Optical properties of Zn1−xMnxSe (x≤0.78) epilayers

The optical properties of Zn1−xMnxSe with x up to 0.78 grown by molecular beam epitaxy on GaAs (001) substrates are reported. The complex dielectric functions ϵ=ϵ1+iϵ2 are obtained by spectroscopic ellipsometry in the photon range from 3.5 to 5.5 eV at room temperature. The critical-point energies E1 and E1+Δ1 for x≤0.52 are determined by fitting the calculated second-derivative spectra of ϵ to the standard line shape. For the sample with x=0.78, the peak position in the ϵ2 spectrum is taken as an estimate for E1. While the fundamental band gap E0 increases with x, the E1 and E1+Δ1 energies decrease almost linearly with x. Comparing our results with those of the other experimental and theoretical studies, we consider the sp–d hybridization between the Mn 3d level and the sp band states to be an important factor affecting the band structures at the L point in the Brillouin zone over the whole range of Mn concentration.