Electronics

Establishing Next-Generation Electronic Systems

We help students deepen their understanding of electronics and information-communications technology, which are key in society today. At the same time, we foster engineers and researchers who have the ability to lead developments in new technology by utilizing their expertise and who are equipped with the overall ability to adapt new technologies to social needs.

Educational Program

The educational program to realize our educational objectives has been organized in line with the following policy.

Our lectures cover a wide range of areas, such as materials, plasmas, devices, circuits, electromagnetic waves, optics, signal processing, communications and systems. In addition, we instruct students to familiarize themselves with the computer as a tool for design, analysis, measurement, control and more. Moreover, we encourage students to take program-wide courses designed to develop their insights through social perspectives, such as intellectual property rights, to enhance their ability to write a thesis in English and to develop their communication skills. We encourage students to study abroad to foster global high-level engineers with leadership skills who can underpin any country’s industrial foundation as well as spurring the globalization of their local community. We encourage students to participate in internship programs in order to contribute to the promotion of local industries and to foster human resources in the field of engineering. Under the university’s “3 x 3” system, in which in practice, fourth-year undergraduate students are regarded as zero-year master’s program students (“M0” students), we permit them to take master’s courses before registering for our master’s program.

Our lectures cover a wide range of areas, such as materials, plasmas, devices, circuits, electromagnetic waves, optics, signal processing, communications and systems. In addition, we instruct students to familiarize themselves with the computer as a tool for design, analysis, measurement, control and more. Moreover, we encourage students to take program-wide courses designed to develop their insights through social perspectives, such as intellectual property rights, to enhance their ability to write a thesis in English and to develop their communication skills. We encourage students to study abroad to foster global high-level engineers with leadership skills who can underpin any country’s industrial foundation as well as spurring the globalization of their local community. We encourage students to participate in internship programs in order to contribute to the promotion of local industries and to foster human resources in the field of engineering. Under the university’s “3 x 3” system, in which in practice, fourth-year undergraduate students are regarded as zero-year master’s program students (“M0” students), we permit them to take master’s courses before registering for our master’s program.

Laboratory Information

Digital and Analog Integrated Circuits Cyber-Physical (Merging) Systems Engineering
Integrated circuits have been scaled down aggressively to nanoscale. Recent approaches to low power consumption have enabled the development of small, lightweight, and high-performance electronic components. In fact, cell phones and high-performance game devices could not have been developed without integrated circuits. The MOS transistor, which is a basic component for semiconductor integrated circuits, has been microfabricated to nanometer size. We investigate topics such as the characteristic modeling of nano-scaled transistors, reliability issues and integration of power electronics. In particular, we focus on simulation models of current and future-generation transistors and gate drivers for GaN HEMT and SiC MOSFET, and address problems that threaten reliability, including soft errors, bias temperature instability (BTI) and random telegraph noise (RTN)

Research themes: Modeling and Reliability Issues on Integrated System, and Gate Drivers of Power Transistors
Keywords: Integrated Circuits/Gate Drivers/Power Electronics/GaN HEMT/SiC MOSFET/Simulation/Soft Error/Aging Degradation
The world’s population is concentrating in urban areas. Smooth functioning of information distribution, mobility (movement of people and goods), and energy distribution are essential for this urbanization. To achieve effective mobility and avoid traffic congestion in a system with electric vehicles that provide comfortable, safe, and automatic travel, for example, we need to merge real world data acquisition technology, information and communication technology, and efficient electrical energy application technology into closely integrated. Systems we are building a testbed for just such a merged system in close collaboration with the cyber world of data and information communication technology to validate its effectiveness. This is being done in cooperation with the industrial world, and centering on research into how to configure and control a power router which function as a node in autonomous electric power distribution networks.

Research themes: Realization of power routing function in autonomous distributed power networks
Keywords: Cyber-physical merging/Energy distribution/System control/Next generation DC microgrid
Microwave Engineering Advanced Electromagnetic Wave Engineering
Wireless telecommunication is essential to modern society and our daily lives. We research applied technology involving electromagnetic phenomena, particularly those related to information communication. To produce creative and pioneering engineers, we are studying how to use information and communication technologies effectively to solve problems in society. We are constantly working to find ways to make life tomorrow more comfortable and safer than today by refining RF circuits and antennas.
We mainly research (1) small antennas for wireless communication devices and RF circuits for wearable devices, as wireless communication is an essential requirement for any wearable device, and (2) wireless communication technology in the sub-gigahertz band, with the goal of applying this technology to on-farm sensor networks for smart agriculture.

Research themes: Antennas and related radio frequency circuits for wearable wireless devices
Keywords: Radio engineering/Radio frequency circuit/Antenna/Radio wave propagation/Conductive textile
Artificial electromagnetic structures, referred to as “metamaterials,” are composed of elements much smaller than the wavelength, and have been studied in order to discover exciting new and unique electromagnetic phenomena and to invent state-of-the art functional circuits and antennas. Our research group has been working on metamaterials and their applications in the microwave region, such as non-reciprocal metamaterials based on broken time-reversal and space-inversion symmetries, dielectric metamaterials for artificial magnetic media, chiral metamaterials as well as metamaterial-inspired antennas, for applications in wireless communications and power transmission systems.
In addition, we are working on basic theories on wave scattering from randomly rough surfaces and wave propagation in random media by means of the stochastic functional approach. Such a theoretical approach is of great importance for imaging, remote sensing, and non-destructive measurement technologies using electromagnetic waves.

Research themes: Microwave and millimeter-wave circuits and antennas for wireless communications and wireless power transfer, metamaterials and their applications, electromagnetic wave scattering in random media
Optoelectronics and Optical Communication Optoelectronics and Optical Communication
Optical signals that can function in a wide frequency band enable high-speed communication up to several terabits per second. Optoelectronic technologies have been the central focus of system-level power consumption reduction. We study photonic networks for high-speed internet access as well as optoelectronic and optical devices using new functional materials and photonic nanostructures for next generation systems.
In the area of optical device development, we are creating waveguides, light-emitting devices, and solar cells with novel organic materials. We are also conducting research on photonic crystals for highly functional optical devices with low power consumption.
In the development of novel communication systems, we design systems 1) that do not require signal conversion into (or from) the electrical domain, and 2) that enable high-speed mobile communication such as the visible-light and radio-on-fiber communication systems without any bandwidth limitations.

Research themes: Visible-light communication. Optical wireless communication. Quality of experience in optical/wireless communication
Optoelectronic technologies have been the central focus of system-level power consumption reduction as well as the system enhancement. We study optoelectronic and optical devices using new functional materials and photonic nanostructures for next generation systems.
We are creating waveguides, light-emitting devices, and solar cells with novel organic materials. We are also conducting research on photonic crystals for highly functional optical devices with low power consumption.

Research themes: Highly functional optoelectronic devices using organic materials and nanophotonic structures
Integrated Photonics Imaging Photonics
We are working on photonics and electronics convergence for realizing future portable supercomputers. We are trying to establish fundamental techniques for large-capacity optical interconnects between high-end electronic chips. Our approach is research and development of new design methods and fabrication/packaging technology with demonstration of epoch-making photonic devices. We collaborate with Japan’s National Institute of Advanced Industrial Science and Technology (AIST), and participate in discussions and deliberations on the future of these devices with major related companies. Various passive and functional photonic devices are proposed and demonstrated for oscillation control of semiconductor lasers, application of semiconductor lasers to sensors. and mass-production of high-efficiency diffractive optical elements.

Research themes: Integrated photonic device engineering, especially with radiation-mode coupling
Keywords: Integrated photonics/Diffraction optics/Optical device engineering/Optical interconnects/Optical sensors
It is said that humans obtain more than 90% of all their information on the external world through vision. This fact is clearly expressed by the proverb “A picture is worth a thousand words.” In recent years, as seen in two-dimensional high-definition images and moving image transmission, image quality has improved in terms of performance and functionality. High-performance images are of great value and are now in increasingly high demand. This trend will continue in the future. We research new, unprecedented imaging technology and systems that take advantage of the physical features of light, such as three-dimensional (3D) image displays, 3D moving image measurements, and ultrafast / high-speed image recording and observation. We are also expanding our research into the realms of new optical elements and optical information processing technology for these image technologies and systems.

Research themes: 3D imaging techniques/Systems, and Ultrafast imaging techniques/Systems
Keywords: Optical Engineering/Image Engineering/Optical Imaging/Holography/3D Imaging
Advanced Sensing Engineering Electronics Device Engineering
Recently, in bio-sensing, vehicle-mounted sensors or displays, and other advanced sensing methods and devices, lasers are being used in a variety of ways. In bio-sensors, the information from micro-biological materials such as proteins, polymers and DNA are measured by detecting their fluorescent and scattered light. In vehicle-mounted sensors or displays, information from objects that could potentially cause collisions is detected by reflected light from the objects and projected on the windshield in front of the driver. Even smaller highly sensitive, high-precision devices with even faster scanning rates are anticipated. Our goal is to contribute advanced sensing by developing light sources. In particular, we are developing semiconductor lasers that will enable us to freely control the physical properties of light, including its intensity, polarization, phase and direction.

Research themes: Development of single chip lasers for advanced sensing
Keywords: Quantum optoelectronics/Singular optics/Photonic crystal
We are creating sensor technology oriented electronic devices that combine intelligent nanomaterial properties, semiconductor integration technology, and MEMS / NEMS (microelectromechanical system) technology. These newly emerging future IoT edge devices will become increasingly important in IoT technology. Oxide-based materials continue to show many excellent functional and intelligent properties for next-generation electron devices. We apply these in our research, focusing on new neuron synaptic device principals for AI development and ultralow power (ferroelectric and resistive change) integrated nonvolatile memory. As for bioelectronics, we develop biosensor and biosensing technologies based on original detection principles for important biomarker targets using smart artificial cell membranes. Furthermore, we develop and improve high-speed, high-resolution and real-time able biochemical image sensor technologies for the label-free detection of multiple analytes and concentration distributions.

Research themes: IoT edge devices that efficiently express and utilize emerging properties of intelligent nanomaterials
Keywords: IoT edge device/Intelligent nanomaterial/Neuron synaptic device/Sensor/Nonvolatile memory/Bioelectronics/Chemical imaging
Electronics Device Engineering Semiconductor Engineering
We are working on the PiezoMEMS (piezoelectric micro-electro-mechanical systems) devices using piezoelectric materials that mutually convert electrical energy and mechanical energy. Our research field is spread from material science to design and fabrication of the devices and systems for applications including microgenerators for IoT’s, next-generation robotics and automatic driving systems, and advanced sensors beyond human vision, auditory and tactile sensations. We are collaborating with overseas researchers in material science and with industry in device applications. Our graduate students are supported to learn the theory of the research field and microfabrication process technology, join the collaborations and gain the skill to create their own new devices/systems.


Research themes: From generators to sensor systems: piezoMEMS devices and systems
Keywords: Piezoelectrics/MEMS/Sensors/Harvesters/Sensing systems
The focus of our laboratory is novel materials for semiconductor devices.
Specifically:
1) creation of new semiconductor-semimetal alloys for novel communication laser devices that produce oscillations with temperature-independent wavelengths.
2) development of ultra-wide bandgap oxide semiconductors for next-generation power-switching applications with extremely low energy losses.
3) research of new photosynthesis systems that optical semiconductors are organically combined with functional bacteria with extracellular electron transfer capability.
We provide graduate students with an environment that fosters an ever broadening scope by advancing not only seed-based research that proposes new semiconductor materials and functions, in collaboration with research groups inside and outside the university, but also needs-based research for solving specific issues currently facing industry.

Research themes: Creation of next-generation semiconductor materials/Devices
Keywords: Next-generation communication lasers/Semi-metal semiconductor alloys/Oxide semiconductors/Power devices
Functional Materials Science and Engineering Electronic Science and Engineering
Hydrogen fuel sourced via water splitting with sunlight is now thought to be an important zero-emission energy source, particularly for hydrogen-powered vehicles. There is an urgent need to accelerate the development of highly-efficient hydrogen production devices. One obstacle interfering in this development is the absence of a highly efficient sunlight absorber. We have been exploring the possibility of heavy transition metal (TM) doping of aluminum nitride (AlN) films to confer sunlight absorption. AlN itself can absorb only deep ultraviolet light. With doping of TMs such as V, Cr, Mn and Ni, we have succeeded in producing ultraviolet-visible-infrared absorbing films with high efficiency. Very recently, we have also found that Ti-doped AlN films can be used for water oxidation and hydrogen reduction and can be effective when used in combination with other TM doped AlN films. We are now working toward the practical use of these promising new materials.

Research themes: Band structure engineering of AlN by heavy doping of 3d transition metals for highly efficient artificial photosynthesis devices
Keywords: Photoconversion/Artificial photosynthesis/Nitride semiconductors
We use plasma technology to fabricate electronic materials as well as researching and developing their processes and measurement technologies. Recently, to research nanotechnology that takes advantage of plasma technology, we have been examining electronic material fabrication technology for next-generation electronics devices and materials.
We create nanocarbon materials such as carbon nanotubes and graphenes, and research the application of these materials to electronic devices, energy devices such as hydrogen storage apparatus and capacitors, and medicine. Our goal is to develop plasma processes for the development of information processing devices of the future, energy and environment-related equipment, and medical applications. Our specific research targets involve: (1) the basic and applied physics of dusty plasmas, (2) super-fine machining of high-dielectric gate insulating materials and electrode materials for next-generation integrated circuits, (3) low dielectric thin film formation important in the creation of ultrahigh-speed logic elements, and (4) the destroying, deactivation, or elimination of all forms of life and other biological agents (sterilization).

Research themes: Microelectronics fabrication, bio-application and microgravity sciences by using plasmas
Keywords: Plasma/Dusty Plasma/Microelectronics Process/Medical/Agriculture/Microgravity Science
Plasma Science and Technology Nano Structure Science
We explore several novel subjects in the frontier of the research field of plasma science and technology.
(1) We have a middle-size toroidal machine in which a spherical reversed-field pinch plasma has been intensively studied. The machine is now being modified for creating a spherical tokamak as well. Using those toroidal plasmas, we systematically explore the fundamental physics of the toroidal plasmas and develop novel diagnostics that could be applied to a toroidal fusion plasma that will come up by 2025 for testing a nuclear fusion power reactor.
(2) We have a unique linear trap in which both pure ion and electron plasmas can be not only independently but also simultaneously confined in the trap for long time. Using those plasmas so called non-neutral plasmas, we have been experimentally studying two-fluid plasmas, which is one of the unexplored areas of plasma physics.
(3) We have collaborated with a world-wide industrial company that manufactures semiconductors. With the company, we have tried to develop a novel method for producing ultra-thin films by using reactive negative ions and a novel passive diagnostics to find where impurities are contained in low-temperature plasmas that are applied to plasma processing.
In our laboratory, we prepare many introductive programs for students. Those programs are basically for learning plasma science and technology but also being dedicated to acquire basic skills including electronics, scientific apparatus, and programming. Details are explained in our website.

Research themes: Advanced Nuclear Fusion, Advanced Plasma Physics, and Advanced Plasma Nanotechnology
Keywords: Plasma Physics and Technology/Nuclear Fusion/Plasma Processing/Plasma Nanotechnology/Applied Plasma Electronics
Research on nanotechnology is the cutting-edge manufacturing technology of the 21st century. Even in the field of advanced electronic and optical devices, basic research on ultrafine nanoscale machining, device structure fabrication, and physical property control is becoming increasingly important to the development of new functional devices in which various materials such as semiconductors, metals, dielectric materials, and magnetic materials are closely combined. In this laboratory, we alternate the use of electron beams, ion beams and laser beams to research ultrafine machining, actual device structure fabrication, and evaluation technology to create new devices with advanced functions that can be realized by such nanoscale structures.

Research themes: Nano material and process technology and its application to photonic devices
Keywords: Nano-scale fabrication/Nano photonics/Plasmonics/Metasurface
Nano Structure Science Electronic Material Science
Substances are formed by many different kinds and arrangements of atoms that enable them to exhibit specific characteristics or physical properties. To develop useful materials and to take advantage of the properties of substances, it is important to examine and control the arrangement of atoms at the nanometer scale. This technology is a fundamental element in today’s nanotechnology. We use electron beams to research nanostructure analysis technology for substances. We have used electron microscopy to develop some nano-evaluation techniques, and the results have been used for the development and application of new raw materials and devices such as semiconductors, metals, ceramics, and polymers. We are educating students on the basics of nanostructure analysis through lectures, seminars, and special studies.

Research themes: Nano-structural analyses of electronic material and devices by electron microscopy
Keywords: Nano-structural analyses/Crystal defects assessment/Electron microscopy
Electrons with inherent charge and spin behave dynamically in solids bringing about various physical properties. Our interests center on macroscopic quantum effects on such electron systems. We perform sensitive physical experiments on realized electron systems under low-temperature condition. As for the study of superconductivity of oxide systems, we pursue the synthesis of new materials and novel electrotransport phenomena by developing material synthesis processes and new methods of electric / magnetic measurement. We also work on research to explore new electrodynamic effects by integrating fundamental physics and advanced measurement technology.
Additionally, we are interested in new materials for future green electronics and the investigation of their physical properties. In particular, we have studied the fundamentals of oxide semiconductor materials and the development of functional new devices based on them. Furthermore, we have studied nitride semiconductors for future power-transistors and the materials related to them and have focused on layered-materials such as graphene and molybdenum disulfide and addressed the research to apply them to the electronic devices.

Research themes: Experimental physics for solids as electron systems
Keywords: Superconductivity/Ferromagnetism/General physics/Optical physics/Solid state spectroscopy/Plasmonics