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arXiv 1806.01894cond-mat.mtrl-sci
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CdS中空穴-空穴相关导致的大而持久的光电导性

Large and Persistent Photoconductivity due to Hole-Hole Correlation in CdS

Han Yin, Austin Akey, R. Jaramillo

发表信息：
Phys. Rev. Materials 2, 084602 (2018)
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摘要：

半导体中大而持久的光电导（LPPC）是由于光生少数载流子在晶体缺陷处的俘获。理论已经表明，II-VI族半导体中的阴离子空位是由于负U行为导致LPPC的原因，由此两个少数载流子在光激发后通过晶格弛豫而被动力学捕获。通过对CdS的光电导进行详细的分析，我们为LPPC的负U模型提供了实验支持。我们还表明，LPPC与缺硫相关。我们利用这种认识，通过控制化学浴沉积过程中Cd^{2+}和S^{2-}离子的活性，将CdS薄膜的光电导性改变了9个数量级，并将LPPC特征衰减时间从秒改变到10^4秒。我们提出了一种筛选方法，以确定其他材料的长寿命，非平衡，光激发态的基础上的缺陷氧化还原反应后的原子重排的基态计算的结果，与极化子形成的概念连接。

英文摘要：

Large and persistent photoconductivity (LPPC) in semiconductors is due to the trapping of photo-generated minority carriers at crystal defects. Theory has suggested that anion vacancies in II-VI semiconductors are responsible for LPPC due to negative-U behavior, whereby two minority carriers become kinetically trapped by lattice relaxation following photo-excitation. By performing a detailed analysis of photoconductivity in CdS, we provide experimental support for this negative-U model of LPPC. We also show that LPPC is correlated with sulfur deficiency. We use this understanding to vary the photoconductivity of CdS films over nine orders of magnitude, and vary the LPPC characteristic decay time from seconds to 10^4 seconds, by controlling the activities of Cd^{2+} and S^{2-} ions during chemical bath deposition. We suggest a screening method to identify other materials with long-lived, non-equilibrium, photo-excited states based on the results of ground-state calculations of atomic rearrangements following defect redox reactions, with a conceptual connection to polaron formation.

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