Doping limits of grown in situ doped silicon nanowires using phosphine

Structural characterization and electrical measurements of silicon nanowires (SiNWs) synthesized by Au catalyzed vapor-liquid-solid growth using silane and axially doped in situ with phosphine are reported. We demonstrate that highly n-doped SiNWs can be grown without structural defects and high selectivity and find that addition of the dopant reduces the growth rate by less than 8% irrespective of the radius. This indicates that also the dopant incorporation is radius-independent. On the basis of electrical measurements on individual wires, contact resistivities as low as 1.2 × 10-7 Ω cm-2 were extracted. Resistivity measurements reveal a reproducible donor incorporation of up to 1.5 × 1020 cm -3 using a gas phase ratios of Si/P = 1.5 × 10-2. Higher dopant gas concentrations did not lead to an increase of the doping concentration beyond 1.5 × 1020 cm-3. © 2009 American Chemical Society.