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The authors have calculated the electronic band structure of Nb-Ta (001) superlattices by means of the surface-Green-function-matching method. An empirical tight-binding Hamiltonian including d orbitals and up to second-neighbour interactions is employed. The influences of the interactions at the interfaces and the relative thicknesses of the constituent materials on the superlattice spectrum are studied and discussed.

We compare measured and calculated polarization-angle dependences of the intensity of the photoluminescence (PL) emission from a GaInP2 epitaxial layer grown by metalorganic vapor phase epitaxy and analyze the change in the strain within the crystal lattice of the layer. We measured the polarization-angle dependences of the PL emission propagating along the [110] direction at different temperatures. Symmetry considerations were used to calculate the polarization-angle dependences of the relative intensity of the PL emission. At room temperature, this dependence shows that the layers have almost no strain. At temperatures near 70 K, we observed changes in the polarized PL pattern induced by the thermal strain due to the differences between the thermal expansion coefficients of the layer and the substrate. At 10 K, this dependence changed drastically showing the presence of a different recombination process, which is consistent with the S-shaped temperature dependence of the PL emission peak maximum. Comparing the experimental and calculated PL polarization-angle dependences obtained at different temperatures, we estimate the amount of crystal lattice biaxial strain.