Semiconductor surface and interface passivation by cyanide treatment

H. Kobayashi, M. Takahashi, O. Maida, A. Asano, T. Kubota, J. Ivančo, A. Nakajima, K. Akimoto

Research output: Contribution to journalConference articlepeer-review

14 Citations (Scopus)


Cyanide treatment which simply involves immersion of semiconductors in cyanide solutions can passivate interface states as well as surface states. When Si surfaces are treated with KCN solutions, a surface photovoltage greatly increases, and the surface recombination velocity is calculated to be decreased from ∼3000 cm/s to less than 200 cm/s. When the cyanide treatment is applied to ultrathin SiO 2 /single-crystalline Si structure, interface states are passivated. The passivation of the SiO 2 /Si interface states increases the energy conversion efficiency of 〈indium tin oxide (ITO)/SiO 2 /Si〉 MOS solar cells to 16.2% and decreases the leakage current density for 〈aluminum (Al)/SiO 2 /Si〉 MOS diodes to 1/3-1/8. When the cyanide treatment is performed on polycrystalline (poly-) Si, defect states in Si up to at least 0.5 μm depth from the surface are passivated, resulting in a vast increase in the energy conversion efficiency of 〈ITO/SiO 2 /poly-Si〉 solar cells and a decrease in the dark current density of 〈Al/SiO 2 /poly-Si〉 MOS diodes to 1/100-1/15 that without cyanide treatment. The defect passivation is attributed to the formation of Si-CN bonds from defect states. Si-CN bonds are found not to be ruptured by heat treatment at 800°C and AM 1.5 100 mW/cm 2 irradiation for more than 1000 h. Density functional calculations show that the thermal and irradiation stability results from strong Si-CN bonds with the bond energy of 4.5 eV. When the cyanide treatment is performed on oxide/GaAs(1 0 0) structure, the interface state density decreases to ∼50%. The cyanide treatment can also passivate defect states in Cu 2 O films, resulting in increases in the carrier density and the band-to-band photoluminescence intensity.

Original languageEnglish
Pages (from-to)279-292
Number of pages14
JournalApplied Surface Science
Issue number3
Publication statusPublished - 2004 Aug 15
EventProceedings of 3rd International Workshop on Semiconductor - Ustron, Poland
Duration: 2003 Sep 152003 Sep 17


  • Cu O
  • Cyanide treatment
  • Defect states
  • Interface states
  • MOS
  • Si
  • Silicon oxide
  • Solar cells

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Physics and Astronomy(all)
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films


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