Arsenic and phosphorus diffusion and activation-related phenomena in co-doped germanium substrates were studied using conventional thermal annealing. Chemical profiles were obtained by secondary ion mass spectroscopy, sheet resistance was estimated by the Van der Pauw method. The study covered the temperature range from 600 to 750C. The dopant profiles were accurately described by a quadratic dependence of the dopant diffusion coefficient upon the free electron concentration. In the simulations, dopant pile-up near to the surface and dopant loss due to out-diffusion during annealing were considered. Although the double donor co-doping technique had no advantage over mono-doping with P concerning the level of activation and junction depth, it was interesting to observe the different diffusion behavior of the two dopant. Whereas the diffusion of As indicated a retardation under co-doping the diffusion of P remained either unaffected or was slightly enhanced by co-doping. The activation level of the co-doped samples remained lower compared to the respective mono-doped samples, except for the highest annealing temperature.

Experiments and Simulation on Diffusion and Activation of Codoped with Arsenic and Phosphorus Germanium. P.Tsouroutas, D.Tsoukalas, H.Bracht: Journal of Applied Physics, 2010, 108[2], 024903