Browsing by Subject "Carrier dynamics"

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    Interfacial charge and energy transfer in van der Waals heterojunctions
    (John Wiley and Sons Inc, 2022-03) Hu, Zehua; Liu, Xue; Hernández-Martínez, Pedro Ludwig; Zhang, Shishu; Gu, Peng; Du, Wei; Xu, Weigao; Demir, Hilmi Volkan; Liu, Haiyun; Xiong, Qihua
    Van der Waals heterojunctions are fast-emerging quantum structures fabricated by the controlled stacking of two-dimensional (2D) materials. Owing to the atomically thin thickness, their carrier properties are not only determined by the host material itself, but also defined by the interlayer interactions, including dielectric environment, charge trapping centers, and stacking angles. The abundant constituents without the limitation of lattice constant matching enable fascinating electrical, optical, and magnetic properties in van der Waals heterojunctions toward next-generation devices in photonics, optoelectronics, and information sciences. This review focuses on the charge and energy transfer processes and their dynamics in transition metal dichalcogenides (TMDCs), a family of quantum materials with strong excitonic effects and unique valley properties, and other related 2D materials such as graphene and hexagonal-boron nitride. In the first part, we summarize the ultrafast charge transfer processes in van der Waals heterojunctions, including its experimental evidence and theoretical understanding, the interlayer excitons at the TMDC interfaces, and the hot carrier injection at the graphene/TMDCs interface. In the second part, the energy transfer, including both Förster and Dexter types, are reviewed from both experimental and theoretical perspectives. Finally, we highlight the typical charge and energy transfer applications in photodetectors and summarize the challenges and opportunities for future development in this field. © 2022 The Authors. InfoMat published by UESTC and John Wiley & Sons Australia, Ltd.
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    Polar vs. nonpolar InGaN/GaN quantum heterostructures: Opposite quantum confined electroabsorption and carrier dynamics behavior
    (IEEE, 2010) Sarı, Emre; Nizamoğlu, Sedat; Choi J.H.; Lee, S.J.; Baik, K.H.; Lee I.H.; Baek J.H.; Hwang, S.-M.; Demir, Hilmi Volkan
    We present a study of quantum confined electroabsorption and carrier dynamics in polar c-plane and nonpolar a-plane InGaN/GaN quantum heterostructures. We demonstrate red-shifting absorption edge, due to quantum confined Stark effect, in nonpolar InGaN/GaN quantum structures in response to increased electric field, while we show the opposite effect with blue-shifting absorption spectra in polar quantum structures. Moreover, confirmed by time-resolved photoluminescence measurements, we prove that carrier lifetimes increase with increasing electric field for nonpolar structures, whereas the opposite occurs for polar ones.