Large enhancement of the effective lifetime of n-type multicrystalline silicon by two step spin-on phosphorus diffusion and SiO2 passivation

A large improvement of the effective lifetime of n-type phosphorus doped multicrystalline silicon to reach 950 mu s has been realized by combining both two step phosphorus treatments and surface oxidation. The average lifetime increases after the phosphorus diffusion process is mainly attributed to the remove of killer impurities which induces impurity gettering effects at the external surfaces. But an evident decrease of the electrical activity of some grain boundaries after that process was also observed due to the formation of heavily n+-type front layer of a floating junction and tunneling oxide along them. Moreover, low quality n-type substrates with an oxide passivated emitter are shown to suppress the effect of light induced degradation. (C) 2011 American Institute of Physics. [doi:10.1063/1.3641882]