Abstract
In this study, self-assembled inclined (1-10-3)-oriented GaN nanorods (NRs) were grown on nanoimprinted (10-10) m-sapphire substrates using catalyst-free metal-organic chemical vapor deposition. According to X-ray phi-scans, the inclined GaN NRs were tilted at an angle of ∼57.5° to the [10-10]sapp direction. Specifically, the GaN NRs grew in a single inclined direction to the [11-20]sapp. Uni-directionally inclined NRs were formed through the one-sided (10-11)-faceted growth of the interfacial a-GaN plane layer. It was confirmed that a thin layer of a-GaN was formed on r-facet nanogrooves of the m-sapphire substrate by nitridation. The interfacial a-GaN nucleation affected both the inclined angle and the growth direction of the inclined GaN NRs. Using X-ray diffraction and selective area electron diffraction, the epitaxial relationship between the inclined (1-10-3) GaN NRs and interfacial a-GaN layer on m-sapphire substrates was systematically investigated. Moreover, the inclined GaN NRs were observed to be mostly free of stacking fault-related defects using high-resolution transmission electron microscopy.
Highlights
According to X-ray phi-scans, the inclined GaN NRs were tilted at an angle of ∼57.5◦ to the [10]sapp direction
Many studies on GaN nanorods (NRs) have utilized vertical arrays along the [0001] c-axis direction, which is perpendicular to the substrate surface, because of the growth mechanism that governs the crystallographic relationship between GaN and substrates such as c-sapphire, Si (111), MgO (111), and γ-LiAlO2.2,4 In recent studies, the growth of inclined GaN NRs was investigated including metal catalyst initiated inclined GaN NRs on a thick a-GaN film formed on r-sapphire15,16 and strain induced inclined GaN NRs grown on Si(111)
We observed that an interfacial a-GaN nucleation layer was formed on r-facet nanogrooves of the m-sapphire substrate by nitridation
Summary
The bottom-up growth of GaN nanostructures has been achieved using various techniques, including catalyst-assisted vapor–liquid–solid growth, selective area growth, and catalyst-free self-assembled growth. The applications of GaN nanostructures focus primarily on light-emitting diodes, nanolasers, solar cells, and high-electron-mobility transistors. many studies on GaN nanorods (NRs) have utilized vertical arrays along the [0001] c-axis direction, which is perpendicular to the substrate surface, because of the growth mechanism that governs the crystallographic relationship between GaN and substrates such as c-sapphire, Si (111), MgO (111), and γ-LiAlO2.2,4 In recent studies, the growth of inclined GaN NRs was investigated including metal catalyst initiated inclined GaN NRs on a thick a-GaN film formed on r-sapphire and strain induced inclined GaN NRs grown on Si(111). self-organized inclined GaN NRs on an AlN nucleation formed on r-sapphire. The well-ordered inclined NRs array could be utilized to anti-reflection and light-trapping applications for the improvement of photovoltaic device efficiency. a few reports discuss the epitaxial growth of (1-10-3)-oriented GaN thin films on m-sapphire substrates, the growth of single inclined (1-10-3)-oriented GaN NRs on m-sapphire has not yet been reported or studied to date. The bottom-up growth of GaN nanostructures has been achieved using various techniques, including catalyst-assisted vapor–liquid–solid growth, selective area growth, and catalyst-free self-assembled growth.. Many studies on GaN nanorods (NRs) have utilized vertical arrays along the [0001] c-axis direction, which is perpendicular to the substrate surface, because of the growth mechanism that governs the crystallographic relationship between GaN and substrates such as c-sapphire, Si (111), MgO (111), and γ-LiAlO2.2,4 In recent studies, the growth of inclined GaN NRs was investigated including metal catalyst initiated inclined GaN NRs on a thick a-GaN film formed on r-sapphire and strain induced inclined GaN NRs grown on Si(111).. Self-organized inclined GaN NRs on an AlN nucleation formed on r-sapphire.. The well-ordered inclined NRs array could be utilized to anti-reflection and light-trapping applications for the improvement of photovoltaic device efficiency.. Previous attempts at growing (1-10-3)-oriented GaN thin films on m-sapphire have resulted in twinning, which occurred in two
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