Privious Issue

Volume 46 Number 3 (2015.9)

Special Feature

Power Semiconductor Devices

Part I. Special Feature

2. Approaching the Limit of Switching Loss Reduction in Silicon Power Devices(564kB)

pages 1-7
Satoru Machida, Kenichi Ito and Yusuke Yamashita

This paper reports the reduction limit of switching loss in silicon IGBTs. It became clear that suppression of dynamic avalanche adjacent to the trench bottom plays a key role in turn-off loss reduction. As a result, a 20% improvement in trade-off performance was achieved nearly reaching the turn-off limit.

3. Effect of Carrier Lifetime and Injection Efficiency on Relationship between Forward Voltage and Reverse Recovery Charge of PiN Diode (682kB)

pages 9-17
Yusuke Yamashita and Satoru Machida

The control of the forward voltage and reverse recovery charge of silicon PiN power diodes by carrier lifetime or carrier injection control techniques was theoretically investigated. This study demonstrates that when the rate of current density decreasing dj/dt is low, carrier injection control can decrease the reverse recovery charge while maintaining a constant forward voltage.

4. Ultra-low Feedback Capacitance SiC JFET for High-frequency Operation (938kB)

pages 19-24
Tsuyoshi Ishikawa, Katsuya Nomura, Yasunori Tanaka, Tsutomu Yatsuo and Koji Yano

We propose a novel SiC VJFET with low feedback capacitance C_rss. A p⁺ screen grid, which is inserted between the gate and drain, effectively reduces C_rss by about 80% compared with a conventional VJFET. Due to the low C_rss, the proposed VJFET has a lower total power dissipation than any existing SiC transistor.

5. Analysis of Dislocation Structure in Repeated a-face Grown Silicon Carbide Crystals(2,244kB)

pages 25-31
Itaru Gunjishima, Yasushi Urakami, Hiroyuki Kondo, Fusao Hirose, Ayumu Adachi, Shoichi Onda and Koichi Nishikawa

SiC single crystals with a low dislocation density were fabricated by our original “Repeated a-face (RAF) growth method”. The characteristics of the dislocation morphology in improved quality SiC crystals were quantitatively analyzed by applying a two-dimensional fast Fourier transform (2D-FFT) to dislocation images of the RAF crystals.

6. Imaging of Current Collapse and Degradation in Schottky Gate AlGaN/GaN HEMT by Electric Field-induced Optical Second-harmonic Generation Measurement(1,233kB)

pages 33-41
Takashi Katsuno, Takaaki Manaka, Tsuyosihi Ishikawa, Hiroyuki Ueda, Tsutomu Uesugi and Mitsumasa Iwamoto

2 dimensional (2D) imaging of current collapse and degradation in Schottky gate AlGaN/GaN high electron mobility transistor (HEMT) device was achieved by using an optical electric field-induced second-harmonic generation (EFISHG) measurement. In collapse imaging, the signal location was well corresponding to the location of virtual gate model. In degradation imaging, the determination point was identified by EFISHG clearly.
7. Evaluation of Dry Etching-induced Damage in p-type GaN by Hard X-ray Photoelectron Spectroscopy(1,109kB)

pages 43-50
Daigo Kikuta, Tetsuo Narita, Naoko Takahashi, Keita Kataoka, Yasuji Kimoto, Kazuyoshi Tomita, Tsutomu Uesugi, Tetsu Kachi and Masahiro Sugimoto

Dry etching-induced damage in p-type GaN and the effect of post-etching processes were investigated using hard X-ray photoelectron spectroscopy. Dry-etching induced damage causes a thicker depletion layer in p-type GaN. Exposure to O₂ plasma with subsequent HF treatment is most effective to reduce the depletion layer thickness and built-in potential.

8. Fuel Cell Research at Toyota Central R&D Labs., Inc. (956kB)

pages 51-65
Kazuo Kawahara

We have considered that fuel cells would be a good solution to the power source of future vehicles in a clean and energy-saving society, and started our fundamental research work in 1989. A polymer electrolyte fuel cell was selected as the research target and all our works has contributed to fuel cell vehicle development by Toyota.

9. Neuroergonomics of Absent-minded Driving: State of the Art and Future Research Directions(705kB)

pages 67-74
Hiroyuki Sakai

Absent-minded driving is far less understood than distracted driving, such as texting or talking while driving. This paper reviews empirical evidence from the existing neuroscience literature relating to spontaneous attentional decoupling (SAD). Future research directions toward realizing countermeasure technologies against absent-minded driving are then discussed based on the current neural-level understanding of SAD.

10. Microwave Processing and Applications to Future Automobile(1,898kB)

pages 75-92
Hideoki Fukushima

Microwave processing has many advantages over conventional methods such as rapid heating, selective heating, and internal heating. An extremely high-speed heating of 100 ℃/s was achieved. As applications to auto-industry using microwave heating in near future, the hydrogen production by microwave reforming, the microwave saccharification of cellulosic biomass, and the microwave heating of non-magnetic metal powders were investigated.

11. Indoor Localization Method Based on WiFi and Depth Camera(570kB)

pages 93-95
Seigo Ito

This paper presents WiFi and depth camera based localization, a new method for robust localization in indoor environments. Our approach mainly consists of the following two steps. First, the system estimates a coarse global position using WiFi. Second, the system estimates an accurate position by using visual odometry and a landmark that can be calculated from a range camera.