Substitution of Impurity Atoms by Self-Interstitials in Thermal Neutron Irradiated Germanium
Abstract
We have used the recoil energy associated with capture gamma-ray emission subsequent to thermal-neutron absorption to introduce a predetermined concentration of activated 71Ge self-interstitial atoms into Ge. Some of the 71Ge may have recombined with vacant lattice sites, but we found that most of the 71Ge was mobile and migrated to replace a substitutional n- or p-type dopant impurity atom, making it interstitial, if a sufficient concentration of such dopant atoms was available. This model of a replacement is consistent with that proposed by previous investigators for electron-irradiated Si and Ge. Irradiation in another reactor locale with a much lower thermal-to-fast neutron ratio was found to introduce complex defect structures from fast neutron collisions with Ge atoms that trapped a significant fraction of the 71Ge in an interstitial position.