Self-catalyzed growth of highly vertical GaAs core-shell nanowires on chemically-treated Si(111) surfaces

The reproducibility of self-catalyzed molecular beam epitaxy growth of GaAs nanowires (NWs) on oxide-covered Si(111) substrates depends on the consistent quality of the oxide layer. We have developed an effective chemical treatment method to create oxide surfaces that are conducive to the nucleation of vertical GaAs NWs on Si(111). Here we demonstrate a high yield, exceeding 90%, of vertical GaAs NWs with density in the order of 10
⁹
cm
^-2
. Using a combination of chemical oxide treatment and in situ growth conditions, we investigate how to achieve a good control of the morphology and density of GaAs and GaAs/III-As core-shell NWs grown on Si.