Herein, we present experimental data on the record length uniformity within the ensembles of semiconductor nanowires. The length distributions of Ga-catalyzed GaAs nanowires obtained by cost-effective lithography-free technique on silicon substrates systematically feature a pronounced sub-Poissonian character. For example, nanowires with the mean length ⟨L⟩ of 2480 nm show a length distribution variance of only 367 nm2, which is more than twice smaller than the Poisson variance h⟨L⟩ of 808 nm2 for this mean length (with h = 0.326 nm as the height of GaAs monolayer). For 5125 nm mean length, the measured variance is 1200 nm2 against 1671 nm2 for Poisson distribution. A supporting model to explain the experimental findings is proposed. We speculate that the fluctuation-induced broadening of the length distribution is suppressed by nucleation antibunching, the effect which is commonly observed in individual vapor-liquid-solid nanowires but has never been seen for their ensembles. Without kinetic fluctuations, the two remaining effects contributing to the length distribution width are the nucleation randomness for nanowires emerging from the substrate and the shadowing effect on long enough nanowires. This explains an interesting time evolution of the variance that saturates after a short incubation stage but then starts increasing again due to shadowing, remaining, however, smaller than the Poisson value for a sufficiently long time.
Keywords: III−V nanowires; Self-catalyzed VLS growth; growth kinetics; molecular beam epitaxy; size distribution.