Dopant diffusion and activation in silicon nanowires fabricated by ex situ doping: A correlative study via atom-probe tomography and scanning tunneling spectroscopy

Zhiyuan Sun, Ori Hazut, Bo Chao Huang, Ya Ping Chiu, Chia Seng Chang, Roie Yerushalmi, Lincoln J. Lauhon, David N. Seidman

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Dopants play a critical role in modulating the electric properties of semiconducting materials, ranging from bulk to nanoscale semiconductors, nanowires, and quantum dots. The application of traditional doping methods developed for bulk materials involves additional considerations for nanoscale semiconductors because of the influence of surfaces and stochastic fluctuations, which may become significant at the nanometer-scale level. Monolayer doping is an ex situ doping method that permits the post growth doping of nanowires. Herein, using atom-probe tomography (APT) with subnanometer spatial resolution and atomic-ppm detection limit, we study the distributions of boron and phosphorus in ex situ doped silicon nanowires with accurate control. A highly phosphorus doped outer region and a uniformly boron doped interior are observed, which are not predicted by criteria based on bulk silicon. These phenomena are explained by fast interfacial diffusion of phosphorus and enhanced bulk diffusion of boron, respectively. The APT results are compared with scanning tunneling spectroscopy data, which yields information concerning the electrically active dopants. Overall, comparing the information obtained by the two methods permits us to evaluate the diffusivities of each different dopant type at the nanowire oxide, interface, and core regions. The combined data sets permit us to evaluate the electrical activation and compensation of the dopants in different regions of the nanowires and understand the details that lead to the sharp p-i-n junctions formed across the nanowire for the ex situ doping process.

Original languageEnglish
Pages (from-to)4490-4500
Number of pages11
JournalNano Letters
Volume16
Issue number7
DOIs
Publication statusPublished - 2016 Jul 13

Keywords

  • Silicon nanowire
  • atom-probe tomography
  • diffusion
  • ex situ doping
  • monolayer doping

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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