Ultrafast Electrical Measurements of Isolated Silicon Nanowires and Nanocrystals

Matthew R. Bergren, Chito E. Kendrick, Nathan R. Neale, Joan M. Redwing, Reuben T. Collins, Thomas E. Furtak, Matthew C. Beard

Research output: Contribution to journalArticlepeer-review

21 Scopus Citations


We simultaneously determined the charge carrier mobility and picosecond to nanosecond carrier dynamics of isolated silicon nanowires (Si NWs) and nanocrystals (Si NCs) using time-resolved terahertz spectroscopy. We then compared these results to data measured on bulk c-Si as a function of excitation fluence. We find >1 ns carrier lifetimes in Si NWs that are dominated by surface recombination with surface recombination velocities (SRV) between ∼1100-1700 cm s-1 depending on process conditions. The Si NCs have markedly different decay dynamics. Initially, free-carriers are produced, but relax within ∼1.5 ps to form bound excitons. Subsequently, the excitons decay with lifetimes >7 ns, similar to free carriers produced in bulk Si. The isolated Si NWs exhibit bulk-like mobilities that decrease with increasing excitation density, while the hot-carrier mobilities in the Si NCs are lower than bulk mobilities and could only be measured within the initial 1.5 ps decay. We discuss the implications of our measurements on the utilization of Si NWs and NCs in macroscopic optoelectronic applications.

Original languageAmerican English
Pages (from-to)2050-2057
Number of pages8
JournalJournal of Physical Chemistry Letters
Issue number12
StatePublished - 19 Jun 2014

NREL Publication Number

  • NREL/JA-5900-61371


  • carrier dynamics
  • mobility
  • silicon nanocrystals
  • silicon nanowires
  • time-resolved terahertz spectroscopy


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