Dielectric response of strained and relaxed Si1-x-yGexCy alloys grown by molecular beam epitaxy on Si(001)

Using spectroscopic ellipsometry, we measured the pseudodielectric function of Si(1-x-y)G(x)C(y) alloys (0 less than or equal to x less than or equal to 0.48,0 less than or equal to y less than or equal to 0.05) grown on Si(001) using molecular beam epitaxy, For pseudomorphically strained layers, the energy shifts of the E(1), E(1) + Delta(1), E(0)', and E(2) transitions are determined by line shape analysis and are due to alloy composition effects, as well as hydrostatic and shear strain. We developed expressions for hydrostatic and shear shift from continuum elasticity theory, using deformation potentials for Si and Ge, for biaxial stress parallel to the (001) growth plane in a diamond or zinc blende-type crystal and applied this to the ternary Si-Ge-C alloy, The energies of E(1) and its spin-orbit split partner E(1) + Delta(1) agree fairly well with theory. The E(2) transitions in Si1-xGex at around 4.3 eV depend linearly on Ge concentration, In case of relaxed layers, the E(1) and E(1) + Delta(1) transitions are inhomogeneously broadened due to the influence of misfit and threading dislocations. For a silicon cap on top of a dislocated, relaxed SiGe layer, eve recovered the hulk Si dielectric function. (C) 1996 American Institute of Physics.