a semiconductor material is doped or alloyed under vacuum with an impurity by thermal decomposition and by sedimentation resulting from centrifugal force . the doping material is alternatively applied by evaporation before being subjected to centrifugal force and may be heated up to the melting point before completion of the centrifugal action . a centrifuge is provided having a thermal insulating layer between the outer wall of a rotor and a support for basic semiconductor material to be doped . the doping impurity material to be evaporated onto the basic solid state material is placed in the center of the centrifuge rotor .