Fabrication and characterization of freestanding GaAs/AlGaAs core-shell nanowires and AlGaAs nanotubes by using selective-area metalorganic vapor phase epitaxy

We fabricated GaAs/AlGaAs core-shell nanowires by using selective-area metalorganic vapor phase epitaxy. First, GaAs nanowires were selectively grown on partially masked GaAs (111)B substrates; then AlGaAs was grown to form freestanding heterostructured nanowires. Investigation of nanowire diameter as a function of AlGaAs growth time suggested that the AlGaAs was grown on the sidewalls of the GaAs nanowires, forming GaAs/AlGaAs core-shell structures. Microphotoluminescence measurements of GaAs and GaAs/AlGaAs core-shell nanowires reveal an enhancement of photoluminescence intensity in GaAs/AlGaAs core-shell structures. Based on these core-shell nanowires, AlGaAs nanotubes were formed by using anisotropic dry etching and wet chemical preferential etching to confirm the formation of a core-shell structure and to explore a new class of materials. (c) 2005 American Institute of Physics.