BRIDGMAN AND CZOCHRALSKI GROWTH OF GE-SI ALLOY CRYSTALS

Ge1-xSix crystals were grown with the Bridgman and the Czochralski met hod over a wide concentration range. With the Bridgman process single crystals up to 40 at.% Si were possible. The reasons for polycrystalli ne growth were the permanent contact of the interface with the crucibl e wall in combination with curvature towards the crystal and inclusion s of high Si concentration. Analysis of striations in Czochralski grow n material showed that in this process the crystal does not continuous ly grow in one direction but consists of piece-wise grown crystals in which the composition permanently changes. According to that fact the main reason for polycrystalline growth in the Czochralski process is c ommon due to lattice mismatch between the seed and equilibrium concent ration transients in the crystal corresponding to the microscopic grow th rates.