Question

A p-n junction is obtained at a depth of 3 x 10-3 cm below the surface by diffusion of antimony (Sb) into p-type germanium. What is the donor concentration in the bulk germanium if the diffusion is carried out for three hours at 790 C? Express your answer in number of donor atoms per cubic centimeter. Assume the surface concentration of antimony is held constant at 8 x 1018 cm-3 and that the diffusivity at 790 C is 4.8 x 10-11 cm2/s.