An investigation was made on the infrared absorption spectra of gallium phosphide single crystals doped with different impurities in the temperature range from 90 to 420°K. With decreasing temperature a transformation of the absorption spectrum due to interband transitions between conduction band valleys to the absorption spectrum due to impurity states was observed. On the basis of a theoretical analysis of the results obtained, a number of parameters of the GaP band structure and impurity states characteristics have been determined. Copyright © 1969 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim