I am trying to understand the dependence of hole mobility on the boron dopant concentration in boron doped silicon, it seems like there is a minimum of around 47cm2/vs, even when keeping increased dopant atom. Why isn't it continuously decreasing with more impurity scattering, but working in a different way?
Is it related to the formation of impurity band and possibly a different scattering mode?
On the other hand, I found some papers saying that there is a solid solubility of boron in silicon at several 10e19/cm^3, over this there should be dopant segregation, could the above mobility minimum be a result of non-uniform dopant distribution?
In the case of poly-Si important factor which affect on the mobility is the presence of grain boundaries. Grain boundaries primarily act as scattering sites and potential barriers leading to reduced carrier mobility in p-Si. At sufficiently high doping levels, the resistivity of p-Si can increase due to the reduced carrier mobility as a result of the presence of high concentrations of active ionized impurities, which act as scattering sites. Additionally, the existence the dopant segregation may also takes place. The deactivation of ionized impurities in a results of the formation of complex centers with the participation of intrinsic defects may be occurs that can decreases of scattering process and increases the mobility. It should be noted that a high temperature annealing (up to 1350°C) allows greater B solubility, and therefore lower resistance. Thus, the grain boundary and ionized impurities strongly affect on mobility in p-Si as well as the presence of other intrinsic defects.
@yuriy sir is right
but fuwei i attatching some some calculations i guess it will further help
Data SILICON: REDUCED MOBILITY AT ZERO RESISTANCE
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