Role of nonlinear effects in nanowire growth and crystal phase
We study theoretically and experimentally nonlinear effects during the “vapor-liquid-solid” growth of semiconductor nanowires. Nonlinear growth equation considered contains kinetic coefficients from the surface and sidewall diffusion which can be of either signs. We predict four possible growth scenarios: (I) infinite growth; (II) decomposition; (III) averaging growth to a finite length; and (IV) continuing growth such that nanowires of small initial length decay and longer nanowires grow infinitely. We present the experimental evidence of nontrivial scenarios (II) and (IV) during the Au-assisted molecular-beam epitaxy of GaAs nanowires. Scenario (II) corresponds to the evaporation of GaAs nanowires during the annealing. Scenario (IV) is observed during two-step growth procedure where a low-temperature growth is followed by deposition at 630 °C. We show that the growth via scenario (IV) enables to control the crystal phase and to obtain the stacking-fault-free sections of zinc-blende GaAs NWs having only 15–20 nm in radius.