Amphoteric property of electrically active nickel in silicon

Deep levels in nickel-doped n- and p-type silicon have been studied by the Hall effect and deep level transient spectroscopy (DLTS) under various diffusion and isothermal annealing conditions. It was found that nickel introduces an acceptor level of 0.47±0.04 eV from the conduction band and a donor level of 0.18±0.02 eV from the valence band, and that the concentrations of the two levels are practically identical. Isothermal annealing experiments have revealed stable behaviors of the two levels. The results suggest that the two levels are different charge states of the same substitutional nickel atoms in silicon.