Localized vibrational modes of impurities in gallium phosphide are observed in infrared absorption. Tentative assignments for the observed absorption bands are as follows: &ohgr;L=453 cm−1is due to SiGa, 464 cm−1to NPor OP569 cm−1to11BGa, and 592 to10BGa. Other defect bands are observed at 443, 527, and 606 cm−1. However, present experimental results are not sufficient to permit identification of the impurities.