Behaviours of the lattice-polarity inversion in AlN growth on c-Al2O3 (0001) substrates by ammonia-free high temperature metalorganic chemical vapor deposition
Behaviours of the lattice-polarity inversion in AlN growth on c-Al2O3 (0001) substrates by ammonia-free high temperature metalorganic chemical vapor deposition
复制标题
DOI：
10.1039/d2ce00652a
复制
发表时间：
2022-07-19
期刊：
影响因子：
3.1
通讯作者：
Kojima, Kazutoshi
中科院分区：
文献类型：
--
作者：
Shen, Xuqiang;Matsuhata, Hirofumi;Kojima, Kazutoshi
我们通过实验研究了通过无氨高温金属有机化学气相沉积 (AFHT-MOCVD) 生长的 c-Al2O3 (0001) 衬底上 AlN 外延层的微观结构和生长特征。除了AlN外延层中传统的穿透位错（TD）和AlN外延层/衬底界面处的空隙之外，在AlN生长中还证实了晶格极性反转现象，其中观察到横向分布的之字形反转域边界（IDB）。 AlN 外延层中不同点的晶格极性可通过高分辨率扫描透射电子显微镜 (HR-STEM) 直接测定。使用和不使用 KOH 蚀刻的扫描电子显微镜 (SEM) 进行的一系列 AlN 形态表征忠实地再现了不同 AlN 生长阶段的晶格极性反转过程。首先在蓝宝石衬底上生长具有N极性的AlN微晶。然后，晶格极性反转过程开始出现，并形成小的 Al 极性 AlN 梯形。随着生长的进行，由于 Al-极性 AlN 在垂直和横向方向上的生长速率较高，因此实现了横向分布的锯齿形 IDB 形成。最后，最初生长的 N 极性 AlN 完全被 Al 极性 AlN 覆盖，从而在顶部形成纯 Al 极性 AlN 外延层。我们在这项研究中的结果深入了解了高质量 AlN 生长的独特生长技术背后的机制，这对于光学和电子器件应用非常重要。
We experimentally investigate the microstructures and growth features of AlN epilayers on c-Al2O3 (0001) substrates grown by ammonia-free high-temperature metalorganic chemical vapor deposition (AFHT-MOCVD). Besides the conventional threading dislocations (TDs) in the AlN epilayer and the voids at the AlN epilayer/substrate interface, a lattice-polarity inversion phenomenon is confirmed in the AlN growth, where a laterally distributed zigzag inversion domain boundary (IDB) is observed. Lattice-polarity at different points in the AlN epilayer is directly determined with a high-resolution scanning transmission electron microscope (HR-STEM). A series of AlN morphological characterizations by scanning electron microscope (SEM) with and w/o KOH etching faithfully reproduces the lattice-polarity inversion process at the different AlN growth stages. An AlN micro-crystal with N-polarity is first grown on the sapphire substrate. Then the lattice-polarity inversion process begins to appear here and there with the formation of small Al-polar AlN trapezoids. With the growth in progress, an IDB formation with a laterally distributed zigzag shape is achieved due to the higher growth rates in Al-polar AlN both in the vertical and lateral directions. Finally, the initially grown N-polar AlN is completely covered by the Al-polar AlN, resulting in a pure Al-polar AlN epilayer on the top. Our results in this study give deep insights into the mechanism behind the unique growth technique for high-quality AlN growth, which is important for optical and electronic device applications.