Hybrid GaAsSb/GaAs heterostructure core-shell nanowire/ graphene and photodetector applications

We report the growth of vertical, high-quality GaAs_0.9Sb_0.1 nanowires (NWs) with improved density on oxygen (O₂) plasma-treated monolayer graphene/SiO₂/p-Si(111) by self-catalyzed molecular beam epitaxy. An O₂ plasma treatment of the graphene under mild conditions enabled modification of the surface functionalization and improved reactivity of the graphene surface to semiconductor adatoms. The rise in the disorder peak of the Raman mode, decreased surface conductivity, and creation of additional O₂ groups of plasma-treated graphene compared to that of pristine graphene confirmed functionalization of the graphene. To enhance the nucleation centers further for the vertical yield of NWs on the graphene surface, NWs were grown on a higher Sb composition GaAs_0.6Sb_0.4 stem for surface engineering the graphene surface via the surfactant effect of Sb and for better lattice matching. The NWs grown under optimal conditions exhibited a zinc blende crystal structure with no discernible structural defects. The NWs with a GaAs-passivated shell exhibited photoluminescence emission at 1.35 eV at 4 K and 1.28 eV at room temperature. The ensemble device fabricated with a top segment of GaAsSb NW-doped n-type using a GaTe captive source exhibited an optical responsivity of 110 A/W with a detectivity of 1.1 × 10¹⁴ Jones. These results of hybrid GaAsSb NW heterostructure/graphene devices show significant potential toward the fabrication of flexible near-infrared photodetector device applications. Further, the simple and efficient O₂ plasma treatment approach for surface engineering of graphene in conjunction with a high Sb compositional stem has shown to be a promising route that can be broadly applicable for the growth of other III-V ternary material systems for improving the vertical yield of NWs.