Refractive indices of GaAs and AlAs at high temperature have been extracted by combining the high resolution X-ray diffraction and optical reflectivity measurement techniques. The comparison between the empirical formulas and experimental data on the indices of GaAs and AlAs has been made. A good agreement between them allows us to use empirical formulas to calculate the indices of GaAs and AlAs at high temperature over a wide wavelength range. The extracted data have been successfully employed in GaAs/AlAs DBR NIBE growth. (C) 2002 Elsevier Science B.V. All rights reserved.