Evaluation of Mn uniformity in CdMnTe crystal grown by the vertical Bridgman method

Cd _1-x Mn _x Te is a typical diluted magnetic semiconductor, as well as substrate for the epitaxial growth of Hg _1-x Cd _x Te. In this paper, the homogeneity of a Cd _1-x Mn _x Te (x = 0.2) single-crystal ingot grown by the vertical Bridgman method was studied. The crystal structure and quality of the as-grown ingot were evaluated. Near-infrared (NIR) transmission spectroscopy was adopted to develop a simple optical determination of the Mn concentration in the as-grown ingot. A correlation equation between cut-off wavelength λ _co from NIR transmission spectra and Mn concentration by inductively coupled plasma atomic emission spectrometry (ICP-AES) was established. Using this equation, we investigated the Mn concentration distribution in both the axial and radial directions of the ingot. It was found that the segregation coefficient of Mn in the axial direction of the ingot was 0.95, which is close to unity. The Mn concentration variation in the wafers from the middle part of the ingot was 0.001 mole fraction. All these results proved that homogeneous Cd _0.8Mn _0.2Te crystals can be grown from the vertical Bridgman method.