1999 Fiscal Year Final Research Report Summary
Basic Research on Electronic Properties and Memory Effect of Silicon-Quantum-Dot Array and Its Application to Memory Device
| Project/Area Number |
10450125
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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 |
Electronic materials/Electric materials
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| Research Institution | Fukuoka University (1999)
Hiroshima University (1998) |
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Principal Investigator |
KOHNO Atsushi Fukuoka University, Faculty of Science, Lecture, 理学部, 講師 (30284160)
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| Co-Investigator(Kenkyū-buntansha) |
MIYAZAKI Seiichi Hiroshima University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (70190759)
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| Project Period (FY) |
1998 – 1999
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| Keywords | silicon quantum dot / self-assembling / memory effect / floating gate MOS memory / threshold voltage shift / room temperature operation / multilevel electron charging / Coulombic interaction |
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| Research Abstract |
Electrical and optical properties of silicon-quantum-dot array have been investigated to reveal the quantum confinement effect. The memory operation of metal-oxide-semiconductor (MOS) structures in which a Si quantum dot (QD) layer is embedded as a floating gate has been confirmed by analyzing the electrical characteristics. The research results on electron charging characteristics of Si QDs are summarized as follows.
1. The memory operation of Si QD floating gate MOSFETs has been demonstrated at room temperature. The hysteresis and the current bumps were observed in the drain current versus gate voltage (Id-Vg) characteristics of the MOSFETs, resulting in the electron charging of the Si QD floating gate. After discharging of QDs, stair-like changes in Id-t characteristics were observed, indicating that the charged state of QDs reaches the final stable state via the metastable state. Furthermore it was confirmed that the multilevel electron charging to Si QDs occurs by applying a positive gate pulse.
2. The electrical characteristics of Si QD floating gate MOS capacitors have quantitatively investigated to revel the electron charging and discharging characteristics of Si QDs. The bistability of the charging states for the quantum dots was confirmed around zero bias at room temperature. The number of retained electron per dot around zero gate bias was evaluated to be approximately one. It was also demonstrated that the measured flat-band voltage shift after writing operation to QDs is larger than the case of the uniform-plate floating gate. Furthermore it was suggested that Coulombic repulsive force among charged dots controls the electron discharge kinetics in a QD floating gate MOS structure.
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