Yoshiyuki Yonezawa

National Institute of Advanced Industrial Science and Technology

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Hajime Okumura

University of Tsukuba

Tomohisa Kato

National Institute of Advanced Industrial Science and Technology

Shinsuke Harada

National Institute of Advanced Industrial Science and Technology

Mitsuru Sometani

National Institute of Advanced Industrial Science and Technology

Ryoji Kosugi

National Institute of Advanced Industrial Science and Technology

Hayato Ogawa

University of Virginia

Kazuhiro Mochizuki

Hosei University

Caldwell Wm

Kazutoshi Kojima

National Institute of Advanced Industrial Science and Technology

Hahn Aw

Missouri College

Cooperative Institutions

National Institute of Advanced Industrial Science and Technology

110

Fuji Electric (Japan)

The University of Tokyo

Kyoto University

Osaka University

Tohoku University

Tokyo Institute of Technology

Hiroshima Institute of Technology

Advanced Power Electronics (United States)

University of Tsukuba

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A microcomputer-based daily living activity recording system.

PubMed (2003)

Satoshi Matsuoka Yoshiyuki Yonezawa Hiroki Maki Haruo Ogawa Hahn Aw

A new daily living activity recording system has been developed for monitoring health conditions and living patterns, such as respiration, posture, activity/rest ratios and general activity level. The system employs a piezoelectric sensor, a dual axis accelerometer, two low-power active filters, a low-power 8-bit single chip microcomputer and a 128 MB compact flash memory. The piezoelectric sensor, whose electrical polarization voltage is produced by mechanical strain, detects body movements. Its high-frequency output components reflect body movements produced by walking and running activities, while the low frequency components are mainly respiratory. The dual axis accelerometer detects, from body X and Y tilt angles, whether the patient is standing, sitting or lying down (prone, supine, left side or right side). The detected respiratory, behavior and posture signals are stored by the compact flash memory. After recording, these data are downloaded to a desktop computer and analyzed.

Supine position

Micro computer

Tilt sensor

Sitting

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Citations (2)

A wrist-mounted activity and pulse recording system

M. Aritomo Yoshiyuki Yonezawa W.M. Caldwell

A wrist movement and arterial pulse recording system has been developed for continuous data acquisition in studies of activity/rest time periods, sleep quantity and quality, general activity level, resting heart rate and circadian rhythms. The system employs a wrist-mounted optical sensor, low-power 8-bit single chip microcomputer and a compact flash memory. The microcomputer detects whether the wrist is moving or inactive; if it is moving, activity signals are recorded by the compact flash memory. If the wrist is at rest, the arterial pulse waveform is continuously recorded.

Micro computer

10.1109/iembs.1999.803848

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Citations (19)

Influence of basal-plane dislocation structures on expansion of single Shockley-type stacking faults in forward-current degradation of 4H-SiC p–i–n diodes

Japanese Journal of Applied Physics (2018)

Shohei Hayashi Tamotsu Yamashita Junji Senzaki Masaki Miyazato Mina Ryo

The origin of expanded single Shockley-type stacking faults in forward-current degradation of 4H-SiC p–i–n diodes was investigated by the stress-current test. At a stress-current density lower than 25 A cm−2, triangular stacking faults were formed from basal-plane dislocations in the epitaxial layer. At a stress-current density higher than 350 A cm−2, both triangular and long-zone-shaped stacking faults were formed from basal-plane dislocations that converted into threading edge dislocations near the interface between the epitaxial layer and the substrate. In addition, the conversion depth of basal-plane dislocations that expanded into the stacking fault was inside the substrate deeper than the interface. These results indicate that the conversion depth of basal-plane dislocations strongly affects the threshold stress-current density at which the expansion of stacking faults occurs.

Stacking fault

Basal plane

10.7567/jjap.57.04fr07

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Citations (29)

Relationship between Current Density and Stacking Fault Expansion Origin in Forward Degradation of 4H-SiC PiN Diodes

Extended Abstracts of the 2020 International Conference on Solid State Devices and Materials (2017)

Shohei Hayashi Takako Yamashita Junji Senzaki Masaki Miyazato Mina Ryo

Degradation

Stacking fault

PIN diode

10.7567/ssdm.2017.n-2-04

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Citations (0)

Effect of HCL on Surface Free Energy of SiC during CVD Trench Filling

Materials science forum (2019)

Kazuhiro Mochizuki Shiyang Ji Ryoji Kosugi Yoshiyuki Yonezawa Hajime Okumura

Trench-filling epitaxial growth of 4H-SiC by chemical vapor deposition (CVD) with and without HCl was analyzed based on a continuum-diffusion model including the Gibbs–Thomson effect. Qualitative reproduction of the reported observation showed that the effective surface free energy of SiC during CVD can be doubled by the addition of HCl

10.4028/www.scientific.net/msf.963.136

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Citations (3)

Pragmatic Approach to the Characterization of SiC/SiO<sub>2</sub> Interface Traps near the Conduction Band with Split C-V and Hall Measurements

Materials science forum (2016)

Tetsuo Hatakeyama Kazuto Takao Yoshiyuki Yonezawa Hiroshi Yano

A simple and practical method of characterizing traps at SiC/SiO 2 interfaces close to the bottom of the conduction band by using the split C−V and Hall measurements is proposed. This technique was applied to the characterization of traps at a wet-oxidized SiC/SiO 2 interface on C-face and those at an oxynitrided SiC/SiO 2 interface on Si-face. It was shown that the density of traps near the conduction band of the oxynitrided SiC/SiO 2 interface was more than 10 times larger than that of the wet-oxidized SiC/SiO 2 interface.

Characterization

Interface (matter)

10.4028/www.scientific.net/msf.858.477

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Citations (3)

Relationship between depth of basal-plane dislocations and expanded stacking faults by application of forward current to 4H–SiC p-i-n diodes

Applied Physics Express (2019)

Shohei Hayashi Tamotsu Yamashita Junji Senzaki Tomohisa Kato Yoshiyuki Yonezawa

The influence of basal-plane dislocation (BPD) depth on the expansion of single Shockley-type stacking faults (1SSFs) was investigated during the forward-current degradation of 4H–SiC p–i–n diodes. The 1SSF expanded from the BPD converted into a threading edge dislocation (TED) in the substrate. The hole density that was injected into the substrate increased with the stress-current density; therefore, BPDs converted into TEDs at a greater depth caused the expansion of 1SSFs under higher stress-current density.

Basal plane

Threading (protein sequence)

10.7567/1882-0786/ab1305

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Citations (20)

An ultrasonic stride length measuring system employing two digital compasses.

PubMed (2014)

Hiromichi Maki Hayato Ogawa Yoshiyuki Yonezawa Hahn Aw Caldwell Wm

We have developed an ultrasonic stride length measuring system for analyzing the human gait. All elements of the system are quite small and each fit into an appropriate package. An ultrasonic transmitter, a digital compass, a radio transmitter and a microcontroller are attached to the subjects heel on the right shoe and in the direction of the left shoe. Two ultrasonic receivers, a digital compass, a radio receiver, a microcontroller and a 1GB SD memory card are installed on the left shoe. The ultrasonic receivers are attached to the toe and heel in the direction of the right shoe. The walking direction is thus detected by the compass attached on the right and left shoes, respectively. The stride length is detected by the difference between the radio wave and ultrasonic propagation velocities. The stride length is corrected by the detected walking direction, and then the corrected stride length is stored in the SD memory card. When downloaded, the memory card gives the accurate stride length which then is used to characterize the subjects gait during daily activity.

Compass

STRIDE

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Static and dynamic performance evaluation of > 13 kV SiC p-channel IGBTs at high temperatures

Tadayoshi Deguchi Tomonori Mizushima Hiroyuki Fujisawa Kensuke Takenaka Yoshiyuki Yonezawa

To examine the effect of the device structure on the on-state voltage (V on ), several types of ultrahigh-voltage 4H-SiC p-channel insulated-gate bipolar transistors (IGBTs) were fabricated. A p-channel IGBT with a retrograde charge storage layer (CSL) and an additional JFET ion implantation region exhibited the lowest V on at 200 °C. To obtain a blocking voltage (BV) greater than 13 kV, a junction termination extension (JTE)-dose dependence of the BV was also investigated. Furthermore, ampere-class p-channel IGBTs with optimized device structures were fabricated for the evaluation of the switching loss (5 kV/1 A). Although the turn-off loss increased with an increase in the temperature, the loss remained as low as less than 10 mJ up to 250 °C. This performance renders the ultrahigh-voltage 4H-SiC p-channel IGBTs suitable for high-temperature and high-power applications.

JFET

Insulated-gate bipolar transistor

High Voltage

10.1109/ispsd.2014.6856026

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Citations (10)

The Effect of Crystal Faces on the trap density in nitrided SiO 2 / SiC Interfaces Close to the Conduction Band Edge

The Japan Society of Applied Physics (2017)

Tetsuo Hatakeyama Yuji Kiuchi Mitsuru Sometani Dai Okamoto Shinsuke Harada

Trap (plumbing)

Crystal (programming language)

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