Vertically oriented GaAs nanowires (NWs) are
grown on Si(111) substrates using metal–organic chemical vapor deposition. Controlled epitaxial
growth along the 〈111〉 direction is demonstrated following the deposition of
thin GaAs buffer layers and the elimination of structural defects, such as twin
defects and stacking faults, is found for high growth rates. By systematically
manipulating the AsH3 (group-V) and TMGa (group-III) precursor flow rates, it
is found that the TMGa flow rate has the most significant effect on the
nanowire quality. After capping the minimal tapering and twin-free GaAs NWs
with an AlGaAs shell, long exciton lifetimes (over 700 ps) are obtained for
high TMGa flow rate samples. It is observed that the Ga adatom concentration
significantly affects the growth of GaAs NWs, with a high concentration and
rapid growth leading to desirable characteristics for optoelectronic nanowire
device applications including improved morphology, crystal structure and
optical performance.
Source:IOPscience
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