Direct evidences of enhanced Ga interdiffusion in InAs vertically aligned free-standing nanowires.

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• III-V nanowires are crucial for advanced electronic and photonic devices.
• Understanding growth mechanisms is key to controlling nanowire properties.
• Molecular beam epitaxy (MBE) is a primary technique for III-V nanowire fabrication.

Purpose of the Study:

• To investigate the direct evidence of enhanced Gallium (Ga) interdiffusion in Indium Arsenide (InAs) nanowires.
• To elucidate the growth mechanism in InAs nanowires grown on Gallium Arsenide (GaAs) substrates.
• To develop a generalized nanowire growth model incorporating interdiffusion.

Main Methods:

• Direct experimental evidence using Scanning Electron Microscopy (SEM).
• Compositional analysis via Energy Dispersive X-ray Spectroscopy (EDX).
• Structural characterization using X-ray Diffraction (XRD) in coplanar and grazing incidence geometries.

Main Results:

• Nominally grown InAs nanowires were confirmed to be In0.86Ga0.14As alloy due to significant Ga interdiffusion.
• Nanowire formation is driven by diffusion-induced growth and substantial Ga interdiffusion from the substrate.
• Experimental findings deviate from typical vapor-liquid-solid (VLS) growth mechanisms.

Conclusions:

• Ga interdiffusion is a dominant factor in InAs nanowire growth on GaAs at moderate temperatures.
• A novel nanowire growth model accounting for Ga interdiffusion has been proposed.
• The presented growth model offers broad applicability to the MBE of III-V nanowires.