Impurity Effects in Amorphous Semiconductors.
Abstract
This research is directed toward the discovery of the preparation conditions and material properties which will yield amorphous silicon-hydrogen alloys with the lowest density of defect-related states in the energy gap and/or the best photo-response. Among the effects investigated were the results of varying the substrate temperature and the partial pressures of hydrogen, argon and oxygen in the sputter-gas mixture. It was established that too high a substrate temperature (say, greater than 300 C) led to the incorporation of less hydrogen and to a larger gap state density. It was also established that films containing the same concentration of hydrogen, but prepared under different conditions of hydrogen partial pressure, showed different behavior as regards transport, photo transport, photoluminescence and absorption. These data were explained in terms of different state densities in the energy gap. Variation of the argon partial pressure was shown to give films of different conductivity and photoconductivity, and an argument was made that there was an optimum argon pressure: the critical argon pressure corresponded to that which was sufficient to reduce the mean free path of the sputtered silicon below the interelectrode separation. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1979
- Accession Number
- ADA067599
Entities
People
- W Paul Duprex
Organizations
- Harvard University