| Project/Area Number |
09450136
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
電子デバイス・機器工学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
SAKAKI Hiroyuki The University of Tokyo, Institute of Industrial Science, Professor, 生産技術研究所, 教授 (90013226)
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| Co-Investigator(Kenkyū-buntansha) |
NODA Takeshi The University of Tokyo, Research Center for Advanced Science and Technology, Re, 先端技術研究センター, 助手 (90251462)
TAKAHASHI Takuji The University of Tokyo, Research Center for Advanced Science and Technology, As, 先端技術研究センター, 助教授 (20222086)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥9,100,000 (Direct Cost: ¥9,100,000)
Fiscal Year 1998: ¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 1997: ¥5,400,000 (Direct Cost: ¥5,400,000)
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| Keywords | 10nm InAs quantum dot / Self-assembly / Inverted HEMT structure / Memory function / Optical detector / Quantum point contact / Resonant tunnel structure / Capacitance-voltage spectroscopy / 自己形成量子箱 / FET / 量子化コンダクタンス / ヒステリシス特性 / InAs量子箱 / 逆HEMT / 電子状態 / クーロン相互作用 |
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| Research Abstract |
Semiconductors (e.g., InAs) deposited on a lattice-mismatched substrate (e.g., GaAs) yields 10 nm-scale Quantum dots (QDs) spontaneously. We have exploited them to make memory devices, in which the presence and absence of a single electron in InAs QDs correspond to "1" and "0". We have also investigated electronic properties of such QDs.
First, we prepared an inverted high electron mobility transistors (HEMT), in which InAs QDs are embedded between the surface gate electrode and a two dimensional electron channel at the GaAs/n-AlGaAs heterojunction. By applying gate voltage (Vg) over 0.9 V, the threshold voltage of the transistor shifted to the positive side by DELTAV, resulting from the supply of electrons from the channel to QDs. This proves the feasibility of new memory effect. Analytical studies of transport characteristics have shown that each QD stores one electron each, since the Coulombic repulsion originating from the first trapped electron prevents the trapping of second electron. If the second electron is stored in the QD, it easily tunnels out from the QD.In addition, we studied the "write" and "erase" (i.e., charge and discharge) processes controlled by the light illumination. Further, we prepared and studied a prototype device of a quantum point contact, in which the charge trapping in QDs near the point contact leads to a clear hysteresis characteristics in the quantized conductance.
We have studied electronic levels of InAs QDs in AlGaAs layer by photoluminescence and capacitance-voltage spectroscopy. The quantized state in QDs was found to increase by ^- 200 meV when the Al content in AlGaAs barrier layer is raised. We clarified also the shape of wavefunctions of electrons confined in QDs by magneto-tunneling spectroscopy.
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