Growth of Si_(0.5)Ge_(0.5) Single Crystals by the Traveling Liquidus-zone Method and their Structural Characterization

摘要

We have succeeded in growing compositionally homogeneous Si_(0.5)Ge_(0.5) crystals with a newly developed growth method named the travelling liquidus-zone (TLZ) method. In this method, a narrow liquidus-zone saturated by a solute is formed at relatively low temperature gradients, 5-15 °C/cm. Since the solubility depends on temperature, solute concentration gradient is established at the freezing interface. The concentration gradient causes diffusion of the solute towards a low concentration side. At the freezing interface, crystal growth proceeds due to the decrease in solute. As a result, solute concentration increases at the opposite side of the zone by transported solute and part of the remaining feed is dissolved. Thus, the zone travels under the temperature gradient spontaneously. Here, we report on 30 mm diameter homogeneous Si_(0.5)Ge_(0.5) crystal growth by the TLZ method. Compositional homogeneity of grown crystals was excellent but the length of single crystal was limited to about 2 mm and origins of polycrystallization were discussed.