Effect of Annealing in Various Gases on the Bulk Lifetime of Germanium

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Abstract
High resistivity germanium single crystals were annealed at 500°C in various gases. For an oxygen atmosphere with a trace of water vapor present, the bulk lifetime more than doubled, then decreased to below the initial value. For dry oxygen and for nitrogen, helium, hydrogen, or argon in the presence of water vapor, the lifetime first remained constant, and then decreased. Prolonged annealing in dry helium did not affect the lifetime. The data have been interpreted in terms of a ``leaching out'' of an impurity recombination center by a water catalyzed surface oxidation, and a simultaneous formation of an oxide of germanium which diffuses into the bulk and on precipitation acts as a recombination center.