Solute redistribution during the accelerated crucible rotation Bridgman growth of Hg_1-xMn_xTe

In order to study the Mn macrosegregation in accelerated crucible rotation Bridgman (ACRT-B) growth of Hg_1-xMn_xTe crystal, a mathematics model was established for the evaluation of the solute (Mn) distribution in the growth direction based on quantitative analyses and several assumptions. The results reveal that in Hg_1-xMn_xTe crystal grown by ACRT-B method, Mn content is much higher than the average value in the initial region and reduces gradually to a lower value in the final region because of solute redistribution. Only a section of the crystal fit the required composition with the acceptable error. The crystal section with acceptable composition can be also obtained in Hg_1-xMn_xTe ingot grown from the melt with no stoichiometric compositions. The length of the section increases with decreasing in x₀ value. Meanwhile, it moves toward the initial region. To grow Hg_1-xMn_xTe crystal with a certain composition, such as x=0.11, it is preferable to use the melt with a lower average Mn content, so that the crystal with the acceptable composition will be longer and located in the early region where the crystalline quality is better. A 5mm-diameter Hg_0.89Mn_0.11Te ingot was grown by ACRT-B method for the comparison. A single crystal is obtained in the early part of the ingot after the competitive growth of several grains in the initial region. However, the single crystal is blocked by several new grains, which were nucleated on the ampoule wall after about 1 cm. The composition distribution along the growth direction was analyzed by electron microprobe. The experimental data are essentially coincident with the calculation result in the main part of the ingot, but lower than it in the initial region and higher in the final region. These errors may tem from the approximation of homogeneous mixture in the liquid in the mathematical model, which is not true in the initial and final regions because the convection there is limited.