Defect-Impurity Interactions in Irradiated Germanium

The purpose of these experiments was to formulate a better model for the structures of lattice defects and defect-impurity complexes in irradiated n-type Ge. Single crystals were grown by the Czochralski process from P, As, or Sb-doped melts, and ¿ 1015 to ¿ 1017 oxygen cm-3 was added to the furnace chamber after ~ 1/3 of the crystal had been solidified. Hall coefficient and resistivity measurements (at 77°K) were used to determine the initial donor concentration due to the dopant and clustered oxygen, and infrared absorption measurements (at 11.7 ¿) were used to determine the dissociated oxygen concentration. Certain impurity and defect-impurity interactions were then investigated that occurred as a consequence of selected annealing, quenching, Li diffusion, and irradiation experiments at ~ 300°K with 60Co photons, 1.5-2.0 MeV electrons, or thermal energy neutrons. Particular attention was given to determining the electrical role of the irradiation produced interstitial and vacancy, and to look for any evidence from electrical and optical measurements of vacancy-oxygen, lithium-oxygen, and lithium-vacancy interactions. A tentative model was developed for the lattice defect and defect-impurity structures, however, it was evident that any interpretation of defect-impurity interactions as a consequence of irradiation or annealing was subject to considerable error if the concentration and electrical role of certain impurities was not determined.