Nuclear Transmutation Doping from the Viewpoint of Radioactivity Formation
The doping of semiconductor materials by nuclear transmutation is associated with the formation of radioactivity. In the case of semiconducting silicon, Si-31 activity, surface contamination and P-32 activity stemming from the silicon are of significance. While the Si-31 activity will have decayed to zero after about 4 days, the surface contamination can be removed by an etching treatment applied to the silicon. The P-32 activity produced by further activation in the silicon can be ignored up to a concentration of 2 µCi/kg. At higher concentrations, observance of the 10 µCi exempt limit must be checked. The formation of P-32 activity can be controlled to a certain extent by a suitable choice of neutron flux density. It is shown that high neutron flux densities are preferable to low ones from economic considerations.
Despite theoretically good possibilities for the use of nuclear transmutation for doping other semiconductor material as well, such as germanium, arsenic or III-V compounds, this application appears to founder on the considerably greater radiation protection problems involved.
KeywordsNeutron Flux Radioactive Material Short Irradiation Time Etching Treatment Nuclear Transmutation
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