Recent experiments suggest that Mg condensation at threading dislocations induce current leakage, leading to degradation of GaN-based power devices. To study this issue, we perform first-principles total-energy electronic-structure calculations for various Mg and dislocation complexes. We find that threading screw dislocations (TSDs) indeed attract Mg impurities, and that the electronic levels in the energy gap induced by the dislocations are elevated towards the conduction band as the Mg impurity approaches the dislocation line, indicating that the Mg-TSD complex is a donor. The formation of the Mg-TSD complex is unequivocally evidenced by our atom probe tomography in which Mg condensation and diffusion through [0001] screw dislocations is observed in p-n diodes. These findings provide a novel picture that the Mg being a p-type impurity in GaN diffuses toward the TSD and then locally forms an n-type region. The appearance of this region along the TSD results the reverse leakage current.

中文翻译：

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将 p 型 GaN 转化为 n 型的螺旋位错：p-n 二极管中 Mg 冷凝和漏电流的微观研究

最近的实验表明，在穿透位错处的 Mg 冷凝会导致电流泄漏，从而导致基于 GaN 的功率器件的退化。为了研究这个问题，我们对各种镁和位错配合物进行了第一性原理总能量电子结构计算。我们发现螺纹螺旋位错 (TSD) 确实吸引了 Mg 杂质，并且随着 Mg 杂质接近位错线，位错引起的能隙中的电子能级向导带升高，表明 Mg-TSD 复合物是捐赠者。我们的原子探针断层扫描明确证明了 Mg-TSD 复合物的形成，其中在 pn 二极管中观察到 Mg 冷凝和扩散通过 [0001] 螺旋位错。这些发现提供了一个新的图景，即 GaN 中的 p 型杂质 Mg 向 TSD 扩散，然后局部形成 n 型区域。该区域沿 TSD 的出现导致反向漏电流。