Public Release: 

Researchers quantify factors for reducing power semiconductor resistance by two-thirds

Discovery expected to lower energy consumption in electric power equipment

University of Tokyo

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IMAGE: Electron scattering under the silicon carbide (SiC) interface is limited by three factors: roughness of the SiC interface, charges under the SiC interface and atomic vibration. view more 

Credit: 2017 Mitsubishi Electric Corporation.

A research group in Japan announced that it has quantified for the first time the impacts of three electron-scattering mechanisms for determining the resistance of silicon carbide (SiC) power semiconductor devices in power semiconductor modules. The university-industry team consisting of researchers from the University of Tokyo and Mitsubishi Electric Corporation has found that resistance under the SiC interface can be reduced by two-thirds by suppressing electron scattering by the charges, a discovery that is expected to help reduce energy consumption in electric power equipment by lowering the resistance of SiC power semiconductors.

Electric power equipment used in home electronics, industrial machinery, trains and other apparatuses requires a combination of maximized efficiency and minimized size. Mitsubishi Electric, a leading Japanese electronics and electrical equipment manufacturer, is accelerating use of SiC devices for power semiconductor modules, which are key components in electric power equipment. SiC power devices offer lower resistance than conventional silicon power devices, so to further lower their resistance it is important to understand correctly the characteristics of the resistance under the SiC interface.

"Until now, however, it had been difficult to measure separately resistance-limiting factors that determine electron scattering," says Satoshi Yamakawa, senior manager of the SiC Device Development Center at Mitsubishi Electric's Advanced Technology R&D Center.

Electron scattering focusing on atomic vibration was measured using technology from the University of Tokyo. The impact that charges and atomic vibration have on electron scattering under the SiC interface was revealed to be dominant in Mitsubishi Electric's analyses of fabricated devices. Although it has been recognized that electron scattering under the SiC interface is limited by three factors, namely, the roughness of the SiC interface, the charges under the SiC interface and the atomic vibration, the contribution of each factor had been unclear. A planar-type SiC metal-oxide-semiconductor field-effect transistor (SiC-MOSFET), in which electrons conduct away from the SiC interface to around several nanometers, was fabricated to confirm the impact of the charges.

"We were able to confirm at an unprecedented level that the roughness of the SiC interface has little effect while charges under the SiC interface and atomic vibration are dominant factors," says Koji Kita, an associate professor at the University of Tokyo's Graduate School of Engineering and one of scientists leading the research.

Using an earlier planar-type SiC-MOSFET device for comparison, resistance was reduced by two-thirds owing to suppression of electron scattering, which was achieved by making the electrons conduct away from the charges under the SiC interface. The previous planar-type device has the same interface structure as that of the SiC-MOSFET fabricated by the electronics maker.

For the test, Mitsubishi Electric handled the design, fabrication and analysis of the resistance-limiting factors and the University of Tokyo handled the measurement of electron-scattering factors.

"Going forward, we will continue refining the design and specifications of our SiC MOSFET to further lower the resistance of SiC power devices," says Mitsubishi Electric's Yamakawa.

This research achievement was announced at the 63rd International Electron Devices Meeting (IEDM) in San Francisco, California, on December 4, 2017.

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Conference:

63rd International Electron Devices Meeting

Collaborating organization:
Mitsubishi Electric Corporation

Links:

Kita Research Group, Graduate School of Engineering, The University of Tokyo
Advanced Technology R&D Center, Mitsubishi Electric Corporation

Research contact:

Associate Professor Koji Kita
Graduate School of Engineering, The University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 JAPAN
Tel: 81-3-5841-7164
Fax: 81-3-5841-7164
Email: kita@scio.t.u-tokyo.ac.jp

Press contacts:

Yayoi Miyagawa
Public Relations Office, Graduate School of Engineering, The University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 JAPAN
Tel: 81-3-5841-1790
Fax: 81-3-5841-0529
Email: kouhou@pr.t.u-tokyo.ac.jp

Niels Meinke
Public Relations Division
Mitsubishi Electric Corporation
Tel: 81-3-3218-2831
Email: prd.gnews@nk.MitsubishiElectric.co.jp
http://www.MitsubishiElectric.com/news/

About the University of Tokyo:

The University of Tokyo is Japan's leading university and one of the world's top research universities. The vast research output of some 6,000 researchers is published in the world's top journals across the arts and sciences. Our vibrant student body of around 15,000 undergraduate and 15,000 graduate students includes over 2,000 international students. Find out more at http://www.u-tokyo.ac.jp/en/ or follow us on Twitter at @UTokyo_News_en.

About Mitsubishi Electric Corporation

With over 90 years of experience in providing reliable, high-quality products, Mitsubishi Electric Corporation (TOKYO: 6503) is a recognized world leader in the manufacture, marketing and sales of electrical and electronic equipment used in information processing and communications, space development and satellite communications, consumer electronics, industrial technology, energy, transportation and building equipment. Embracing the spirit of its corporate statement, Changes for the Better, and its environmental statement, Eco Changes, Mitsubishi Electric endeavors to be a global, leading green company, enriching society with technology. The company recorded consolidated group sales of 4,238.6 billion yen (US$37.8 billion*) in the fiscal year ended March 31, 2017. For more information visit: http://www.MitsubishiElectric.com

*At an exchange rate of 112 yen to the US dollar, the rate given by the Tokyo Foreign Exchange Market on March 31, 2017

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