Comparative study of catalyst-induced doping and metal incorporation in silicon nanowires

Abstract

Foreign atoms incorporated into the crystal structure of a semiconductor have profound effects on the electronic structure and charge transport in the material, particularly in nanoscale systems. Here, we demonstrate that catalyst-induced doping of silicon nanowires (SiNWs) can be used as an effective way for controlling dopant density and electrical conductivity in SiNWs, allowing the construction of p-n junctions. We investigate and compare metal incorporation and charge transport in SiNWs grown by six different metal catalysts (In, Sn, Bi, Ga, Pb, and Au) in plasma-enhanced chemical vapor deposition. The distribution of the catalytic metals within SiNWs was mapped by scanning transmission electron microscopy using high-angle annular dark-field imaging. The metals are either homogenously distributed or segregated in clusters on the surface or in the core of the nanowires, depending on the metal catalyst used. Each of the metal catalysts is found to play a unique role in the charge transport of SiNWs. Sn, Pb, and Au yield semiconducting SiNWs, Ga and In produce p-type self-doped SiNWs, and Bi catalyzes n-type self-doped SiNWs. A combination of these different nanowires may provide a bottom-up growth strategy for fabrication of different nanowire-based electronic components.