Ramiation and Annealing Studies on Oxygen-Doped and Lithium Diffused Germanium

Hall coefficient and resistivity measurements were used to determine the apparent carrier concentration and mobility of n-type Ge doped with specific impurities, or grown to contain oxygen, and then altered by annealing, Co60 photon irradiation, or Li diffusion. Annealing at 350°C increased the donor concentration and decreased the mobility of oxygen-doped Ge as a consequence of oxygen clustering. Subsequent annealing at 500°C decreased the donor concentration and increased the mobility as a consequence of oxygen dissociation. Clustering and dissociation were repeated many times with no apparent alteration of total oxygen content. The apparent rate of introduction of lattice defects by Co60 photons was essentially independent of oxygen concentration in Ge containing up to ~ 1016 dissociated oxygen cm-3. Formation of a primary defect state at Ec -0.2 eV was observed for all concentrations. There was no evident interaction between the radiation induced defects and oxygen after defect formation, but some evidence was observed of defect stabilization against annealing in oxygen-doped Ge. There also was no evident interaction between Li and normal donors or oxygen in Ge after Li diffusion, precipitation, and annealing (~ 400°C), but Li interacted with "deep-level" acceptor impurities (Ag, Au or Cu) to form donors that were stable up to ¿ 500°C.