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.