First-principles study of temperature-dependent optical properties of semiconductors from ultraviolet to infrared regions

We present a first-principles approach to take into account lattice vibration in calculating the ultraviolet-to-infrared optical response of semiconductors, without using any empirical parameters. Electron-phonon interactions are shown to be the main contributions to thermal corrections in the electronic band structure, whereas phonon-phonon interactions affect the infrared absorption spectra of polar semiconductors. Ranging from room temperature on up, the temperature-dependent dielectric functions of silicon for the ultraviolet-visible regions are calculated through combining the Allen-Heine-Cardona method with the Bethe-Salpeter equation. Temperature effects of the infrared optical spectra of gallium arsenide are also discussed; we use first-principles method to take into account anharmonic contributions. By introducing electron-phonon and phonon-phonon interactions, the calculated optical spectra show clear temperature dependence that is in good agreement with experimental data. Thermal expansion contributions are verified to be negligible compared to contribution from lattice vibration.