Detached crystal growth from melt by the axial heat processing technique

Abstract

Detached/attached growth has been investigated in this study. Several antimony-doped germanium crystals have been grown by the axial heat processing technique with two different initial growth geometries, conical and round. Experiments have taken place in slow/fast flowing argon or in argon pressure. Growth velocities have ranged from 3 to 20mm/h, and initial melt concentrations of up to 1.5×1020 Sb atoms/cm3 have been used. Experiments have showed that crystals grown with the conical initial geometry in all growth environments have attached to their crucibles after growth. This behavior has been attributed to the lack of a gap to compensate for the differential thermal contraction of graphite crucible and germanium crystal that has grown with the same diameter as the crucible. In contrast, crystals grown from a round seed have displayed detachment whenever an oxide scale has formed on the liquid meniscus. The oxide scale has increased the surface tension between the liquid and the crucible, stabilized the liquid meniscus, and helped detachment.