Molecular Beam Epitaxial Growth of High Quality Ga-Catalyzed GaAs 1-xSbx (x>0.8) Nanowires on Si (111) with Photoluminescence Emission reaching 1.7 μm

The advancement of ternary GaAsSb mismatched alloy system toward the Sb-rich corner of the phase diagram in the nanowire (NW) configuration on silicon remains a challenge. A large lattice mismatch between the silicon substrate and GaAsSb with an Sb-rich composition, along with the low supersaturation and low solubility of Sb in the Ga droplet in the vapor-liquid-solid growth mechanism, causes significant issues during Ga-assisted molecular beam epitaxial growth of these NWs. In this work, we have carried out a systematic study of Sb-rich GaAs1-xSbx NWs grown on Si (111) using variations of the Ga, As, and Sb beam equivalent pressures (BEP) to minimize undesirable parasitic growth and achieve photoemission up to 1.7 µm. Ga-assisted molecular beam epitaxy is the enabling growth technology for the growth of these self-catalyzed GaAs1-xSbx (x>0.8) NWs. The use of a dual substrate temperature approach along with low As background pressure and a low Ga BEP were found to be the key growth components in achieving a well-faceted NW morphology with a low parasitic layer on the substrate. Energy-dispersive X-ray spectroscopy analysis confirms uniform compositional homogeneity along the NWs, while selected-area electron diffraction patterns in the transmission electron microscope revealed a zinc-blende crystal structure. A peak µ-photoluminescence emission of 1680 nm with a narrow FWHM was obtained at 4K. Raman spectra at room temperature exhibit only GaSb related LO and TO modes, which attest to the high quality of the NWs grown. This is a promising approach due to the broad scope of applicability to grow other mismatched alloy material systems in a NW configuration.