3D Atomic‐Scale Insights into Anisotropic Core–Shell‐Structured InGaAs Nanowires Grown by Metal–Organic Chemical Vapor Deposition

Abstract

III-V ternary InGaAs nanowires have great potential for electronic and optoelectronic device applications; however, the 3D structure and chemistry at the atomic-scale inside the nanowires remain unclear, which hinders tailoring the nanowires for specific applications. Here, atom probe tomography is used in conjunction with a first-principles simulation to investigate the 3D structure and chemistry of InGaAs nanowires, and reveals i) the nanowires form a spontaneous core-shell structure with a Ga-enriched core and an In-enriched shell, due to different growth mechanisms in the axial and lateral directions; ii) the shape of the core evolves from hexagon into Reuleaux triangle and grows larger, which results from In outward and Ga inward interdiffusion occurring at the core-shell interface; and iii) the irregular hexagonal shell manifests an anisotropic growth rate on {112}A and {112}B facets. Accordingly, a model in terms of the core-shell shape and chemistry evolution is proposed, which provides fresh insights into the growth of these nanowires.

Compositional Varied Core–Shell InGaP Nanowires Grown by Metal–Organic Chemical Vapor Deposition

“…36 Furthermore, the mass transport has also been reported in core−shell InGaAs nanowires. 14,21 In our core−shell heterostructured nanowires, the compositional difference between nanowire core and shell is significant, the interdiffusion between them (Ga diffusion outward and In diffusion inward in this case) is expected for strain relaxation. As can be seen in Figure 3b−d, the core− shell interface becomes blurry toward to the nanowire bottoms where the compositional difference between nanowire cores and shells decreases, suggesting the continuous In/Ga interdiffusion occurred during the entire nanowire growth.…”

Quantitative Determination of How Growth Conditions Affect the 3D Composition of InGaAs Nanowires

“…(Gault et al, 2012) Our previous work has demonstrated the complexity of the ternary InGaAs nanowire growth: a spontaneous core-shell structure can be formed by the concomitant action of VLS and VS mechanism with a Ga rich core and an In rich shell. Moreover, the shell experienced anisotropic lateral growth with the faster rate on {112}A over that on {112}B, whereas the In composition is higher on {112}B facets than A (Qu et al, 2017). The composition of the core of nanowire is predominantly determined by the VLS growth mechanism.…”

“…Among various as-grown nanowire systems (Krylyuk et al, 2011; Chou et al, 2012; Huang et al, 2015; Han et al, 2016; Maliakkal et al, 2016; Nagashima et al, 2016; Yang et al, 2017), the InGaAs type is regarded as one of the most appealing systems for nano-device fabrication due to its versatile features such as excellent optical properties, high carrier mobility, absence of defects, and superb quantum confinement (Kim et al, 2006; 2017; Heurlin et al, 2015; Shen et al, 2015; Chen & Dayeh, 2017; Qu et al, 2017). Moreover, the optical spectrum of InGaAs type nanowires is theoretically predicted to cover a broad range, from visible light up to the infrared region by tuning the content of In in In x Ga 1− x As, which is of great significance for booming photonic applications.…”

“…However, many factors during nanowire growth increase the complexity of In compositional modulation, including growth temperature, seed and substrate type, solubility of species inside the metallic seed, flow rate, etc. It has been suggested that the ternary nanowires are inclined to form core-shell structure because of the discrepancy of thermal pyrolysis behavior among several organic precursors in terms of VLS and vapor liquid (VL) mechanisms, (Wibowo et al, 2011; Zhang et al, 2015; Qu et al, 2017) which makes research into the influence of composition on properties difficult. Compositional information from different nanowire regions has to be collected with an energy-dispersive X-ray spectroscopy (EDS) by preparing a transmission electron microscope (TEM) cross-sectional sample with focus ion beam (FIB) or ultramicrotome.…”

Understanding the Effect of Catalyst Size on the Epitaxial Growth of Hierarchical Structured InGaP Nanowires

“…1 In between these two distinct parts, there exists a "transition area", which has a ZB-WZ polytype structure (Figure 3e-f). Since spontaneous formation of core-shell structures have been reported in ternary III-V nanowires, 19,[40][41][42] it is necessary to check the radial elemental distribution in our nanowires. Figure 4 shows representative TEM images (viewed along the 〈110〉/〈112 ̅ 0〉 zone-axes) and EDS linescan profiles respectively taken from the two types of nanowires.…”