Vertical silicon nanowires grown on (111) Si substrate by the VLS (vapor-liquid-solid) process were doped by implantation of B⁺and P⁺ or As⁺ ions to achieve p-type as well as n-type doping of the nanowires. For annealing of the radiation defects a variety of different thermal treatments is used including the liquid-phase epitaxy of nanowires amorphized by As⁺ implantation.

The detailed electrical characterization of doped nanostructures is a serious problem so far. Analysis of individual nanowires can be performed, for instace, by I-V measurements and sequential surface removal. It will be demonstrated that the scanning spreading resistance microscopy (SSRM), a technique based on the conductive atomic force microscopy, is a powerfull tool to verify the dopant activation inside the nanowire.

Two-dimensional (2D) carrier profiles of the nanowires are derived from the measured spreading resistance values and calibrated with the known carrier concentration of the underlying substrate. [1]  A 3D SSRM profile of a nanowire is obtained for measuring the nanowire cross sections at different depths by repeated scanning of the same nanowire.

The achieved 3D carrier profiles reveal a core-shell structure of the carrier distribution across the diameter which consists of a lower doped core region and a higher doped shell region. The results indicate a dopant segregation close to the nanowire surface.

 

 

[1]      X. Ou, P. Das Kanungo, R. Kögler, P. Werner, U. Gösele, W. Skorupa, X. Wang, Nano Lett. 10 (2010) 171.

 

Reinhard Kögler*, Forschungszentrum Dresden-Rossendorf, Germany
Xin Ou, Forschungszentrum Dresden-Rossendorf, Germany
Pratyush Das Kanungo, MPI-Halle, Germany
Peter Werner, MPI-Halle, Germany
Michael Zier, Forschungszentrum Dresden-Rossendorf, Germany
Wolfgang Skorupa, Forschungszentrum Dresden-Rossendorf, Germany

*presenting author