Undoped samples were irradiated with 2MeV electrons at 4K to fluences of between 1015 and 1019/cm2. Two main annealing stages were observed. The first was between 150 and 250K and was attributed to the annealing of Frenkel pairs. The second stage was between 350 and 450K and was observed after irradiation to fluences above 1017/cm2. It was attributed to the annealing of a complex which comprised a vacancy and an impurity atom. Shallow positron traps were detected after irradiation. This defect annealed out within a wide temperature range above 330K.

Defects in electron-irradiated Ge studied by positron lifetime spectroscopy A.Polity, F.Rudolf: Physical Review B, 1999, 59[15], 10025-30