Growth and Characterization of GaAs/AlGaAs Core-Shell Nanowires and AlGaAs Nanotubes
J. Noborisaka, J. Motohisa, S. Hara and T. Fukui
Hokkaido University, JP
nanowires, nanotubes, GaAs, MOVPE
We report on the fabrication of GaAs/AlGaAs core-shell nanowires (NWs) and AlGaAs nanotubes by SA-MOVPE and their photoluminescence characterization. The fabrication started from a preparation of patterned GaAs (111) B substrates partially covered with SiO2 mask. Arrays of mask hole with diameter ranging from 50-100 nm were defined by using electron beam lithography and wet chemical etching. GaAs and AlGaAs were successively grown epitaxially and selectively in the hole region by MOVPE. Free-standing GaAs/AlGaAs core-shell NWs with a height of 3_m and diameters of 200 to 300 nm were formed in the mask opening. Diameters of GaAs core were from 50 to 100nm. We observed free-standing AlGaAs nanotubes after two step etching process, namely, anisotropic dry etching of top AlGaAs and preferential wet etching of GaAs core. From these results we conclude that GaAs/AlGaAs core-shell NWs were successfully formed by SA-MOVPE. PL spectra of core-shell and bare GaAs NWs measured at 290K. The PL intensity of core-shell NWs is much stronger than that of bare GaAs NWs. This enhancement is due to the reduction of nonradiative recombination centers at the GaAs surface. Thus, it is concluded that high-quality GaAs/AlGaAs core-shell NWs were formed by SA-MOVPE.
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Nanotech 2005 Conference Program Abstract