The parallel measurements were carried out on the n-type Si single crystal and the n-type Si single crystal doped with Er and Gd.All these crystals were irradiated with 14MeV neutrons. The measurementS of resistivity were made

and the infrared absorption spectra were recorded using a Nicolet 170SX FT-IR spectrophotometer.No new infrared absorption peaks of the rare-earth elements in Si were observed after irradiation.However

the measurements of resistivity indicated much smaller changes of resistivity ratio in Si（Er）or Si（Gd）than that in Si.