium voltage SiC MOSFETs. The definitions of capacitive couplings are presented and the impacts raised by parasitic capacitive couplings are reviewed. In addition, the similarities of different capacitive couplings introduced by components in practical medium voltage systems are presented and summarized. Lastly, the challenges and future work with respect to parasitic capacitive couplings in medium voltage power electronics converter systems are shared from the authors' perspective.

Low-Temperature Sinterable Cu@Ag Paste with Superior Strength Driven by Pre-Heating Process

To preserve the structural integrity of power semiconductor devices, ensuring a reliable connection between wide-bandgap (WBG) chips and their substrates at temperatures above 200 °C is crucial. Therefore, easily processable chip-attach materials with high bonding strengths at high temperatures should be developed. Herein, we determined the optimal pre-heating conditions of chip-attach materials to achieve highly reliable WBG semiconductor devices. Sintering with silver-coated copper (Cu@Ag) particle paste was investigated as a model system for chip attachment in electric power devices. After printing the paste onto a direct-bonded ceramic substrate and placing the Si chip on the paste, the pre-heating process was conducted at 50 and 70 °C for different periods of time. Finally, the samples were sintered at a pressure of 9 MPa at 250 °C in an N2 atmosphere for 1 h. The quality of the obtained Cu@Ag joints significantly varied depending on the pre-heating temperature and time. When Cu@Ag joints were pre-heated at 50 °C, more reliable and reproducible bonding was achieved than at 70 °C. In particular, high-quality sintered joints were obtained with a pre-heating time of 4 min. However, after excessive pre-heating time, cracks and voids were generated impacting negatively the performance of the sintered joints.

A Review on Modular Converter Topologies Based on WBG Semiconductor Devices in Wind Energy Conversion Systems

This paper presents a comprehensive review on the employment of wide bandgap (WBG) semiconductor power devices in wind energy conversion systems (WECSs). Silicon-carbide- (SiC) and gallium-nitride (GaN)-based power devices are highlighted and studied in this review, focusing on their application in the wind energy system. This is due to their premium characteristics such as the operation at high switching frequency, which can reduce the switching losses, and the capability to operate at high temperatures compared with silicon (Si)-based devices. These advantages promote the replacement of the conventional Si-based devices with the WBG semiconductor devices in the new modular converter topologies due to the persistent demand for a more-efficient power converter topology with lower losses and smaller sizes. The main objective of this paper was to provide a comprehensive overview of the WBG power devices commercially available on the market and employed in the modular converter topologies for renewable energy systems. The paper also provides a comparison between the WBG power technologies and the traditional ones based on the Si devices. The paper starts from the conventional modular power converter topology circuits, and then, it discusses the opportunities for integrating the SiC and WBG devices in the modular power converters to improve and enhance the system’s performance.

Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications

Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications

Call for Papers for a Special Issue of IEEE Transactions on Electron Devices on "Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications"

Call for Papers for a Special Issue of IEEE Transactions on Electron Devices on "Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications"

Call for Papers for a Special Issue of IEEE Transactions on Electron Devices on “Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications”

Call for Papers for a Special Issue of IEEE Transactions on Electron Devices on “Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications”

Call for Papers for a Special Issue of IEEE Transactions on Electron Devices on "Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications"

Call for Papers for a Special Issue of IEEE Transactions on Electron Devices on "Wide and Ultrawide Band Gap Semiconductor Devices for RF and Power Applications"