DC conductivity, photoconductivity, magnetoresistance, and ESR of polycrystalline silicon films have been measured as functions of doping and temperature. Native defect states of about 10 18 cm -3 distributed mainly in the grain boundary region are reduced with phosphorus doping and completely eliminated at doping ratios above 4 × 10 -5 . This defect compensation by dopant atoms results in a decrease of local band bending in the grain boundary as confirmed from the analysis of photoconductivity. A rapid decrease in resistivity occurs around a doping ratio of 3 × 10 -5 at which the density of doped phosphorus atoms starts to approach the native defect density. Carrier transport in doped polycrystalline silicon is found to be well understood in terms of a potential fluctuation model describing the electronic density of state distribution in the energy gap.
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Taniguchi et al. (1980) studied this question.