Growth of Si1-xGex bulk crystals with highly homogeneous composition for thermoelectric applications

Compositionally homogeneous Si0.52Ge0.48 bulk crystals were grown under a mild temperature gradient using a Si(seed)/Ge/Si(feed) sandwich structure for thermoelectric (TE) applications. The furnace temperature was kept constant for 300 h for the growth of homogeneous Si1-xGex bulk crystal with various temperature gradients. The temperature gradient of 0.4 degrees C/mm resulted in homogeneous Si0.52Ge0.48 bulk crystals of 22 mm length with a Ge compositional fluctuation of about 0.0023/mm. The compositions of the grown crystals were determined by means of Electron Probe Micro-Analysis (EPMA). Electrical resistivity and Seebeck coefficient of the prepared samples were measured using in-house built measurement system. It was found that the compositional fluctuation of Ge was decreased as the temperature gradient of the furnace decreased. The prepared Si0.52Ge0.48 sample showed high Seebeck coefficient compared to that of pure Si and Ge crystals.