Strain dependence and deformation potential of the E1 and E1+Δ1 transitions of ZnTe grown on a GaAs (001) substrate

ZnTe epitaxial films grown on GaAs (001) substrates with varying film thicknesses were investigated by spectroscopic ellipsometry (SE). As the epilayer thickness decreases, the interband-transition structures near 3.6 and 4.2 eV due to E1 and E1+Δ1 edges, respectively, shift gradually to higher energies and their energy splitting Δ1 increases, indicating the increase in lattice-mismatch-induced strain with decreasing film thickness. The exact energies of the E1 and E1+Δ1 edges are obtained by a line-shape analysis of numerical second derivative spectra of the dielectric functions. From the strain dependences of the E1 and E1+Δ1 energies, the deformation potentials (DP), D11 and D33, at the L point of the Brillouin zone (BZ) are estimated.