Abstract
The concentration of carbon in semiconductor silicon and the behavior of carbon in the fusion and crystallization of silicon have been studied by the use of charged particle activation analysis. The solubility of carbon in solid silicon has been found to be 
or slightly less at the melting point, and the equilibrium distribution coefficient of carbon between solid and liquid silicon has been determined to be 
. Carbon content over the above solubility value has seldom been observed in silicon single crystals produced by modern industrial techniques. The content appears to depend more on the growth conditions of the single crystal than on the chemical purification method. The phase diagram of the C‐Si system in the extremely low carbon concentration range is given, together with a discussion of the kinematics of the carbon behavior in zone melting. Also, a new technique for studying the evaporation of carbon from the silicon melt is shown.