Temperature coefficients of some characteristic reflectivity structure of ZnSe and ZnS

Wavelength modulated reflection spectrometry is used to obtain the temperature coefficients for the fundamental and higher transitions in ZnSe and ZnS up to 8 eV. The experimentally obtained values are compared to results of a Brooks-Yu type calculation. Agreement is satisfactory for higher transitions. The temperature shift of the spectral site of the fundamental exciton is explained in terms of the influence of phonon generated microfields.