Carrier recombination mechanism at defects in wide band gap two-dimensional materials from first principles
Carrier recombination mechanism at defects in wide band gap two-dimensional materials from first principles
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DOI：
10.1103/physrevb.100.081407
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发表时间：
2019-06
影响因子：
3.7
通讯作者：
Feng Wu;T. Smart;Junqing Xu;Y. Ping
中科院分区：
文献类型：
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作者：
Feng Wu;T. Smart;Junqing Xu;Y. Ping
二维（2D）材料中缺陷作为有希望的单个光子发射器（SPE）的识别和设计需要对基础载体重组机制有深入的了解。然而，在2D材料中缺陷处的载体重组的主要机制尚未得到充分理解，并且仍然存在一些出色的问题：在2D和3D系统之间，缺陷的重组过程有何不同？哪些因素决定了2D材料在室温下的缺陷？为了解决这些问题，我们开发了第一原理方法，以使用$ h $ bn作为典型示例，准确计算2D材料中缺陷的辐射和非放射性重组率。我们揭示了2D材料中缺陷的载体重组机制主要由缺陷 - 缺陷状态重组主导，而在大多数3D半导体中，缺陷 - 粉状状态重组相反。特别是，我们将非辐射重组机制分解为关键物理量：零 - 音波线和黄-rhys因子。最后，我们确定应变可以有效地调整缺陷中心的电子 - 音波耦合，并大大改变非辐射重组率。我们的理论发展是一个通用平台，用于了解2D材料中缺陷的载体重组，同时为SPES量子效率的工程提供了途径。
The identification and design of defects in two-dimensional (2D) materials as promising single photon emitters (SPEs) requires a deep understanding of the underlying carrier recombination mechanisms. Yet, the dominant mechanism of carrier recombination at defects in 2D materials has not been well understood, and some outstanding questions remain: How do recombination processes at defects differ between 2D and 3D systems? What factors determine defects in 2D materials as excellent SPEs at room temperature? In order to address these questions, we developed first-principles methods to accurately calculate the radiative and nonradiative recombination rates at defects in 2D materials, using $h$-BN as a prototypical example. We reveal the carrier recombination mechanism at defects in 2D materials being mostly dominated by defect-defect state recombination in contrast to defect-bulk state recombination in most 3D semiconductors. In particular, we disentangle the nonradiative recombination mechanism into key physical quantities: the zero-phonon line and Huang-Rhys factor. At the end, we identified that strain can effectively tune the electron-phonon coupling at defect centers and drastically change the nonradiative recombination rates. Our theoretical development serves as a general platform for understanding carrier recombination at defects in 2D materials, while providing pathways for engineering of quantum efficiency of SPEs.