How does increased impurity concentration affect charge-carrier mobility in a semiconductor?

In a semiconductor, increasing the concentration of impurities—a process known as doping—is primarily performed to increase the number of charge carriers and thereby enhance electrical conductivity.12

However, this process has a trade-off regarding charge-carrier mobility. While doping increases the total number of available conduction electrons or holes, it simultaneously increases electron scattering caused by the presence of these additional impurity atoms within the crystal lattice. This increased scattering acts as an impediment to the movement of charge carriers, which results in a reduction of their mobility.12

In summary, while higher impurity concentrations successfully raise the overall conductivity of the material by providing more charge carriers, they also lead to a decrease in the mobility of those individual carriers due to enhanced impurity scattering.12