Direct determination of epitaxial interface structure in Gd2O3 passivation of GaAs
Direct determination of epitaxial interface structure in Gd2O3 passivation of GaAs
复制标题
GaAs Gd2O3 钝化中外延界面结构的直接测定
DOI：
10.1038/nmat735
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发表时间：
2002
期刊：
影响因子：
41.2
通讯作者：
R. Clarke
中科院分区：
文献类型：
--
作者：
Y. Yacoby;M. Sowwan;E. Stern;J. Cross;D. Brewe;R. Pindak;J. Pitney;E. Dufresne;R. Clarke
获得外延膜和界面的准确结构信息比半导体钝化层更重要，其中原子结构和键合的细节决定了界面电子态的性质。各种非破坏性方法已被用来研究薄膜和界面的结构1,2,3,4,5,6，但它们的解释取决于模型，有时会导致错误的结论。我们开发了一种用于直接测定外延结构的新 X 射线方法，即相干布拉格棒分析 (COBRA)。我们的技术的实用性通过以原子精度绘制在 (100) GaAs 衬底上外延生长的 Gd2O3 薄膜的界面区域的结构来证明。我们的研究结果揭示了现有结构方法之前未提出的有趣行为，特别是面内 Gd 原子位置与衬底的 Ga/As 原子位置的锁定。此外，我们发现放弃了 Gd2O3 原子层的体堆叠，取而代之的是与衬底堆叠顺序直接相关的新结构。这些结果对于 Gd2O3 作为 GaAs 的有效钝化层具有重要意义（参考文献 7）。我们的工作表明，COBRA 技术利用插入装置同步加速器 X 射线源的优点，广泛适用于外延膜和界面。
Obtaining accurate structural information on epitaxial films and interfaces is nowhere more critical than in semiconductor passivation layers, where details of the atomic structure and bonding determine the nature of the interface electronic states. Various non-destructive methods have been used to investigate the structure of films and interfaces1,2,3,4,5,6, but their interpretation is model-dependent, leading occasionally to wrong conclusions. We have developed a new X-ray method for the direct determination of epitaxial structures, coherent Bragg rod analysis (COBRA). The usefulness of our technique is demonstrated by mapping, with atomic precision, the structure of the interfacial region of a Gd2O3 film grown epitaxially on a (100) GaAs substrate. Our findings reveal interesting behaviour not previously suggested by existing structural methods, in particular a lock-in of the in-plane Gd atomic positions to those of the Ga/As atoms of the substrate. Moreover, we find that the bulk stacking of the Gd2O3 atomic layers is abandoned in favour of a new structure that is directly correlated with the stacking sequence of the substrate. These results have important implications for Gd2O3 as an effective passivation layer for GaAs (ref. 7). Our work shows that the COBRA technique, taking advantage of the brilliance of insertion device synchrotron X-ray sources, is widely applicable to epitaxial films and interfaces.