Researches
7 research themes have been selected with several high-impact publications in all themes.
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You can check the publications of each theme from 'Publications' page.
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Peer-review requests of every themes are welcome (main research topic is 'numerical simulation', however other topics are also welcome).
c-Si Photovoltaics
Design, development and evaluation of c-Si photovoltaic cells
Developments of next-generation crystalline-Si (c-Si) photovoltaic cells include several structural or electrical parameters as the structures become much complex. Next-generation c-Si photovoltaic cells include PERC (Passivated Emitter and Rear Cell), IBC (Interdigitated Back Contact), SHJ (Silicon Hetero-Junction), TOPCon (Tunnel Oxide Passivated Contact) technologies. Also, bifacial structure enables to enhance output powers by absorbing both the forwarded light and ground-reflected light simultaneously. My method establishes high-reliable cell simulation modelings based on realistic cells to enable to optimize or reveal cell characteristics.
keywords: PERC, IBC, TOPCon, SHJ, Bifacial cell, TCO
Semiconductor Piezoresistance
Establishment of new simulation modeling on semiconductor piezoresistance
Semiconductor piezoresistance is known as the resistivity changes of materials by mechanical stresses applied. The magnitudes of resistivity changes are much higher than those of metals, and applications to mechanical stress sensors are researched. New materials such as wide band-gap (WBG) semiconductors of silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga2O3) have several attractive material characteristics over Si, however their piezoresistance phenomena are still unknown. My research established new simulation modeling that have well reproduced the piezoresistance operations of such materials, that enabled to predict material reactions against mechanical stresses.
keywords: Wide band-gap semiconductors, Ionization energy
Condensed Matter
Determinations of material parameters
Condensed matter physics are the fundamental characterizations of materials, that are important to model materials for numerical calculations. For WBG semiconductors, impact ionization (II) is known as one of the critical ones as II is the dominant mechanism on device breakdown. II is expressed by impact ionization coefficient (IIC) that is the unique value on every semiconductor. For Ga2O3, its hole IIC had not known, and our researches determined its hole IIC on different crystal orientations. IIC values are useful to predict device operations to avoid electrical malfunctions.
keywords: Gallium oxide, Impact ionization, Crystal orientation
Transistor
Designs of ultrashort-gate transistors: More Moore
Transistor is the most important semiconductor device that are widely used on large-scale-integration (LSI) chips. Currently, its gate-length reaches x-nm scale and further shrink needs large efforts. My researches aim to design 1 - 2 nm actual gate-length transistors by numerical simulations for the next decade transistor designs.
keywords: UTB-SOI, Quantum effect
Analog LSI
Developments of more-than Moore analog LSIs
Analog LSIs are widely implemented especially for Internet of Things (IoT) applications that processes environment conditions. IoT needs new on-chip devices to achieve this function, such as self power sources, environment sensors, wireless communicators. My researches have proposed several such devices of high-performance on-chip photovoltaic cells, new sensors of optical and mechanical environments.
keywords: More than Moore, Energy harvesting, Sensors, Reference circuits
Silicon Photonics
New optical sensor designs
Silicon photonics shows high-compatibilities to CMOS LSIs as it can be fabricated on standard CMOS technologies. My researches developed new optical sensors designed on standard CMOS LSIs. Sensors enable to measure visible (RGB), ultraviolet (UV) and infrared (Ir) lights without color filters.
keywords: Photodiode, Color sensors
Power Electronics
Wide band-gap semiconductor power devices
Wide band-gap semiconductors in power electronics field are recently focused. My research aims to evaluate the applications in this field using numerical simulations.
keywords: Silicon carbide, Schottky barrier diode, Mechanical stress