Long lifetimes of quantum-dot intersublevel transitions in the terahertz range.
Long lifetimes of quantum-dot intersublevel transitions in the terahertz range.
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DOI：
10.1038/nmat2511
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发表时间：
2009-10
期刊：
影响因子：
41.2
通讯作者：
E. Zibik;E. Zibik;Thomas Grange;Thomas Grange;B. A. Carpenter;N. E. Porter;R. Ferreira;G. Bastard;D. Stehr;S. Winnerl;Manfred Helm;Huiyun Liu;Huiyun Liu;M. S. Skolnick;L. R. Wilson
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文献类型：
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作者：
E. Zibik;E. Zibik;Thomas Grange;Thomas Grange;B. A. Carpenter;N. E. Porter;R. Ferreira;G. Bastard;D. Stehr;S. Winnerl;Manfred Helm;Huiyun Liu;Huiyun Liu;M. S. Skolnick;L. R. Wilson
载流子弛豫是决定半导体光电器件工作效率的关键问题。由于预测的长量子点激发态寿命，结合半导体量子点的器件具有克服基于量子阱的器件的许多限制的潜力。例如，基于量子阱的器件（量子级联激光器）中的太赫兹激光器操作所需的粒子数反转从根本上受到激光能级之间的有效散射的限制，这在量子阱的平面中形成连续谱。在这种情况下，半导体量子点是一个非常有吸引力的替代太赫兹器件，因为它们的固有的离散能级。在这里，我们提出了第一次测量，和理论描述，子级间载流子弛豫量子点的过渡能量在几个太赫兹范围内。长的点内弛豫时间（1.5 ns）被发现为14毫电子伏（3.4太赫兹）的水平分离，非常强烈地减少到30毫电子伏（7太赫兹），在非常好的协议与我们的微观理论的载流子弛豫过程。我们的研究为量子点太赫兹器件的开发铺平了道路，提供了最佳器件设计所需的载流子弛豫时间的基本知识。
Carrier relaxation is a key issue in determining the efficiency of semiconductor optoelectronic device operation. Devices incorporating semiconductor quantum dots have the potential to overcome many of the limitations of quantum-well-based devices because of the predicted long quantum-dot excited-state lifetimes. For example, the population inversion required for terahertz laser operation in quantum-well-based devices (quantum-cascade lasers,) is fundamentally limited by efficient scattering between the laser levels, which form a continuum in the plane of the quantum well. In this context, semiconductor quantum dots are a highly attractive alternative for terahertz devices, because of their intrinsic discrete energy levels. Here, we present the first measurements, and theoretical description, of the intersublevel carrier relaxation in quantum dots for transition energies in the few terahertz range. Long intradot relaxation times (1.5 ns) are found for level separations of 14 meV (3.4 THz), decreasing very strongly to ∼2 ps at 30 meV (7 THz), in very good agreement with our microscopic theory of the carrier relaxation process. Our studies pave the way for quantum-dot terahertz device development, providing the fundamental knowledge of carrier relaxation times required for optimum device design.