A Study of Two-Dimensional Exciton Localization and Mobility Edge by Ultrafast Time-Resolved Spectroscopy

超快时间分辨光谱研究二维激子局域化和迁移边缘

• 批准号: 61540221
• 负责人: NAKAMURA Arao
• 金额: $ 1.15万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1986
• 资助国家: 日本
• 起止时间: 1986 至 1987
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-61540221/
• 关键词: short-period superlattices; picosecond time-resolved spectroscopy; exciton localization; two-dimensional excitons; carrier sink; Tunneling effect; 共鳴トンネル効果; トンネル効果を伴った再結合過程; 二次元励起子量子井戸のキャリヤ吸い込み

In this project, we have studied dynamics of exciton localization and correlation between localization and exciton transfer perpendicular to the superlatticelayers by means of the picosecond time-resolve spectroscopy. We have used GaAs/AlAs short-period superlattices with a an enlarged well (SQW) which is intentionally introduced.In order to perform time-resolved spectroscopy, we have installed a time-correlated single photon counting apparatus including a constant fraction discriminator and a fast timing amplifier. We could obtain 50ps time-resolution using this photon counting system and a mode-locke Nd:YAG laer.We have performed time-resolved photoluminescence experiments in GaAs/AlAs short-period superlattices(SPS). We have found, for the first time, the tunneing-assisted recombination of electrons and holes in different wells of SPS with thin barriers. It is also found that the direct correlation between the carrier flow from SPS and the carrier sink into SQW.Perpendicular transport is strongly dependent on the barrier thickness. Varying the barrier thickness from 0.9nm to 1.8nm, we have observed the increase in the tunneling transfer and then the formation of the miniband state for the thiner barrier.In coclusion, picosecond time-resolved spectroscopy of GaAs/AlAs short-period superlattices gives us some important informations on the quantum confinement of carriers and excitons, i.e. the localization(two-dimensionality) and the perpendicular transport(three-dimensionality) due to the formation of Bloch states by the coupling between wells.

在本项目中，我们利用皮秒时间分辨光谱研究了激子局域化动力学以及局域化与垂直于超晶格层的激子转移之间的关系。我们使用了GaAs/AlAs短周期超晶格，并有意引入了一个放大阱（SQW）。为了进行时间分辨光谱，我们安装了一个时间相关的单光子计数装置，包括一个恒定分数鉴别器和一个快速时序放大器。利用该光子计数系统和锁模Nd:YAG激光器可以获得50ps的时间分辨率。我们在GaAs/AlAs短周期超晶格（SPS）上进行了时间分辨光致发光实验。我们首次在具有薄势垒的SPS的不同阱中发现了调谐辅助的电子和空穴复合。研究还发现，SPS的载流子流与进入SQW的载流子汇之间存在直接的相关关系。垂直输运强烈依赖于势垒厚度。当势垒厚度从0.9nm增加到1.8nm时，我们观察到在较薄的势垒中隧穿转移增加，然后形成小带态。综上所述，GaAs/AlAs短周期超晶格的皮秒时间分辨光谱为我们提供了载流子和激子的量子约束的一些重要信息，即由于阱间耦合形成Bloch态而导致的局域化（二维）和垂直输运（三维）。

项目成果

A. Nakamura: "Dynamics of Photoexcited Carriers and Resonant Tunneling Effects in GaAs/AlAs Short-Period Superlattices" Physical Review. (1988)

A. Nakamura：“GaAs/AlAs 短周期超晶格中的光激发载流子动力学和共振隧道效应”物理评论。

A. Nakamura: "Dynamics of Photoexcited Carriers Sinking into an Enlarged Well in Short-Period Superlattices" Physical Review. B34. 9019-9022 (1986)

A. Nakamura：“短周期超晶格中光激发载流子沉入扩大井的动力学”物理评论。

A.Nakamura: Journal of Luminescence. 39. 719-720 (1988)

A.Nakamura：发光杂志。

A.Nakamura: Physical Review. (1988)

A.Nakamura：《物理评论》。

K. Fujiwara: "Polarization Anisotropy and Valence Subband Mixing in Short-Period Superlattices" IEEE Journal of Quantum Electronics. (1988)

K. Fujiwara：“短周期超晶格中的偏振各向异性和价子带混合”IEEE 量子电子杂志。