Temperature-dependent changes of the exciton absorption spectra in polar semiconductors

Abstract

Using the model of dielectric continuum for phonons and effective mass approximation for electrons, the influence of longitudinal optical phonons on the formation of exciton spectra in polar semiconductors is studied with the Green function technique. The calculations are made in frame of the Mott-Vannier model for the exciton in nS-states (n = 1, 2 and 3) for a number of semiconductors of A 2 B 6 and A 3 B 5 groups. The results confirm that interaction of the exciton with longitudinal optical (LO) phonons manifests itself in shifting of absorption band peaks towards low-energy region. The shift differs for different states and depends on temperature. Unlike the main exciton band (n = 1), the changes in the positions and widths of the next bands (n = 2 and 3) resulted from the interaction with the LO phonons are inessential for all the crystals under analysis.