1999 Fiscal Year Final Research Report Summary
Inter-dot interaction and photo-conductivity in quantum dot ensemble.
| Project/Area Number |
09831004
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
極微細構造工学
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| Research Institution | Konan University |
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Principal Investigator |
SUGIMURA Akira Konan University, Faculty of Science, Professor, 理学部, 教授 (30278791)
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| Co-Investigator(Kenkyū-buntansha) |
パブロ バッカロ ATR環境適応通信研究所, 研究員
FUJITA Kazuhisa ATR Adaptive Communication Research Labs., Senior Researcher, 主任研究員
UMEZU Ikuro Konan University, Faculty of Science, Asociate Professor, 理学部, 助教授 (30203582)
VACCARO Publo o ATR Adaptive Communication Research Labs., Researcher
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| Project Period (FY) |
1997 – 1999
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| Keywords | quantum dot / inter-dot interaction / coupling / photo-conductivity / photoluminescence / strong correlation / InGaAs / dot density |
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| Research Abstract |
InAs/GaAs quantum dot ensembles with different dot densities were prepared self-consistently using Stranski-Krastanov growth mode. Photoluminescence spectrum measured at 12K showed asymmetric shape indicating longer tail at lower energy side when the dot density was high enough. We measured the dot size distribution by using atomic force microscope. Although the size of each dot is not uniform, inhomogeneous broadening of the quantum levels due to this size distribution is found to be unable to explain the experimentally observed asymmetric spectrum. We theoretically showed that the quantum states of the three-dot system are split into asymmetric levels, one bonding state and two anti-bonding states, when the inter-dot coupling is introduced. Based on this idea, we numerically calculated the coupled electronic states of the randomly distributed many dot system by directly diagonalizing the coupled wave equations. Since the result showed asymmetric shape with longer tail at lower energy side, the experimentally observed asymmetric spectrum can be attributed to the inter-dot coupling. In addition, we investigated the photo-conductive properties of the samples. We observed nonlinear current-voltage characteristics with a peak in differential registance when the dot density is high enough. The peak position moves as the illuminated light intensity is changed. These experimental results suggest that the nonlinear electron transport is caused by the Coulomb repulsion of the two electrons sited on a quantum dot.
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