Coulon Pierre-Marie, Kusch Gunnar, Fletcher Philip, Chausse Pierre, Martin Robert W, Shields Philip A
Centre of Nanoscience & Nanotechnology & Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK.
Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, UK.
Materials (Basel). 2018 Jul 5;11(7):1140. doi: 10.3390/ma11071140.
As a route to the formation of regular arrays of AlN nanorods, in contrast to other III-V materials, the use of selective area growth via metal organic vapor phase epitaxy (MOVPE) has so far not been successful. Therefore, in this work we report the fabrication of a highly uniform and ordered AlN nanorod scaffold using an alternative hybrid top-down etching and bottom-up regrowth approach. The nanorods are created across a full 2-inch AlN template by combining Displacement Talbot Lithography and lift-off to create a Ni nanodot mask, followed by chlorine-based dry etching. Additional KOH-based wet etching is used to tune the morphology and the diameter of the nanorods. The resulting smooth and straight morphology of the nanorods after the two-step dry-wet etching process is used as a template to recover the AlN facets of the nanorods via MOVPE regrowth. The facet recovery is performed for various growth times to investigate the growth mechanism and the change in morphology of the AlN nanorods. Structural characterization highlights, first, an efficient dislocation filtering resulting from the ~130 nm diameter nanorods achieved after the two-step dry-wet etching process, and second, a dislocation bending induced by the AlN facet regrowth. A strong AlN near band edge emission is observed from the nanorods both before and after regrowth. The achievement of a highly uniform and organized faceted AlN nanorod scaffold having smooth and straight non-polar facets and improved structural and optical quality is a major stepping stone toward the fabrication of deep UV core-shell-based AlN or AlGaN templates.
与其他III-V族材料不同，作为形成AlN纳米棒规则阵列的一种途径，通过金属有机气相外延（MOVPE）进行选择性区域生长的方法至今尚未成功。因此，在本工作中，我们报道了使用一种替代性的自上而下蚀刻与自下而上再生长相结合的混合方法制造高度均匀且有序的AlN纳米棒支架。通过结合位移塔尔博特光刻和剥离工艺来制作Ni纳米点掩膜，随后进行氯基干法蚀刻，从而在整个2英寸的AlN模板上制造出纳米棒。额外使用基于KOH的湿法蚀刻来调整纳米棒的形态和直径。经过两步干湿蚀刻工艺后得到的纳米棒光滑且笔直的形态被用作模板，通过MOVPE再生长来恢复纳米棒的AlN晶面。针对不同的生长时间进行晶面恢复，以研究AlN纳米棒的生长机制和形态变化。结构表征突出显示，首先，两步干湿蚀刻工艺后获得的直径约130 nm的纳米棒实现了有效的位错过滤；其次，AlN晶面再生长引发了位错弯曲。在再生长前后的纳米棒中均观察到强烈的AlN近带边发射。获得具有光滑且笔直的非极性晶面、结构和光学质量得到改善的高度均匀且有序的多面AlN纳米棒支架，是朝着制造基于深紫外核壳结构的AlN或AlGaN模板迈出的重要一步。
