MBE growth of GaAs nanowires with a silicon rich particle on the top

The paper discusses the low-temperature growth of gallium arsenide (GaAs) nanowires on a silicon substrate initiated by a thin layer of lead. Typically, the growth of III-V semiconductor nanowires occurs via a vapor-liquid-solid mechanism with a droplet at the tip of the nanowire. The particles on the nanowire's tip act as physical catalysts, reducing the nucleation barrier. In case of GaAs nanowire, the droplet at the tip typically consists of Ga and a foreign catalyst. However, at a low growth temperature of 350 °C, a different situation was observed. The particle at the nanowire tip was found to contain a high concentration of arsenic. This suggests that the mechanism of nanowire formation is different from the classic vapor-liquid-solid process. The particle at the tip turned out to be a mixture of silicon and arsenic, rather than lead and gallium, indicating that the growth process followed a vapor-solid-solid mechanism.