A comparative study of ion implantation and irradiation-induced defects in Ge crystals

After electron irradiation a sequence of point defects was generated, the detailed spectrum of which depended on the impurity content of the material. In oxygen lean Ge the DLTS spectrum was dominated by the E-center (vacancy-group-V-impurity atom pair). In oxygen-rich material the V-O pair was the center present in the greatest concentration. The annealing kinetics of the observed centers are reported. The situation in ion-implanted material is more complex. It is often not possible to measure the as-implanted material with DLTS due to carrier removal and, in some cases, type conversion. DLTS spectra of the high-dose-implanted samples after annealing show evidence of broader features characteristic of defect clusters. The evolution of these defects with annealing is discussed in the context of known defect reactions. Because diffusion of dopant species in Ge is thought to be vacancy mediated the focus of this analysis is on vacancy-related clusters.