Impact of sapphire nitridation on formation of Al-polar inversion domains in N-polar AlN epitaxial layers
Impact of sapphire nitridation on formation of Al-polar inversion domains in N-polar AlN epitaxial layers
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DOI：
10.1063/1.5008480
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发表时间：
2017-10-21
影响因子：
3.2
通讯作者：
Albrecht, M.
中科院分区：
文献类型：
--
作者：
Stolyarchuk, N.;Markurt, T.;Albrecht, M.
在这项工作中，我们研究了生长初始阶段的基本过程，该过程控制通过金属有机化学气相沉积在 c 面蓝宝石衬底上生长的 N 极性 AlN 薄膜的极性。更具体地说，我们通过原子力显微镜、高分辨率透射电子显微镜和高分辨率高角度环形暗场扫描透射电子显微镜研究了薄膜的形态和原子结构与氮化条件（即持续时间和温度）的关系。我们的实验结果表明，超过 1000 摄氏度的临界温度，除了无所不在的二维铝氮氧化物层之外，还会形成三维 Al 极性 AlN 岛。虽然氧氮化铝层在高温生长条件下不稳定并产生N极性薄膜，但Al极性岛是稳定的并在N极性AlN薄膜中诱导Al极性柱状反型域。适当的氮化条件（T = 850°C-950°C 下约 10 分钟）和生长参数（反应器压力、NH3 通量等）的调整可防止 Al 极性岛的形成，这对于获得无反型域的 N 极性薄膜至关重要。由 AIP 出版社出版。
In this work, we study the basic processes during the initial stages of growth which control polarity in N-polar AlN films grown on c-plane sapphire substrates by metalorganic chemical vapor deposition. More specifically, we study the morphology and atomic structure of the films as dependent on nitridation conditions, i.e., duration and temperature, by atomic force microscopy, high resolution transmission electron microscopy, and high resolution high-angle annular dark field scanning transmission electron microscopy. Our experimental results show that beyond a critical temperature of 1000 degrees C in addition to an omnipresent two-dimensional aluminum-oxynitride layer, three-dimensional Al-polar AlN islands form. While the aluminum-oxynitride layer is unstable under high temperature growth conditions and results in N-polar films, Al-polar islands are stable and induce Al-polar columnar inversion domains in the N-polar AlN films. Appropriate nitridation conditions (approximately 10 minutes at T = 850 degrees C-950 degrees C) and adjustment of growth parameters (reactor pressure, NH3 flux, etc.) prevent the formation of Al-polar islands, which is essential for achieving N-polar films free of inversion domains. Published by AIP Publishing.