2022 Fiscal Year Final Research Report
Theory of gap states at metal/semiconductor interfaces; annihilation mechanism and deformation in electric fields
Project/Area Number |
20K03815
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Research Category |
Grant-in-Aid for Scientific Research (C)
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Allocation Type | Multi-year Fund |
Section | 一般 |
Review Section |
Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
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Research Institution | Chiba University |
Principal Investigator |
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Project Period (FY) |
2020-04-01 – 2023-03-31
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Keywords | 金属/半導体界面 / ギャップ状態 / 第一原理計算 / ショットキーバリア / pn接合 / トンネル電流 / 電場環境下 / エネルギー共鳴 |
Outline of Final Research Achievements |
Mechanisms of annihilation and deformation of band-gap states have been studied around metal/semiconductor interfaces in electric fields based on the first-principles calculations. This project has clarified the following physical pictures; (1) as for simple metals such as Bi and Pb, since their atomic radii are large and their electron densities are low, the metal atoms do not form effective atomic bonds with the semiconductor layers, and thus the metal-induced gap states (MIGS) on the semiconductor side disappear, (2) since the bandgap of the semiconductor is effectively reduced under an electric field, the penetration depth of gap states is extended, and (3) when there are some defect levels in the semiconductor pn junction in an electric field, the energy resonance occurs between gap states and conduction/valence-band states, which enlarges the penetration depth of gap states and increases the tunnel current by several orders of magnitude.
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Free Research Field |
物性理論、表面界面物理、半導体物理、ナノサイエンス
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Academic Significance and Societal Importance of the Research Achievements |
金属/半導体界面においては、金属の電子が「ギャップ状態」として半導体のバンドギャップ内に侵入し、界面に多量の欠陥を発生させたり界面を介しての電子の移動障壁を大きく変化させる。しかし、このギャップ状態を消滅させる仕組みや、電場下でギャップ状態がどのように変質するかは明らかでなかった。本研究では、量子力学に基づく数値計算を行い、これら疑問点を解明した。特に、電場下においてギャップ状態が欠陥と結びつくと侵入長は大きく伸び、界面を介した電流を数桁増大させることを解明したが、この結果は学術的に大きな意義を持つだけでなく、将来のデバイス応用にも多くの知見を与えると期待される。
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