Infrared ellipsometry of GaAs epilayers on Si(100)

Infrared spectroscopic ellipsometry is used to characterize the structure of molecular-beam-epitaxial grown GaAs layers on Si(100) before and after thermal cycle (TC) annealing. The dielectric function of the GaAs epilayer has been described by the sum of a factorized form and a classical Drude model in the spectral fitting procedure. The epilayer LO phonon frequency shifts toward lower frequency with increasing TC number while the opposite is seen for TO phonon. The shift of the LO mode indicates that the tensile stress increases with increasing TC number, while the shift of the TO mode is attributed mainly to the self-energy effect in GaAs:Si. Unequal thermal diffusion of SiAs- and SiGa+ is indicated