Au-catalysed MOVPE growth of GaAs/AlGaAs core-shell nanowires using TBA

Free-standing quasi 1-dimensional (1D) semiconductor nanostructures (nanowires) based on III-V compound semiconductors are considered ideal building blocks for the realization of photonic and electronic nanodevices. Metal-catalyst assisted MOVPE is a most promising bottom-up technology for the synthesis of III-V compound semiconductor nanowires and related 1D nanostructures. MOVPE growth of 1D nanostructures with a modulation of the material composition in either the axial or radial direction has been demonstrated for a number of III-V systems. The applications of GaAs nanowires to novel nanophotonic devices is hindered by the proclivity of GaAs to readily oxidise in air, leading to the formation of surface states that reduce carrier lifetimes and quench the material optical emission. The growth of a shell using a large band-gap material around GaAs nanowires reduces the effects of surface states and enhances the radiative efficiency of GaAs nanowires; besides, changing the band-gap of the shell material allows to control the carrier confinement within the GaAs core and may also improve the optical confinement of the photons by acting as an optical cavity. For these reasons, emphasis has been placed in the recent literature on the growth of GaAs-based core-shell nanowire structures. The Au-catalysed MOVPE growth and optical properties of GaAs/GaInP core-shell nanowires were already reported; however, alloy ordering of GaInP induces compositional and band gap variations in the shell, leading to potential fluctuations within the shell and likely different strain states in the core. A reduced carrier transport from shell to core was also observed under external light excitation, which again weakens carrier recombination efficiency within the core. The use of AlGaAs as shell material in substitution of GaInP avoids the problem of alloy ordering; further it allows to work with an almost strain-free material, simplifying the analysis of the nanowire electronic and optical properties. The luminescence of single GaAs/AlGaAs core-shell nanowires grown by Au-catalyst assisted MOVPE using AsH3 were reported in the leterature. In this work we report for the first time on Au-catalysed MOVPE growth of GaAs/AlGaAs core-shell nanowires on (111)B-GaAs using tertiarybutylarsine (TBAs) as As precursor. The nanowire morphology and size control, along with a preliminary study of the luminescence properties of as-grown core-shell structures will be presented.