Growth of ge crystals with extremely low dislocation density

Germanium (Ge) single crystals with an extremely low density of or almost free from grown-in dislocations were grown by the Czochralski technique using boron oxide (B₂O₃) and a silica crucible, where generation of GeO₂ particles, harmful for dislocationfree crystal growth, was effectively suppressed by the partially-or fully-coverage of the melt surface with B₂O₃ liquid. In a further evolution of the above growth technique, Ge crystals with various concentrations of interstitially dissolved oxygen atoms up to 5.5 × 10¹⁷ cm^-3, two orders higher than that in a conventionally grown Ge crystals, were grown by full coverage of the Ge melt surface with B₂O₃ liquid and addition of GeO₂ powder. The effective segregation coefficient of oxygen atoms was estimated to be 1.0-1.4. These Ge crystals are expected for application as high quality and thermo-mechanically stable materials, free from grow-in dislocations, for high-speed ULSI devices and GaAs solar cell substrates.