Homogeneous SiGe crystals grown by using the traveling liquidus-zone method

It is indispensable to estimate a diffusion coefficient in a solution zone in order to grow a homogeneous crystal by using the traveling liquidus-zone (TLZ) method. To estimate the diffusion coefficient of Ge in the SiGe solution zone, result of a two-dimensional numerical simulation is compared with an experimental result. From the comparison, the diffusion coefficient is estimated to be 9.5×10⁻⁵ cm²/s. By using this coefficient, a sample translation rate for obtaining a homogeneous SiGe crystal is determined. By translating samples with appropriate rates, homogeneous Si_0.5Ge_0.5 crystals are successfully grown. The typical Ge composition is 0.496±0.006 for more than 13 mm long. The experimental result shows the homogeneity of ±1.2% in the mole fraction. This deviation corresponds to the variation of less than ±0.03% in the lattice constant. Since this variation is negligibly small, the homogeneity is excellent. Thus it is found that the TLZ method is the universal growth technique, which is applicable to the crystal growth of not only the III–V compounds but also the IV–IV compounds.