Annealing of electron-induced defects in $n$-type germanium

$n$-type, ${10}^{13}$ and 2 × ${10}^{15}$ ${\mathrm{cm}}^{-3\mathrm{}}$ doped germanium has been irradiated with ∼ 1-MeV electrons at liquid-helium and room temperatures. With the use of transient-capacitance spectroscopy, six electron traps and one hole trap were observed following irradiation at 4 K. Their energy levels have been determined to be at $E_c-40,120,120,260,390,\mathrm{and} 530$ meV, and at $E_v+250\mathrm{}$ meV. The isochronal annealing behavior of these traps, in addition to that of the four electron traps and of the four hole traps produced by room-temperature irradiation, has been studied in detail. Comparison of our results with previously published ones indicates that (i) the divacancy anneals around 150°C and the $E$ center around 100°C, (ii) the two levels at $E_c-120\mathrm{}$ meV are associated with the germanium interstitial or complexes involving a germanium interstitial, and (iii) there appears to be a vacancy level in the range 100-200 meV from the conduction band, which anneals at ∼ 100 K.