Origin of the Variation of Exciton Binding Energy in Semiconductors
Origin of the Variation of Exciton Binding Energy in Semiconductors
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DOI：
10.1103/physrevlett.110.016402
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发表时间：
2013-01-02
影响因子：
8.6
通讯作者：
Wu, Zhigang
中科院分区：
文献类型：
--
作者：
Dvorak, Marc;Wei, Su-Huai;Wu, Zhigang
激子效应对于光学性质是至关重要的，并且在技术上重要的半导体中激子结合能E-b从仅仅几meV变化到大约100 meV。然而，这种巨大的变化并没有得到很好的理解。本文采用基于密度泛函理论和多体微扰理论的第一性原理计算方法，利用绿色函数，研究了半导体中电子能带结构与激子结合能之间的关系。我们的结果清楚地表明，E-b增加的本地化价电子的增加，由于减少电子屏蔽。此外，在离子半导体如ZnO中，E-b增加，因为与简单的两能级耦合模型相反，它具有强烈地位于阴离子位点上的导带和价带边缘态，导致增强的电子-空穴相互作用。这些趋势是量子化的电子结构从密度泛函理论，因此，我们的方法可以应用于了解复杂的半导体材料中的激子效应。DOI：10.1103/PhysRevLett.110.016402
Excitonic effects are crucial to optical properties, and the exciton binding energy E-b in technologically important semiconductors varies from merely a few meV to about 100 meV. This large variation, however, is not well understood. We investigate the relationship between the electronic band structures and exciton binding energies in semiconductors, employing first-principles calculations based on the density functional theory and the many-body perturbation theory using Green's functions. Our results clearly show that E-b increases as the localization of valence electrons increases due to the reduced electronic screening. Furthermore, E-b increases in ionic semiconductors such as ZnO because, contrary to the simple two-level coupling model, it has both conduction and valence band edge states strongly localized on anion sites, leading to an enhanced electron-hole interaction. These trends are quantized by electronic structures obtained from the density functional theory; thus, our approach can be applied to understand the excitonic effects in complex semiconducting materials. DOI: 10.1103/PhysRevLett.110.016402