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

Abstract

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 As 2 or As 4 molecules. In a wide range of growth temperatures, As 4 leads to growth rates twice faster than As 2. The shape of the NWs also depends on the arsenic species: with As 4, regular rods can be obtained, while pencil-like shape results from growth with As 2. 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 As 2 flux as compared to that under As 4 flux. It follows that As 2 flux is favourable to the formation of radial heterostructures, whereas As 4 flux is preferable to maintain pure axial growth.