Effect of vacuum annealing on charge transport and trapping in a-Si 1-xCx:H/c-Si heterostructures

Y. V. Gomeniuk, S. O. Gordienko, A. N. Nazarov, A. V. Vasin, A. V. Rusavsky, V. G. Stepanov, V. S. Lysenko, D. Ballutaud, S. Ashok

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The processes of charge transport and trapping in amorphous Si 1 - xCx:H films deposited on crystalline p-type Si wafers and annealed in vacuum in the temperature range 300-650 °C have been evaluated. Current-voltage (I-V), capacitance-voltage (C-V) and admittance-temperature (G-T) characteristics were measured in the temperature range 100-350 K. The spectrum of thermal effusion of hydrogen was measured from room temperature up to 1000 °C. C-V characteristics indicate a slight increase of the dielectric constant k and a large hysteresis after annealing at 450 °C. The hysteresis is believed to be associated with mobile hydrogen effusion from the a-SiC:H film, and it is not seen after a 650 °C anneal. From I-V data the maximum rectification ratio is observed after annealing at 450 °C. Variable-range hopping (VRH) conduction at the Fermi level is found to dominate the forward current of the as-deposited structure. After annealing at 450 °C the forward current can be described by space-charge limited (SCL) mechanisms with trapping at shallow levels with energy of about 0.12 eV. After annealing at 650 °C the process of VRH conduction appears again, but the density of hopping sites is much higher than in the as-grown sample. From admittance spectra, the energy position of respective traps in a-SiC:H is at (EV + 0.45) eV for as-deposited material and it decreases slightly after vacuum annealing. On the basis of these results, an energy band diagram of the a-Si1 - xCx:H/p-Si structure annealed at 450 °C is proposed.

Original languageEnglish (US)
Pages (from-to)168-173
Number of pages6
JournalJournal of Non-Crystalline Solids
Issue number2
StatePublished - Jan 15 2012

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Materials Chemistry


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