Optical anisotropies of InP(001) surfaces

Metalorganic vapor phase epitaxy grown InP samples capped with a protective As/P double layer were used to study clean (001) surfaces in ultrahigh vacuum. By the thermal desorption of As and P cap layers, InP surfaces producing sharp 2×4 low energy electron diffraction (LEED) patterns were prepared. The reconstructed surface and intermediate preparation stages were studied by using reflectance anisotropy spectroscopy (RAS), LEED, and Auger electron spectroscopy. Features in the optical anisotropy related to the contribution of P–P and In–In surface bonds are identified and discussed. The results show that the surface-related optical anisotropy of the 2×4 In-rich reconstruction of InP(001) is due to In–In bonds along the [110] direction that produce a large optical anisotropy below 2 eV. Furthermore, at intermediate annealing stages, information by RAS on a P-rich 1×1 reconstructed phase was obtained. The contribution of P dimers to surface reflectance anisotropy above 3 eV is discussed.