Investigations of Cd1−xMnxTe crystals by means of ellipsometry and Auger electron spectroscopy

Cd1−xMnxTe crystals, obtained by the high-pressure Bridgman method for x=0, 0.27, 0.49, 0.67 and 0.8, were investigated. Crystal composition was determined by electron microprobe analysis. For an Mn content lower than 0.7, a single phase of pure zinc blend structure was found. In Cd0.2Mn0.8Te samples a two-phase structure was revealed. Auger electron spectroscopy (AES) was used to determine the composition of the crystal surfaces. AES depth profiles obtained by argon sputtering and AES analysis allowed to find the distribution of Cd, Mn and Te inside the sub-surface region. Spectroscopic ellipsometry was applied to determine the complex dielectric function ε of the samples. Ellipsometric measurements were performed at room temperature in the photon energy range 0.75–6.5 eV. The spectral dependence of ε was used to find the energy gaps Eg of the alloys with different Mn content. Ellipsometric data were correlated with the compositional results obtained from the electron microprobe and AES depth profile investigations. A linear increase of energy gaps with increasing x was observed for chemically homogeneous CdMnTe crystals.