Ge distribution in Si0.9Ge0.1 alloy ingot grown from thin melt layer

We have studied experimentally and theoretically the possibility to obtain a uniform single crystal of SiGe alloy enriched at the Si side. The content of the second component in a crystal 15 mm in diameter and 40 mm in length grown by the modified floating zone technique from the charge of 79.8 at.% Si and 20 at.% Ge composition with 0.2% B admixture has been investigated using selected area X-ray analysis in different points and in line scanning mode along and across the crystal axis. The longitudinal changes in the germanium concentration proved to be well described by the analytical equation previously derived for conditions of Sb (Ga) doped Ge growth from a thin melt layer in the presence of a heater submerged into the melt. For a more accurate description of the experimental data we have made allowance for the change in the melt layer thickness between the growing crystal and the bottom of the submerged heater. The lateral distribution of the second component not exceeding 5% over the crystal diameter can be significantly improved by reducing the curvature of the phase interface during the growth.