Preparation of Isotopically Enriched Polycrystalline Germanium via Monogermane Pyrolysis

High-purity isotopically enriched germanium has been prepared by a hydride method, and the main factors capable of reducing the germanium yield in the monogermane pyrolysis process have been identified. To raise the germanium yield, we have optimized pyrolysis conditions in a laboratory-scale flow apparatus. At a monogermane flow rate at the reactor inlet of 30 mL/min, the optimal monogermane decomposition temperature is 420–450°C. Such conditions ensure a decomposition rate of ~6 g/h and a high product yield and make it possible to obtain most of the germanium in polycrystalline form. Using isotopically enriched monogermane pyrolysis, we have obtained high-purity isotopically enriched germanium samples in the form of polycrystalline ingots with a yield above 95%. The ingots are n-type and range in resistivity from 25 to 50 Ω cm. The content of regulated impurities in the 72Ge-,73Ge-, 74Ge-, and 76Ge-enriched germanium ingots thus prepared does not exceed 0.01 to 1 ppm by weight.