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

Precursor Flow Rate Manipulation for the Controlled Fabrication of Twin-Free GaAs Nanowires on Silicon Substrates. J.H.Kang, Q.Gao, P.Parkinson, H.J.Joyce, H.H.Tan, Y.Kim, Y.Guo, H.Xu, J.Zou, C.Jagadish: Nanotechnology, 2012, 23[41], 415702