Vol.6 No.3 2014

Research paper : Development of diamond-based power devices (S. SHIKATA et al.)−154−Synthesiology - English edition Vol.6 No.3 (2013) others will be conducted toward the practical use of Schottky diode, to promote the practical utilization of high-output, high-performance diodes. At the same time, the research for MIS (MOS) type field effect transistors (FET) and pn junction transistors will be done jointly with several universities. As an application, development will be done with prospects in mind as shown in Fig. 13 through interviews with companies.We have just started the Full Research that may require a long time. However, we wish to speed up the development to enable this material to become the main material and device of the 21st century, to meet the national interest of Japan in terms of resource and safety, and also to help solve the issue of global warming. AcknowledgementWe are deeply thankful to the researchers who worked with us at the time: Hiromichi Yoshikawa, Researcher, AIST (currently, Tomei Diamond Co., Ltd.); Kazuhiro Ikeda, Special Researcher, AIST (currently, Sumitomo Electric Industries, Ltd.); Ramanujam Kumaresan (currently, Kobe University); A. M. M. Omer (currently, Sumitomo Chemical Co., Ltd.); Natsuo Tatsumi (dispatched from Sumitomo Electric Industries, Ltd.); Masanori Nagase, Researcher (currently, Nanosystem Research Institute, AIST); Hideyuki Watanabe, Senior Researcher, Diamond Research Lab; Yukako Kato, Researcher; as well as the members of the Wafer Development Team (Akiyoshi Chayahara, Deputy Director; Yoshiaki Mokuno, Senior Researcher; Nobuteru Tsubouchi, Senior Researcher; and Hideaki Yamada, Senior Researcher). We are also deeply thankful to Professor Funaki of Osaka University, with whom we engaged in joint research on the switching property.Part of this research was conducted with the grant from “Project for Developing Innovative Energy-Saving Technology” of the New Energy and Industrial Technology Development Organization (NEDO).Note) http://www.enecho.meti.go.jp/policy/coolearth_energy/coolearth-hontai.pdf TerminologiesTerm 1.Field relaxing structure: The structure of the device is made to maintain breakdown voltage by dispersing and avoiding the concentration of electric field. Field plate and junction termination structures are well known.Term 2.Drift layer: This is the active layer that operates as the power device.Term 3.Vertical structure and pseudo vertical structure: Since large current flows through the power device, the current is led through the whole surface using a structure with vertical current route, rather than through a lateral structure device used in LSI and high-frequency devices. The pseudo vertical device is a test device with insulated substrate, and only its active layer is vertical, while the extraction of current is done from the top. See Fig. 3.Term 4.Themionic field emission (TFE) model: Of the three models of carrier conduction in the Schottky barrier junction, this model incorporates both the effects of thermo electron and field emission.Term 5.Avalanche breakdown: The phenomenon that leads to destruction as massive current flows like an avalanche, as free electrons are accelerated in the field and collision ionization occurs repeatedly.References[1]B. J. Baliga: Semiconductors for high-voltage, vertical channel field-effect transistors, J. Appl. Phys., 53, 1759 (1982).[2]H. Ohashi: Pawa debaisu no genjo to shorai tenbo (Current situation and future prospect of power devices), FED Journal, 11 (2), 3-7 (2000) (in Japanese).[3]W. Saito, I. Omura, T. Ogura and H. Ohashi: Theoretical limit estimation of lateral wide band-gap semiconductor power-switching device, Solid-State Electron., 48, 1555- 1562 (2004).[4]A. Q. Huang: New unipolar switching power device figures of merit, IEEE Electron. Device Lett., 25 (5), 298-301 (2004).[5]K. Arai and S. Yoshida: Dai 5 Sho Debaisu Sekkei Hyoka (Chapter 5 Device Design and Assessment), SiC Soshi No Kiso To Oyo (Foundation and Application of SiC Elements), Ohmsha (2003) (in Japanese).[6]H. Umezawa and S. Shikata: Diamond high-temperature power devices, Int’l Symp. Power Semiconductor Devices, 259-262 (2009).[7]A. Chayahara, Y. Mokuno, N. Tsubouchi and H. Yamada: Development of single-crystalline diamond wafers - Enlargement of crystal size by microwave plasma CVD and wafer fabrication technology, Synthesiology, 3 (4), 272-280 (2010) (in Japanese) [Synthesiology English edition, 3 (4), 259-267 (2010)].[8]H. Yamada, A. Chayahara, Y. Mokuno, H. Umezawa, S. Shikata and N. Fujimori: Fabrication of 1 inch mosaic crystal diamond wafers, Appl. Phys. Express, 3, 051301 (2010).[9]H. Yamada, A. Chayahara, Y. Mokuno, N. Tsubouchi, H. Umezawa, Y. Kato and S. Shikata: Inchi saizu no tankessho daiyamondo setsugo ueha no sakusei to daimensekika ni muketeno torikumi (Fabrication of inch-size monocrystal diamond juction wafer and effort toward increasing the surface area), 25th Diamond Symposium, 8 (2011) (in Japanese).[10]N. Kobayashi, M. Akamatsu, M. Okaji, S. Togashi, K. Harada and N. Yumoto: Analysis of synthetic approaches described in papers of the journal Synthesiology - Towards establishing synthesiological methodology for bridging the gap between scientific research results and society, Synthesiology, 5 (1), 36-52 (2012) (in Japanese) [Synthesiology English edition, 5 (1), 37-52 (2012)].[11]N. Tatsumi, H. Umezawa and S. Shikata: Reduction of epitaxial defects in diamond for high power device, Int’l


page 21