We present detailed temperature dependent absorption spectra of GaP and GaAs at wavenumbers from 20 cm-1 to 350 cm-1 and temperatures between 10 K and 295 K. Comparison of the experimental data with the predictions of recent ab initio anharmonic lattice calculations for these materials shows good qualitative and quantitative agreement in the phonon overtone, sum-band, and difference-band absorption at frequencies below the fundamental transverse-optical (TO) modes. Prominent features in the absorption spectra, long identified with phonons having wavevectors at critical points in the zincblende hexagonal Brillouin zone, are found to be reproduced by the theory with position, oscillator strength, and temperature dependence that follow the observed data.
Citation: Physica C-Superconductivity and Its Applications
Pub Type: Journals
absorption, far-infrared, GaAs, GaP, multiphonon