2020 Fiscal Year Final Research Report

Elucidation of photoluminescence mechanism due to polariton-like spatial propagation in exciton inelastic scattering processes

Research Project

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Project/Area Number	18K03494
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
Research Institution	Osaka City University
Principal Investigator	NAKAYAMA Masaaki 大阪市立大学, 大学院工学研究科, 教授 (30172480)
Project Period (FY)	2018-04-01 – 2021-03-31
Keywords	励起子非弾性散乱 / 励起子－励起子散乱 / 励起子－電子散乱 / 光子性ポラリトン空間伝播 / 空間分解発光分光法 / 時間分解発光分光法 / 多重量子井戸・超格子 / 半導体薄膜
Outline of Final Research Achievements	We have investigated the spatially-resolved and time-resolved photoluminescence (PL) properties of exciton inelastic scattering processes such as exciton-exciton scattering and exciton-electron scattering in various semiconductors such as GaAs/AlAs multiple quantum wells, superlattices, GaN-related thin films, ZnO thin films, and CuI thin films. We found that a PL spot appears at a sample edge and that the PL from exciton inelastic scattering is selectively observed at the sample edge. This fact indicates that the photon-like polariton, which is the final state of the inelastic scattering process, spatially propagates from an excitation spot to the sample edge, which leads to conversion to a photon by breakdown of translational symmetry at the sample edge. Furthermore, we revealed that the PL decay rate of exciton-exciton scattering can be scaled by the group velocity of the photon-like polariton.
Free Research Field	半導体光物性
Academic Significance and Societal Importance of the Research Achievements	励起子非弾性散乱過程（励起子－励起子散乱と励起子－電子散乱）は、レーザー発振の起源となる誘導放出（光増幅）が生じる光学過程として1970年代中頃から現在に至るまで盛んに研究が行われてきた。しかし、励起子非弾性散乱過程の本質的な特性である発光過程のポラリトン性（励起子と光子の混成状態の特性）については、明らかではなかった。本研究成果の学術的意義は、発光過程の終状態である光子性ポラリトンの空間伝播が、励起子非弾性散乱による発光過程を支配していることを空間分解発光特性と時間分解発光特性の観点から明らかにしたことであり、発光過程を制御するための重要な知見を提示するものである。