Ultrafast carrier dynamics in the 10fs-time range probed by time-domain terahertz emission spectroscopy

通过时域太赫兹发射光谱探测 10fs 时间范围内的超快载流子动力学

• 批准号: 12450140
• 负责人: HIRAKAWA Kazuhiko
• 金额: $ 8.58万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12450140/
• 关键词: Terahertz radiation; nonequilibrium transport; superlattice; Bloch oscillation; femtosecond spectroscopy; heterostructures; ultrafast transistors; coherence; テラヘルツ電磁波; フェムト秒レーザー; トンネル効果; テラヘルツ; フェムト秒レーザ; 速度オーバーシュート; 非定常伝導; ポンプ・プローブ法; 電気光学効

In ultrafast transistors with cutoff frequencies higher than 500 GHz, carriers are expected to travel in the channel in a very nonstationary manner. It is, therefore, essential to understand nonequilibrium transport of carriers subjected to high electric fields. The aim of this study was to make a quantitative comparison between the nonequilibrium transport data obtained by the time-domain THz spectroscopy and ensemble Monte Carlo (EMC) results and extract intrinsic carrier transport properties. It is found that the experimental results are strongly affected by finite sample thickness. Furthermore, the contribution of holes to the THz signal is found to become significant when the acceleration field is greater than 20 kV/cm. When the sample geometries and the photoexcitation conditions were property taken into account, the agreement between the THz data and the EMC calculations was good.Furthermore, we have also investigated the quantum mechanical transport in quantum heterostructures. … More Since the first proposal of Bloch oscillators by Esaki and Tsu, considerable effort from both experiments and theories has been made to search for Bloch oscillations and obtain terahertz (THz) emission. Even after three decades from the proposal, however, THz Bloch oscillators have not been realized yet It is, therefore, of prime importance to establish an understanding of the dynamical electron motion in the THz regime.In this work, we obtained a strong experimental support for the THz gain due to Bloch oscillating electrons in wide miniband GaAs/Al_<0.3>Ga_<0.7>/As SLs. For determining the high-frequency electron conductivity in SL minibands, we proposed a totally new approach, by noting that the time-domain THz spectroscopy inherently measures the step-response of the electron system to the applied bias electric field and that the Fourier spectra of the THz emission is closely related with the high-frequency electron conductivity. The Fourier spectra of the emitted THz electromagnetic wave were compared with the predicted conductivity spectra. The excellent agreement between theory and experiment strongly suggests that the THz gain due to Bloch oscillating electrons persists at least up to 1.7THz. Less

在截止频率高于500 GHz的超快晶体管中，预计载流子将以非常不稳定的方式在沟道中行进。因此，理解高电场下载流子的非平衡输运是非常必要的。本研究的目的是将时域太赫兹光谱获得的非平衡输运数据与系综蒙特卡罗（EMC）结果进行定量比较，并提取本征载流子输运性质。实验结果表明，有限的样品厚度对实验结果有很大的影响。当加速场大于20 kV/cm时，空穴对THz信号的贡献变得显著.当考虑样品的几何形状和光激发条件时，THz数据与EMC计算结果吻合较好。此外，我们还研究了量子异质结构中的量子力学输运。 ...更多信息 自江崎和大津首次提出布洛赫振荡器以来，人们从实验和理论两方面对布洛赫振荡进行了大量的研究，并获得了太赫兹辐射。然而，从提出到现在已经过去了30年，太赫兹布洛赫振荡器还没有被实现。因此，建立对太赫兹区电子动力学运动的理解是至关重要<0.3>的<0.7>。为了确定SL微带中的高频电子电导率，我们提出了一种全新的方法，注意到时域太赫兹光谱固有地测量电子系统对外加偏置电场的阶跃响应，并且太赫兹发射的傅立叶光谱与高频电子电导率密切相关。发射的太赫兹电磁波的傅立叶谱与预测的电导率谱进行了比较。理论和实验之间的良好一致性强烈表明，由于布洛赫振荡电子的太赫兹增益至少持续到1.7THz。少

项目成果

S.-W.Lee, K.Hirakawa, Y.Shimada: "Mid-Infrared Photodetector Using Self-Assembled InAs Quantum Dots Embedded In Modulation Doped GaAs Quantum Wells"MRS Symposia Proceedings. Vol.607 Infrared. 147-152 (2000)

S.-W.Lee、K.Hirakawa、Y.Shimada：“使用嵌入调制掺杂 GaAs 量子阱中的自组装 InAs 量子点的中红外光电探测器”MRS 研讨会论文集。

Ph. Lelong, S. -W. Lee, K. Hirakawa, and H. Sakaki: "Fano profile in intersubband transitions in InAs quantum dots"Physica E. 7. 174-178 (2000)

勒隆博士，S.-W。

O. Astafiev, S. Komiyama, T. Kutsuwa, V. Antonov, Y. Kawaguchi, and K. Hirakawa: "Single photon detector in the microwave range"Applied Physics Letters. 80, No.22. 4250-4252 (2002)

O. Astafiev、S. Komiyama、T. Kutsuwa、V. Antonov、Y. Kawaguchi 和 K. Hirakawa：“微波范围内的单光子探测器”应用物理快报。

Y.Shimada, T.Matsuo, K.Hirakawa: "Thz Emission due to Miniband Transport in GaAs/AlGaAs Superlattices"Japanese Journal of Applied Physics. vol.40, No.4B. 3009-3010 (2001)

Y.Shimada、T.Matsuo、K.Hirakawa：“GaAs/AlGaAs 超晶格中微带传输引起的太赫兹发射”日本应用物理学杂志。

Ph.Lelong,K.Hirakawa,K.Hirotani,S.-W.Lee,and H.Sakaki: "Fano profiles in bound-to-continuum intersubband transitions in negatively charged InAs quantum dots"Proceedings of the 25th International Conference on the Physics of Semiconductors. (印刷中).

Ph.Lelong、K.Hirakawa、K.Hirotani、S.-W.Lee 和 H.Sakaki：“带负电荷的 InAs 量子点中束缚到连续谱间子带跃迁的 Fano 剖面”第 25 届国际会议论文集半导体物理学（正在出版）。