Practical model for electrical properties of highly doped p-type polysilicon

This paper describes a new approach to practical modelling of electrical properties of polycrystalline semiconductors. The model combines the electro-physical properties of microcrystalline silicon films with that of monocrystalline silicon so that the former properties are attributed to the grain boundaries regions and the latter to intragrain regions. The model is used to describe the dependence of resistivity (ρ), its temperature coefficient (TCρ) and gauge factor (G) of highly boron doped polycrystalline silicon, 4.10²⁵ to 10²⁷ m^-3, on the dopant concentration for different grain sizes, 10^-8 to 10^-6 m. It is shown that at the high doping level ρ (TCρ) of polysilicon is higher (lower) than that of monosilicon, being dependent on the average grain size. The gauge factor of polysilicon is lower than that of monosilicon not only because of the “random” orientation of the grains but also because of lower values of gauge factor at the grain boundaries. For lower doping concentration (smaller grain sizes) the TCρ of polysilicon becomes negative revealing the higher contribution of grain boundaries