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We investigated by means of transmission electron microscopy (TEM) the final growth stage of GaAs/AlGaAs core-shell nanowires (NWs) self-assembled by Au-catalyst assisted metalorganic vapor phase epitaxy (MOVPE). TEM observations and energy dispersive x-ray spectroscopy revealed the presence of an AlGaAs tapered region of varying chemical composition nearby the NW extreme end (i.e. between the core-shell NW trunk and the Au nanoparticle catalyst). Our findings evidence that this region exhibits an unintentional AlyGa1−yAs/AlxGa1−xAs core-shell structure, a result of the combined axial (vapor-liquid-solid, VLS) self-assembly and conventional (vapor-solid, VS) overgrowth of the material. While the VS-grown AlxGa1−xAs alloy retains the Al composition (x=0.3) of the AlGaAs shell along the NW trunk, the central AlyGa1−yAs section is made of an Al-rich (y≈0.8–0.9) alloy segment formed during …
Publication date: 
1 Jul 2017

Mario Scuderi, Paola Prete, Nico Lovergine, Corrado Spinella, Giuseppe Nicotra

Biblio References: 
Volume: 65 Pages: 108-112
Materials Science in Semiconductor Processing