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Published online by Cambridge University Press: 10 February 2011
We report on the preparation and properties of a-Si:H devices prepared at high temperatures on stainless steel substrates using low pressure ECR plasma deposition techniques. The devices were prepared using either Hydrogen or Helium as the plasma diluent gas. The use of He as the plasma gas led to films having significantly lower H concentration(4–5%) and a lower bandgap than comparable films made using hydrogen dilution. We find that we can make excellent devices, with good fill factors(over 70%) and voltages(over 0.86 V) using either H or He dilution. The use of He led to devices having smaller bandgap, by about 35–40 meV compared to devices made using H dilution. Detailed quantum efficiency measurements show that the hole collection in both types of devices is excellent, and that Urbach energies of tail states in each case is in the range of 43–45 meV.
