Direct observation of an electrically degenerate interface layer in a GaN/sapphire heterostructure.
Direct observation of an electrically degenerate interface layer in a GaN/sapphire heterostructure.
复制标题
DOI：
10.1039/c9nr01803d
复制
发表时间：
2019-04
期刊：
影响因子：
6.7
通讯作者：
Young-Min Kim;S. Lee;Jaekwang Lee;S. Oh
中科院分区：
文献类型：
--
作者：
Young-Min Kim;S. Lee;Jaekwang Lee;S. Oh
电简并层使生长在绝缘体衬底上的宽带隙半导体的光电性能劣化。这种不利影响可以通过使用缓冲层来隐藏各种晶格缺陷来被动地避免。然而，关于退化界面层的微观起源以及界面处的原子结构和化学环境的局部变化对所需膜的功能性的影响的长期存在的科学问题仍然没有答案。此外，这是开发可编程光电子器件的关键信息。在这项研究中，我们讨论了在原子尺度上的GaN/蓝宝石界面处的简并界面相的直接观察。通过结合高分辨透射电子显微镜和电子能量损失谱，我们检测到GaN/蓝宝石界面附近存在一个α-Ga 2 O3-x（约6.5 μ m）层，该层承受约4.5%的双轴压应变，并含有大量的氧空位。密度泛函理论计算表明，GaN/蓝宝石异质结构中缺陷α-Ga 2 O3-x薄层的存在显著降低了α-Ga 2 O3-x导带与GaN价带之间的能带偏移，从而对界面的电导增强产生显著影响.我们的研究结果提供了一个前所未有的完整的画面，在原子尺度上的简并界面现象，这将演变的宽带隙半导体异质结构系统的基本理解。
An electrically degenerate layer deteriorates the optoelectric performance of a wide band gap semiconductor grown on an insulator substrate. This detrimental effect can be passively avoided by using a buffer layer to harbor various lattice defects. However, the longstanding scientific questions regarding the microscopic origin of the degenerate interface layer and the effect of local changes in the atomic structure and chemical environment at an interface on the functionality of a desired film have remained unanswered. Moreover, this is key information for the development of ultrathin optoelectronic devices. In this study, we discuss the direct observation of a degenerate interface phase at the GaN/sapphire interface on an atomic scale. By combining high-resolution transmission electron microscopy and electron energy loss spectroscopy, we detect the presence of an ultrathin (∼6.5 Å) α-Ga2O3-x layer near the GaN/sapphire interface, which is subjected to ∼4.5% biaxial compressive strain and contains many oxygen vacancies. Density functional theory calculations show that the presence of a defective α-Ga2O3-x thin layer in the GaN and sapphire heterostructure remarkably reduces the band offset between the α-Ga2O3-x conduction band and the GaN valence band, thereby exerting a significant influence on the conductivity enhancement of the interface. Our results provide an unprecedented integrated picture of the degenerate interface phenomenon on an atomic scale, which would evolve the fundamental understanding about a wide band gap semiconductor heterostructure system.