2005 Fiscal Year Final Research Report Summary
Investigation of dynamical conductivity in quantum nanostructures by time-domain terahertz spectroscopy
| Project/Area Number |
15206037
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electron device/Electronic equipment
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| Research Institution | The University of Tokyo |
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Principal Investigator |
HIRAKAWA Kazuhiko University of Tokyo, Institute of Industrial Science, Professor, 生産技術研究所, 教授 (10183097)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAKI Hiroyuki University of Tokyo, Institute of Industrial Science, Professor, 生産技術研究所, 教授 (90013226)
ARAKAWA Yasuhiko University of Tokyo, Research Center for Advanced Science and Technology, professor, 先端科学技術研究センター, 教授 (30134638)
OTSUKA Yukiko University of Tokyo, Institute of Industrial Science, Research associate, 生産技術研究所, 助手 (00251463)
SEKINE Norihiko The National Institute of Information and Communications Technology, Researcher, 研究員 (10361643)
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| Project Period (FY) |
2003 – 2005
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| Keywords | terahertz radiation / quantum nanostructures / superlattices / Bloch oscillation / transistors / quantum dots / molecular devices / femtosecond spectroscopy |
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| Research Abstract |
In this research project, we investigated dynamical conductivities in quantum nanostructures by using terahertz (THz) radiation as a probe for ultrafast carrier motion. The main results are ;
1.Carrier dynamics in semiconductor superlattices and THz gain of Bloch oscillating electrons : By analyzing the THz waveforms emitted from semiconductor superlattices pumped by femtosecond laser pulses, we have shown that Bloch oscillating electrons have dispersive THz gain for the first time. Furthermore, the dominant dephasing mechanism of Bloch oscillation has been identified to be interface roughness scattering.
2.Non-equilibrium transport in ultrafast transistors: To understand the performance of ultrafast transistors, we have investigated the THz radiation from non-equilibrium transport in bulk GaAs. It is found that the initial acceleration of photoexcited electrons starts to decrease with increasing field above 50 kV/cm, suggesting the importance of band mixing effect. Furthermore, we proposed a novel method to characterize the cutoff frequencies of ultrafast transistors beyond the frequency region accessible by conventional network analyzers.
3.Conduction dynamics of single molecule/dot junctions : We planned to investigate the conduction dynamics of nanojunctions in which single molecules or quantum dots are probed by nanogap electrodes. Although we could measure dc characteristics, THz dynamics could not be characterized mainly due to their stability problem. This sub-project is being continued in our new project "Physics and control of terahertz dynamics of quantum nanosystems" (Grant in Aid No.18201027).
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Research Products
(104 results)
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[Journal Article] Spin transport through a single self-assembled InAs quantum dot with ferromagnetic leads2007
Author(s)
K.Hamaya, S.Masubuchi, M.Kawamura, T.Machida, M.Jung, K.Shibata, K.Hirakawa, T.Taniyama, S.Ishida, Y.Arakawa
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Journal Title
Applied Physics Letters vol. 90, No. 5
Pages: 053108-1-3
Description
「研究成果報告書概要(和文)」より
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[Journal Article] Collective and single-particle intersubband excitations in narrow quantum wells selected by infrared absorption and resonant Raman scattering2006
Author(s)
T.Unuma, K.Kobayashi, A.Yamamoto, M.Yoshita, K.Hirakawa, Y.Hashimoto, S.Katsumoto, Y.Iye, Y.Kanemitsu, H.Akiyama
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Journal Title
Physical Review B Vol. 74, No. 19
Pages: 195306-1-5
Description
「研究成果報告書概要(和文)」より
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