Irradiation-induced defects in Ge studied by transient spectroscopies

Abstract

Irradiation-induced impurity-point defect complexes have been investigated in n-type germanium crystals that were doped with either antimony or oxygen. Several majority-carrier traps and one minority-carrier trap are characterized by means of deep-level transient spectroscopy and minority-carrier transient spectroscopy. The antimony-vacancy complex $(E$ center) ${E}_{0.37}$ is found to anneal in a way that is fundamentally different from that in silicon, since it is retarded under reverse bias. Temperature-dependent carrier capture cross sections of the E center are an order of magnitude lower than those of the oxygen-vacancy complex $(A$ center) ${E}_{0.27}$ $({\ensuremath{\sigma}}_{n}\ensuremath{\sim}1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}$ and $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17} {\mathrm{cm}}^{2},$ respectively). A trap ${E}_{0.23}$ which is antimony related grows in at room temperature, seemingly by interstitial capture. A trap ${E}_{0.29}$ is assigned to the divacancy, since it is observed after proton irradiation but not after electron irradiation. A minority-carrier trap ${H}_{0.30},$ displaying a strong Poole-Frenkel effect, is Sb related and possibly related to the E center. In view of the experiments, we comment on a range of diverging results in the literature.