Impact of growth parameters on the morphology and microstructure of epitaxial GaAs nanowires grown by molecular beam epitaxy

• Defect-free wurtzite GaAs nanowires were obtained by MBE at low growth temperature.
• Some GaAs nanowires grown at low temperature show the morphology of two shoulders.
• High growth temperature favors the formation of nanowires with uniform diameter.
• Low V/III flux ratio causes many kinked GaAs nanowires.
• A phase separation of the catalyst is observed under very Ga-rich condition.

The effect of the growth temperature and V/III flux ratio on the morphology and microstructure of GaAs nanowires grown on GaAs (1 1 1)B substrates by Au-assisted molecular beam epitaxy with solid As4 source was investigated. It has been found that a low growth temperature of 400 °C can result in defect-free wurtzite structured nanowire with syringe-like morphology, while nanowires with more homogeneous diameter can be obtained at high temperatures (500 °C and 550 °C) with many stacking faults. It was also found that, at a low V/III flux ratio, GaAs nanowires had a shrinking neck section, while a high V/III flux ratio may result in disappearance of the shrinking necking section. For the Ga very rich condition, a phase separation of the catalysts can be observed, leaving a small Au–Ga droplet covered by the outer pure Ga droplet.