Double-hump diffusion profiles of copper and nickel in germanium wafers yielding vacancy-related information

Diffusion of Cu and Ni into Ge was investigated between 700 and 900 degrees C with the aid of rapid isothermal lamp annealing and spreading-resistance profiling. Using row-dislocation-density single-crystal Ge wafers with a backside gold layer, we observed typical double-hump diffusion profiles of both Cu and Ni. These profiles can be described within the dissociative model by taking into account that the front surface acts as source for both vacancies (V) and Cu or Ni while the back surface combines the V-source feature with a Cu, Ni-sink property. Profile fitting yields data regarding the V-assisted Ge self-diffusion coefficient and the equilibrium concentration of vacancies as a function of temperature. (C) 2000 American Institute of Physics. [S0003-6951(00)01231-6].