Codiffusion of Gallium and Phosphorus Atoms in Silicon

It has been found that the gas-phase diffusion of gallium and phosphorus atoms into silicon provides not only the compensation but also partial interaction of the elements with each other. Analysis under a scanning electron microscope has shown that, after diffusion and surface treatment, gallium and phosphorus atoms are present on the silicon surface in similar concentrations. Studies of the concentration distribution of charge carriers over depth have shown that, upon codiffusion, the solubility of gallium increases by an order of magnitude, while the charge carrier mobility decreases by a factor of three to four. Based on the obtained data, the concentration (~10 19 cm –3 ) and energy of formation (~0.62 eV) of neutral complexes [Ga – P + ] have been calculated. The results can be attributed to the electrostatic interaction of gallium and phosphorus ions during diffusion, which leads to a change in the concentration distribution of the impurities and the formation of quasi-neutral complexes of the [Ga – P + ] type in the silicon lattice.