Study of Fermi level pinning at metal/germanium interface and its alleviation mechanism

• Project/Area Number: 25420320
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Electron device/Electronic equipment
• Research Institution: The University of Tokyo
• Principal Investigator: Nishimura Tmonori 東京大学, 工学(系)研究科(研究院), 技術専門職員 (10396781)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Project Status: Completed (Fiscal Year 2015)
• Budget Amount: ¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000); Fiscal Year 2015: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2014: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2013: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
• Keywords: MOSFET / ゲルマニウム / フェルミレベルピンニング / 金属/半導体界面 / 半導体

Outline of Final Research Achievements

To prepare ideal Ge surface, we demonstrated a formation of step and terrace structure with atomically flat surface by H2 annealing. However, it does not effective to weaken the Fermi level pinning even though an atomically flat Ge channel improve its mobility at high electric field. On the other hand, we demonstrated an alleviation of Fermi level pinning at germanide/Ge interface, and we found out strong surface orientation dependence of Ge substrate on its Schottky barrier height. The Schottky barrier height at direct metal/Ge interface is controllable by appropriate metal and interface structure selections. It is possibly explained by intrinsic metal induced gap states with considering free electron densities in contact metal.

Research Products

• [Journal Article] "Atomically flat planarization of Ge(100), (110), and (111) surfaces in H2 annealing. " (2014)
  • Author(s): Tomonori Nishimura, Shoichi Kabuyanagi, Wenfeng Zhang, Choong Hyun Lee, Takeaki Yajima, Kosuke Nagashio, and Akira Toriumi
  • Journal Title: Applied Physics Express Volume: 7 Issue: 5 Pages: 051301-051301
  • DOI: 10.7567/apex.7.051301
  • NAID: 210000137073
  • Peer Reviewed
• [Presentation] Design of Metals for Fermi-level Pinning Modulation at Ge/Metal Interfaces (2016)
  • Author(s): T. Nishimura, T. Yajima, and A. Toriumi
  • Organizer: International SiGe Technology and Device Meeting 2016 (ISTDM2016) and 7th International Symposium on Control of Semiconductor Interfaces (ISCSI-VII)
  • Place of Presentation: 名古屋大学 （愛知県名古屋市）
  • Year and Date: 2016-06-07
  • Int'l Joint Research
• [Presentation] 界面ダイポール密度の制御による金属/Ge界面のフェルミレベルピンニング緩和の試み (2016)
  • Author(s): 西村知紀，矢嶋赳彬，鳥海明
  • Organizer: 第63回応用物理学会春季学術講演会
  • Place of Presentation: 東京工業大学 （東京都目黒区）
  • Year and Date: 2016-03-19
• [Presentation] Atomically Flat Germanium (111) Surface by Hydrogen Annealing (2013)
  • Author(s): T. Nishimura, S. Kabuyanagi, C. H. Lee, T. Yajima, K. Nagashio, and A. Toriumi
  • Organizer: 224th Electrochemical Society Meeting
  • Place of Presentation: San Francisco, California, U.S.
• [Presentation] Charge neutrality level shift in the Bardeen limit of Fermi-level pinning at atomically flat Ge/metal interface (2013)
  • Author(s): T. Nishimura, T. Nakamura, T. Yajima, K. Nagashio and A.Toriumi
  • Organizer: 2013 International Conference on Solid State Devices and Materials
  • Place of Presentation: Fukuoka, Kyushu University
• [Presentation] Study of Strong Fermi Level Pinning at Metal/Germanium Interface Based on the Impact of Ultra-thin Insulator Insertion (2013)
  • Author(s): T. Nishimura, T. Nakamura, and A. Toriumi
  • Organizer: 6th International Symposium on Control of Semiconductor Interface
  • Place of Presentation: Fukuoka, Hilton Fukuoka sea hawk