This review aims at providing a retrospective, as well as a description of the state-of-the-art and future prospects regarding the theoretical and experimental characterisation of negative-U defects in semiconductors. This is done by complementing the account with a description of the work that resulted in some of the most detailed, and yet more complex defect models in semiconductors. The essential physics underlying the negative-U behaviour is presented, including electronic correlation, electron-phonon coupling, disproportionation, defect transition levels and rates. Techniques for the analysis of the experimental data and modelling are also introduced, namely defect statistics, kinetics of carrier capture and emission, defect transformation, configuration coordinate diagrams and other tools. We finally include a showcase of several works that led to the identification of some of the most impacting negative-U defects in group-IV and compound semiconductors.

中文翻译：

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半导体中负 U 缺陷的表征

本综述旨在提供回顾，并描述半导体中负 U 缺陷的理论和实验表征的最新技术和未来前景。这是通过用对导致半导体中一些最详细但更复杂的缺陷模型的工作的描述来补充说明来完成的。介绍了负 U 行为的基本物理学，包括电子相关性、电子-声子耦合、歧化、缺陷跃迁水平和速率。还介绍了实验数据分析和建模的技术，即缺陷统计、载流子捕获和发射动力学、缺陷转换、配置坐标图和其他工具。