Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Yamamoto Keisuke Last modified date:2019.03.27

Assistant Professor / Department of Internationalization and Future Conception / Faculty of Engineering Sciences


Papers
1. Wei-Chen Wen, Keisuke Yamamoto, Dong Wang, Hiroshi Nakashima, Border trap evaluation for SiO2/GeO2/Ge gate stacks using deep-level transient spectroscopy, Journal of Applied Physics, 10.1063/1.5055291, 124, 20, 205303 1-205303 11, 2018.11, A border trap (BT) evaluation method was established for SiO2/GeO2/Ge gate stacks by using deep-level transient spectroscopy with a lock-in integrator. Ge metal-oxide-semiconductor capacitors (MOSCAPs) with SiO2/GeO2/Ge gate stacks were fabricated by using different methods. The interface trap (IT) and BT signals were successfully separated based on their different dependences on the intensity of injection pulses. By using p-type MOSCAPs, BTs at the position of 0.4 nm from the GeO2/Ge interface were measured. The energy of these BTs was centralized at the position near to the valence band edge of Ge, and their density (Nbt) was in the range of 1017-1018 cm-3. By using n-type MOSCAPs, BTs at the position range of 2.8-3.4 nm from the GeO2/Ge interface were measured, of which Nbt varied little in the depth direction. The energy of these BTs was distributed in a relatively wide range near to the conduction band edge of Ge, and their Nbt was approximately one order of magnitude higher than those measured by p-MOSCAPs. This high Nbt value might originate from the states of the valence alternation pair with energy close to 1 eV above the conduction band edge of Ge. We also found that Al post metallization annealing can passivate both ITs and BTs near to the valence band edge of Ge but not those near to the conduction band edge..
2. Keisuke Yamamoto, Ryutaro Noguchi, Masatoshi Mitsuhara, Minoru Nishida, Toru Hara, Dong Wang, Hiroshi Nakashima , Wide range control of Schottky barrier heights at metal/Ge interfaces with nitrogen-contained amorphous interlayers formed during ZrN sputter deposition, Semiconductor Science and Technology, 10.1088/1361-6641/aae4bd, 33, 11, 114011, 2018.10.
3. Hiroshi Nakashima, Hayato Okamoto, Keisuke Yamamoto, Dong Wang, Achievement of Ultralow Contact Resistivity of Metal/n+-Ge Contacts with Zr-N-Ge Amorphous Interlayer
, ECS Transactions, 10.1149/08004.0097ecst , 80, 4, 97-106, 2017.10, [URL].
4. Hidenori Higashi, Kouhei Kudo, Keisuke Yamamoto. Shinya Yamada, Takeshi Kanashima, Isao Tsunoda, Hiroshi Nakashima, Kohei Hamaya , Electrical properties of pesudo-single-crystalline Ge films grown by Au-induced layer exchange crystallization at 250oC
, Journal of Applied Physics, 10.1063/1.5031469, 123, 21, 215704-1-215704-7, 2018.06, [URL].
5. Takayuki Maekura, Kentaro Tanaka, Chisato Motoyama, Ryota Yoneda, Keisuke Yamamoto, Hiroshi Nakashima, Dong Wang, Effect of n-type doping level on direct band gap electroluminescence intensity for asymmetric metal/Ge/metal diodes
, Semiconductor Science and Technology, 10.1088/1361-6641/aa827f, 32, 10, 104001, 2017.08, [URL].
6. T. Kanashima, R. Yamashiro, M. Zenitaka, Keisuke Yamamoto, Dong Wang, J. Tadano, S. Yamada, H. Nohira, Hiroshi Nakashima, K. Hamaya, Electrical properties of epitaxial Lu- or Y-doped La2O3/La22O3/Ge high-k gate-stacks, Materials Science in Semiconductor Processing, 10.1016/j.mssp.2016.11.016, 70, 1, 260-264, 2016.11, [URL].
7. Yuta Nagatomi, Tomoki Tateyama, Shintaro Tanaka, Keisuke Yamamoto, Dong Wang, Hiroshi Nakashima, Achievement of low parasitic resistance in Ge n-channel metal-oxide-semiconductor field-effect transistor using embedded TiN-source/drain structure, Semiconductor Science and Technology, 10.1088/1361-6641/32/3/035001, 32, 3, 035001, 2016.11, [URL].
8. Yuta Nagatomi, Tomoki Tateyama, Shintaro Tanaka, Wei-Chen Wen, Taisei Sakaguchi, Keisuke Yamamoto, Liwei Zhao, Dong Wang, Hiroshi Nakashima, Mechanism of mobility enhancement in Ge p-channel metal-oxide-semiconductor field-effect transistor due to introduction of Al atoms into SiO2/GeO2 gate stack, Materials Science in Semiconductor Processing, 10.1016/j.mssp.2016.11.014, 70, 1, 246-253, 2016.11, [URL].
9. Keisuke Yamamoto, Hayato Okamoto, Dong Wang, Hiroshi Nakashima, Fabrication of asymmetric Ge Schottky tunneling source n-channel field-effect transistor and its characterization of tunneling conduction, Materials Science in Semiconductor Processing, 10.1016/j.mssp.2016.09.024, 70, 1, 283-287, 2016.10, [URL].
10. Kenji Kasahara, Hidenori Higashi, Mario Nakano, Yuta Nagatomi, Keisuke Yamamoto, Hiroshi Nakashima, Kohei Hamaya, Effect of post annealing on hole mobility of pseudo-single-crystalline germanium films on glass substrates, Materials Science in Semiconductor Processing, 10.1016/j.mssp.2016.07.004, 70, 1, 68-72, 2016.10, [URL].
11. Yuichi Fujita, Michihiro Yamada, Yuta Nagatomi, Keisuke Yamamoto, Shinya Yamada, Kentarou Sawano, Takeshi Kanashima, Hiroshi Nakashima, Kohei Hamaya, A low-temperature fabricated gate-stack structure for Ge-based MOSFET with ferromagnetic epitaxial Heusler-alloy/Ge electrodes, Japanese Journal of Applied Physics, 10.7567/JJAP.55.063001, 55, 6, 063001-1-063001-4, 2016.04, [URL].
12. Takayuki Maekura, Keisuke Yamamoto, Dong Wang, Hiroshi Nakashima, Influences of metal/Ge contact and surface passivation on direct band gap light emission and detection for asymmetric metal/Ge/metal diodes, Japanese Journal of Applied Physics, 10.7567/JJAP.55.04EH08, 55, 4S, 04EH08-1-04EH08-5, 2016.03, [URL].
13. Dong Wang, Hiroshi Nakashima, Keisuke Yamamoto, Takayuki Maekura, Direct band gap light emission and detection at room temperature in bulk germanium diodes with HfGe/Ge/TiN structure, Thin Solid Films, 10.1016/j.tsf.2015.09.074, 2015.10, [URL].
14. Hiroshi Nakashima, Keisuke Yamamoto, Dong Wang, Electrical Properties of Group 4 Metal-Nitride/Ge Contacts and the Application to Ge Optoelectronic Devices, ECS Transactions, 10.1149/06910.0055ecst, 69, 10, 55-66, 2015.10, [URL].
15. Kenji Kasahara, Yuta Nagatomi, Keisuke Yamamoto, H. Higashi, M. Nakano, Shinya Yamada, Dong Wang, Hiroshi Nakashima, Kohei Hamaya, Electrical properties of pseudo-single-crystalline germanium thin-film-transistors fabricated on glass substrates, Applied Physics Letters, 10.1063/1.4932376 , 107, 14, 142102-1-142102-5, 2015.10, [URL].
16. Keisuke Yamamoto, Ryutaro Noguchi, Mitsuhara Masatoshi, Minoru Nishida, Toru Hara, Dong Wang, Hiroshi Nakashima, Electrical and structural properties of group-4 transition-metal nitride (TiN, ZrN, and HfN) contacts on Ge, Journal of Applied Physics, 10.1063/1.4930573, 118, 11, 115701-1-115701-12, 2015.09, [URL].
17. Yuta Nagatomi, Shintaro Tanaka, Yuichi Nagaoka, Keisuke Yamamoto, Dong Wang, Hiroshi Nakashima, Fabrication of PtGe/Ge contacts with high on/off ratio and its application to metal source/drain Ge p-channel MOSFETs, Japanese Journal of Applied Physics, 10.7567/JJAP.54.070306, 54, 7, 070306-1-070306-4, 2015.06, [URL].
18. Dong Wang, Takayuki Maekura, Sho Kamezawa, Keisuke Yamamoto, Hiroshi Nakashima, Direct band gap electroluminescence from bulk germanium at room temperature using an asymmetric fin type metal/germanium/metal structure, Applied Physics Letters, 10.1063/1.4913261, 107, 7, 071102-1-071202-3, 2015.02, [URL].
19. Yuta Nagatomi, Yuichi Nagaoka, Keisuke Yamamoto, Dong Wang, Hiroshi Nakashima, Investigation of Al-PMA Effect on Al2O3/GeOx/Ge Gate Stack, ECS Transactions, 10.1149/06406.0261ecst, 64, 8, 261, 2014.10, [URL].
20. Keisuke Yamamoto, Mitsuhara Masatoshi, Keisuke Hiidome, Ryutaro Noguchi, Minoru Nishida, DONG WANG, Hiroshi Nakashima, Role of an interlayer at a TiN/Ge contact to alleviate the intrinsic Fermi-level pinning position toward the conduction band edge
, Applied Physics Letters, 10.1063/1.4870510, 104, 14, 132109-1-132109-5, 2014.04, [URL].
21. DONG WANG, Nagatomi Yuta, Kojima Shuta, Yamamoto Keisuke, Hiroshi Nakashima, Low-temperature fabrication of Y2O3/Ge gate stacks with ultrathin GeOx interlayer and low interface states density characterized by a reliable deep-level transient spectroscopy method, Thin Solid Films, 10.1016/j.tsf.2013.10.065, 557, 288-291, 2014.04, [URL].
22. Yamamoto Keisuke, DONG WANG, Hiroshi Nakashima, Fabrication of Metal-Nitride/Si Contacts with Low Electron Barrier Height, ECS Transactions, 10.1149/05809.0053ecst, 58, 9, 53, 2013.10, [URL].
23. Hiroshi Nakashima, Yamamoto Keisuke, DONG WANG, Development of Metal Source/Drain Ge-CMOS Using TiN/Ge and HfGe/Ge contacts, ECS Transactions, 10.1149/05809.0167ecst, 58, 9, 167, 2013.10, [URL].
24. Yamamoto Keisuke, Takahiro Sada, DONG WANG, Hiroshi Nakashima, Dramatic enhancement of low electric-field hole mobility in metal source/drain Ge p-channel metal-oxide-semiconductor field-effect transistors by introduction of Al and Hf into SiO2/GeO2 gate stack, Applied Physics Letters, 10.1063/1.4821546, 103, 12, 122106, 2013.09, [URL].
25. D. Wang, S. Kojima, K. Sakamoto, K. Yamamoto, H. Nakashima, An accurate characterization of interface-state by deep-level transient spectroscopy for Ge metal-insulator-semiconductor capacitors with SiO2/GeO2 bilayer passivation, Journal of Applied Physics, 10.1063/1.4759139, 112, 8, 083707, 2012.10, [URL].
26. K. Yamamoto, K. Harada, H. Yang, D. Wang, H. Nakashima, Fabrication of TiN/Ge Contact with Extremely Low Electron Barrier Height, Japanese Journal of Applied Physics, 10.1143/JJAP.51.070208, 51, 7, 070208, 2012.07, [URL].
27. K. Yamamoto, T. Yamanaka, K. Harada, T. Sada, K. Sakamoto, S. Kojima, H. Yang, D. Wang, H. Nakashima, Schottky Source/Drain Ge Metal-Oxide-Semiconductor Field-Effect Transistors with Directly Contacted TiN/Ge and HfGe/Ge Structures, Applied Physics Express, 10.1143/APEX.5.051301, 5, 5, 051301, 2012.05, [URL].
28. M. Iyota, K. Yamamoto, D. Wang, H. Yang, H. Nakashima, Ohmic contact formation on n-type Ge by direct deposition of TiN, Applied Physics Letters, 10.1063/1.3590711, 98, 19, 192108, 2012.05, [URL].
29. K. Yamamoto, T. Yamanaka, R. Ueno, K. Hirayama, H. Yang, D. Wang, H. Nakashima, Source/drain junction fabrication for Ge metal-oxide-semiconductor field-effect transistors, Thin Solid Films, 10.1016/j.tsf.2011.10.047, 520, 8, 3382, 2012.02, [URL].
30. D. Wang, K. Yamamoto, H. Gao, H. Yang, H. Nakashima, Defect Evaluation by Photoluminescence for Uniaxially Strained Si-On-Insulator, Journal of the Electrochemical Society, 10.1149/2.037112jes, 158, 12, H1221, 2011.11, [URL].
31. H. Nakashima, Y. Iwamura, K. Sakamoto, D. Wang, K. Hirayama, K. Yamamoto, H. Yang, Postmetallization annealing effect of TiN-gate Ge metal-oxide-semiconductor capacitor with ultrathin SiO2/GeO2 bilayer passivation, Applied Physics Letters, 10.1063/1.3601480, 98, 25, 252102, 2011.06, [URL].
32. K. Yamamoto, R. Ueno, T. Yamanaka, K. Hirayama, H. Yang, D. Wang, H. Nakashima, High-Performance Ge Metal-Oxide-Semiconductor Field-Effect Transistors with a Gate Stack Fabricated by Ultrathin SiO2/GeO2 Bilayer Passivation, Applied Physics Express, 10.1143/APEX.4.051301, 4, 5, 051301, 2011.04, [URL].
33. D. Wang, K. Yamamoto, H. Gao, H. Yang, H. Nakashima, Defect Evaluation by Photoluminescence for Uniaxially Strained Si-On-Insulator, ECS Transactions, doi: 10.1149/1.3567723, 34, 1, 1117, 2011.03, [URL].
34. H. Nakashima, Y. Sugimoto, Y. Suehiro, K. Yamamoto, M. Kajiwara, K. Hirayama, D. Wang, Electrical and structural evaluations of high-k gate dielectrics fabaricated using plasma oxidation and the subsequent anneling for a Hf/SiO2/Si structure, Semiconductor Science and Technology, 10.1088/0268-1242/23/12/125020, 23, 12, 125020, 2008.12, [URL].
35. Y. Sugimoto, K. Yamamoto, M. Kajiwara, Y. Suehiro, D. Wang, H. Nakashima, Dependences of effective work functions of TaN on HfO2 and SiO2 on post-metallization anneal, Thin Solid Films, 10.1016/j.tsf.2008.08.058, 517, 1, 204, 2008.11, [URL].
36. Y. Sugimoto, M. Kajiwara, K. Yamamoto, Y. Suehiro, D. Wang, H. Nakashima, Effective work function modulation of TaN metal gate on HfO2 after postmetallization annealing, Applied Physics Letters, 10.1063/1.2783472, 91, 11, 112105, 2007.09, [URL].
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38. Y. Sugimoto, K. Yamamoto, H. Nakashima, Electrical and Structural Properties of TaN Gate Electrodes Fabricated by Wet Etching Using NH4OH/H2O2 Solution and Hf Metal Hard Mask, Japanese Journal of Applied Physics, 10.1143/JJAP.46.L211, 46, 8, L211, 2007.02, [URL].
39. Y. Sugimoto, H. Adachi, K. Yamamoto, D. Wang, Hideharu Nakashima, Hiroshi Nakashima, Electrical characterization of high-k gate dielectrics fabricated using plasma oxidation and post-deposition annealing of a Hf/SiO2/Si structure, Materials Science in Semiconductor Processing, 10.1016/j.mssp.2006.10.020, 9, 6, 1031, 2006.12, [URL].