The preparation method of the ultra-high-purity
germanium single crystal comprises the following steps: S1, putting corroded 12N high-purity
germanium polycrystals into a
crucible; s2, vacuumizing, introducing
nitrogen for purging, and maintaining the pressure; s3, high-purity
hydrogen is introduced, exhaust is maintained, and flowing type vacuum is maintained; s4, under flowing type vacuum, heating to 950-1000 DEG C, and melting the materials; s5, descending the
seed crystal to the liquid level of the melt in the
crucible, and preheating the
seed crystal; s6, starting
crucible rotation and
crystal rotation in opposite rotation directions, inserting the
seed crystal below the liquid level of the melt to form an aperture, and pulling to grow a
crystal bar; s7, the pulling furnace is cooled, and the
crystal bar is annealed; s8, descending the crystal bar into the crucible; s9, raising the temperature of the lifting furnace, completely melting the crystal bar again, and lifting the seed crystal away from the crucible; s10, repeating the steps S6 to S9 for specified times; s11, after the step S10 is repeated for the specified number of times, the step S6 and the step S7 are repeated, and the crystal bar is a product crystal bar; and S12, cooling, stopping
crystal rotation and crucible rotation, opening the lifting furnace, and
cutting off the product crystal bar.