Effect of arsenic species on the kinetics of GaAs nanowires growth by molecular beam epitaxy

GaAs nanowires (NWs) are grown on GaAs (1 1 1) B substrates in a molecular beam epitaxy system, by Au-assisted vapor–liquid–solid growth. We compare the characteristics of NWs elaborated with As2 or As4 molecules. In a wide range of growth temperatures, As4 leads to growth rates twice faster than As2. The shape of the NWs also depends on the arsenic species: with As4, regular rods can be obtained, while pencil-like shape results from growth with As2. From the analysis of the incoming fluxes, which contributes to the NWs formation, we conclude that the diffusion length of Ga adatoms along the NW sidewalls is smaller under As2 flux as compared to that under As4 flux. It follows that As2 flux is favourable to the formation of radial heterostructures, whereas As4 flux is preferable to maintain pure axial growth.