Doping of Self-Catalyzed Nanowires under the Influence of Droplets

Controlled and reproducible doping is essential for nanowires (NWs) to realize their functions. However, for the widely used self-catalyzed vapor-liquid-solid (VLS) growth mode, the doping mechanism is far from clear, as the participation of the nanoscale liquid phase makes the doping environment highly complex and significantly different from that of the thin film growth. Here, the doping mechanism of self-catalyzed NWs and the influence of self-catalytic droplets on the doping process are systematically studied using beryllium (Be) doped GaAs NWs. Be atoms are found for the first time to be incorporated into NWs predominantly through the Ga droplet that is observed to be beneficial for setting up thermodynamic equilibrium at the growth front. Be dopants are thus substitutional on Ga sites and redundant Be atoms are accumulated inside the Ga droplets when NWs are saturated, leading to the change of the Ga droplet properties and causing the growth of phase-pure zincblende NWs. This study is an essential step toward the design and fabrication of nanowire devices.