Improved Czochralski Growth of Germanium Single Crystals from a Melt Covered by Boron Oxide

In germanium (Ge) crystal growth, a serious problem in growing high quality Ge crystals is the formation of germanium-oxide-particles on the melt surface. In addition, B doping in Ge crystals is very difficult because of the segregation coefficient, which is greater than unity, and the instability of free B atoms in the Ge melt. We have found a unique solution, which is CZ-Ge crystal growth from a melt covered by boron oxide ($B_2O_3$). Ge crystals which are dislocation-free and/or oxygen-enriched can be grown by these improved CZ techniques. Current and planned research using such Ge crystals is introduced.