Chemically doped radial junction characteristics in silicon nanowires

We evaluate the boron (B) and phosphorus (P) core-surface codoped radial p-n junction characteristics in silicon nanowires (SiNWs) using density functional theory calculations. We find that the formation of radial p-n junction is energetically favorable. The stability depends on the diameter of SiNWs and the dopant concentration. Generally, a higher concentration of B-P pair dopants results in a more stable nanowire. More importantly, we predict that the radial p-n junction can evolve into a Schottky-like junction in relatively highly doped SiNWs when the diameter increases, attributing to the change of the core p-doping characteristic, that is, the core p-junction becomes metallic, while the n-junction near the surface remains semiconducting. The interfacial contact between the junctions is found to be the key for such change. Our calculated results support an experimental observation in SiNW solar cells.