Growth mechanism of GaN nanowires: preferred nucleation site and effect ofhydrogen

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The growth mechanism of epitaxial GaN nanowires grown using particle-mediated chemicalvapour deposition was investigated. By examining the diameter-dependent growth rate ofGaN nanowires, we show that the kinetic reaction-limited growth of GaN nanowiresoriginates from the combination of mono-nuclear and poly-nuclear growth rather than theGibbs–Thompson effect. We present a generalized nucleation-mediated growth model todescribe the diameter dependence of the nanowire growth rate and show that thenucleation of sources occurs at the vapour/liquid/solid three-phase boundary. Fromthe same model, we demonstrate that increased hydrogen concentration in thecarrier gas reduces the supersaturation, leading to a reduced GaN nanowire growthrate. Our approach can be applied to other nanowire materials systems, and itallows the determination of the preferred nucleation site during nanowire growth.