In situ observation of strain-induced optical anisotropy of ZnS_xSe_1-x/GaAs(110) during molecular-beam epitaxy

In-plane optical anisotropy induced by biaxial strain of pseudomorphic ZnS_xSe_1-x layers grown on GaAs(110) is observed around the band-gap energy by reflectance difference spectroscopy (RDS). The evolution of the strain-induced peaks with increasing film thickness is analyzed by the three-phase (substrate-overlayer-ambient) model. The magnitude and shape of the peaks are, respectively, correlated with the strain and the film thickness. Dielectric-function anisotropies of the pseudomorphic overlayers are obtained using a decomposition method of RD spectra and their imaginary part have a sharp peak at fundamental-gap energy.