Resistivity Striations in Germanium Single Crystals

Resistivity striations resulting from periodic distribution of impurities have been observed in single crystals of germanium grown horizontally. The period of the striations ranges from 0.1 to 0.6 mm, depending upon growth conditions. It is proportional to the average growth rate and inversely proportional to the temperature gradient with in the crystal near the solid-liquid interface. This relation can be explained by assuming the supercooled state in the course of germanium crystal growth by the zone leveling technique. By the repeated supercooling and recovery from it, the crystalization proceeds periodically, resulting in the periodic change of the transient growth rate and the periodic segregation of impurities.