Towards the modeling of impurity-related defects in irradiated $n$-type germanium: a challenge to theory

Electrical measurements on heavily doped $n$-type germanium subjected to gamma-irradiation show that the features of impurity-related defect formation before $n\to p$ conversion of conductivity type are the same as those previously observed in lightly and moderately doped materials, thus extending the range of doping from $\approx$ 10$^{14}$ to $\approx$ 10$^{16}$ cm$^{-3}$. It is clear now that the presently adopted model of the dominant impurity-related defects as simple vacancy-impurity pairs in irradiated $n$-Ge, in analogy to such defects reliably identified in irradiated $n$-Si, appears to be inconsistent with the experimental information collected so far. As a consequence, the impurity diffusion simulations in heavily doped Ge based on this model need to be reconsidered. The requirements to be met while modeling impurity-related defects in irradiated $n$-Ge in accordance with the reliable experimental data are established.