GaN晶体缺陷形成能和性质的第一原理计算预测

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理论计算技术的最新发展显著提高了基于密度泛函方法的计算预测能力，并在阐述GaN晶体本征缺陷方面取得了诸多进展。来自美国海军研究实验室的John L. Lyons和加州大学圣塔芭芭拉分校的Chris G. Van de Walle最近对此作了综述性评论。文章首先回顾了本征缺陷的计算方法，讨论了密度泛函带隙计算不准确对本征缺陷计算的影响，着重分析了修正后的半局域泛函（如广义梯度近似）进行的计算能在多大程度上得出准确带隙计算结果。文章接着介绍了GaN中的空穴、空隙和反占位缺陷的性质，以及它们与常见杂质的相互作用；结合第一原理计算结果与实验检测，讨论了本征缺陷及其复合物如何影响了氮化物器件的性能。文章认为，带隙修正的广义梯度近似泛函方法，可以得出更加准确的定性计算结果。然而，这些计算方法在某些重要情况下，特别在光学跃迁和局域载流子等体系，有可能误算重要的物理现象。该文近期发表于npj Computational Materials 3: 12 (2017)，英文标题与摘要如下，点击阅读原文可以自由下载文章PDF。

原文链接：

http://www.nature.com/articles/s41524-017-0014-2

Computationally predicted energies and properties of defects in GaN

John L. Lyons & Chris G. Van de Walle

Recent developments in theoretical techniques have significantly improved the predictive power of density-functional-based calculations. In this review, we discuss how such advancements have enabled improved understanding of native point defects in GaN. We review the methodologies for the calculation of point defects, and discuss how techniques for overcoming the band-gap problem of density functional theory affect native defect calculations. In particular, we examine to what extent calculations performed with semilocal functionals (such as the generalized gradient approximation), combined with correction schemes, can produce accurate results. The properties of vacancy, interstitial, and antisite defects in GaN are described, as well as their interaction with common impurities. We also connect the first-principles results to experimental observations, and discuss how native defects and their complexes impact the performance of nitride devices. Overall, we find that lower-cost functionals, such as the generalized gradient approximation, combined with band-edge correction schemes can produce results that are qualitatively correct. However, important physics may be missed in some important cases, particularly for optical transitions and when carrier localization occurs.

原文链接：

http://www.nature.com/articles/s41524-017-0014-2

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