The influence of unintentional Au impurities on the doping properties of Si nanowires

• The Au impurity prefer to occupy at the substitutional site in the centre of nanowire, forming the combination centre of carriers.
• Both n- and p-type doping efficiency is strongly inhibited by the unintentional Au impurity of the nanowire.
• Some effective methods should be adopted to reduce the concentration of Au impurities in the silicon.

Gold is the most commonly used catalyst for the growth of silicon nanowires. During the growth process, Au atoms are inevitably incorporated into the nanowire. In this study, the impact of Au impurities on the doping of silicon nanowires is systematically studied based on first-principles calculations. Our calculations demonstrate that the Au impurity prefers to occupy the substitutional site in the centre of nanowire, which results in midgap deep defect levels, forming a carrier combination centre. Further analysis indicates that both n- and p-type doping efficiencies are strongly inhibited by the unintentional Au impurity in the nanowire. Our results suggest that effective methods should be adopted to reduce the concentration of Au impurities in silicon nanowires, such as low-temperature growth and self-catalysed growth techniques.