Li Tianbao, Liu Chenyang, Zhang Zhe, Yu Bin, Dong Hailiang, Jia Wei, Jia Zhigang, Yu Chunyan, Gan Lin, Xu Bingshe, Jiang Haiwei
Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Ministry of Education, Taiyuan, 030024, China.
College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan, 030024, China.
Nanoscale Res Lett. 2018 Apr 27;13(1):130. doi: 10.1186/s11671-018-2546-x.
The growth mechanism of GaN epitaxial layers on mechanically exfoliated graphite is explained in detail based on classic nucleation theory. The number of defects on the graphite surface can be increased via O-plasma treatment, leading to increased nucleation density on the graphite surface. The addition of elemental Al can effectively improve the nucleation rate, which can promote the formation of dense nucleation layers and the lateral growth of GaN epitaxial layers. The surface morphologies of the nucleation layers, annealed layers and epitaxial layers were characterized by field-emission scanning electron microscopy, where the evolution of the surface morphology coincided with a 3D-to-2D growth mechanism. High-resolution transmission electron microscopy was used to characterize the microstructure of GaN. Fast Fourier transform diffraction patterns showed that cubic phase (zinc-blend structure) GaN grains were obtained using conventional GaN nucleation layers, while the hexagonal phase (wurtzite structure) GaN films were formed using AlGaN nucleation layers. Our work opens new avenues for using highly oriented pyrolytic graphite as a substrate to fabricate transferable optoelectronic devices.
基于经典成核理论详细解释了机械剥离石墨上GaN外延层的生长机制。通过O等离子体处理可以增加石墨表面的缺陷数量，从而提高石墨表面的成核密度。添加元素Al可以有效提高成核速率，促进致密成核层的形成以及GaN外延层的横向生长。用场发射扫描电子显微镜对成核层、退火层和外延层的表面形貌进行了表征，表面形貌的演变与三维到二维的生长机制相吻合。用高分辨率透射电子显微镜对GaN的微观结构进行了表征。快速傅里叶变换衍射图谱表明，使用传统的GaN成核层可获得立方相（闪锌矿结构）GaN晶粒，而使用AlGaN成核层可形成六方相（纤锌矿结构）GaN薄膜。我们的工作为使用高度取向的热解石墨作为衬底制造可转移光电器件开辟了新途径。
