Optical characterization of double layers containing epitaxial ZnSe and ZnTe films

摘要

In this paper results of the optical characterization of double layers consisting of ZnTe and ZnSe thin films prepared by molecular beam epitaxy onto GaAs single crystal substrates are presented. For this optical characterization the optical method based on combining variable angle spectroscopic ellipsometry and near-normal spectroscopic reflectometry is used in the multi-sample modification applied within the spectral region 230-850 nm. Using this method the spectral dependences of the optical constants of the upper ZnTe thin films are determined within the spectral region mentioned above. Spectral dependences of the optical constants of the lower ZnSe thin films were determined within the spectral region 450-850 nm. Boundary roughness of these double layers and overlayers is respected. RMS values of the heights of the irregularities of the boundaries and thicknesses and optical constants of the overlayers are determined by means of the combined optical method as well. The uppermost boundaries of the double layers are, moreover, analysed using atomic force microscopy because of verification of the RMS values of these boundaries obtained by the optical method. The spectral dependences of the optical constants of the upper ZnTe films and lower ZnSe films determined in this paper are compared with those presented for ZnTe single layers and ZnSe single layers in the literature.