OPTICAL ANISOTROPY IN MISMATCHED INGAAS/INP HETEROSTRUCTURES

Epitaxial layers of In(x)Ga(1-x)As (0.35 < x < 0.85) were grown on (001) InP and characterized by double-crystal x-ray diffraction (DCXRD) and a new technique, variable azimuthal angle ellipsometry (VAAE), in which ellipsometric measurements are taken in various crystallographic directions on the wafer. VAAE reveals significant optical anisotropy in many samples. The degree of this anisotropy is shown to be a function of lattice mismatch and relaxation as measured by DCXRD. The VAAE results exhibit a consistent cosine-shape pattern with respect to the [110] and [110BAR] directions. We explain these observations by the presence of misfit dislocations which form in an asymmetric network. Ellipsometry emerges as a potentially powerful tool for the characterization of mismatched zinc-blende heterostructures.