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We propose two unique Czochralski (CZ) techniques for growing germanium (Ge) crystals with an extremely low dislocation density and high interstitial oxygen concentration ([Oi]) using boron oxide (B 2 O 3 ) and a silica crucible. When a Ge melt is partially covered with liquid B 2 O 3 , but only on the outer region of the melt surface, germanium-oxide (GeO 2 )-related particles forming naturally in the melt are effectively dissolved by the liquid B 2 O 3 . The clean central portion of the melt produces dislocation-free undoped or Ga-doped Ge crystals. In addition, Ge crystals with [Oi] up to 6  10 17 cm -3 can be grown from a melt fully covered by liquid B 2 O 3 with added GeO 2 powder. The reaction and transportation of oxygen atoms during the growth process using B 2 O 3 was investigated, revealing that liquid B 2 O 3 acts like a catalyst without heavy contamination of the growing Ge crystal by B and Si atoms.

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